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DESIGN AND FABRICATION OF SOLAR OVEN
Bachelor of Science
In
Mechanical Engineekamranmujahid760@gmail.comring _______________________ ____________________ Project
Declaration I declare that the work contained in this thesis is my own, except where explicitly stated otherwise. In addition this work has not been submitted to obtain another degree or professional qualification.
Gawhar Ali ___________________
Malak Yaseen Khan ___________________
Dawood Ahmad Khan
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Abstract
In this design project the idea of solar cooking is used for making of solar oven. The aim of this project is to design and fabricate a small-scale solar oven which could be used when the sun is shining to bake foods up to two pounds at temperature of 1300c. The advantage of this oven over conventional oven is that it can be used without any conventional energy source and it is portable as well. The design was finalized to obtain maximum advantage from solar radiation. Dimension and material was finalized and then fabrication was done as per finalized design. Experiment were performed in different days of March and April. 12:00 PM to 2:00 PM it is the best day time for achieving the maximum temperature. The maximum temperature achieved is 1170c between 01:50 PM to 02:40PM on 7 April 2017.
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Dedication
Every challenging work needs self-efforts as well as guidance of elders especially those who were very close to our heart. Our humble effort we dedicate to our sweet and loving parents whose affection, love, encouragement and prays of day and night make us able to complete our project successfully in time. Along with all the hard working and respected teachers.
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Acknowledgment
First of all we would like to express our sincere and greatest thank to our supervisor Engr Sajid Raza who encouraged and guided us to carry out our final year project. Special thanks to Saeed Nazir for their advices, and help in fabrication of solar oven. Last but not least, we thank our beloved family especially our parents who encouraged us and provided financial support for this project.
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Table of Contents Declaration...................................................................................................................................... ii Abstract.......................................................................................................................................... iii Dedication...................................................................................................................................... iv Acknowledgment ........................................................................................................................... vi List of figures................................................................................................................................. ix List of tabels................................................................................................................................... xi Abbreviations................................................................................................................................ xii Chapter 1 Introduction:................................................................................................................... 1 1.1Background: ........................................................................................................................... 1 1.2Advantages of solar cooking:................................................................................................. 3 1.3Rural and urban wood energy consumption in Pakistan:....................................................... 4 1.4Existing cooking sources:....................................................................................................... 4 1.4.1Firewood:......................................................................................................................... 5 1.4.2Liquefied Petroleum Gas (LPG):..................................................................................... 5 1.4.3Crop residues:.................................................................................................................. 5 1.4.4Cow dung:........................................................................................................................ 5 1.4.5Kerosene:......................................................................................................................... 6 1.4.6Biogas:............................................................................................................................. 6 1.4.7Electricity: ....................................................................................................................... 6 1.4.8Solar cooking:.................................................................................................................. 7 1.5Existing solar cooking methods and their disadvantages:...................................................... 7 1.5.1Box type solar cooker:..................................................................................................... 7 1.5.2Panel cooker: ................................................................................................................... 8
vii 1.5.3Parabolic cooker: ............................................................................................................. 9 1.5.4Funnel cooker: ............................................................................................................... 10 1.5.5Scheffler cooker:............................................................................................................ 11 1.5.6 Other Types: ................................................................................................................. 12 Chapter 2 Literature review: ......................................................................................................... 14 Chapter 3 Design and Fabrication: ............................................................................................... 34 3.1System Description: ............................................................................................................. 34 3.1.1Wooden box:.................................................................................................................. 35 3.1.2Black pint mild steel box:.............................................................................................. 35 3.1.3Mirror reflector:............................................................................................................. 36 3.1.4Glass wool ..................................................................................................................... 36 3.2 Calculation: ......................................................................................................................... 37 3.3 Fabrication of solar oven..................................................................................................... 40 3.3.1 Tool and Instrument Used: ........................................................................................... 40 3.3.2 Material:........................................................................................................................ 40 3.3.3 Cutting (wood hand saw) process:................................................................................ 40 3.3.4 Mild steel box:.............................................................................................................. 42 3.4 Joint process:....................................................................................................................... 43 3.4.1 Insulation: ..................................................................................................................... 43 Chapter 4 Experimentation and Results:....................................................................................... 47 4.1 Experimental procedures:.................................................................................................... 47 4.2 Solar oven without reflector:............................................................................................... 47 4.3 Solar oven with reflector:.................................................................................................... 49 4.4 Solar oven with reflector:.................................................................................................... 51 4.5 Solar oven with reflector:.................................................................................................... 52
viii 4.6 Solar oven with reflector:.................................................................................................... 53 Conclusion: ................................................................................................................................... 55 References:.................................................................................................................................... 56
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List of Figures Figure 1-1: The three categories of solar coking: (a) Box Ovens, (b) Parabolic Cooker and (c) Panel Cookers. ................................................................................................................................ 2 Figure 1-2: Basic box type solar cooker ......................................................................................... 8 Figure 1-3: Basic penal type solar cooker....................................................................................... 9 Figure 1-4: A typically parabolic solar cooker ............................................................................. 10 Figure 1-5: Solar funnel cooker .................................................................................................... 11 Figure 1-6: Scheffler cooker ......................................................................................................... 12 Figure 2-1: Schematic drawing of the solar oven, its components and dimensions ..................... 15 Figure 2-2: Temperature on the external surface of the oven....................................................... 17 Figure 2-3: Pictorial view of solar oven with and without reflectors ........................................... 18 Figure 3-1: Block diagram of solar oven ...................................................................................... 34 Figure 3-2: Wooden box ............................................................................................................... 35 Figure 3-3: Mild steel box............................................................................................................. 35 Figure 3-4: Mirror reflector .......................................................................................................... 36 Figure 3-5: Glass wool.................................................................................................................. 36 Figure 3-6: 3D Creo design........................................................................................................... 39 Figure 3-7: 2D Creo design........................................................................................................... 39 Figure 3-8: Wood cutting.............................................................................................................. 42 Figure 3-9: Joining of wood......................................................................................................... 42 Figure 3-10: wooden box.............................................................................................................. 43 Figure 3-11: Mild steel sheet ........................................................................................................ 44 Figure 3-12: Mild steel box........................................................................................................... 44 Figure 3-13: Sealed with rubber ................................................................................................... 45 Figure 3-14: Frame for reflector and transparent glass................................................................. 46 Figure 3-15: Joins the frame with box ......................................................................................... 46 Figure 3-16: Joins adjuster............................................................................................................ 47 Figure 3-17: Complete fabricated model ...................................................................................... 48 Figure 4-1: Time vs temperature without reflector....................................................................... 49 Figure 4-2: Time vs temperature with reflector............................................................................ 50
x Figure 4-3: Time vs temperature with and without reflector in March 2017 ............................... 51 Figure 4-4: Time vs temperature with reflector............................................................................ 52 Figure 4-5: Time vs temperature with reflector............................................................................ 53 Figure 4-6: Time vs temperature with reflector............................................................................ 54 Figure 4-7: Time vs temperature with and without reflector........................................................ 55
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List of Tables Table 1-1: Sources of firewood for urban and rural households by income class, Pakistan .......... 4 Table 4-1: Solar oven without reflector ........................................................................................ 49 Table 4-2: Solar oven with reflector ............................................................................................. 50 Table 4-3: Solar oven with reflector ............................................................................................. 52 Table 4-4: Solar oven with reflector ............................................................................................. 53 Table 4-5: Solar oven with reflector ............................................................................................. 54
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Abbreviations
(WHO) World Health Organization (LPG) liquefied petroleum gas
(EPS) Expanded polystyrene (IPCC) Intergovernmental Panel on Climate Change (UNFCCC) Convention Nations Framework Convention on Climate Change (Tb) box temperature (DHS) Direct Heat Storage (PCM) Phase change materials
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CHAPTER 1
Introduction
A 'Solar Oven' is a device which uses the energy of direct sunlight to heat, cook or pasteurize food. Many solar oven currently in use are relatively inexpensive, low-tech devices, although some are as powerful or as expensive as traditional stoves, and advanced, large-scale solar oven can cook for hundreds of people Because they use no fuel and cost nothing to operate, many nonprofit organizations are promoting their use worldwide in order to reduce fuel costs (especially where monetary reciprocity is low) and air pollution, and to slow down the deforestation and desertification caused by gathering firewood for cooking. Solar cooking is a form of outdoor cooking and is often used in situations where minimal fuel consumption is important, or the danger of accidental fires is high, and the health and environmental consequences of alternatives are severe.
1.1 Background: The major problems of world community are the degradation to the ozone layer and the Global warming. Since in 1980‘s the international Toronto conference began with the changing atmosphere in Canada. The IPCC's First Assessment Report in Sundsvall, Sweden (August 1990) was created. The IPCC (Intergovernmental Panel on Climate Change) is an indicator of climate change as a statistically significant variation in a parameter mean climatic and variability. In June 1992 happened at Rio de Janeiro, Brazil, the Convention Nations Framework Convention on Climate Change (UNFCCC) on ECO-1992. In 1997, the United Nations created The Kyoto protocol, an international treaty with more stringent commitments to reduce gases emissions that exacerbate global warming. The world efforts are to appropriate utilization of source energy, reduce deforestation process and CO2 emission, and many actions. One of these is the developing of equipment‘s with low ambient impacts like the solar cooking. According to Wetter (2006) the solar cookers are an important contribution towards halting the deforestation process and thereby preserve the environment. At the same time they help in fighting poverty. 500 solar cookers save 5,500 tons of wood a year, which translates into 1,000 hectares of woodland in the south of Madagascar. There is no CO2 emission, which is the main agent responsible for climate change. The population will become less dependent on wood and charcoal. Besides
2 environmental reasons there are also economical and practical reasons to favor the solar cooker. Families spend a lot less money on wood and charcoal. There is a pay back on the investment after only six months of using the solar cooker. The solar cooking was invented in Switzerland in 1767 by naturalist Horace de Saussure. The cooking took spend centuries to be broadcast throughout the world. Fornosolar (2009). Solar cooking has three main categories Box Ovens, Parabolic Cooker and Panel Cookers. Box Ovens Are the most common type of solar oven, and their use is widespread, particularly in developing countries. Hundreds of thousands of box ovens are used in India alone. Box ovens or cookers typically are square or rectangular and have a clear glass lid. Panel reflectors inside conduct heat throughout whatever is being cooked. Box ovens tend to cook at moderate to high temperatures, and they are primarily used for slow cooking. Parabolic or curved concentrator solar cookers use concentrated sunlight. They typically have a large, dish-shaped design and a reflective surface. The parabolic cookers are useful for cooking foods quickly at high temperatures. They can be used to prepare individual meals or for large-scale institutional cooking. One of the primary disadvantages of a parabolic cooker is that must be monitored and adjusted frequently to ensure that the correct amount of sunlight is being directed toward the surface. Parabolic cookers also present a higher risk for fires or burns. Panel Cookers combine elements of two categories. They are the easiest of the three to construct and use the typically feature a pot that rests inside a plastic or glass enclosure and is surrounded by three to five reflective panels. Panel cookers generally cook food at much lower temperatures, making it much more difficult to overcook or burn food. Their lower cooking temperature does limit the types of foods you can prepare and they typically work best with foods they have high moisture content. Unlike parabolic, panel cookers do not require constant monitoring or adjustment. After the January 2010 Haiti earthquake was donated hundreds of solar painel cooker kits to Haiti. Figure 1-1: The three categories of solar coking: (a) Box Ovens, (b) Parabolic Cooker and (c) Panel Cookers.
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1.2 Advantages of solar cooking:
1.4.1 Firewood: This is a very commonly used cooking fuel in rural areas. Frequently used hardwood has energy content of 14.89MJ/kg. Out of this about 10.423MJ/kg is recoverable. Smoke from burning of firewood contains water vapor, carbon dioxide and other chemical and aerosol particulates. Wood and wood waste emit 195lbs/106Btu of carbon dioxide. Depending on population density, topography, climatic conditions and combustion equipment used, wood heating may substantially contribute to air pollution, particularly particulates. Wood combustion products can include toxic and carcinogenic substances. Particulate air pollution can contribute to human health problems like asthma and heart diseases [5].
1.4.2 Liquefied Petroleum Gas (LPG): LPG is a mixture of hydrocarbon gases used as a fuel in heating appliances like cooking, water heating and in vehicles. It is also being used as aerosol propellant and a refrigerant to reduce damage to the ozone layer [6]. LPG is synthesized by refining petroleum or wet natural gas, and is usually derived from fossil fuel sources, being manufactured during the refining of crude oil, or extracted from oil or gas streams as they emerge from the ground. Most commonly available
5 LPG is a mixture of propane (60%) and butane (40%) having calorific value of 46.1MJ/kg [6]. LPG is a low carbon emitting (139lbs/106Btu of CO2) hydrocarbon fuel available in rural areas, emitting 19% less CO2 per kWh than oil, 30% less than coal and greater than 50% less than coal-generated electricity distributed via the grid [5].
1.4.3 Crop residues: There are two types of agricultural crop residues, field residues and process residues. Field residues are materials left in agricultural field or orchard after the crop has been harvested, like stalks, stubble (stems), leaves etc. Process residues are those materials left after processing of the crop into usable resource. Materials like husks, seeds, bagasse (fibrous residue obtained from sugarcane) and roots are used as cooking fuel in most part of the rural places.
1.4.4 Cow dung: Cow dung is used as fuel as well as fertilizer in most of the developing countries like India. Caked and dried cow dung is most common cooking fuel in rural India. Dried cow dung is used as fuel in traditional cook stoves which are not properly ventilated. This has led to many respiratory health issues. Additionally it is found to be causing arsenic poisoning in unsuspecting villagers. People are simply exposed to 1859.2 ng arsenic per day through direct inhalation, of which 464.8 ng could be absorbed in respiratory tract. Inhalation of arsenic leads to respiratory problems such as persistent coughs and reduced lung capacity [7].
1.4.5 Kerosene: Kerosene is a combustible hydrocarbon liquid which is also known as paraffin. The heat of combustion is similar to that of diesel, having heating value around 43MJ/kg. Its use as a cooking fuel is limited to some portable stoves for backpackers and to less developed countries, where it is usually less refined and contains impurities. Usage of kerosene is not recommended for closed indoor areas without a chimney due to the danger of building up of carbon monoxide gas. Carbon dioxide emitted from kerosene is around 159 lbs. /106Btu.
1.4.6 Biogas: Biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as manure or sewage, biomass, municipal waste, green waste and crop residues. This is produced by the biological breakdown of organic matter in the absence of oxygen. Biogas
6 primarily comprises of methane (50%-75%) and carbon dioxide (25%-50%). Small amount of nitrogen, hydrogen, hydrogen sulfide and oxygen is also present in biogas. The other major type of biogas is wood gas which is created by gasification of wood or other biomass. This type of biogas comprises primarily of nitrogen, hydrogen, and carbon monoxide, with trace amounts of methane [8]. Biogas is used as low cost heating application like cooking and also can be used as modern waste management facility where it is used to generate either mechanical or electrical power.
1.4.7 Electricity: The first technology for cooking using electricity used resistive heating coils which heated iron hotplates or coil, on top of which the vessels were placed. Later in 1970s, glass ceramic cooktops started to appear. This has very low thermal conductivity, but let‘s infrared radiation pass very well, heating up the materials to be cooked. Halogen lamps are also used in some places as a heating element, which gives better efficiency of 60% compared to electric coil which has an efficiency of 55%. A Recent technology which is developed first for professional cooking and has entered domestic market is the induction cooking, which gives around 90% efficiency. These heat the cookware directly through electromagnetic induction. For using this type of cooking, pots and vessels with ferromagnetic bottoms are required. This form of flameless cooking has some advantages over conventional gas flame and electric cookers as it provides rapid heating, improved thermal efficiency, greater heat consistency, plus the same or greater degree of controllability as LPG [9].
1.4.8 Solar cooking: Due to exponential raise in the world‘s population and resulting growth of industrial activities, the energy requirements are such that fossil fuel cannot be the only source on a sustainable basis. This implies that one has to look for alternate sources of energy which are more environmental friendly, cleaner and renewable. As cooking is an integral part of every human being, it consumes a major fraction of the household energy requirement. Existing cooking fuels are either derived from fossil fuels like LPG, kerosene etc. or air polluting like firewood, crop residue, cow dung etc. In this respect, solar cooking is a very simple, clean and environment friendly alternative.
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1.5 Existing solar cooking methods and their disadvantages: Many scientists of 17th century knew about the principle of greenhouse effect where glass is used to trap heat from the sun. But Horace de Saussure, a French-Swiss scientist extended this principle to heat up food materials. As early as 250 years ago European scientists started exploring on solar energy, which is considered to be the father of today‘s solar cooking movement. Lots of modifications and exploration has been done on solar cooking in order to improve the efficiency and ease of cooking [10–11]. The existing solar cooking methods are discussed in the following paragraphs.
1.5.1 Box type solar cooker: Box type cooker is one of the basic solar cooking models. It is a simple rectangular box covered with either glass or plastic [12–13]. Sun beam entering the cooker through this cover turns to heat energy when it is absorbed by the black colored absorber plate and cooking vessel. This heat input raises the temperature inside the box cooker until the heat loss from the box equals to the solar heat input. The box is thermally insulated to reduce the heat loss to ambient, so as to attain higher temperature and better efficiency [14, 15]. Heat is trapped inside the box due to greenhouse effect. Radiation from sun easily passes through the glass cover and is absorbed by dark materials like absorber plate and vessel. These hot objects emit longer wavelength heat energy which is blocked by the glass cover. Hence this trapped energy raises the temperature of the space inside the box. In order to improve the box temperature, reflectors are used. Single or multiple reflectors are used, which are oriented such that the incident sunlight falling on the reflector, get directed to the box [16–17].
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Figure 1-2: Basic box type solar cooker Disadvantages of box type cooker
• Cooking has to be done outdoor and the cook has to stand in sunlight for a long time.
• Very slow cooking compared to conventional cooking. This takes 2-3 hours to cook and even more time during cloudy days with respect to less than half an hour taken by conventional methods.
• It is not possible to cook during rainy days.
• There is no control over the rate of cooking.
• This is not an interactive cooking.
1.5.2 Panel cooker: Panel cookers are very inexpensive and can be easily built using reflecting material like aluminum foil and cardboard. This uses shiny material to reflect sunlight to a cooking vessel which is enclosed in a clear plastic bag. Solar Cookers International developed a
panel cooker model in 1994, commonly known as ‘Cook it‘. This can be manufactured locally by pasting reflecting material onto a folded cardboard. Food to be cooked is kept in a dark container covered with a tightly fitted lid. This is placed at the center of the panel. Variety of designs are available in this type of cooker like simple panel, high back, panel for tropics, bubble panel, Dars Diamond cooker etc. Disadvantages of panel cooker are
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• Cooking has to be done outdoor and not possible to cook during rainy season.
• Very slow cooking compared to conventional cooking. At least one hour is required to cook during clear sunny day.
• Control over the rate of cooking is not there. Figure 1-3: Basic penal type solar cooker
1.5.3 Parabolic cooker: Parabolic cooker is used for cooking at better cooking rates. It is comparable to conventional cooking and also for community level cooking of food [18–19]. Using a reflector of parabolic shape, sun beam is reflected onto a pot or vessel kept at the focus of the parabola. The axis of the parabola should be parallel to the sun beam so that maximum heat energy is obtained at the pot. Since highly focused light is obtained, temperature can go well above 150oC. Linear parabolic collector is also used for concentrating the sun light on to a pot kept at the focal line [20, 21]. Design and analysis of parabolic square dish solar cooker has been presented by others [22]. Disadvantages of parabolic cooker
1.5.4 Funnel cooker: In funnel cooker, sun light is concentrated into a cooking vessel or pot using a funnel shaped cooker. This makes use best of both parabolic and box type cooker. Sun beam is concentrated using a reflector like aluminums foil pasted on a folded cardboard. Black colored pot is kept inside a plastic cover which traps the heat by greenhouse effect. A simple system allows pressure-cooking to increase the cooking rate while releasing steam. This cooker can be used for cooking and pasteurizing water. Disadvantages of funnel cooker
• Cooking has to be done outdoor
• There is no control over the cooking rate and very slow cooking compared to conventional cooking.
11 Figure 1-5: Solar funnel cooker
1.5.5 Scheffler cooker: Scheffler cooker is also known as parabolic dish with fixed focus on ground. Cooking can be carried out in the kitchen without moving out using this type of cooker. The concentrating reflectors track the movement of the sun, reflecting the light of the sun and concentrating it at a fixed position. The reflected and concentrated sunlight enters a nearby kitchen directly to strike a cooking vessel or frying surface. High temperatures can be attained as it focuses the sunlight. Hence the time taken for cooking is comparable to conventional cooking. In some configurations, the concentrated sunlight is used first to create steam which is transported by pipes to a nearby kitchen. Concentrating reflectors are placed on both the equatorial and polar sides of the receiver. These receivers are attached to the steam pipes that transport the steam to kitchen. Since this steam is generated directly for cooking, the whole system has to be maintained clean. This type of cooking is suitable for preparing food for large mass. The cooking temperature is limited to around 100 o C. Disadvantages of Scheffler cooker
• The seasonal variation in the height of the sun requires changing not only the angle between the concentrating reflector and its axis of rotation, but also the shape of the reflector.
•Since focus point is fixed, continuous tracking is necessary.
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• Focused sunlight falls only on outer part of the cooking vessel resulting in uneven cooking.
• Highly focused light is very hazardous as cooking is done at the focal point.
• There is no option for either decreasing or increasing the rate of cooking. Figure 1-6: Scheffler cooker
1.5.6 Other Types: In order to cook during cloudy days or night, either auxiliary source of energy is used or some kind of energy storage facility is provided. Box-type cooker with auxiliary heater inside the box is used to cook during cloudy days [23]. Solar cooker is also used as food processor where it is also utilized for solar water heating, solar still and solar drier [24] and electric energy is used as auxiliary source in [25]. For collecting energy from sun, different methods like evacuated (vacuum) tube collectors are used which prevents the convection loss from the receiver improving the collector efficiency. Hot plate cooking system powered by solar thermal energy using concentrating evacuated tubular collector has been proposed in [26]. A solar cooking system using vacuum-tube collectors with heat pipes containing a refrigerant as working fluid has been proposed and analyzed [27]. A split-system solar cooker is described which has its flat plate collector outdoors and the cooking chamber inside the kitchen, with heat pipes transferring the energy between the two [28]. Similarly vacuum-tube collector with integrated long heat pipes directly leading to the oven plate has been tried [29]. A solar cooking system with or without temporary heat storage
13 has been developed and installed in different countries of the world [30, 31]. To reduce the complete dependency on solar insolation, energy storage system is being used. Phase change materials (PCM) are used for many solar thermal applications [32–33]. Solar cooker based on an evacuated tube collector with PCM storage unit has been investigated. Solar energy is stored in the PCM storage unit during sunshine hours and is utilized for cooking in late evening/night time [34–35].
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CHAPTER 2
Literature review The entire human uses the sun light in the start of life. Sun light is one of the important sources of energy for all living thing without sun light life is not possible. The following paper shows the history of this line of research. Mr. Rodrigo de Freitas Gurgel presents a solar oven for baking food, manufactured from a thermal box of EPS(Expanded polystyrene). The solar oven is a prototype of solar concentration for baking food. The main innovation of the work is the use of EPS cooler, widely available, low cost and with a structure already define and manufactured, avoiding the production of mold to get the box. It should be noted that the EPS thermal box is already a very efficient thermal insulator. This thermal property of the materials of the EPS box is important due to not require the use of insulating materials on the sides and bottom of the solar oven, to minimize heat losses. The inside of the box EPS enclosure baking oven, was coated on the bottom and side sheets by mirrors forming the profile which gives the greater concentration of solar radiation. Above the floor of the oven is system with plane mirror reflector, directing the solar rays into the oven where the food displaced into the baking. Some aspects describe of construction of solar oven. And compare the time of baking which obtain from other solar ovens presented by solar literature and also compared to gas conventional ovens. Preliminary tests have shown the feasibility of using such solar oven, temperature levels achieved for the purpose of baking of various types of foods. The tests show that the solar oven reached the maximum temperature of 123.8°C and baking various foods such as pizza, lasagna, cake, bun, and other in an average time 50 minutes. The firewood is probably the oldest energy used by man and still has great Importance in the Brazilian energy matrix, participating with about 10% of primary energy production About 40% of wood produced in Brazil is transformed into charcoal. The residential sector is the most expensive wood (29%). Usually it is for cooking food in rural areas. A family of eight requires Approximately 2.0 m³ of wood per month to prepare their meals. The Industrial sector comes next with about 23% of consumption. The main industries that consume fuel in the country are food and beverages, ceramics and pulp and paper (National Energy Balance 2009 - www.mme.gov.br).These data show the that massive use of wood, putting at risk the health of
15 the planet, point to need the mass use of solar cooker for cooking food to prevent nature and also to prevent firewood. The use of solar energy for cooking is the oldest and spread this energy source, and its main characteristic its social function. The people in Africa use solar ovens and massively contributing to a policy of non-use of wood. The use of solar ovens in the solar scrub promises to reverse or at least mitigate this situation by allowing backcountry better living conditions. It presents a solar oven for baking food, manufactured from a thermal box of EPS. The solar oven made from a scrap box EPS presented the following dimensions: - external - Length: 0.74 m, width 0.56 m and height: 0.20 m; - Internal - length: 0.625 m, width: 0,44 m . The outdoor area corresponded to 0.41 m² and the external volume 0,083 m³; internal area corresponded to 0.28 m². The area of the reflecting surface that lines the inner walls of the furnace corresponded to 0.36 m². The outer reflective surface presented a catchments area of solar radiation corresponding to 0.18 m². box show in figure 2.1. Figure 2-1: Schematic drawing of the solar oven, its components and dimensions The enclosure of the oven was covered with a transparent flat glass of three mm thick. The glass is seated in the box. Eps material facilitates loading and unloading of food offered for cooking. The furnace structure was fabricated. Using angles and provides rotational movement to facilitate the handling of the oven. Tests were performed without load for determining the temperature of the furnace box type solar studied. Temperatures were measured every five minutes or so. The tests were conducted for the period from 10:00 to 14:00 hours. Tests were also performed to load the two baking pizza 400g, breaded chicken and 500g of a cake 700 g,
16 determining the time required for this purpose. The same parameter measure without load at same time interval. Were also measured the temperature inside the oven. The inner side temperature was measured by chromelalumel thermo couple type K coupled to a digital thermometer. The efficiency of the solar oven studied was around 78%, since the energy lost corresponded to 22% of the energy that went into the baking enclosure of the oven. The solar oven was placed on exposure to the sun 10:20 are. The average ambient temperature was 29 ° C and thermal sensation of 33°C during the test. The maximum temperatures in the absorber surface and internal air of solar oven corresponding to 114°C and 105°C, respectively, were significant and suitable to provide the baking of foods. The average temperatures for these parameters during the test duration, at around 102.4°C and 94.6 C, respectively, are also suitable for obtaining the desired end. A cake was baked at 11:45 am. After placing the cake the temperature of the absorber were 40°C and the internal of the oven of 82°C to the air temperature inside the oven. The environment average temperature during the test was 30.5°C. The complete baking of cake taking 45 minutes. Another test for pizza baking the test performed at 12:30 pm temperature before placing is 41°C for the shape temperature and 80 ° to the air temperature inside the oven. The environment average temperature is 30.8°C during the test. The complete baking of pizza taking 15 minute. A third test preformed for chicken fingers, five units each have mass 100g total 500g. Test began at 12:30 pm. The temperatures of breaded before baking were 46°C for the absorber temperature and 71 ° C to the air temperature inside humidity of 60%. The complete baking the breaded happened in twenty-five minutes. For the diagnosis of thermal loss from the oven temperatures were measured from their surfaces. Figure 2.2 shows the mean values of temperatures measured during the test without load at 1 hour.
17 Figure 2-2: Temperature on the external surface of the oven .Solar oven bake food very good from the 9:00am to 2:00 am. The solar oven has become competitive with conventional gas oven. The manufacturing of solar oven is easy and low cost. All the food in the oven is baked under solar cooking time competitive with conventional oven. It is important to have another conventional source for cooking food to replace the proposed solar cooker on days with insufficient solar conditions for its use. [36] Mr. Bbdul Waheed Badar investigates the thermal performance of a unique box type solar oven whose five sides are exposed to ambient and provisions are also provided to install the reflectors to enhance the intensity of incident solar radiation on the oven. Experiments were performed where temperatures attained inside the box cavity are recorded on different days and times of the day corresponding to various intensities of available solar radiation. A steady sate heat transfer numerical model of the solar oven without reflectors is also developed based on six individual thermal resistance networks which account for the heat losses through each flat-side of the oven box and a good agreement with the experimental data is achieved. A parametric study based on numerical calculations and experiments is then carried out to study the effects of various parameters on oven‘s thermal performance, e.g. number of glazing, distance between glazing and box, type of absorber coating, etc. Higher box temperature is attained using double glazing than single glazing. As compared to black paint, selective surface coating results in
18 significantly higher oven temperatures (up to 40 0 C). Plate spacing of 20-30 mm is found to be optimum distance between oven box and glass covers. A solar oven uses solar energy to heat ,cook , and pasteurized food material. Solar cooker are easily available in the market most of them are in expensive and other are expensive advanced are a stove. Studies have been done on the thermal performance and parameters that affect the performance of simple box type solar ovens which takes solar radiations from the top surface. In this work, a unique five sided double glazed solar oven with a black painted box as the cooking cavity is investigated. In the fig show the practical view of the oven with and without reflectors. The design of this solar cooker is unique it diffuses and ground reflected solar radiation from five side with the aid of upper and lower reflectors which augment the incident radiation intensity. The major advantage of this cooker that during cooking the person does not shade the cooker and also there is no possibility to come indirect contact with the concentrated intense radiation. Figure 2-3: Pictorial view of solar oven with and without reflectors Experiment were conducted on solar oven with and without reflector to record the maximum temperature during various time. Different food were also cooked e.g. boils potatoes, rice, eggs and noodles. The experimental test were carried out on march and April. During experiment the solar oven were placed in a position that the projection of sun rays on the ground and surface normal coincides. Oven was placed in the sun in several hours. Temperature in side the oven recorded though a temperature probe (UT33B, Uni-Trend) inserted inside the cavity. Solar radiation was also recorded using pyrometer. In clear sky day typical box temperature in the range of 1400 C and 100 0C with and without reflector. Also the required safe temperature most
19 of the food is (i.e, 60-90 0C). Parametric analysis of the solar oven was done to study the effect of various parameters on its thermal performance. Radiation increased for single glazed solar oven compare to double glazing. The thermal performance of a 5-sided solar oven is investigate experimental analysis show that temperature attend with and without in the box in the range of 50 -150 0C. Which is adequate for cooking purposes. Parametric study is then conducted to analyze the effect of various key parameters. Double glazing results in better thermal performance than single glazing. Using a selective coating (i.e. TiNox) on the outer surface of the oven box temperature Tb can be increased up to 50 0C, when compared to black paint. Below 20 mm of spacing between oven box and glazings results in significant drop of box temperature Tb. Plate spacing of 25 mm and above does not improve the oven thermal performance appreciably. [37] Mr. Jebaraj S. and Srinivasa Rao P.Today‘s presented that society pollution increasing problems. Since solar energy is clean free energy that can be harnessed, solar energy can be incorporated in our daily lives to produce energy to conserve other non-renewable energy .solar oven use to cook the food through solar energy. It is planned to design a high efficiency oven which is convenient and comfortable for all Kind of cooking, baking and heating without spoiling the food. This solar oven is capable of making a temperature change up to 150 ⁰C in 60 minutes. Once the prototype was completed several experiment were conducted to determine the efficiency between two designs which are without the parabolic dish and with parabolic dish. The efficiency with parabolic dish is greater than without parabolic dish. The efficiency attend with parabolic collector is 150minutes is 53.62% whereas, for the same duration the efficiency of solar oven without parabolic collector is 35.86%. This solar oven would be very useful to conserve electricity and healthy food cooking. The sun is a constant source of energy. Most of sun energy com in the form of visible light. Sun light is the most important source of energy for all living things. Sun light use for such everyday jobs , cooking, heating water or warming of homes. The challenge is to transform sunlight into usable heat. In order to make better use of sunlight, in attempt has been developed a high efficiency solar oven for tropical countries. One of them that it is eco-friendly doesn‘t depend on gas and electricity and it is economic.
20 Solar oven are of two types box type and parabolic type. Box oven is the most common type solar oven it is designed in base of the concept of traditional modern oven. The temperature of the oven can reach to 300° F (150° C) which is plenty hot to cook any food. Food containing
large amount of moisture can‘t much hotter then 100o C so it is not necessary to cook at higher temperature. The parabolic oven can reach high temperature more quickly. Some parabolic oven are limited in the quantity of food that is possible to be cooked at one time since they usually one pot that is suspended in the center of the path of highest solar energy concentration. In the present work it is attempt to combine of the box and parabolic oven and increase the efficiency. The sun light energy is collect through parabolic collector with series of mirror attached with it to reflect the sunlight. The sunlight entre to inside of solar oven and the black absorber convert it in to heat by the dark absorber plate. A layer of polystyrene is added inside the box to minimize the temperature loss. The melting temperature of polystyrene is 240o c. heat from the sun light to heat up the box through greenhouse effect. The inner surface of the box is black to absorbed sunlight and convert it into heat. The parabolic collector is important. The parabolic collector bounce the additional sunlight through the glass. The parabolic collector reflect more sunlight and concentrated more sunlight to the box. Nat system is perfect and have 100% efficiency. Their will be heat loss through convection, conduction and radiation. For generating heat inside the box use a square box and grade A glass on the top of it the sunlight entre the box and produce heat inside the box Styrofoam is use to reduce the heat loss it is used is an insulator for all side. The Styrofoam we warp using aluminum foil to reflect heat and absorbed by the food at the bottom MDF is use to reduce the heat loss at the bottom. The experiment were performing in two stages solar oven without parabolic collector and with parabolic collector. The reading were tabulated for 30 minutes. The heat inside the oven with parabolic collector is greater than heat without parabolic collector. In this research attempt has been made to design and construct solar oven with and without parabolic reflector. The experiment were performed for regular interval of 30 minutes the heat energy absorbed with parabolic collector is 2420.5 KJ/m2 and without parabolic collector is 1563.4 KJ/m2 respectively for the time duration of 150 minutes. It concluded in this research that the solar oven would be very much helpful to conserve the electricity and eco-friendly food production. [38]
21 M. Abu-Khader studied In this paper about two types of solar cooker. The one is painted black base and the other has internal reflecting mirrors. Both designs ware tested. Both designs ware tested on two conditions on tracking system. The efficiencies range of black base cooker was recorded from 17 % to 41 % at maximum sun light of the day 11 – 12 and its average efficiency is around to 27 %. While the efficiencies range of internal reflecting mirrors cooker was recorded from 25.3 % to 53.1 % and its average efficiency is around to 46.6 %. The advantage of sun tracking system is to maintain a higher range of thermal efficiencies. The increases prices of fuel and energy using the alternative of energy is necessary. The solar energy is good option. In solar energy the solar cooker is important applications in thermal solar energy conversion. Solar cooker is used widely for cooking in developed countries. The solar cooker highly quality and easily available easily is portable. Current deigns of cooker is like a box cooker, concentrators and flat plate are used. The solar cooker is used for cooking, purify water. And solar cooker the interior surface of box is heated because the black absorber absorbed the heat .This heat increase the temperature inside the box cooker to rise until the heat loss of the cooker is equal to the solar gain. And the temperature for cooking and purify water is easily gained. The tests on the solar cookers were carried out during the successive days from the 29th and 31st /10/2007 and 2nd /11/ 2007. Each experiment starts from 7:30 am in the morning to 4:00 pm. The first part of this research work concentrated on testing of two box type cookers: traditional black painted cooker and internal installed mirrors cooker. Both cookers are fixed at a position towards the south. The second part is testing the traditional black painted cooker with a tracking system to the sun movement. After testing the data obtained from the cookers. It is clear that both types of cooker at fixed position give similar thermal performance where the average water and pot temperature is 7 % errors. The efficiencies range is from 12 % to 41 % at maximum sun light of the day and the average efficiency is 27.6 % while in the interior reflector ranger is 25.3 % to 53.1 % while average efficiency is 40.6 %.[39] F. Yettou show In this type of solar cooker with mirror reflectors two types of tracking system is used. It receives solar radiations both directly by reflection of mirrors reflectors. The
22 addition of reflectors to improve the work of the cooker is interesting in particular in winter, where the elevation of the sun is relatively low. The combination of mirror reflectors are good for more energy, the cooker is enabling to cook during day time. It is good thinking to use sun light for cooking. Solar cooker is used for cooking in the presence of sun light. The use of solar cooker is save fuel, money and other energy. The solar cooking is developing the word. Different types of solar cookers are made and tested all the word. There has been improved the designed, developed and testing of different types of solar cooker. Solar cooker is much used in the word it‘s easily available and it is portable. Solar cooker with tracking mirrors reflectors and see performance of cooker. The north-south facing reflectors use to track the weather variation and the east –west reflectors use to track at day time. The distribution of concentrated solar energy is uniform on the plate absorber of the cooker in the case of north-south tracking which is suitable for cooking temperatures. The combination of reflectors is increase and improves the collection of energy and performances of cooker to gain and absorbed heat. This is very important for cooking in winter season when the solar elevation is low. [40] Ajay Chandak In this paper used two concentrator one is SK-14 and other is PRINCE- 15.the SK-14 is widely used in domestic level. If the bowel of solar concentrator is made then the concentrators becomes heavy and transportability is problem. if use only reflectors sheets the transportability is improved.PRINCE-15 is new geometry of solar concentrators with square and rectangular shape. This new design has an excellent transportability. The testing was done with these two solar concentrators in the presence of sun light with different geometrics. This test proved that PRINCE-15 is not only better transportability but have also high efficiency. Solar cooker is used in the presence of sunlight to cook food. The widely using of solar cooker saves money fuel and money and time. All these things are important in life. SK-14 concentrator developed by Dr. Ing. And many companies of germen made it and sell it. SK-14 concentrators is used widely and domestic level. The diameter of 1400 mm and his performance is 700 watts. In this solar concentrators is manufactured in a bowel used in it‘s the rings of bowel is made of steel wires .Such bowels are strong and not easily damaged. For this reason few companies have come up with bowel stitched with bolts and screws and all reflectors sheets are joined together
23 and form of bowel. This improved the transportability but the bowel weaker and high wind or stone damaged it easily. The study of these two solar concentrators SK-14 and PRINCE-15 testing was planned at the same time. At the same time the testing eliminated the possibility of errors because of difference winds speed, ambient temperature and variation in solar radiation. Mild steel plates were used for stagnation temperature test and thermocouples are connected to the mild steel plate. Similarly water is also used heat test and its temperature was recorded. Test duration was fixed at 25 minutes to keep the water peak temperature below 900 0C. This limit was decided during the trial itself. Solar radiation is measured using Apogee solar sensors for total and diffused radiation. Different results are obtained compering both concentrators with same sun lights areas same materials for reflectors but the geometric system is different. SK-14 is circular and PRINCE-15 is rectangular dish concentrators. Reading was taking continuously both on both and avoids any variation because of wind and solar radiation.so the PRINCE-15 is showing the it‘s better from SK-14 and every level. [41] Paras Soni said The continuous development of technology increases the demand of energy. There alternative devices are achieved which is based on renewable energy. Food is not only a basic human need, but also a culturally important part of daily life. Thus, we seek to implement solar cookers in a way that is not only environmentally sustainable but also culturally sensitive. To made this solar oven to increase the performance parameter. The major source of energy is derived from fossil fuels. Due to the limited availability or depletion of these sources with time, balance between the demand and supply of energy seems to be degrading in the coming years. Moreover the fossil fuels are polluting in nature. In order to maintain a balance between demand and supply of energy, there is a need to exploit renewable sources to the maximum limit possible. A solar cooker, or solar oven, is a device which uses the energy of direct sunlight to heat, cook or pasteurize food or drink. Over the past many decades, a number of designs of solar cooker have been developed. The majority of solar cookers presently in use are relatively cheap, low-tech devices. Although solar cookers have been available for many years, there is continuing interest in their performance optimization.
24 In this study it was observed that in any climate conditions performance of every element of solar cooker has great importance and direct effect. For quality cooking no one parameter has been eliminated among these. [42] Himanshu Agrawal studied in this paper the theoretical analysis of parabolic dish type solar collector by using thermodynamic equations, it was calculated by measuring heat input and output system, that there is loss in various systems. By the calculation of relative error and by comparing theoretical and experimental data, the efficiency of system was found to be 4 to 9 %. Solar energy has become the most promising energy substitute from the last few decades and many efforts has been made to utilize this energy in cooking in the form of solar cooker, replacing the fuel or wood alternatives, based on box type collector, solar collectors a, parabolic trough collector and dish collector, with phase change thermal storage unit, but none of them worked with sensible heat storage unit. Solar cooking system with heat storage or without it were experimented, revealing various interesting features like heat flow control in pots and modularity, indoor cooking and baking adjustments. The investigation of solar cooker with PCM based on parabolic dishes has been observed to have 1.63 to 4.44 times faster. The test section of solar cooker is based on parabolic dish type collector. This system consists of parabolic dish collector and solar cooker. The solar dish is a point focusing collector. At the focus of parabolic dish collector, a holding tray is provided upon which cooker is to be place. The tracking of parabolic dish collector is done manually after 30 minutes. [43] In this paper Dr. Tony Robinson studied the Characterization and design methods of solar cookers & ovens. He write the problem of cooking that Half the world‘s people must burn wood
or dried dung to cook their food. Nearly 1.2 billion people, a fifth of the world‘s population, do not have access to clean drinking water. Over 1 million children die yearly because of un-boiled drinking water. Wood cut for cooking purposes contributes to the 16 million hectares of forest
destroyed annually. Half the world‘s population is exposed to indoor air pollution, mainly the result of burning solid fuels for cooking and heating. Dr. Tony Robinson design a solar cooker through the bases of first law of thermo dynamics that Energy can be neither created nor destroyed, it can only change form Provides a basis for
25 studying the relationships among the various forms of energy and energy interactions. Also from the energy balance the net change (increase or decrease) in the total energy of an any system during any process is equal to the difference between the total energy entering and the total energy leaving the system during that process. [44] M.r Seguin R. BELLO and Simon Ogbeche ODEY study the Development of Hot Water Solar Oven for Low Temperature Thermal Processes. He say that The most useful form of the Hottel-Whiller-Bliss generalized performance equations for flat plate collector utilizing heat removal factor and loss coefficients is used to model a solar oven- water heating system for low thermal process application. The water heating system was designed, tested and evaluated with a daily collector efficiency of 51.82%, an average daily solar radiation of 689.23 (w/ºc) per day and a useful gain by collector of 563.85 (w/ºc). Loss in collector is 116.39 (w/ºc) and total average daily heat gain by water in collector is 292.26 (w/ºc). Average Daily storage heat capacity of 582.83 (KJ) and the daily converted heat delivered to test chamber is 147.07 (KJ). The overall System efficiency of 25.24% was obtained. Renewed interest of solar as an energy source in heating systems has gained relevance in various fields and in agricultural operations such as dairy farm hot water supply and food preservation. Microwave heating and food irradiation using solar systems have also been used on commercial scale. Many of these applications require heated air at relatively low temperatures. Traditional heat production is through wood, natural gas or LP gas. Fuel wood account for over 50% of the overall energy consumption in Nigeria, about 80% of these are consumed as firewood mainly in the rural households, [1]. The average daily consumption is 0.5-1kg of dry fuel wood per person, which is equivalent to 10-20 mega joules per day [2]. The current rate of consumption of fuel wood far exceeded the replenishing rate to such extent that acute ecological problems of deforestation soil erosion, and desertification are well recognized problems in the country today . Solar heaters have been used in other operations involving water heating, but interests in heat transfer in oven using water, as heat transfer medium have not been fully investigated. Research investigation has measured the amount of solar energy transmitted by collector and the feasibility of heating ventilating air by passing it though roofing and sidings whose exterior surfaces were painted black. Okonkwo et al indicated that built in thermal storage solar water space conditioning system could be used efficiently in chick brooding in Nigeria. Their work utilizes a
26 water storage tank constructed with 2mm thick galvanized metal sheet measuring 3m x 1m x 2m insulated with wooden materials, 5cm thick [3]. The behavior of solar dryers is influenced by loading capacity, orientation and angle of inclination [4]. The effect of beam or directional radiation on the collector surface can be maximized when tilted at right angles to the incident beam adding that an inclined surface may receive a significant proportion of its irradiant through reflection from the ground adjacent to it [4]. The works of Mac Craken, Eckhoff Ohos & Shorf and Hansen and Smith as reviewed by [5] reported the use of phase change materials such as salt, dry soil, pond, and a pile of rock for sensible heat storage in collector design. Water heating constitutes 15% to 25%, or more, of the energy use at home. The approximate annual cost to operate water heaters ranges from $200 for a minimum efficiency gas-fired unit to as much as $500 for a minimum efficiency electric unit. Heaters have been reported to reduce annual operating costs by 50% to 80% using free energy from the sun. As a result of this research activity on the development of thermal solar systems for application in residential housing for the purpose of space heating, a cost effective thermal solar collector with Direct Heat Storage (DHS) was developed. Selection of material of construction is dependent on the properties of the materials that give better performance. The design consisted of a flat plate collector mounted on a stand with variable angle of inclination, a test chamber and a water reservoir mounted on a stand. The units were set out and an insulated water hose used to connect the systems together. In experimental procedure he write the Basic workshop tools were used in the fabrication process and a PRO Level and Angle Finder used in tilt angle graduation on the collector . Five laboratory thermometers of range -10º to 110ºc were installed on to measure inside and outside temperatures-one at the cold water storage, two installed within the collector; each at the extreme ends of the absorber, in-between the cover and the absorber surface one measures the surface temperature while the other measures the air temperature within the collector-glass space. Another thermometer measures the hot water temperature entering the oven and two others measure the heating chamber temperature. Leakages in the flow line along the tubes in the system were corrected and several tests were run to collect temperature and flow data. The flow rate required to deliver water to the collector to achieve maximum heat harvest from the collector determined for experimental procedures is M = 0.25l/min and a tilt
27 angle of 50° to the horizontal. Temperature data were collected at hourly interval of 5 minutes for the hours of sunshine for the days under test. For purpose of analysis temperature profile data were collected per day on clear days. A solar water heating system has been designed and constructed. Performance evaluation carried out indicates an overall system efficiency of 25.98% and absorber temperature of 72ºc. Efficiency of collector varies with water flow rates. The collector is more efficient at low radiations; 52.85% at 630.08 w/m2 and 51.00% at 739.40w/m2. This is obvious at lower operating temperatures for collectors Solar radiation, heat gain and collector temperature are highest between 1300hr and 1400hrs because of the collector tilt angle (optimum tilt angle=50º) causing a larger percentage of incoming radiation to be incident on the collector. The system is efficient to be used for low temperature processes as pasteurization and also can be adapted for use in incubation. [45] Mr. O.A. Jaramillo study a solar oven for intertropical zones: Opto geometrical design in this paper, a novel design of a solar oven for the intertropical zones is presented. The oven box has seven faces instead of the six faces of most common designs reported in the literature; two of them are alternatively used as bases. This oven has four fixed mirrors to concentrate solar energy. The main advantage of this novel design is that the oven needs only four simple movements in order to obtain an adequate solar concentration throughout the year. This feature has been possible due to the opto geometrical design that is presented. A simple theoretical model of the oven concentration is developed. According to the model, the concentration achieved by the oven at noon is greater than 1.95 for all days of the year. In order to analyze the optical performance of the solar cooker, an experimental evaluation was conducted by using a scale model of the solar cooker and a heliodor. Solar cookers, as their name indicates, are devices that use solar energy to raise the temperature of food to cook it. These solar devices are based on the simple principles of reflection, concentration, glazing, absorption and the greenhouse effect to store energy in order to increase the temperature. Various types of solar cookers exist, harnessing one or more of these principles. Solar cookers have attracted the attention of many researchers; in addition, many designers and small scale producers have, in recent years, made notable progress in the technical advancement of solar cookers. Since there is different availability of solar energy and there are different styles and traditions in the cuisine around the world, one can find a great variety of solar cooker
28 designs. Solar cookers fit into many categories some are given solar box cooker, concentrator cooker and collector cooker. The objective of this research is to design a solar oven for the intertropical zones. The design is based on the idea of having two faces of the box that are alternatively used as the base of the solar oven and having four fixed reflectors. Thus, the solar oven is easy to use (with only a few movements throughout the year), and during the operation time, the solar oven obtains a good solar energy gain. A two dimensional ray tracing technique was employed to design the geometry. The oven has been designed on the basis of the two days with the maximum solar declination: the day with maximum declination angle to the South (December 23) and the one to the North (June 22) and the winter and summer solstices. The main design condition is that, for these two selected days, the rays of the sun must fall perpendicular to the transparent face (cover) at noon at the design place in Mexico (latitude 18500N). This condition implies that the oven cover presents different inclinations. This was resolved by designing a box with two different bases. As the cover has two possible inclinations, whose difference is 30, the days when the oven has to be moved are defined the condition that the angle formed by the cover and the sun rays at noon during all the year has to be less than or equal to 15o. The experiment was performed in March, July and December. The experimental tests were done by using a scale model of the solar oven (scale 1:6) and a heliodor. A heliodor is an efficient tool for studying the patterns of the shadows and how the beam radiation is reflected into the solar oven. The evaluation of the radiative energy collected by the solar oven was done using an array of calibrated photo resistances distributed equidistantly on the cover area of the oven scale model. The performance factor model, although simple, is a useful tool to evaluate the gain of solar energy due to the inclination of the cover and the presence of the reflectors throughout the year, and it can be used to evaluate the energy that the solar oven receives if the insolation data over the horizontal plane is available. The theoretical model results show that, at noon, the solar cooker achieves a concentration level greater than 1.95 throughout the year. It is expected that these concentration values are enough to increment the meal temperature for the cooking process. [46]
29 This paper considers the design, use, and social acceptance of solar cookers that are constructed by their users. Several generations of oven design are described and their field testing in Indonesia are reported, the first generation design having been described in a previous paper. The second generation design reached 1758C0 in oven temperature, and it used only local materials in its manufacture. Results of field testing of sixty four units in East Nusa Tenggara Provence, Timor Island, Sulamu village, and at Maumere City of the Sikka Regency in Flores Island, all in Indonesia, are reported. Social observations via questionnaires and direct conversation were conducted as part of the field study. Preliminary results showed promising tendencies of acceptance (up to 28%), and the solar ovens proved their ability to cook effectively. The most recent generation of design has reached 2028C in oven temperature, while costing 10% less than the previous one. The dissemination of thirty units of this design in two villages in West Nusa Tenggara Province is reported on. [47]
Solar cooking is often considered ‗‗a solution looking for a problem‘‘. Solar cookers have long been presented as an interesting solution to the world‘s problem of dwindling fuel wood sources and other environmental problems associated with wood fuel demand for cooking. However, recent GTZ field work in South Africa showed different benefits instead: the use of solar cookers resulted in appreciable fuel and time savings as well as increased energy security for households using commercial fuels. These observations are based on field tests in South Africa that started in 1996 to investigate the social acceptability of solar cookers and to facilitate local production and commercialisation of the technology. Impact studies and use rate studies have been carried out by a number of different organizations since the inception of the project and although commercialisation of the technology has not been achieved to its fullest potential, impact studies indicate that solar cookers have a positive development impact on households through fuel-, energy- and time savings. The article aims to summaries the findings of the various studies and presents an overview of use rates and impact data. A variety of factors influence solar cooker use rates, which in turn determine impacts. Some factors are related to the user, some to the environment in which the cooker is used and some to the cooker itself. Ultimately, the data shows that on average, only 17% of solar cooker owners do not use their stoves after purchase and that active solar cooker users utilize their stoves on average for 31% of their cooking incidences. Since the majority of solar stove buyers actually uses their stoves and
30 obtains real benefits, this suggests that those solar cookers are indeed not a solution looking for a problem but a solution worth promoting. Solar cookers have generally been promoted in areas where fuel wood shortages are experienced such as rural areas and refugee camps. However, results from the GTZ/ DME field test indicated highest user rates in an electrified area and subsequent sales were mostly to electricity users. Although fuel wood shortages may be an important push factor to promote the use of solar cookers, the cost and scarcity of commercial fuels can also convince users to take up the technology. External conditions which can promote the use of solar cooking are therefore, the general lack of adequate energy sources and a desire to achieve savings (time or monetary) by end-users. Important aspects concerned with the user of a solar cooker were identified: There must be adequate motivation to use the cookers. Potential savings were the most important motivation mentioned by users to purchase and use their solar cookers while an element of curiosity was also found to be conducive to encourage the purchase of a solar cooker. Male buyers reported curiosity as the most important motivational aspect while women reported potential savings (Palmer Development Consulting, 2002a, b). Successful solar cooking requires a basic a form of training and being exposed to a solar cooking demonstration was rated highly by users to ensure cooking success and therefore on-going use. A variety of instruments were used to inform users how to use their solar cookers successfully, for example, pamphlets, user instructions, brochures and recipe books were distributed with the cookers (GTZ and DME, 2002a) while approximately 500 wet demonstrations were carried out throughout the implementation period (GTZ and DME, 2002a).Using solar cookers requires adaptation mostly in terms of kitchen management. Planning ahead and preparing food becomes important—you cannot decide to solar cook a chicken stew 1h before mealtime. Once solar cookers are integrated in the process of kitchen management and cooking, users chose to use them regularly as indicated by an average use level of 31%. Despite the failure of the programmed to achieve large scale commercialisation and local production of solar cookers in South Africa, households using solar cookers reported quantifiable benefits. Strong evidence emerged from all the studies that the users of solar cookers experience savings. It should be noted that the average saving of R68 found may be under reported as it is often difficult for users to estimate savings achieved through the use of a solar cooker since
31 savings depend on a wide variety of issues such as fuel use, frequency of cooking and type of food cooked. Evidence from recorded fuel, monetary and time-savings as well as the noted development impacts, especially for women therefore, indicate that the use of solar cookers does have positive development impacts at the household level. [48] This paper uses a previously published report coupled with recently collected empirical information on the diffusion of solar cookers among the Basotho of Lesotho. Drawing upon diffusion practice and theory, the authors cite several present-day instances where diffusion is taking place. The conclusion, however, is unfortunate, in that the outlook for the use of solar cookers and their effective diffusion in Lesotho is rather bleak. Once upon a time, perched atop the Drakensberg Mountains above the Republic of South Africa, there lay a tiny country called Lesotho. Lesotho was, and still is, inhabited by Basotho (singular "Mosotho") who farmed the mountainous terrain. One day, trekking over the crags, a group of foreigners arrived in the village of Thaba Tseka in the center of Lesotho. They carried with them forty-five odd-looking boxes which they said could use the light of the sun to cook food. The boxes were a gift for the people of Thaba Tseka. A. A. Eberhard reports that the Basotho of Thaba Tseka indicated that, since they already used fires to heat their homes, they preferred to cook over their fires rather than use the solar cookers. Thus, the first of five key characteristics that help to explain the rate of adoption of any innovation, as perceived by potential users, was negative. This first characteristic is "relative advantage," which means "the degree to which an innovation is perceived as better than the idea it supersedes." The remaining four characteristics which "past research indicates are the most important characteristics of innovations in explaining the rate of adoption. This paper points to several projects that have already targeted people who were thought to need and want solar cookers the most, the rural women and the wanna-be's. A brief review of past and present projects and the application of diffusion theory have failed to show much hope for the diffusion of this innovation – solar cookers in present day Lesotho. Because the diffusion of innovation is a cooperative process, the people of Thaba Tseka will not adopt solar cookers until a suitable change aide, with a bridge tie into their clique, convinces them that sunlight can, indeed, cook their food. [49]
32 In this paper the John J. TODD1 and Sunny MILLER study the Performance Testing of Cardboard, Solar Box-Cookers. A simple solar box cooker was tested using a standard test method and a comparative test method. Various design changes were examined. Results show the advantages of double glazing and black absorption plates in the base of the cooker. The optimum combination of design changes resulted in an increase of 175% in cooking power compared to the basic design. Cooking temperatures of 70°C were reached in one hour and water boiled within two hours. These temperatures and heating rates allow practical cooking of many foods. Construction and testing of solar cookers is an excellent educational tool, illustrating many important features of solar design. Solar box-cookers represent a simple, low cost and effective application of solar energy. In many developing countries they can play vital roles in improving health by lowering exposure to wood-smoke and reducing pressure on firewood resources. They can be used to sterilize drinking water. They can also be locally manufactured. It is not surprising that many papers (e.g. Lenssen 1989; Sun World 1988) and books (e.g. Kerr 1991) have been written on the subject, extolling the virtues of solar cookers. The potential benefits of increased solar cooker use by rural poor are not in dispute. But does the solar cooker have a role to play in the developed countries. The principles of passive solar design can be demonstrated and understood. Children can build their own cookers. It is also very instructive for adults to see and operate such appliances. It is unlikely that solar cookers will substitute for conventional gas or electric cooking in developed countries, although they serve as an interesting diversion at barbeques (e.g. a cake can be cooked in less than two hours on a sunny day). In Australia, the cost of cooking a meal with gas or electricity is only a few tenths of a dollar, so financial savings attributable solar cooking is almost trivial. A solar cooked meal will reduce Greenhouse gas emissions by 0.5 to 1.5 kg of CO2. Small compared to average per capita emissions of 15 t CO2, but nonetheless a reduction. Thus, education, rather than economic or ecological gain, is likely to be the key justification for promoting solar cookers in Australia and New Zealand. The principles of solar box cookers are so simple and elegant. If they were more widely promoted people would gain a greater appreciation of solar energy. Also, some of the benefits of this technology might be carried with aid workers and tourists as they travel or work in regions of the world where solar cookers could play a crucial role in saving lives and improving the quality of the environment. With these principles in mind, this paper sets out to illustrate some basic design features of solar cookers.
33 We hope that this will stimulate interest by ANZSES members. The paper also illustrates the importance of a standard method for comparing the performance of solar cookers.The ovens were exposed to the sun about 20 minutes after recording began at which point the water in the pots in both ovens started to warm. After three hours the water in pot-B was near boiling, the water in pot-A was about 20°C cooler. Towards the end of the test, the windy conditions on this day caused the lid of oven-A to blow closed and the water started to cool. The final 40 minutes of the test were, therefore, not valid. The design and testing of these simple solar cookers proved interesting and instructive. It reinforced our views that these devices could play an important education role in Australia and New Zealand. If testing is done systematically, the cookers become more than just a novelty demonstration of solar energy. They teach some very important basic principles relevant to many other solar energy applications. There are numerous good research and implementation programs on solar cookers throughout the world. [50]
34
3.1 System Description: A solar oven is made of mild steel box, wooden box, mirror reflector, transparent glasses and glass whole is use is a special insulating material. The block diagram is shown in Figure 3-1. Figure 3-1: Block diagram of solar oven
3.1.1 Wooden box: Wood box is use because Wood is a good insulating material and it‘s easy and its thermal conductivity is very low .the manufacturing of wood is simple and easy because of that wood box is use show is Figure 3-2.
35 Figure 3-2: Wooden box
3.1.2 Black pint mild steel box: Although mild steel is soft steel that can be easily welded and cut with a torch. When mild steel is black painted then its thermal absorptivity increases and mild steel is easily available in the market because of that mild steel box is use show in Figure 3-3. Figure 3-3: Mild steel box
3.1.3 Mirror reflector: Concentrated solar mirror reflector is a device use to (also called concentrating solar to concentrate a large area of sunlight, or solar thermal energy, onto a small area show in Figure 3- 4.
36 Figure 3-4: Mirror reflector
3.1.4 Glass wool: Glass wool is use around all the sides of the oven between mild steel box and wooden box because glass wool is a good insulating material. Glass wool is an insulating material made from fibers of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties show in Figure 3-5. Figure 3-5: Glass wool
37
3.2 Calculation: The calculation is done on the bases of stiffen boltsman law of radiation. Stiffen boltsman equation is;
q = εa σ Ac (Th4 – Ts4) Where, q Is average is radiation, εa is absorptivity, Th is the desired temperature, Ts is the surrounding temperature, σ Stiffen Boltzman law constant =5.67X10-8 .,Ac is area of the oven=? The values is, Average radiation of texila=800 w/m2 Absorptivity of mild steel=0.60, Th is the temperature that we achieve=130 o c T
s the surrounding temperature=25 0c
σ Stiffen Boltzman law constant =5.67X10-8 A
c is area of the oven=? Putting the values in the formula
q = εa σ Ac (Th4 – Ts4) 800=A (5.67X10-8) (0.60) (4034-2984) 800=A (3.402X10-8) (1.8494X1010) 800=629.16 A A= 1.350 m2 A=1.350/2 L=0.762 W=0.60 Convert in to inch,
38 Length of the box=L=30 inch Width=W=18 inch.
39
3D Creo design Figure 3-6: 3D Creo design
2D Creo Design Figure 3-7: 2D Creo design
40
41
3.3 Fabrication of solar oven
3.3.1 Tool and Instrument Used:
The following tool use in fabrication of solar oven.
Hand saw.
Hammer
Nail and glow.
Vaenier caliper
Measuring tape
Bending machine
Welding machine
3.3.2 Material:
Wood thickness= 25.4mm‖
Mild steel thickness =2mm
Upper glass thickness=6mm,
Reflector
Insulation glass
Adjuster
Temperature gauge
Caster wheel.
3.3.3 Cutting (wood hand saw) process: Deyar wood easily available in market are in different sizes as compare with our required size so hand saw used for cutting sheet for required shapes. Usually, measured the point where the cutting action takes place and perpendicular to the direction of blade movement. Cut the five parts of wood according to our required dimensions of 0.606m, 0.762m and 0.2032m
42 Figure 3-8: Wood cutting Then joint the parts of wood to each other through nails and white glue show in Figure 3-9. Figure 3-9: Joining of wood.
43 Make a simple box and then joint a four caster wheel at the bottom of the box show in figure 3- 10. Figure 3-10: wooden box.
3.3.4 Mild steel box: Take a sheet of mild steel and cut it according to the required dimensions of Length=22.5 ―, Wedith=16.5‖ and Hight=4‖. Show in Figure 20.
44 Figure 3-11: Mild steel sheet Bind the four sides of the sheet through bending machine and the four sides corner are joint through gas welding show in figure 3-12. Figure 3-12: Mild steel box
3.4 Joint process: Then put the mild steel box inside the wood box and filled gape between the mild steel box and wood box with the whole of fiber glass then sealed the upper edges with wood and then sealed it with rubber to minimize the heat losses. And pint the mild steel box with black color.
45
3.4.1 Insulation: Filled gape between the mild steel box and wood box with the whole of fiber glass then sealed the upper edges with wood and then sealed it with rubber to minimize the heat losses. Figure 3-13: Sealed with rubber
3.4.2 Frame for reflector and transparent glass: Make a frame for reflector and transparent glass and put the reflector and glass in the frame show in figure 3-14.
46 Figure 3-14: Frame for reflector and transparent glass Then join the reflector and glass with box through hinges and nail show in figure 3-15. Figure 3-15: Joins the frame with box Join an adjuster with reflector and box for different angle changing of reflector. Join a handle on both sides for easily lifting show in figure 3-16.
47 Figure 3-16: Joins adjuster
48 Figure 3-17: Complete fabricated model
49
CHAPTER 4
Experimentation and Results
4.1 Experimental procedures: The experiment was conducted in two stages namely solar oven without reflector and solar oven with the reflector. The readings were tabulated for every 50 minutes in different times and in different days. The different readings of temperature of solar oven determined for both the cases with reflector and without reflector listed in table-4.1 and table-4.2.
4.2 Solar oven without reflector: In table-4.1 the experiment were conducted on Sunday March 13, 2017 in various times on solar oven without reflector. The below data is obtain Table 4-1: Solar oven without reflector Time Environment Temperature Oven Temperature 10:00-10:50 22.8 0 c 54 0 c 11:20-12:10 23 0 c 68 0 c 12:40-01:30 240 c 77 0 c 01:40-02:30 24.8 0 c 82 0 c From the table 4-1 it is clear that the temperature of solar oven increases as the time increases. Also it is observed that the maximum temperature achieve by solar oven without reflector is 820c day time at 01:40pm to 02:30pm. Figure 4-1: Time vs temperature without reflector
50
4.3 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Monday, March 14, 2017 at various times. The data obtain from solar oven with reflector is given below in table 4-2. Table 4-2: Solar oven with reflector Time Environment Temperature Oven Temperature 11:00-11:50 23 0 c 70 0 c 12:0-12:50 23.5 0 c 78 0 c 01:00-01:50 24 0 c 91 0 c 01:50-02:40 25 0 c 104 0 c In table 4-2 the maximum value of temperature of solar oven with reflector is 104 0 c at 01:50pm to 02:40pm. Figure 4-2: Time vs temperature with reflector From figure 4-1 and 4-2 it is observed that the temperature of solar oven with reflector is higher when compared with the temperature of solar oven without reflector. The maximum achievable
51 temperature without reflector is 82oc and the maximum temperature that achieve with reflector is 104oc. show in figure 4.2. Figure 4-3: Time vs temperature with and without reflector in March 2017
52
4.4 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Monday, April 05, 2017 at various times. The data obtain from solar oven with reflector is given below in table4-3. Table 2-3: Solar oven with reflector Time Environment Temperature Oven Temperature 11:00-11:50 27 0 c 80 0 c 12:0-12:50 31.5 0 c 93 0 c 01:00-01:50 32 0 c 102 0 c 01:50-02:40 33 0 c 109 0 c From the table 4-3 it is clear that the temperature of solar oven increases as the time increases. Also it is observed that the maximum temperature achieve by solar oven with reflector is 1090c day time at 01:40pm to 02:30pm. Figure 4-4: Time vs temperature with reflector
53
4.5 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Tuesday, April 06, 2017 at various times. The data obtain from solar oven with reflector is given below in table 4-4. Table 4-4: Solar oven with reflector Time Environment Temperature Oven Temperature 10:00-10:50 23.3 0 c 70 0 c 11:20-12:10 26 0 c 91 0 c 12:40-01:30 310 c 1070 c 01:40-02:30 31.5 0 c 113 0 c In table 4-4 the maximum value of temperature of solar oven with reflector is 113 0 c at 01:50pm to 02:40pm. Figure 4-5: Time vs temperature with reflector
54
4.6 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Monday, April 07, 2017 at various times. The data obtain from solar oven with reflector is given below in table 4-5. Table 4-5: Solar oven with reflector Time Environment Temperature Oven Temperature 11:00-11:50 27 0 c 95 0 c 12:0-12:50 31.5 0 c 104 0 c 01:00-01:50 32 0 c 108 0 c 01:50-02:40 33 0 c 1170 c From the table 4-5 it is clear that the temperature of solar oven increases as the surrounding temperature increases. Also it is observed that the maximum temperature achieve by solar oven with reflector is 1170c day time at 01:50pm to 02:40pm. Figure 4-6: Time vs temperature with reflector
55 All the temperatures of solar oven is shown in figure 4-7. The experiments were conducted in various days of March and April the maximum temperature achieved in April is 1170c. The maximum temperature difference between oven and environment temperature is 810c with reflector in March and 940c in April. Figure 4-7: Time vs temperature with and without reflector.
56
Conclusion
The maximum temperature achieved without reflector in March 13, 2017 was 820c from 01:40 to 02:30PM when the surrounding temperature was 25 0c.
The maximum temperature achieve with reflector in March 14, 2017 was 1040c from 01:50 to 02:40PM when the surrounding temperature was 25oc.
Three experiments were conducted with reflector in April 2017. The maximum temperature achieve was 117oc from 01:50 to 02:40PM when the surrounding temperature was 33oc in April 07, 2017.
Time duration to achieve maximum temperature value is 50 minutes and the best day time for achieving the maximum temperature value is 12:00 PM to 2:00 PM.
The average temperature achieve in April was higher then the average temperature achieve in March.
This oven is able to bake cakes or grill meat without any traditional source of energy in remote areas. .
57
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DESIGN AND FABRICATION OF SOLAR OVEN
Bachelor of Science
In
Mechanical Engineekamranmujahid760@gmail.comring _______________________ ____________________ Project
Declaration I declare that the work contained in this thesis is my own, except where explicitly stated otherwise. In addition this work has not been submitted to obtain another degree or professional qualification.
Gawhar Ali ___________________
Malak Yaseen Khan ___________________
Dawood Ahmad Khan
iii
Abstract
In this design project the idea of solar cooking is used for making of solar oven. The aim of this project is to design and fabricate a small-scale solar oven which could be used when the sun is shining to bake foods up to two pounds at temperature of 1300c. The advantage of this oven over conventional oven is that it can be used without any conventional energy source and it is portable as well. The design was finalized to obtain maximum advantage from solar radiation. Dimension and material was finalized and then fabrication was done as per finalized design. Experiment were performed in different days of March and April. 12:00 PM to 2:00 PM it is the best day time for achieving the maximum temperature. The maximum temperature achieved is 1170c between 01:50 PM to 02:40PM on 7 April 2017.
iv
Dedication
Every challenging work needs self-efforts as well as guidance of elders especially those who were very close to our heart. Our humble effort we dedicate to our sweet and loving parents whose affection, love, encouragement and prays of day and night make us able to complete our project successfully in time. Along with all the hard working and respected teachers.
v
Acknowledgment
First of all we would like to express our sincere and greatest thank to our supervisor Engr Sajid Raza who encouraged and guided us to carry out our final year project. Special thanks to Saeed Nazir for their advices, and help in fabrication of solar oven. Last but not least, we thank our beloved family especially our parents who encouraged us and provided financial support for this project.
vi
Table of Contents Declaration...................................................................................................................................... ii Abstract.......................................................................................................................................... iii Dedication...................................................................................................................................... iv Acknowledgment ........................................................................................................................... vi List of figures................................................................................................................................. ix List of tabels................................................................................................................................... xi Abbreviations................................................................................................................................ xii Chapter 1 Introduction:................................................................................................................... 1 1.1Background: ........................................................................................................................... 1 1.2Advantages of solar cooking:................................................................................................. 3 1.3Rural and urban wood energy consumption in Pakistan:....................................................... 4 1.4Existing cooking sources:....................................................................................................... 4 1.4.1Firewood:......................................................................................................................... 5 1.4.2Liquefied Petroleum Gas (LPG):..................................................................................... 5 1.4.3Crop residues:.................................................................................................................. 5 1.4.4Cow dung:........................................................................................................................ 5 1.4.5Kerosene:......................................................................................................................... 6 1.4.6Biogas:............................................................................................................................. 6 1.4.7Electricity: ....................................................................................................................... 6 1.4.8Solar cooking:.................................................................................................................. 7 1.5Existing solar cooking methods and their disadvantages:...................................................... 7 1.5.1Box type solar cooker:..................................................................................................... 7 1.5.2Panel cooker: ................................................................................................................... 8
vii 1.5.3Parabolic cooker: ............................................................................................................. 9 1.5.4Funnel cooker: ............................................................................................................... 10 1.5.5Scheffler cooker:............................................................................................................ 11 1.5.6 Other Types: ................................................................................................................. 12 Chapter 2 Literature review: ......................................................................................................... 14 Chapter 3 Design and Fabrication: ............................................................................................... 34 3.1System Description: ............................................................................................................. 34 3.1.1Wooden box:.................................................................................................................. 35 3.1.2Black pint mild steel box:.............................................................................................. 35 3.1.3Mirror reflector:............................................................................................................. 36 3.1.4Glass wool ..................................................................................................................... 36 3.2 Calculation: ......................................................................................................................... 37 3.3 Fabrication of solar oven..................................................................................................... 40 3.3.1 Tool and Instrument Used: ........................................................................................... 40 3.3.2 Material:........................................................................................................................ 40 3.3.3 Cutting (wood hand saw) process:................................................................................ 40 3.3.4 Mild steel box:.............................................................................................................. 42 3.4 Joint process:....................................................................................................................... 43 3.4.1 Insulation: ..................................................................................................................... 43 Chapter 4 Experimentation and Results:....................................................................................... 47 4.1 Experimental procedures:.................................................................................................... 47 4.2 Solar oven without reflector:............................................................................................... 47 4.3 Solar oven with reflector:.................................................................................................... 49 4.4 Solar oven with reflector:.................................................................................................... 51 4.5 Solar oven with reflector:.................................................................................................... 52
viii 4.6 Solar oven with reflector:.................................................................................................... 53 Conclusion: ................................................................................................................................... 55 References:.................................................................................................................................... 56
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List of Figures Figure 1-1: The three categories of solar coking: (a) Box Ovens, (b) Parabolic Cooker and (c) Panel Cookers. ................................................................................................................................ 2 Figure 1-2: Basic box type solar cooker ......................................................................................... 8 Figure 1-3: Basic penal type solar cooker....................................................................................... 9 Figure 1-4: A typically parabolic solar cooker ............................................................................. 10 Figure 1-5: Solar funnel cooker .................................................................................................... 11 Figure 1-6: Scheffler cooker ......................................................................................................... 12 Figure 2-1: Schematic drawing of the solar oven, its components and dimensions ..................... 15 Figure 2-2: Temperature on the external surface of the oven....................................................... 17 Figure 2-3: Pictorial view of solar oven with and without reflectors ........................................... 18 Figure 3-1: Block diagram of solar oven ...................................................................................... 34 Figure 3-2: Wooden box ............................................................................................................... 35 Figure 3-3: Mild steel box............................................................................................................. 35 Figure 3-4: Mirror reflector .......................................................................................................... 36 Figure 3-5: Glass wool.................................................................................................................. 36 Figure 3-6: 3D Creo design........................................................................................................... 39 Figure 3-7: 2D Creo design........................................................................................................... 39 Figure 3-8: Wood cutting.............................................................................................................. 42 Figure 3-9: Joining of wood......................................................................................................... 42 Figure 3-10: wooden box.............................................................................................................. 43 Figure 3-11: Mild steel sheet ........................................................................................................ 44 Figure 3-12: Mild steel box........................................................................................................... 44 Figure 3-13: Sealed with rubber ................................................................................................... 45 Figure 3-14: Frame for reflector and transparent glass................................................................. 46 Figure 3-15: Joins the frame with box ......................................................................................... 46 Figure 3-16: Joins adjuster............................................................................................................ 47 Figure 3-17: Complete fabricated model ...................................................................................... 48 Figure 4-1: Time vs temperature without reflector....................................................................... 49 Figure 4-2: Time vs temperature with reflector............................................................................ 50
x Figure 4-3: Time vs temperature with and without reflector in March 2017 ............................... 51 Figure 4-4: Time vs temperature with reflector............................................................................ 52 Figure 4-5: Time vs temperature with reflector............................................................................ 53 Figure 4-6: Time vs temperature with reflector............................................................................ 54 Figure 4-7: Time vs temperature with and without reflector........................................................ 55
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List of Tables Table 1-1: Sources of firewood for urban and rural households by income class, Pakistan .......... 4 Table 4-1: Solar oven without reflector ........................................................................................ 49 Table 4-2: Solar oven with reflector ............................................................................................. 50 Table 4-3: Solar oven with reflector ............................................................................................. 52 Table 4-4: Solar oven with reflector ............................................................................................. 53 Table 4-5: Solar oven with reflector ............................................................................................. 54
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Abbreviations
(WHO) World Health Organization (LPG) liquefied petroleum gas
(EPS) Expanded polystyrene (IPCC) Intergovernmental Panel on Climate Change (UNFCCC) Convention Nations Framework Convention on Climate Change (Tb) box temperature (DHS) Direct Heat Storage (PCM) Phase change materials
1
CHAPTER 1
Introduction
A 'Solar Oven' is a device which uses the energy of direct sunlight to heat, cook or pasteurize food. Many solar oven currently in use are relatively inexpensive, low-tech devices, although some are as powerful or as expensive as traditional stoves, and advanced, large-scale solar oven can cook for hundreds of people Because they use no fuel and cost nothing to operate, many nonprofit organizations are promoting their use worldwide in order to reduce fuel costs (especially where monetary reciprocity is low) and air pollution, and to slow down the deforestation and desertification caused by gathering firewood for cooking. Solar cooking is a form of outdoor cooking and is often used in situations where minimal fuel consumption is important, or the danger of accidental fires is high, and the health and environmental consequences of alternatives are severe.
1.1 Background: The major problems of world community are the degradation to the ozone layer and the Global warming. Since in 1980‘s the international Toronto conference began with the changing atmosphere in Canada. The IPCC's First Assessment Report in Sundsvall, Sweden (August 1990) was created. The IPCC (Intergovernmental Panel on Climate Change) is an indicator of climate change as a statistically significant variation in a parameter mean climatic and variability. In June 1992 happened at Rio de Janeiro, Brazil, the Convention Nations Framework Convention on Climate Change (UNFCCC) on ECO-1992. In 1997, the United Nations created The Kyoto protocol, an international treaty with more stringent commitments to reduce gases emissions that exacerbate global warming. The world efforts are to appropriate utilization of source energy, reduce deforestation process and CO2 emission, and many actions. One of these is the developing of equipment‘s with low ambient impacts like the solar cooking. According to Wetter (2006) the solar cookers are an important contribution towards halting the deforestation process and thereby preserve the environment. At the same time they help in fighting poverty. 500 solar cookers save 5,500 tons of wood a year, which translates into 1,000 hectares of woodland in the south of Madagascar. There is no CO2 emission, which is the main agent responsible for climate change. The population will become less dependent on wood and charcoal. Besides
2 environmental reasons there are also economical and practical reasons to favor the solar cooker. Families spend a lot less money on wood and charcoal. There is a pay back on the investment after only six months of using the solar cooker. The solar cooking was invented in Switzerland in 1767 by naturalist Horace de Saussure. The cooking took spend centuries to be broadcast throughout the world. Fornosolar (2009). Solar cooking has three main categories Box Ovens, Parabolic Cooker and Panel Cookers. Box Ovens Are the most common type of solar oven, and their use is widespread, particularly in developing countries. Hundreds of thousands of box ovens are used in India alone. Box ovens or cookers typically are square or rectangular and have a clear glass lid. Panel reflectors inside conduct heat throughout whatever is being cooked. Box ovens tend to cook at moderate to high temperatures, and they are primarily used for slow cooking. Parabolic or curved concentrator solar cookers use concentrated sunlight. They typically have a large, dish-shaped design and a reflective surface. The parabolic cookers are useful for cooking foods quickly at high temperatures. They can be used to prepare individual meals or for large-scale institutional cooking. One of the primary disadvantages of a parabolic cooker is that must be monitored and adjusted frequently to ensure that the correct amount of sunlight is being directed toward the surface. Parabolic cookers also present a higher risk for fires or burns. Panel Cookers combine elements of two categories. They are the easiest of the three to construct and use the typically feature a pot that rests inside a plastic or glass enclosure and is surrounded by three to five reflective panels. Panel cookers generally cook food at much lower temperatures, making it much more difficult to overcook or burn food. Their lower cooking temperature does limit the types of foods you can prepare and they typically work best with foods they have high moisture content. Unlike parabolic, panel cookers do not require constant monitoring or adjustment. After the January 2010 Haiti earthquake was donated hundreds of solar painel cooker kits to Haiti. Figure 1-1: The three categories of solar coking: (a) Box Ovens, (b) Parabolic Cooker and (c) Panel Cookers.
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1.2 Advantages of solar cooking:
1.4 Existing cooking sources: Source of energy used for cooking vary from place to place depending on its availability [1]. In rural areas, sources like firewood, biomass and crop residues are easily available [2]. LPG, kerosene are used in oil rich countries or countries which can afford fossil fuels [3, 4]. There are different energy sources used worldwide for cooking which are briefly discussed below.Equipment inexpensive and easy to make and use Reduces the use of fuels such as butane or kerosene, firewood and charcoal Reduce air pollution and deforestation, erosion and soil depletion, the reduction of rain and oxygen from the air and the advance of desertification Solar oven can be built small and lightweight, easy to transport Does not cause fires or burns. It is safer Promotes better health because the food cooks slowly and at lower temperatures, preserving the nutrients Enables pasteurize water and milk, canning and dehydrating fruits and seeds, breads, cakes and biscuits baked in the sun, increasing the sources of family income Some disadvantages are they do not work in the morning or at night, on rainy days. Have low efficiency on cloudy days. For a high efficiency, a solar cooking should be used in areas that have high incidence of sunlight. The regions near the equator are usually the best for your use. The international solar ovens have released a list of the twenty countries with the greatest potential for using these. And the criteria were taken in the ranking: the highest average incidence of solar, fuel shortages and population size. 1. India; 2. China; 3. Pakistan;4. Ethiopia;5. Nigeria;6. Uganda;7. Sudan;8. Afghanistan;9. Tanzania;10. South Africa.1.3 Rural and urban wood energy consumption in Pakistan: The rural areas account for the bigger portion of total fuelwood consumption. In Pakistan, for example, the rural fuelwood consumption exceeded urban fuelwood consumption by a factor of more than five, equivalent to 84% of total fuelwood consumption. The Philippines has a slightly lower figure at 82%. Corollarily, more households in rural areas are using fuelwood. In the Philippines, 86% of rural households was using fuelwood in combination with other fuels, particularly kerosene, while only 37% of urban households used fuelwood. In Cambodia, 95% of rural households rely on fuelwood, while 89% of households in urban areas outside Phnom Penh use fuelwood. In Phnom Penh, only 54% use fuelwood because many households use charcoal.4In Pakistan and Maldives, the proportion of rural households using fuelwood is also more than90%.Table 1-1: Sources of firewood for urban and rural households by income class, Pakistan
1.4.1 Firewood: This is a very commonly used cooking fuel in rural areas. Frequently used hardwood has energy content of 14.89MJ/kg. Out of this about 10.423MJ/kg is recoverable. Smoke from burning of firewood contains water vapor, carbon dioxide and other chemical and aerosol particulates. Wood and wood waste emit 195lbs/106Btu of carbon dioxide. Depending on population density, topography, climatic conditions and combustion equipment used, wood heating may substantially contribute to air pollution, particularly particulates. Wood combustion products can include toxic and carcinogenic substances. Particulate air pollution can contribute to human health problems like asthma and heart diseases [5].
1.4.2 Liquefied Petroleum Gas (LPG): LPG is a mixture of hydrocarbon gases used as a fuel in heating appliances like cooking, water heating and in vehicles. It is also being used as aerosol propellant and a refrigerant to reduce damage to the ozone layer [6]. LPG is synthesized by refining petroleum or wet natural gas, and is usually derived from fossil fuel sources, being manufactured during the refining of crude oil, or extracted from oil or gas streams as they emerge from the ground. Most commonly available
5 LPG is a mixture of propane (60%) and butane (40%) having calorific value of 46.1MJ/kg [6]. LPG is a low carbon emitting (139lbs/106Btu of CO2) hydrocarbon fuel available in rural areas, emitting 19% less CO2 per kWh than oil, 30% less than coal and greater than 50% less than coal-generated electricity distributed via the grid [5].
1.4.3 Crop residues: There are two types of agricultural crop residues, field residues and process residues. Field residues are materials left in agricultural field or orchard after the crop has been harvested, like stalks, stubble (stems), leaves etc. Process residues are those materials left after processing of the crop into usable resource. Materials like husks, seeds, bagasse (fibrous residue obtained from sugarcane) and roots are used as cooking fuel in most part of the rural places.
1.4.4 Cow dung: Cow dung is used as fuel as well as fertilizer in most of the developing countries like India. Caked and dried cow dung is most common cooking fuel in rural India. Dried cow dung is used as fuel in traditional cook stoves which are not properly ventilated. This has led to many respiratory health issues. Additionally it is found to be causing arsenic poisoning in unsuspecting villagers. People are simply exposed to 1859.2 ng arsenic per day through direct inhalation, of which 464.8 ng could be absorbed in respiratory tract. Inhalation of arsenic leads to respiratory problems such as persistent coughs and reduced lung capacity [7].
1.4.5 Kerosene: Kerosene is a combustible hydrocarbon liquid which is also known as paraffin. The heat of combustion is similar to that of diesel, having heating value around 43MJ/kg. Its use as a cooking fuel is limited to some portable stoves for backpackers and to less developed countries, where it is usually less refined and contains impurities. Usage of kerosene is not recommended for closed indoor areas without a chimney due to the danger of building up of carbon monoxide gas. Carbon dioxide emitted from kerosene is around 159 lbs. /106Btu.
1.4.6 Biogas: Biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as manure or sewage, biomass, municipal waste, green waste and crop residues. This is produced by the biological breakdown of organic matter in the absence of oxygen. Biogas
6 primarily comprises of methane (50%-75%) and carbon dioxide (25%-50%). Small amount of nitrogen, hydrogen, hydrogen sulfide and oxygen is also present in biogas. The other major type of biogas is wood gas which is created by gasification of wood or other biomass. This type of biogas comprises primarily of nitrogen, hydrogen, and carbon monoxide, with trace amounts of methane [8]. Biogas is used as low cost heating application like cooking and also can be used as modern waste management facility where it is used to generate either mechanical or electrical power.
1.4.7 Electricity: The first technology for cooking using electricity used resistive heating coils which heated iron hotplates or coil, on top of which the vessels were placed. Later in 1970s, glass ceramic cooktops started to appear. This has very low thermal conductivity, but let‘s infrared radiation pass very well, heating up the materials to be cooked. Halogen lamps are also used in some places as a heating element, which gives better efficiency of 60% compared to electric coil which has an efficiency of 55%. A Recent technology which is developed first for professional cooking and has entered domestic market is the induction cooking, which gives around 90% efficiency. These heat the cookware directly through electromagnetic induction. For using this type of cooking, pots and vessels with ferromagnetic bottoms are required. This form of flameless cooking has some advantages over conventional gas flame and electric cookers as it provides rapid heating, improved thermal efficiency, greater heat consistency, plus the same or greater degree of controllability as LPG [9].
1.4.8 Solar cooking: Due to exponential raise in the world‘s population and resulting growth of industrial activities, the energy requirements are such that fossil fuel cannot be the only source on a sustainable basis. This implies that one has to look for alternate sources of energy which are more environmental friendly, cleaner and renewable. As cooking is an integral part of every human being, it consumes a major fraction of the household energy requirement. Existing cooking fuels are either derived from fossil fuels like LPG, kerosene etc. or air polluting like firewood, crop residue, cow dung etc. In this respect, solar cooking is a very simple, clean and environment friendly alternative.
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1.5 Existing solar cooking methods and their disadvantages: Many scientists of 17th century knew about the principle of greenhouse effect where glass is used to trap heat from the sun. But Horace de Saussure, a French-Swiss scientist extended this principle to heat up food materials. As early as 250 years ago European scientists started exploring on solar energy, which is considered to be the father of today‘s solar cooking movement. Lots of modifications and exploration has been done on solar cooking in order to improve the efficiency and ease of cooking [10–11]. The existing solar cooking methods are discussed in the following paragraphs.
1.5.1 Box type solar cooker: Box type cooker is one of the basic solar cooking models. It is a simple rectangular box covered with either glass or plastic [12–13]. Sun beam entering the cooker through this cover turns to heat energy when it is absorbed by the black colored absorber plate and cooking vessel. This heat input raises the temperature inside the box cooker until the heat loss from the box equals to the solar heat input. The box is thermally insulated to reduce the heat loss to ambient, so as to attain higher temperature and better efficiency [14, 15]. Heat is trapped inside the box due to greenhouse effect. Radiation from sun easily passes through the glass cover and is absorbed by dark materials like absorber plate and vessel. These hot objects emit longer wavelength heat energy which is blocked by the glass cover. Hence this trapped energy raises the temperature of the space inside the box. In order to improve the box temperature, reflectors are used. Single or multiple reflectors are used, which are oriented such that the incident sunlight falling on the reflector, get directed to the box [16–17].
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Figure 1-2: Basic box type solar cooker Disadvantages of box type cooker
• Cooking has to be done outdoor and the cook has to stand in sunlight for a long time.
• Very slow cooking compared to conventional cooking. This takes 2-3 hours to cook and even more time during cloudy days with respect to less than half an hour taken by conventional methods.
• It is not possible to cook during rainy days.
• There is no control over the rate of cooking.
• This is not an interactive cooking.
1.5.2 Panel cooker: Panel cookers are very inexpensive and can be easily built using reflecting material like aluminum foil and cardboard. This uses shiny material to reflect sunlight to a cooking vessel which is enclosed in a clear plastic bag. Solar Cookers International developed a
panel cooker model in 1994, commonly known as ‘Cook it‘. This can be manufactured locally by pasting reflecting material onto a folded cardboard. Food to be cooked is kept in a dark container covered with a tightly fitted lid. This is placed at the center of the panel. Variety of designs are available in this type of cooker like simple panel, high back, panel for tropics, bubble panel, Dars Diamond cooker etc. Disadvantages of panel cooker are
9
• Cooking has to be done outdoor and not possible to cook during rainy season.
• Very slow cooking compared to conventional cooking. At least one hour is required to cook during clear sunny day.
• Control over the rate of cooking is not there. Figure 1-3: Basic penal type solar cooker
1.5.3 Parabolic cooker: Parabolic cooker is used for cooking at better cooking rates. It is comparable to conventional cooking and also for community level cooking of food [18–19]. Using a reflector of parabolic shape, sun beam is reflected onto a pot or vessel kept at the focus of the parabola. The axis of the parabola should be parallel to the sun beam so that maximum heat energy is obtained at the pot. Since highly focused light is obtained, temperature can go well above 150oC. Linear parabolic collector is also used for concentrating the sun light on to a pot kept at the focal line [20, 21]. Design and analysis of parabolic square dish solar cooker has been presented by others [22]. Disadvantages of parabolic cooker
1.5.4 Funnel cooker: In funnel cooker, sun light is concentrated into a cooking vessel or pot using a funnel shaped cooker. This makes use best of both parabolic and box type cooker. Sun beam is concentrated using a reflector like aluminums foil pasted on a folded cardboard. Black colored pot is kept inside a plastic cover which traps the heat by greenhouse effect. A simple system allows pressure-cooking to increase the cooking rate while releasing steam. This cooker can be used for cooking and pasteurizing water. Disadvantages of funnel cooker
• Cooking has to be done outdoor
• There is no control over the cooking rate and very slow cooking compared to conventional cooking.
11 Figure 1-5: Solar funnel cooker
1.5.5 Scheffler cooker: Scheffler cooker is also known as parabolic dish with fixed focus on ground. Cooking can be carried out in the kitchen without moving out using this type of cooker. The concentrating reflectors track the movement of the sun, reflecting the light of the sun and concentrating it at a fixed position. The reflected and concentrated sunlight enters a nearby kitchen directly to strike a cooking vessel or frying surface. High temperatures can be attained as it focuses the sunlight. Hence the time taken for cooking is comparable to conventional cooking. In some configurations, the concentrated sunlight is used first to create steam which is transported by pipes to a nearby kitchen. Concentrating reflectors are placed on both the equatorial and polar sides of the receiver. These receivers are attached to the steam pipes that transport the steam to kitchen. Since this steam is generated directly for cooking, the whole system has to be maintained clean. This type of cooking is suitable for preparing food for large mass. The cooking temperature is limited to around 100 o C. Disadvantages of Scheffler cooker
• The seasonal variation in the height of the sun requires changing not only the angle between the concentrating reflector and its axis of rotation, but also the shape of the reflector.
•Since focus point is fixed, continuous tracking is necessary.
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• Focused sunlight falls only on outer part of the cooking vessel resulting in uneven cooking.
• Highly focused light is very hazardous as cooking is done at the focal point.
• There is no option for either decreasing or increasing the rate of cooking. Figure 1-6: Scheffler cooker
1.5.6 Other Types: In order to cook during cloudy days or night, either auxiliary source of energy is used or some kind of energy storage facility is provided. Box-type cooker with auxiliary heater inside the box is used to cook during cloudy days [23]. Solar cooker is also used as food processor where it is also utilized for solar water heating, solar still and solar drier [24] and electric energy is used as auxiliary source in [25]. For collecting energy from sun, different methods like evacuated (vacuum) tube collectors are used which prevents the convection loss from the receiver improving the collector efficiency. Hot plate cooking system powered by solar thermal energy using concentrating evacuated tubular collector has been proposed in [26]. A solar cooking system using vacuum-tube collectors with heat pipes containing a refrigerant as working fluid has been proposed and analyzed [27]. A split-system solar cooker is described which has its flat plate collector outdoors and the cooking chamber inside the kitchen, with heat pipes transferring the energy between the two [28]. Similarly vacuum-tube collector with integrated long heat pipes directly leading to the oven plate has been tried [29]. A solar cooking system with or without temporary heat storage
13 has been developed and installed in different countries of the world [30, 31]. To reduce the complete dependency on solar insolation, energy storage system is being used. Phase change materials (PCM) are used for many solar thermal applications [32–33]. Solar cooker based on an evacuated tube collector with PCM storage unit has been investigated. Solar energy is stored in the PCM storage unit during sunshine hours and is utilized for cooking in late evening/night time [34–35].
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CHAPTER 2
Literature review The entire human uses the sun light in the start of life. Sun light is one of the important sources of energy for all living thing without sun light life is not possible. The following paper shows the history of this line of research. Mr. Rodrigo de Freitas Gurgel presents a solar oven for baking food, manufactured from a thermal box of EPS(Expanded polystyrene). The solar oven is a prototype of solar concentration for baking food. The main innovation of the work is the use of EPS cooler, widely available, low cost and with a structure already define and manufactured, avoiding the production of mold to get the box. It should be noted that the EPS thermal box is already a very efficient thermal insulator. This thermal property of the materials of the EPS box is important due to not require the use of insulating materials on the sides and bottom of the solar oven, to minimize heat losses. The inside of the box EPS enclosure baking oven, was coated on the bottom and side sheets by mirrors forming the profile which gives the greater concentration of solar radiation. Above the floor of the oven is system with plane mirror reflector, directing the solar rays into the oven where the food displaced into the baking. Some aspects describe of construction of solar oven. And compare the time of baking which obtain from other solar ovens presented by solar literature and also compared to gas conventional ovens. Preliminary tests have shown the feasibility of using such solar oven, temperature levels achieved for the purpose of baking of various types of foods. The tests show that the solar oven reached the maximum temperature of 123.8°C and baking various foods such as pizza, lasagna, cake, bun, and other in an average time 50 minutes. The firewood is probably the oldest energy used by man and still has great Importance in the Brazilian energy matrix, participating with about 10% of primary energy production About 40% of wood produced in Brazil is transformed into charcoal. The residential sector is the most expensive wood (29%). Usually it is for cooking food in rural areas. A family of eight requires Approximately 2.0 m³ of wood per month to prepare their meals. The Industrial sector comes next with about 23% of consumption. The main industries that consume fuel in the country are food and beverages, ceramics and pulp and paper (National Energy Balance 2009 - www.mme.gov.br).These data show the that massive use of wood, putting at risk the health of
15 the planet, point to need the mass use of solar cooker for cooking food to prevent nature and also to prevent firewood. The use of solar energy for cooking is the oldest and spread this energy source, and its main characteristic its social function. The people in Africa use solar ovens and massively contributing to a policy of non-use of wood. The use of solar ovens in the solar scrub promises to reverse or at least mitigate this situation by allowing backcountry better living conditions. It presents a solar oven for baking food, manufactured from a thermal box of EPS. The solar oven made from a scrap box EPS presented the following dimensions: - external - Length: 0.74 m, width 0.56 m and height: 0.20 m; - Internal - length: 0.625 m, width: 0,44 m . The outdoor area corresponded to 0.41 m² and the external volume 0,083 m³; internal area corresponded to 0.28 m². The area of the reflecting surface that lines the inner walls of the furnace corresponded to 0.36 m². The outer reflective surface presented a catchments area of solar radiation corresponding to 0.18 m². box show in figure 2.1. Figure 2-1: Schematic drawing of the solar oven, its components and dimensions The enclosure of the oven was covered with a transparent flat glass of three mm thick. The glass is seated in the box. Eps material facilitates loading and unloading of food offered for cooking. The furnace structure was fabricated. Using angles and provides rotational movement to facilitate the handling of the oven. Tests were performed without load for determining the temperature of the furnace box type solar studied. Temperatures were measured every five minutes or so. The tests were conducted for the period from 10:00 to 14:00 hours. Tests were also performed to load the two baking pizza 400g, breaded chicken and 500g of a cake 700 g,
16 determining the time required for this purpose. The same parameter measure without load at same time interval. Were also measured the temperature inside the oven. The inner side temperature was measured by chromelalumel thermo couple type K coupled to a digital thermometer. The efficiency of the solar oven studied was around 78%, since the energy lost corresponded to 22% of the energy that went into the baking enclosure of the oven. The solar oven was placed on exposure to the sun 10:20 are. The average ambient temperature was 29 ° C and thermal sensation of 33°C during the test. The maximum temperatures in the absorber surface and internal air of solar oven corresponding to 114°C and 105°C, respectively, were significant and suitable to provide the baking of foods. The average temperatures for these parameters during the test duration, at around 102.4°C and 94.6 C, respectively, are also suitable for obtaining the desired end. A cake was baked at 11:45 am. After placing the cake the temperature of the absorber were 40°C and the internal of the oven of 82°C to the air temperature inside the oven. The environment average temperature during the test was 30.5°C. The complete baking of cake taking 45 minutes. Another test for pizza baking the test performed at 12:30 pm temperature before placing is 41°C for the shape temperature and 80 ° to the air temperature inside the oven. The environment average temperature is 30.8°C during the test. The complete baking of pizza taking 15 minute. A third test preformed for chicken fingers, five units each have mass 100g total 500g. Test began at 12:30 pm. The temperatures of breaded before baking were 46°C for the absorber temperature and 71 ° C to the air temperature inside humidity of 60%. The complete baking the breaded happened in twenty-five minutes. For the diagnosis of thermal loss from the oven temperatures were measured from their surfaces. Figure 2.2 shows the mean values of temperatures measured during the test without load at 1 hour.
17 Figure 2-2: Temperature on the external surface of the oven .Solar oven bake food very good from the 9:00am to 2:00 am. The solar oven has become competitive with conventional gas oven. The manufacturing of solar oven is easy and low cost. All the food in the oven is baked under solar cooking time competitive with conventional oven. It is important to have another conventional source for cooking food to replace the proposed solar cooker on days with insufficient solar conditions for its use. [36] Mr. Bbdul Waheed Badar investigates the thermal performance of a unique box type solar oven whose five sides are exposed to ambient and provisions are also provided to install the reflectors to enhance the intensity of incident solar radiation on the oven. Experiments were performed where temperatures attained inside the box cavity are recorded on different days and times of the day corresponding to various intensities of available solar radiation. A steady sate heat transfer numerical model of the solar oven without reflectors is also developed based on six individual thermal resistance networks which account for the heat losses through each flat-side of the oven box and a good agreement with the experimental data is achieved. A parametric study based on numerical calculations and experiments is then carried out to study the effects of various parameters on oven‘s thermal performance, e.g. number of glazing, distance between glazing and box, type of absorber coating, etc. Higher box temperature is attained using double glazing than single glazing. As compared to black paint, selective surface coating results in
18 significantly higher oven temperatures (up to 40 0 C). Plate spacing of 20-30 mm is found to be optimum distance between oven box and glass covers. A solar oven uses solar energy to heat ,cook , and pasteurized food material. Solar cooker are easily available in the market most of them are in expensive and other are expensive advanced are a stove. Studies have been done on the thermal performance and parameters that affect the performance of simple box type solar ovens which takes solar radiations from the top surface. In this work, a unique five sided double glazed solar oven with a black painted box as the cooking cavity is investigated. In the fig show the practical view of the oven with and without reflectors. The design of this solar cooker is unique it diffuses and ground reflected solar radiation from five side with the aid of upper and lower reflectors which augment the incident radiation intensity. The major advantage of this cooker that during cooking the person does not shade the cooker and also there is no possibility to come indirect contact with the concentrated intense radiation. Figure 2-3: Pictorial view of solar oven with and without reflectors Experiment were conducted on solar oven with and without reflector to record the maximum temperature during various time. Different food were also cooked e.g. boils potatoes, rice, eggs and noodles. The experimental test were carried out on march and April. During experiment the solar oven were placed in a position that the projection of sun rays on the ground and surface normal coincides. Oven was placed in the sun in several hours. Temperature in side the oven recorded though a temperature probe (UT33B, Uni-Trend) inserted inside the cavity. Solar radiation was also recorded using pyrometer. In clear sky day typical box temperature in the range of 1400 C and 100 0C with and without reflector. Also the required safe temperature most
19 of the food is (i.e, 60-90 0C). Parametric analysis of the solar oven was done to study the effect of various parameters on its thermal performance. Radiation increased for single glazed solar oven compare to double glazing. The thermal performance of a 5-sided solar oven is investigate experimental analysis show that temperature attend with and without in the box in the range of 50 -150 0C. Which is adequate for cooking purposes. Parametric study is then conducted to analyze the effect of various key parameters. Double glazing results in better thermal performance than single glazing. Using a selective coating (i.e. TiNox) on the outer surface of the oven box temperature Tb can be increased up to 50 0C, when compared to black paint. Below 20 mm of spacing between oven box and glazings results in significant drop of box temperature Tb. Plate spacing of 25 mm and above does not improve the oven thermal performance appreciably. [37] Mr. Jebaraj S. and Srinivasa Rao P.Today‘s presented that society pollution increasing problems. Since solar energy is clean free energy that can be harnessed, solar energy can be incorporated in our daily lives to produce energy to conserve other non-renewable energy .solar oven use to cook the food through solar energy. It is planned to design a high efficiency oven which is convenient and comfortable for all Kind of cooking, baking and heating without spoiling the food. This solar oven is capable of making a temperature change up to 150 ⁰C in 60 minutes. Once the prototype was completed several experiment were conducted to determine the efficiency between two designs which are without the parabolic dish and with parabolic dish. The efficiency with parabolic dish is greater than without parabolic dish. The efficiency attend with parabolic collector is 150minutes is 53.62% whereas, for the same duration the efficiency of solar oven without parabolic collector is 35.86%. This solar oven would be very useful to conserve electricity and healthy food cooking. The sun is a constant source of energy. Most of sun energy com in the form of visible light. Sun light is the most important source of energy for all living things. Sun light use for such everyday jobs , cooking, heating water or warming of homes. The challenge is to transform sunlight into usable heat. In order to make better use of sunlight, in attempt has been developed a high efficiency solar oven for tropical countries. One of them that it is eco-friendly doesn‘t depend on gas and electricity and it is economic.
20 Solar oven are of two types box type and parabolic type. Box oven is the most common type solar oven it is designed in base of the concept of traditional modern oven. The temperature of the oven can reach to 300° F (150° C) which is plenty hot to cook any food. Food containing
large amount of moisture can‘t much hotter then 100o C so it is not necessary to cook at higher temperature. The parabolic oven can reach high temperature more quickly. Some parabolic oven are limited in the quantity of food that is possible to be cooked at one time since they usually one pot that is suspended in the center of the path of highest solar energy concentration. In the present work it is attempt to combine of the box and parabolic oven and increase the efficiency. The sun light energy is collect through parabolic collector with series of mirror attached with it to reflect the sunlight. The sunlight entre to inside of solar oven and the black absorber convert it in to heat by the dark absorber plate. A layer of polystyrene is added inside the box to minimize the temperature loss. The melting temperature of polystyrene is 240o c. heat from the sun light to heat up the box through greenhouse effect. The inner surface of the box is black to absorbed sunlight and convert it into heat. The parabolic collector is important. The parabolic collector bounce the additional sunlight through the glass. The parabolic collector reflect more sunlight and concentrated more sunlight to the box. Nat system is perfect and have 100% efficiency. Their will be heat loss through convection, conduction and radiation. For generating heat inside the box use a square box and grade A glass on the top of it the sunlight entre the box and produce heat inside the box Styrofoam is use to reduce the heat loss it is used is an insulator for all side. The Styrofoam we warp using aluminum foil to reflect heat and absorbed by the food at the bottom MDF is use to reduce the heat loss at the bottom. The experiment were performing in two stages solar oven without parabolic collector and with parabolic collector. The reading were tabulated for 30 minutes. The heat inside the oven with parabolic collector is greater than heat without parabolic collector. In this research attempt has been made to design and construct solar oven with and without parabolic reflector. The experiment were performed for regular interval of 30 minutes the heat energy absorbed with parabolic collector is 2420.5 KJ/m2 and without parabolic collector is 1563.4 KJ/m2 respectively for the time duration of 150 minutes. It concluded in this research that the solar oven would be very much helpful to conserve the electricity and eco-friendly food production. [38]
21 M. Abu-Khader studied In this paper about two types of solar cooker. The one is painted black base and the other has internal reflecting mirrors. Both designs ware tested. Both designs ware tested on two conditions on tracking system. The efficiencies range of black base cooker was recorded from 17 % to 41 % at maximum sun light of the day 11 – 12 and its average efficiency is around to 27 %. While the efficiencies range of internal reflecting mirrors cooker was recorded from 25.3 % to 53.1 % and its average efficiency is around to 46.6 %. The advantage of sun tracking system is to maintain a higher range of thermal efficiencies. The increases prices of fuel and energy using the alternative of energy is necessary. The solar energy is good option. In solar energy the solar cooker is important applications in thermal solar energy conversion. Solar cooker is used widely for cooking in developed countries. The solar cooker highly quality and easily available easily is portable. Current deigns of cooker is like a box cooker, concentrators and flat plate are used. The solar cooker is used for cooking, purify water. And solar cooker the interior surface of box is heated because the black absorber absorbed the heat .This heat increase the temperature inside the box cooker to rise until the heat loss of the cooker is equal to the solar gain. And the temperature for cooking and purify water is easily gained. The tests on the solar cookers were carried out during the successive days from the 29th and 31st /10/2007 and 2nd /11/ 2007. Each experiment starts from 7:30 am in the morning to 4:00 pm. The first part of this research work concentrated on testing of two box type cookers: traditional black painted cooker and internal installed mirrors cooker. Both cookers are fixed at a position towards the south. The second part is testing the traditional black painted cooker with a tracking system to the sun movement. After testing the data obtained from the cookers. It is clear that both types of cooker at fixed position give similar thermal performance where the average water and pot temperature is 7 % errors. The efficiencies range is from 12 % to 41 % at maximum sun light of the day and the average efficiency is 27.6 % while in the interior reflector ranger is 25.3 % to 53.1 % while average efficiency is 40.6 %.[39] F. Yettou show In this type of solar cooker with mirror reflectors two types of tracking system is used. It receives solar radiations both directly by reflection of mirrors reflectors. The
22 addition of reflectors to improve the work of the cooker is interesting in particular in winter, where the elevation of the sun is relatively low. The combination of mirror reflectors are good for more energy, the cooker is enabling to cook during day time. It is good thinking to use sun light for cooking. Solar cooker is used for cooking in the presence of sun light. The use of solar cooker is save fuel, money and other energy. The solar cooking is developing the word. Different types of solar cookers are made and tested all the word. There has been improved the designed, developed and testing of different types of solar cooker. Solar cooker is much used in the word it‘s easily available and it is portable. Solar cooker with tracking mirrors reflectors and see performance of cooker. The north-south facing reflectors use to track the weather variation and the east –west reflectors use to track at day time. The distribution of concentrated solar energy is uniform on the plate absorber of the cooker in the case of north-south tracking which is suitable for cooking temperatures. The combination of reflectors is increase and improves the collection of energy and performances of cooker to gain and absorbed heat. This is very important for cooking in winter season when the solar elevation is low. [40] Ajay Chandak In this paper used two concentrator one is SK-14 and other is PRINCE- 15.the SK-14 is widely used in domestic level. If the bowel of solar concentrator is made then the concentrators becomes heavy and transportability is problem. if use only reflectors sheets the transportability is improved.PRINCE-15 is new geometry of solar concentrators with square and rectangular shape. This new design has an excellent transportability. The testing was done with these two solar concentrators in the presence of sun light with different geometrics. This test proved that PRINCE-15 is not only better transportability but have also high efficiency. Solar cooker is used in the presence of sunlight to cook food. The widely using of solar cooker saves money fuel and money and time. All these things are important in life. SK-14 concentrator developed by Dr. Ing. And many companies of germen made it and sell it. SK-14 concentrators is used widely and domestic level. The diameter of 1400 mm and his performance is 700 watts. In this solar concentrators is manufactured in a bowel used in it‘s the rings of bowel is made of steel wires .Such bowels are strong and not easily damaged. For this reason few companies have come up with bowel stitched with bolts and screws and all reflectors sheets are joined together
23 and form of bowel. This improved the transportability but the bowel weaker and high wind or stone damaged it easily. The study of these two solar concentrators SK-14 and PRINCE-15 testing was planned at the same time. At the same time the testing eliminated the possibility of errors because of difference winds speed, ambient temperature and variation in solar radiation. Mild steel plates were used for stagnation temperature test and thermocouples are connected to the mild steel plate. Similarly water is also used heat test and its temperature was recorded. Test duration was fixed at 25 minutes to keep the water peak temperature below 900 0C. This limit was decided during the trial itself. Solar radiation is measured using Apogee solar sensors for total and diffused radiation. Different results are obtained compering both concentrators with same sun lights areas same materials for reflectors but the geometric system is different. SK-14 is circular and PRINCE-15 is rectangular dish concentrators. Reading was taking continuously both on both and avoids any variation because of wind and solar radiation.so the PRINCE-15 is showing the it‘s better from SK-14 and every level. [41] Paras Soni said The continuous development of technology increases the demand of energy. There alternative devices are achieved which is based on renewable energy. Food is not only a basic human need, but also a culturally important part of daily life. Thus, we seek to implement solar cookers in a way that is not only environmentally sustainable but also culturally sensitive. To made this solar oven to increase the performance parameter. The major source of energy is derived from fossil fuels. Due to the limited availability or depletion of these sources with time, balance between the demand and supply of energy seems to be degrading in the coming years. Moreover the fossil fuels are polluting in nature. In order to maintain a balance between demand and supply of energy, there is a need to exploit renewable sources to the maximum limit possible. A solar cooker, or solar oven, is a device which uses the energy of direct sunlight to heat, cook or pasteurize food or drink. Over the past many decades, a number of designs of solar cooker have been developed. The majority of solar cookers presently in use are relatively cheap, low-tech devices. Although solar cookers have been available for many years, there is continuing interest in their performance optimization.
24 In this study it was observed that in any climate conditions performance of every element of solar cooker has great importance and direct effect. For quality cooking no one parameter has been eliminated among these. [42] Himanshu Agrawal studied in this paper the theoretical analysis of parabolic dish type solar collector by using thermodynamic equations, it was calculated by measuring heat input and output system, that there is loss in various systems. By the calculation of relative error and by comparing theoretical and experimental data, the efficiency of system was found to be 4 to 9 %. Solar energy has become the most promising energy substitute from the last few decades and many efforts has been made to utilize this energy in cooking in the form of solar cooker, replacing the fuel or wood alternatives, based on box type collector, solar collectors a, parabolic trough collector and dish collector, with phase change thermal storage unit, but none of them worked with sensible heat storage unit. Solar cooking system with heat storage or without it were experimented, revealing various interesting features like heat flow control in pots and modularity, indoor cooking and baking adjustments. The investigation of solar cooker with PCM based on parabolic dishes has been observed to have 1.63 to 4.44 times faster. The test section of solar cooker is based on parabolic dish type collector. This system consists of parabolic dish collector and solar cooker. The solar dish is a point focusing collector. At the focus of parabolic dish collector, a holding tray is provided upon which cooker is to be place. The tracking of parabolic dish collector is done manually after 30 minutes. [43] In this paper Dr. Tony Robinson studied the Characterization and design methods of solar cookers & ovens. He write the problem of cooking that Half the world‘s people must burn wood
or dried dung to cook their food. Nearly 1.2 billion people, a fifth of the world‘s population, do not have access to clean drinking water. Over 1 million children die yearly because of un-boiled drinking water. Wood cut for cooking purposes contributes to the 16 million hectares of forest
destroyed annually. Half the world‘s population is exposed to indoor air pollution, mainly the result of burning solid fuels for cooking and heating. Dr. Tony Robinson design a solar cooker through the bases of first law of thermo dynamics that Energy can be neither created nor destroyed, it can only change form Provides a basis for
25 studying the relationships among the various forms of energy and energy interactions. Also from the energy balance the net change (increase or decrease) in the total energy of an any system during any process is equal to the difference between the total energy entering and the total energy leaving the system during that process. [44] M.r Seguin R. BELLO and Simon Ogbeche ODEY study the Development of Hot Water Solar Oven for Low Temperature Thermal Processes. He say that The most useful form of the Hottel-Whiller-Bliss generalized performance equations for flat plate collector utilizing heat removal factor and loss coefficients is used to model a solar oven- water heating system for low thermal process application. The water heating system was designed, tested and evaluated with a daily collector efficiency of 51.82%, an average daily solar radiation of 689.23 (w/ºc) per day and a useful gain by collector of 563.85 (w/ºc). Loss in collector is 116.39 (w/ºc) and total average daily heat gain by water in collector is 292.26 (w/ºc). Average Daily storage heat capacity of 582.83 (KJ) and the daily converted heat delivered to test chamber is 147.07 (KJ). The overall System efficiency of 25.24% was obtained. Renewed interest of solar as an energy source in heating systems has gained relevance in various fields and in agricultural operations such as dairy farm hot water supply and food preservation. Microwave heating and food irradiation using solar systems have also been used on commercial scale. Many of these applications require heated air at relatively low temperatures. Traditional heat production is through wood, natural gas or LP gas. Fuel wood account for over 50% of the overall energy consumption in Nigeria, about 80% of these are consumed as firewood mainly in the rural households, [1]. The average daily consumption is 0.5-1kg of dry fuel wood per person, which is equivalent to 10-20 mega joules per day [2]. The current rate of consumption of fuel wood far exceeded the replenishing rate to such extent that acute ecological problems of deforestation soil erosion, and desertification are well recognized problems in the country today . Solar heaters have been used in other operations involving water heating, but interests in heat transfer in oven using water, as heat transfer medium have not been fully investigated. Research investigation has measured the amount of solar energy transmitted by collector and the feasibility of heating ventilating air by passing it though roofing and sidings whose exterior surfaces were painted black. Okonkwo et al indicated that built in thermal storage solar water space conditioning system could be used efficiently in chick brooding in Nigeria. Their work utilizes a
26 water storage tank constructed with 2mm thick galvanized metal sheet measuring 3m x 1m x 2m insulated with wooden materials, 5cm thick [3]. The behavior of solar dryers is influenced by loading capacity, orientation and angle of inclination [4]. The effect of beam or directional radiation on the collector surface can be maximized when tilted at right angles to the incident beam adding that an inclined surface may receive a significant proportion of its irradiant through reflection from the ground adjacent to it [4]. The works of Mac Craken, Eckhoff Ohos & Shorf and Hansen and Smith as reviewed by [5] reported the use of phase change materials such as salt, dry soil, pond, and a pile of rock for sensible heat storage in collector design. Water heating constitutes 15% to 25%, or more, of the energy use at home. The approximate annual cost to operate water heaters ranges from $200 for a minimum efficiency gas-fired unit to as much as $500 for a minimum efficiency electric unit. Heaters have been reported to reduce annual operating costs by 50% to 80% using free energy from the sun. As a result of this research activity on the development of thermal solar systems for application in residential housing for the purpose of space heating, a cost effective thermal solar collector with Direct Heat Storage (DHS) was developed. Selection of material of construction is dependent on the properties of the materials that give better performance. The design consisted of a flat plate collector mounted on a stand with variable angle of inclination, a test chamber and a water reservoir mounted on a stand. The units were set out and an insulated water hose used to connect the systems together. In experimental procedure he write the Basic workshop tools were used in the fabrication process and a PRO Level and Angle Finder used in tilt angle graduation on the collector . Five laboratory thermometers of range -10º to 110ºc were installed on to measure inside and outside temperatures-one at the cold water storage, two installed within the collector; each at the extreme ends of the absorber, in-between the cover and the absorber surface one measures the surface temperature while the other measures the air temperature within the collector-glass space. Another thermometer measures the hot water temperature entering the oven and two others measure the heating chamber temperature. Leakages in the flow line along the tubes in the system were corrected and several tests were run to collect temperature and flow data. The flow rate required to deliver water to the collector to achieve maximum heat harvest from the collector determined for experimental procedures is M = 0.25l/min and a tilt
27 angle of 50° to the horizontal. Temperature data were collected at hourly interval of 5 minutes for the hours of sunshine for the days under test. For purpose of analysis temperature profile data were collected per day on clear days. A solar water heating system has been designed and constructed. Performance evaluation carried out indicates an overall system efficiency of 25.98% and absorber temperature of 72ºc. Efficiency of collector varies with water flow rates. The collector is more efficient at low radiations; 52.85% at 630.08 w/m2 and 51.00% at 739.40w/m2. This is obvious at lower operating temperatures for collectors Solar radiation, heat gain and collector temperature are highest between 1300hr and 1400hrs because of the collector tilt angle (optimum tilt angle=50º) causing a larger percentage of incoming radiation to be incident on the collector. The system is efficient to be used for low temperature processes as pasteurization and also can be adapted for use in incubation. [45] Mr. O.A. Jaramillo study a solar oven for intertropical zones: Opto geometrical design in this paper, a novel design of a solar oven for the intertropical zones is presented. The oven box has seven faces instead of the six faces of most common designs reported in the literature; two of them are alternatively used as bases. This oven has four fixed mirrors to concentrate solar energy. The main advantage of this novel design is that the oven needs only four simple movements in order to obtain an adequate solar concentration throughout the year. This feature has been possible due to the opto geometrical design that is presented. A simple theoretical model of the oven concentration is developed. According to the model, the concentration achieved by the oven at noon is greater than 1.95 for all days of the year. In order to analyze the optical performance of the solar cooker, an experimental evaluation was conducted by using a scale model of the solar cooker and a heliodor. Solar cookers, as their name indicates, are devices that use solar energy to raise the temperature of food to cook it. These solar devices are based on the simple principles of reflection, concentration, glazing, absorption and the greenhouse effect to store energy in order to increase the temperature. Various types of solar cookers exist, harnessing one or more of these principles. Solar cookers have attracted the attention of many researchers; in addition, many designers and small scale producers have, in recent years, made notable progress in the technical advancement of solar cookers. Since there is different availability of solar energy and there are different styles and traditions in the cuisine around the world, one can find a great variety of solar cooker
28 designs. Solar cookers fit into many categories some are given solar box cooker, concentrator cooker and collector cooker. The objective of this research is to design a solar oven for the intertropical zones. The design is based on the idea of having two faces of the box that are alternatively used as the base of the solar oven and having four fixed reflectors. Thus, the solar oven is easy to use (with only a few movements throughout the year), and during the operation time, the solar oven obtains a good solar energy gain. A two dimensional ray tracing technique was employed to design the geometry. The oven has been designed on the basis of the two days with the maximum solar declination: the day with maximum declination angle to the South (December 23) and the one to the North (June 22) and the winter and summer solstices. The main design condition is that, for these two selected days, the rays of the sun must fall perpendicular to the transparent face (cover) at noon at the design place in Mexico (latitude 18500N). This condition implies that the oven cover presents different inclinations. This was resolved by designing a box with two different bases. As the cover has two possible inclinations, whose difference is 30, the days when the oven has to be moved are defined the condition that the angle formed by the cover and the sun rays at noon during all the year has to be less than or equal to 15o. The experiment was performed in March, July and December. The experimental tests were done by using a scale model of the solar oven (scale 1:6) and a heliodor. A heliodor is an efficient tool for studying the patterns of the shadows and how the beam radiation is reflected into the solar oven. The evaluation of the radiative energy collected by the solar oven was done using an array of calibrated photo resistances distributed equidistantly on the cover area of the oven scale model. The performance factor model, although simple, is a useful tool to evaluate the gain of solar energy due to the inclination of the cover and the presence of the reflectors throughout the year, and it can be used to evaluate the energy that the solar oven receives if the insolation data over the horizontal plane is available. The theoretical model results show that, at noon, the solar cooker achieves a concentration level greater than 1.95 throughout the year. It is expected that these concentration values are enough to increment the meal temperature for the cooking process. [46]
29 This paper considers the design, use, and social acceptance of solar cookers that are constructed by their users. Several generations of oven design are described and their field testing in Indonesia are reported, the first generation design having been described in a previous paper. The second generation design reached 1758C0 in oven temperature, and it used only local materials in its manufacture. Results of field testing of sixty four units in East Nusa Tenggara Provence, Timor Island, Sulamu village, and at Maumere City of the Sikka Regency in Flores Island, all in Indonesia, are reported. Social observations via questionnaires and direct conversation were conducted as part of the field study. Preliminary results showed promising tendencies of acceptance (up to 28%), and the solar ovens proved their ability to cook effectively. The most recent generation of design has reached 2028C in oven temperature, while costing 10% less than the previous one. The dissemination of thirty units of this design in two villages in West Nusa Tenggara Province is reported on. [47]
Solar cooking is often considered ‗‗a solution looking for a problem‘‘. Solar cookers have long been presented as an interesting solution to the world‘s problem of dwindling fuel wood sources and other environmental problems associated with wood fuel demand for cooking. However, recent GTZ field work in South Africa showed different benefits instead: the use of solar cookers resulted in appreciable fuel and time savings as well as increased energy security for households using commercial fuels. These observations are based on field tests in South Africa that started in 1996 to investigate the social acceptability of solar cookers and to facilitate local production and commercialisation of the technology. Impact studies and use rate studies have been carried out by a number of different organizations since the inception of the project and although commercialisation of the technology has not been achieved to its fullest potential, impact studies indicate that solar cookers have a positive development impact on households through fuel-, energy- and time savings. The article aims to summaries the findings of the various studies and presents an overview of use rates and impact data. A variety of factors influence solar cooker use rates, which in turn determine impacts. Some factors are related to the user, some to the environment in which the cooker is used and some to the cooker itself. Ultimately, the data shows that on average, only 17% of solar cooker owners do not use their stoves after purchase and that active solar cooker users utilize their stoves on average for 31% of their cooking incidences. Since the majority of solar stove buyers actually uses their stoves and
30 obtains real benefits, this suggests that those solar cookers are indeed not a solution looking for a problem but a solution worth promoting. Solar cookers have generally been promoted in areas where fuel wood shortages are experienced such as rural areas and refugee camps. However, results from the GTZ/ DME field test indicated highest user rates in an electrified area and subsequent sales were mostly to electricity users. Although fuel wood shortages may be an important push factor to promote the use of solar cookers, the cost and scarcity of commercial fuels can also convince users to take up the technology. External conditions which can promote the use of solar cooking are therefore, the general lack of adequate energy sources and a desire to achieve savings (time or monetary) by end-users. Important aspects concerned with the user of a solar cooker were identified: There must be adequate motivation to use the cookers. Potential savings were the most important motivation mentioned by users to purchase and use their solar cookers while an element of curiosity was also found to be conducive to encourage the purchase of a solar cooker. Male buyers reported curiosity as the most important motivational aspect while women reported potential savings (Palmer Development Consulting, 2002a, b). Successful solar cooking requires a basic a form of training and being exposed to a solar cooking demonstration was rated highly by users to ensure cooking success and therefore on-going use. A variety of instruments were used to inform users how to use their solar cookers successfully, for example, pamphlets, user instructions, brochures and recipe books were distributed with the cookers (GTZ and DME, 2002a) while approximately 500 wet demonstrations were carried out throughout the implementation period (GTZ and DME, 2002a).Using solar cookers requires adaptation mostly in terms of kitchen management. Planning ahead and preparing food becomes important—you cannot decide to solar cook a chicken stew 1h before mealtime. Once solar cookers are integrated in the process of kitchen management and cooking, users chose to use them regularly as indicated by an average use level of 31%. Despite the failure of the programmed to achieve large scale commercialisation and local production of solar cookers in South Africa, households using solar cookers reported quantifiable benefits. Strong evidence emerged from all the studies that the users of solar cookers experience savings. It should be noted that the average saving of R68 found may be under reported as it is often difficult for users to estimate savings achieved through the use of a solar cooker since
31 savings depend on a wide variety of issues such as fuel use, frequency of cooking and type of food cooked. Evidence from recorded fuel, monetary and time-savings as well as the noted development impacts, especially for women therefore, indicate that the use of solar cookers does have positive development impacts at the household level. [48] This paper uses a previously published report coupled with recently collected empirical information on the diffusion of solar cookers among the Basotho of Lesotho. Drawing upon diffusion practice and theory, the authors cite several present-day instances where diffusion is taking place. The conclusion, however, is unfortunate, in that the outlook for the use of solar cookers and their effective diffusion in Lesotho is rather bleak. Once upon a time, perched atop the Drakensberg Mountains above the Republic of South Africa, there lay a tiny country called Lesotho. Lesotho was, and still is, inhabited by Basotho (singular "Mosotho") who farmed the mountainous terrain. One day, trekking over the crags, a group of foreigners arrived in the village of Thaba Tseka in the center of Lesotho. They carried with them forty-five odd-looking boxes which they said could use the light of the sun to cook food. The boxes were a gift for the people of Thaba Tseka. A. A. Eberhard reports that the Basotho of Thaba Tseka indicated that, since they already used fires to heat their homes, they preferred to cook over their fires rather than use the solar cookers. Thus, the first of five key characteristics that help to explain the rate of adoption of any innovation, as perceived by potential users, was negative. This first characteristic is "relative advantage," which means "the degree to which an innovation is perceived as better than the idea it supersedes." The remaining four characteristics which "past research indicates are the most important characteristics of innovations in explaining the rate of adoption. This paper points to several projects that have already targeted people who were thought to need and want solar cookers the most, the rural women and the wanna-be's. A brief review of past and present projects and the application of diffusion theory have failed to show much hope for the diffusion of this innovation – solar cookers in present day Lesotho. Because the diffusion of innovation is a cooperative process, the people of Thaba Tseka will not adopt solar cookers until a suitable change aide, with a bridge tie into their clique, convinces them that sunlight can, indeed, cook their food. [49]
32 In this paper the John J. TODD1 and Sunny MILLER study the Performance Testing of Cardboard, Solar Box-Cookers. A simple solar box cooker was tested using a standard test method and a comparative test method. Various design changes were examined. Results show the advantages of double glazing and black absorption plates in the base of the cooker. The optimum combination of design changes resulted in an increase of 175% in cooking power compared to the basic design. Cooking temperatures of 70°C were reached in one hour and water boiled within two hours. These temperatures and heating rates allow practical cooking of many foods. Construction and testing of solar cookers is an excellent educational tool, illustrating many important features of solar design. Solar box-cookers represent a simple, low cost and effective application of solar energy. In many developing countries they can play vital roles in improving health by lowering exposure to wood-smoke and reducing pressure on firewood resources. They can be used to sterilize drinking water. They can also be locally manufactured. It is not surprising that many papers (e.g. Lenssen 1989; Sun World 1988) and books (e.g. Kerr 1991) have been written on the subject, extolling the virtues of solar cookers. The potential benefits of increased solar cooker use by rural poor are not in dispute. But does the solar cooker have a role to play in the developed countries. The principles of passive solar design can be demonstrated and understood. Children can build their own cookers. It is also very instructive for adults to see and operate such appliances. It is unlikely that solar cookers will substitute for conventional gas or electric cooking in developed countries, although they serve as an interesting diversion at barbeques (e.g. a cake can be cooked in less than two hours on a sunny day). In Australia, the cost of cooking a meal with gas or electricity is only a few tenths of a dollar, so financial savings attributable solar cooking is almost trivial. A solar cooked meal will reduce Greenhouse gas emissions by 0.5 to 1.5 kg of CO2. Small compared to average per capita emissions of 15 t CO2, but nonetheless a reduction. Thus, education, rather than economic or ecological gain, is likely to be the key justification for promoting solar cookers in Australia and New Zealand. The principles of solar box cookers are so simple and elegant. If they were more widely promoted people would gain a greater appreciation of solar energy. Also, some of the benefits of this technology might be carried with aid workers and tourists as they travel or work in regions of the world where solar cookers could play a crucial role in saving lives and improving the quality of the environment. With these principles in mind, this paper sets out to illustrate some basic design features of solar cookers.
33 We hope that this will stimulate interest by ANZSES members. The paper also illustrates the importance of a standard method for comparing the performance of solar cookers.The ovens were exposed to the sun about 20 minutes after recording began at which point the water in the pots in both ovens started to warm. After three hours the water in pot-B was near boiling, the water in pot-A was about 20°C cooler. Towards the end of the test, the windy conditions on this day caused the lid of oven-A to blow closed and the water started to cool. The final 40 minutes of the test were, therefore, not valid. The design and testing of these simple solar cookers proved interesting and instructive. It reinforced our views that these devices could play an important education role in Australia and New Zealand. If testing is done systematically, the cookers become more than just a novelty demonstration of solar energy. They teach some very important basic principles relevant to many other solar energy applications. There are numerous good research and implementation programs on solar cookers throughout the world. [50]
34
CHAPTER 3
Design and Fabrication3.1 System Description: A solar oven is made of mild steel box, wooden box, mirror reflector, transparent glasses and glass whole is use is a special insulating material. The block diagram is shown in Figure 3-1. Figure 3-1: Block diagram of solar oven
3.1.1 Wooden box: Wood box is use because Wood is a good insulating material and it‘s easy and its thermal conductivity is very low .the manufacturing of wood is simple and easy because of that wood box is use show is Figure 3-2.
35 Figure 3-2: Wooden box
3.1.2 Black pint mild steel box: Although mild steel is soft steel that can be easily welded and cut with a torch. When mild steel is black painted then its thermal absorptivity increases and mild steel is easily available in the market because of that mild steel box is use show in Figure 3-3. Figure 3-3: Mild steel box
3.1.3 Mirror reflector: Concentrated solar mirror reflector is a device use to (also called concentrating solar to concentrate a large area of sunlight, or solar thermal energy, onto a small area show in Figure 3- 4.
36 Figure 3-4: Mirror reflector
3.1.4 Glass wool: Glass wool is use around all the sides of the oven between mild steel box and wooden box because glass wool is a good insulating material. Glass wool is an insulating material made from fibers of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties show in Figure 3-5. Figure 3-5: Glass wool
37
3.2 Calculation: The calculation is done on the bases of stiffen boltsman law of radiation. Stiffen boltsman equation is;
q = εa σ Ac (Th4 – Ts4) Where, q Is average is radiation, εa is absorptivity, Th is the desired temperature, Ts is the surrounding temperature, σ Stiffen Boltzman law constant =5.67X10-8 .,Ac is area of the oven=? The values is, Average radiation of texila=800 w/m2 Absorptivity of mild steel=0.60, Th is the temperature that we achieve=130 o c T
s the surrounding temperature=25 0c
σ Stiffen Boltzman law constant =5.67X10-8 A
c is area of the oven=? Putting the values in the formula
q = εa σ Ac (Th4 – Ts4) 800=A (5.67X10-8) (0.60) (4034-2984) 800=A (3.402X10-8) (1.8494X1010) 800=629.16 A A= 1.350 m2 A=1.350/2 L=0.762 W=0.60 Convert in to inch,
38 Length of the box=L=30 inch Width=W=18 inch.
39
3D Creo design Figure 3-6: 3D Creo design
2D Creo Design Figure 3-7: 2D Creo design
40
41
3.3 Fabrication of solar oven
3.3.1 Tool and Instrument Used:
The following tool use in fabrication of solar oven.
Hand saw.
Hammer
Nail and glow.
Vaenier caliper
Measuring tape
Bending machine
Welding machine
3.3.2 Material:
Wood thickness= 25.4mm‖
Mild steel thickness =2mm
Upper glass thickness=6mm,
Reflector
Insulation glass
Adjuster
Temperature gauge
Caster wheel.
3.3.3 Cutting (wood hand saw) process: Deyar wood easily available in market are in different sizes as compare with our required size so hand saw used for cutting sheet for required shapes. Usually, measured the point where the cutting action takes place and perpendicular to the direction of blade movement. Cut the five parts of wood according to our required dimensions of 0.606m, 0.762m and 0.2032m
42 Figure 3-8: Wood cutting Then joint the parts of wood to each other through nails and white glue show in Figure 3-9. Figure 3-9: Joining of wood.
43 Make a simple box and then joint a four caster wheel at the bottom of the box show in figure 3- 10. Figure 3-10: wooden box.
3.3.4 Mild steel box: Take a sheet of mild steel and cut it according to the required dimensions of Length=22.5 ―, Wedith=16.5‖ and Hight=4‖. Show in Figure 20.
44 Figure 3-11: Mild steel sheet Bind the four sides of the sheet through bending machine and the four sides corner are joint through gas welding show in figure 3-12. Figure 3-12: Mild steel box
3.4 Joint process: Then put the mild steel box inside the wood box and filled gape between the mild steel box and wood box with the whole of fiber glass then sealed the upper edges with wood and then sealed it with rubber to minimize the heat losses. And pint the mild steel box with black color.
45
3.4.1 Insulation: Filled gape between the mild steel box and wood box with the whole of fiber glass then sealed the upper edges with wood and then sealed it with rubber to minimize the heat losses. Figure 3-13: Sealed with rubber
3.4.2 Frame for reflector and transparent glass: Make a frame for reflector and transparent glass and put the reflector and glass in the frame show in figure 3-14.
46 Figure 3-14: Frame for reflector and transparent glass Then join the reflector and glass with box through hinges and nail show in figure 3-15. Figure 3-15: Joins the frame with box Join an adjuster with reflector and box for different angle changing of reflector. Join a handle on both sides for easily lifting show in figure 3-16.
47 Figure 3-16: Joins adjuster
48 Figure 3-17: Complete fabricated model
49
CHAPTER 4
Experimentation and Results
4.1 Experimental procedures: The experiment was conducted in two stages namely solar oven without reflector and solar oven with the reflector. The readings were tabulated for every 50 minutes in different times and in different days. The different readings of temperature of solar oven determined for both the cases with reflector and without reflector listed in table-4.1 and table-4.2.
4.2 Solar oven without reflector: In table-4.1 the experiment were conducted on Sunday March 13, 2017 in various times on solar oven without reflector. The below data is obtain Table 4-1: Solar oven without reflector Time Environment Temperature Oven Temperature 10:00-10:50 22.8 0 c 54 0 c 11:20-12:10 23 0 c 68 0 c 12:40-01:30 240 c 77 0 c 01:40-02:30 24.8 0 c 82 0 c From the table 4-1 it is clear that the temperature of solar oven increases as the time increases. Also it is observed that the maximum temperature achieve by solar oven without reflector is 820c day time at 01:40pm to 02:30pm. Figure 4-1: Time vs temperature without reflector
50
4.3 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Monday, March 14, 2017 at various times. The data obtain from solar oven with reflector is given below in table 4-2. Table 4-2: Solar oven with reflector Time Environment Temperature Oven Temperature 11:00-11:50 23 0 c 70 0 c 12:0-12:50 23.5 0 c 78 0 c 01:00-01:50 24 0 c 91 0 c 01:50-02:40 25 0 c 104 0 c In table 4-2 the maximum value of temperature of solar oven with reflector is 104 0 c at 01:50pm to 02:40pm. Figure 4-2: Time vs temperature with reflector From figure 4-1 and 4-2 it is observed that the temperature of solar oven with reflector is higher when compared with the temperature of solar oven without reflector. The maximum achievable
51 temperature without reflector is 82oc and the maximum temperature that achieve with reflector is 104oc. show in figure 4.2. Figure 4-3: Time vs temperature with and without reflector in March 2017
52
4.4 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Monday, April 05, 2017 at various times. The data obtain from solar oven with reflector is given below in table4-3. Table 2-3: Solar oven with reflector Time Environment Temperature Oven Temperature 11:00-11:50 27 0 c 80 0 c 12:0-12:50 31.5 0 c 93 0 c 01:00-01:50 32 0 c 102 0 c 01:50-02:40 33 0 c 109 0 c From the table 4-3 it is clear that the temperature of solar oven increases as the time increases. Also it is observed that the maximum temperature achieve by solar oven with reflector is 1090c day time at 01:40pm to 02:30pm. Figure 4-4: Time vs temperature with reflector
53
4.5 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Tuesday, April 06, 2017 at various times. The data obtain from solar oven with reflector is given below in table 4-4. Table 4-4: Solar oven with reflector Time Environment Temperature Oven Temperature 10:00-10:50 23.3 0 c 70 0 c 11:20-12:10 26 0 c 91 0 c 12:40-01:30 310 c 1070 c 01:40-02:30 31.5 0 c 113 0 c In table 4-4 the maximum value of temperature of solar oven with reflector is 113 0 c at 01:50pm to 02:40pm. Figure 4-5: Time vs temperature with reflector
54
4.6 Solar oven with reflector: The experiment was conducted on solar oven with reflector on Monday, April 07, 2017 at various times. The data obtain from solar oven with reflector is given below in table 4-5. Table 4-5: Solar oven with reflector Time Environment Temperature Oven Temperature 11:00-11:50 27 0 c 95 0 c 12:0-12:50 31.5 0 c 104 0 c 01:00-01:50 32 0 c 108 0 c 01:50-02:40 33 0 c 1170 c From the table 4-5 it is clear that the temperature of solar oven increases as the surrounding temperature increases. Also it is observed that the maximum temperature achieve by solar oven with reflector is 1170c day time at 01:50pm to 02:40pm. Figure 4-6: Time vs temperature with reflector
55 All the temperatures of solar oven is shown in figure 4-7. The experiments were conducted in various days of March and April the maximum temperature achieved in April is 1170c. The maximum temperature difference between oven and environment temperature is 810c with reflector in March and 940c in April. Figure 4-7: Time vs temperature with and without reflector.
56
Conclusion
The maximum temperature achieved without reflector in March 13, 2017 was 820c from 01:40 to 02:30PM when the surrounding temperature was 25 0c.
The maximum temperature achieve with reflector in March 14, 2017 was 1040c from 01:50 to 02:40PM when the surrounding temperature was 25oc.
Three experiments were conducted with reflector in April 2017. The maximum temperature achieve was 117oc from 01:50 to 02:40PM when the surrounding temperature was 33oc in April 07, 2017.
Time duration to achieve maximum temperature value is 50 minutes and the best day time for achieving the maximum temperature value is 12:00 PM to 2:00 PM.
The average temperature achieve in April was higher then the average temperature achieve in March.
This oven is able to bake cakes or grill meat without any traditional source of energy in remote areas. .
57
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