GAME: Measuring Length & Weight
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GAME 2:
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Monday, September 14, 2009
Friday, January 30, 2009
My Portable Multipurpose Solar Cooker
Welcome! This post is as part of my assignment, EDZ440 Independent study.
1.0.0 Introduction:
This project is done to fulfill the requirement of my course, EDZ440- Independent Study. It allows us to choose any area and topics that we are interested in. Further study is done on the topics chosen over the semester.
As my particular interest in conservation of environment, I studied on renewable energy—the solar energy. One of the primary demands for energy in this world is for the cooking of food. In developing countries, the major energy sources for cooking are fuel wood and agricultural residues. Generally, the primary energy sources today are fossil fuels, which supply approximately 90% of the energy consumed by people (Botkin and Keller, 2005). All other sources are considered alternatively energy and are divided into renewable energy and non-renewable energy. Non-renewable energy alternative energy sources include nuclear energy and geothermal energy. For examples, nuclear energy as a non-renewable energy source because it requires a mineral fuel mined from Earth. The geothermal energy is considered non-renewable for the most part due to heat can be extracted from the Earth. However, renewable resources are solar energy, hydro power, wind power, hydrogen produced from water, and energy derived from biomass such as crops, wood, and so forth. However, large consumption of fuel wood for cooking contributes to deforestation, desertation and global warming. One alternative that could help supplement the conventional cooking is solar cooking. Solar cooking uses solar energy as the energy source for cooking. It is widely used in developing countries or areas where solar radiation is available at a large scale and there is scarcity of cooking fuel or other energy forms.
Solar energy is a very large and unlimited source of energy. Solar energy is the sun’s energy relies on nuclear fusion, which is an atomic reaction in which the centre of atoms (nuclei) of one kind combine together to make a larger atom of a different kind. A great amount of energy released is resulted by the atoms are bashing together. The hydrogen is converted to helium in the sun, so that the solar atomic fusion four hydrogen nuclei join together to form a single helium nucleus. The total amount of solar energy reaching the Earth’s surface is tremendous. For example, on a global scale, 10 weeks of solar energy is roughly equivalent to the energy stored in all known reserves of oil, coal, and natural gas on Earth. According to Sukhatme (1996), the power from the Sun intercepted by the Earth is approximately 1.8 x 1011 MW, which is very much larger than the entire commercial energy sources consumption rate on the Earth. On the other hand, according to Jackson and Lofstedt (1998), solar energy is absorbed at Earth’s surface at an average rate of 120,000 TW (1 TW equals to 1012 W), which is about 10,000 times the total global demand for energy.
Besides that, solar energy is an environmentally clean source of energy, unlike fossil fuels and nuclear power. It is also free and available abundantly in most countries of the world. These factors make solar energy one of the most promising alternative energy sources. However, there are some problems related with its use. The main problem is that it is a dilute source of energy where the solar radiation flux available even in the hottest regions on Earth is low. Consequently, large collecting areas are needed in many applications which result in excessive cost. In addition to that, its availability varies widely with the time. The variation occurs daily because of the day-night cycle and also seasonally because the Earth’s orbit around the Sun. Variations also occurs because of the local weather conditions.
Thus, the product I produced from my study is a solar cooker. As environmental conservation is concerned, the materials used are mainly recycled materials like old newspaper and boxes. There are many types of solar cookers with difference performance are produced and used by people around the world. The samples of common solar cooker can be accessed via search engines. Two generic types of cookers were identified from the initial invention of the solar cooker, namely the box-type and the solar concentration-type (Ekechukwu & Ugwuoke, 2002). However, the experiment done by Tan (2008) has proven “Hot Pot” as the best solar cooking device.
Box-type cooker is cheaper and simpler to construct and operate than the concentrator types. It is the simplest device to collect the incoming solar radiation and convert it into heat energy. Besides, the problem of tracking for the locations with high diffuse solar radiation ratios is avoided. The item to be cooked has only to be placed inside and taken out, so that with some experience, the operator does not have to spend much time under the Sun. (Sukhatme, 1996). However, the are some disadvantages such as the ineffectiveness of the base design lower the expected performance by the steam condensation on the inside surfaces which reduces the transmission of the glazing and sometimes causes corrosion of the absorber surfaces.
A concentrating cooker such as the parabolic design of the solar cooker is more efficient in sunlight reflection due to its ability to focus light on the main spot point. It is reported to be the most successful solar collector and reflector compared to others solar cooker design. Thus, this model is most commonly promoted, developed and modified for better cooking in indoor and outdoor cooking by the families and also economically produced in the industry. However, the food cooked in the concentrating cooker is spilled frequently unless a vapour tight vessel is used. Furthermore, some form of tracking is needed which adds to the cost of the device. It has been concluded that the cooker aspect ratio, reflector angle and cooker orientation are the main factors affecting the cooker performance (Amer, 2002).
3.0.0 Aim and Learning Outcomes:
3.1.0 Aim:
My personal goal to be achieved from this project is come out with a cost effective, save, durable, and portable solar cooker that can cook utilizing renewable energy.
3.2.0 Learning Outcomes:
I want students to be able to:
* learn in a fun way;
* understand the science concepts behind a solar cooker;
* appreciate and make use of renewable energies;
* design and construct a solar cooker; and
* build up the love to nature and concern on environmental issues.
4.0.0 Science behind the Project:
4.1.0 Heat
The solar cooker only needs the sun’s energy to heat the food. Heat is the energy associated with the random motions of atoms or molecules or even smaller units that compose matter. Heat causes substances to rise in temperature, fuse, evaporate, expand, or undergo various other related changes.
4.2.0 Conduction, convection and radiation
Heat can be transferred by conduction, convection and radiation. These are the three ways in which heat is transferred from one place to another. Conduction is the transfer of heat through matter, particle by particle. When heated, the molecules are move and collide with each another. As a result of the collision, the energy and momentum are exchanged and transferred from one particle to another, in effect transferring heat. Heat transfer through the movement of gases or liquids is called convection. When a non-uniform temperature exists in a fluid, the circulatory movement occurs. The warmer or less dense fluid is pushed away from the source of heat by cooler, dense matter. The energy carried by the moving fluids. For example, ocean current is formed due to convection, since the water at the equator graining more heat from the sun than water at the poles. Radiation is the transfer of heat that does not require matter in transmission. It is an energy travelling as electromagnetic waves. Therefore, there are three types of heat transferation, and all three are used to build a solar cooker.
4.3.0 The law of thermodynamics
The laws of thermodynamics are the laws to describe the system of heat energy. They encompass the idea: energy is never created or destroyed, but is converted from one form to another. At times, energy dissipates and it is hard to measure, but it never “lost”. Heat energy flows in one direction, from warmer matter to cooler, until equilibrium is achieved.
4.4.0 Limitation
The common problems associated with solar cooker design (Kuhnke, 1987; Grupp, 1990) include limitation to daytime and outdoor use during sunny weather, small capacity and slow cooking speed. Therefore, some of the problems need to overcome like an indoor institutional hybrid cookers of the type designed by Scheffler (Oehler and Scheffler, 1994; Otieno and Scheffler, 1989) have been constructed and installed. Sunlight is a “fuel” that required in solar cooking. An outdoor spot is needed for the solar cooker that is sunny for several hours and protected from the strong wind. If the day is cloudy day or at night time, the solar cookers do not function since there is no sunlight.
4.5.0 How solar cooker cook
When the sunlight reached to the surface of food insulated by thin metal pots or glass, the sunlight will convert to the heat energy and cook the food. However, there are difference of sunlight reflectance and absorbance on light surface and black surface of the body. If the body is black colour, the sunlight is more to absorb, while the light surface is more likely to reflect the sunlight. Dark surface get very hot in sunlight, whereas light surface do not. Thus, food cooks best in the dark, shallow, thin metal pots with dark, tight fitting lids to hold in heat and moisture. A transparent heat trap around the dark pot lets in sunlight, but still keeps in the heat. Usually, a clear, heat-resistant plastic bag or large inverted lass bowl or an insulated box with a glass or plastic window is required to retain the heat.
According to Njomo (1995), he stated that using glass as a solar collector cover in rural of developing countries has two major disadvantages, which as its high cost and its fragility both during transportation and in service. However, the transparent plastic covers have been used widely in these zones which are particularly polyethylene because of its widespread availability to construct moderate cost solar air heaters. Choudhury et al. (1995), Sfeir and Guarracino (1981) said it is impossible to predict the performance of a plastic covered solar collector using the classical models which assume that the transparent cover is totally opaque to infrared radiation. The hypothesis is quite correct for a glass cover but is unacceptable for some plastic covers as polyethylene which transmissivity to infrared radiations. However, Njomo (1991) stressed heat transfer model taking into account. This partial transparency of a solar collector covers towards infrared radiation. Solar collector considered by Njomo (1991), the air is passing between the plastic cover and the absorber plate in the air. There are two disadvantages of solar heater operators are the collector performance. First, highly sensitive to air leakage and it is quite difficult to obtain perfect air tightness with plastic cover which the small accidental perforations that can occur.
On the other hand, considering the high dust content of atmosphere during the dry season in tropical countries, materials used must be carefully chosen. Das and Chakraverty (1991) reported dry climate lead to the dust deposits both on the lower face of the plastic cover which is by electrostatic forces and on the lowering of the plastic cover transmittance as well as the absorber plate’s absorbance towards solar radiation. For these reasons, it seems that plastic is the best configuration to get sustainable performances to solar air cooker in tropical countries that with a confined and immobile air layer between the cover and the absorber plate and their air flow to be heated passing between the absorber plate and the bottom of the collector. Njomo (1991) neglected that the infrared absorbance of the plastic cover is no approximation has been done. So, the established radiation balances can be used for any type of transparent cover such as plastic, glass or other.
One or more reflectors are employed to bounce additional light into the solar box to increase cooking temperature. While mirrors are more reflective than simpler such as aluminium foil, the added gain is probably not worth the increased cost and fragility involved with using a mirror. The reflectors had an excellent spectacular characteristic. For example, if the aluminium foil reflectors weathered, winkle and collector dust, the reflectance will substantial reduce. The total potential design space is largely unexplored when a flat plate, concentrating and box type in approach and large variety of inventions and products (Grupp, 1922).
5.0.0 Development of Project:
5.1.0 Resources need:
The materials needed to construct solar cookers are easily available. The materials and tools are listed below:
* Unused boxes
* Old newspaper & magazine
* Microwave wrap
* Aluminium foil
* Paint
* Wasted wood
* Nail
* String * Aluminium soft drink can
* Used food container/ pot
* Scissors
* Masking tape
* Double-sided tape
* Glue
* Hammer
* Meat thermometer
5.2.0 Rationale for materials chosen:
5.2.1 The “GLAD Microwave Wrap”
The top part must be transparent allowing sunlight to goes in, easy to observe the cooking process and easy visual confirmation of when the food is cooked (colour changed). Although Tan (2008) has proven glass lid works better than oven bags, I still use microwave as it is easily available, light weight, water resistance, safe and able to stand for high temperature but not durable. I found a large piece of abandoned glass sheet but I do not use it for “My Portable Multipurpose Solar Cooker” because I could not find a way to cut it. Moreover, it should be portable (easy to carry) and glass is fragile. It breaks easily when knocked or dropped. “GLAD Microwave Wrap” is chosen from the range of microwave wraps because it is the cheapest.
5.2.2 Boxes and old news paper
Boxes and newspaper are easily obtained from the environment. Boxes are sturdy enough and easy to shape.
5.2.3 The “DIAMOND Aluminium foil”
I found unused aluminium sheet from the neighbourhood’s recycle center but aluminium foil is chosen because it is easier to be cut and shape compared to aluminium sheets as planned. Moreover, it is more suitable and easier to be fixed on the solar cooker. It is highly reflective but the reflective level will reduce as it oxidized (although it is wrapped or covered with a layer of microwave wrap). This can easily solved by adding or replacing a new piece of aluminium foil.
5.2.4 Spray paint
I have decided to paint my solar cooker by spay paint as it is easy to apply and cheaper than the Dulux Gloss Finish which I initially planned to use. I made the decision considering the cost factor.
5.3.0 Cost:
1.0.0 Introduction:
This project is done to fulfill the requirement of my course, EDZ440- Independent Study. It allows us to choose any area and topics that we are interested in. Further study is done on the topics chosen over the semester.
As my particular interest in conservation of environment, I studied on renewable energy—the solar energy. One of the primary demands for energy in this world is for the cooking of food. In developing countries, the major energy sources for cooking are fuel wood and agricultural residues. Generally, the primary energy sources today are fossil fuels, which supply approximately 90% of the energy consumed by people (Botkin and Keller, 2005). All other sources are considered alternatively energy and are divided into renewable energy and non-renewable energy. Non-renewable energy alternative energy sources include nuclear energy and geothermal energy. For examples, nuclear energy as a non-renewable energy source because it requires a mineral fuel mined from Earth. The geothermal energy is considered non-renewable for the most part due to heat can be extracted from the Earth. However, renewable resources are solar energy, hydro power, wind power, hydrogen produced from water, and energy derived from biomass such as crops, wood, and so forth. However, large consumption of fuel wood for cooking contributes to deforestation, desertation and global warming. One alternative that could help supplement the conventional cooking is solar cooking. Solar cooking uses solar energy as the energy source for cooking. It is widely used in developing countries or areas where solar radiation is available at a large scale and there is scarcity of cooking fuel or other energy forms.
Solar energy is a very large and unlimited source of energy. Solar energy is the sun’s energy relies on nuclear fusion, which is an atomic reaction in which the centre of atoms (nuclei) of one kind combine together to make a larger atom of a different kind. A great amount of energy released is resulted by the atoms are bashing together. The hydrogen is converted to helium in the sun, so that the solar atomic fusion four hydrogen nuclei join together to form a single helium nucleus. The total amount of solar energy reaching the Earth’s surface is tremendous. For example, on a global scale, 10 weeks of solar energy is roughly equivalent to the energy stored in all known reserves of oil, coal, and natural gas on Earth. According to Sukhatme (1996), the power from the Sun intercepted by the Earth is approximately 1.8 x 1011 MW, which is very much larger than the entire commercial energy sources consumption rate on the Earth. On the other hand, according to Jackson and Lofstedt (1998), solar energy is absorbed at Earth’s surface at an average rate of 120,000 TW (1 TW equals to 1012 W), which is about 10,000 times the total global demand for energy.
Besides that, solar energy is an environmentally clean source of energy, unlike fossil fuels and nuclear power. It is also free and available abundantly in most countries of the world. These factors make solar energy one of the most promising alternative energy sources. However, there are some problems related with its use. The main problem is that it is a dilute source of energy where the solar radiation flux available even in the hottest regions on Earth is low. Consequently, large collecting areas are needed in many applications which result in excessive cost. In addition to that, its availability varies widely with the time. The variation occurs daily because of the day-night cycle and also seasonally because the Earth’s orbit around the Sun. Variations also occurs because of the local weather conditions.
Thus, the product I produced from my study is a solar cooker. As environmental conservation is concerned, the materials used are mainly recycled materials like old newspaper and boxes. There are many types of solar cookers with difference performance are produced and used by people around the world. The samples of common solar cooker can be accessed via search engines. Two generic types of cookers were identified from the initial invention of the solar cooker, namely the box-type and the solar concentration-type (Ekechukwu & Ugwuoke, 2002). However, the experiment done by Tan (2008) has proven “Hot Pot” as the best solar cooking device.
Box-type cooker is cheaper and simpler to construct and operate than the concentrator types. It is the simplest device to collect the incoming solar radiation and convert it into heat energy. Besides, the problem of tracking for the locations with high diffuse solar radiation ratios is avoided. The item to be cooked has only to be placed inside and taken out, so that with some experience, the operator does not have to spend much time under the Sun. (Sukhatme, 1996). However, the are some disadvantages such as the ineffectiveness of the base design lower the expected performance by the steam condensation on the inside surfaces which reduces the transmission of the glazing and sometimes causes corrosion of the absorber surfaces.
A concentrating cooker such as the parabolic design of the solar cooker is more efficient in sunlight reflection due to its ability to focus light on the main spot point. It is reported to be the most successful solar collector and reflector compared to others solar cooker design. Thus, this model is most commonly promoted, developed and modified for better cooking in indoor and outdoor cooking by the families and also economically produced in the industry. However, the food cooked in the concentrating cooker is spilled frequently unless a vapour tight vessel is used. Furthermore, some form of tracking is needed which adds to the cost of the device. It has been concluded that the cooker aspect ratio, reflector angle and cooker orientation are the main factors affecting the cooker performance (Amer, 2002).
3.0.0 Aim and Learning Outcomes:
3.1.0 Aim:
My personal goal to be achieved from this project is come out with a cost effective, save, durable, and portable solar cooker that can cook utilizing renewable energy.
3.2.0 Learning Outcomes:
I want students to be able to:
* learn in a fun way;
* understand the science concepts behind a solar cooker;
* appreciate and make use of renewable energies;
* design and construct a solar cooker; and
* build up the love to nature and concern on environmental issues.
4.0.0 Science behind the Project:
4.1.0 Heat
The solar cooker only needs the sun’s energy to heat the food. Heat is the energy associated with the random motions of atoms or molecules or even smaller units that compose matter. Heat causes substances to rise in temperature, fuse, evaporate, expand, or undergo various other related changes.
4.2.0 Conduction, convection and radiation
Heat can be transferred by conduction, convection and radiation. These are the three ways in which heat is transferred from one place to another. Conduction is the transfer of heat through matter, particle by particle. When heated, the molecules are move and collide with each another. As a result of the collision, the energy and momentum are exchanged and transferred from one particle to another, in effect transferring heat. Heat transfer through the movement of gases or liquids is called convection. When a non-uniform temperature exists in a fluid, the circulatory movement occurs. The warmer or less dense fluid is pushed away from the source of heat by cooler, dense matter. The energy carried by the moving fluids. For example, ocean current is formed due to convection, since the water at the equator graining more heat from the sun than water at the poles. Radiation is the transfer of heat that does not require matter in transmission. It is an energy travelling as electromagnetic waves. Therefore, there are three types of heat transferation, and all three are used to build a solar cooker.
4.3.0 The law of thermodynamics
The laws of thermodynamics are the laws to describe the system of heat energy. They encompass the idea: energy is never created or destroyed, but is converted from one form to another. At times, energy dissipates and it is hard to measure, but it never “lost”. Heat energy flows in one direction, from warmer matter to cooler, until equilibrium is achieved.
4.4.0 Limitation
The common problems associated with solar cooker design (Kuhnke, 1987; Grupp, 1990) include limitation to daytime and outdoor use during sunny weather, small capacity and slow cooking speed. Therefore, some of the problems need to overcome like an indoor institutional hybrid cookers of the type designed by Scheffler (Oehler and Scheffler, 1994; Otieno and Scheffler, 1989) have been constructed and installed. Sunlight is a “fuel” that required in solar cooking. An outdoor spot is needed for the solar cooker that is sunny for several hours and protected from the strong wind. If the day is cloudy day or at night time, the solar cookers do not function since there is no sunlight.
4.5.0 How solar cooker cook
When the sunlight reached to the surface of food insulated by thin metal pots or glass, the sunlight will convert to the heat energy and cook the food. However, there are difference of sunlight reflectance and absorbance on light surface and black surface of the body. If the body is black colour, the sunlight is more to absorb, while the light surface is more likely to reflect the sunlight. Dark surface get very hot in sunlight, whereas light surface do not. Thus, food cooks best in the dark, shallow, thin metal pots with dark, tight fitting lids to hold in heat and moisture. A transparent heat trap around the dark pot lets in sunlight, but still keeps in the heat. Usually, a clear, heat-resistant plastic bag or large inverted lass bowl or an insulated box with a glass or plastic window is required to retain the heat.
According to Njomo (1995), he stated that using glass as a solar collector cover in rural of developing countries has two major disadvantages, which as its high cost and its fragility both during transportation and in service. However, the transparent plastic covers have been used widely in these zones which are particularly polyethylene because of its widespread availability to construct moderate cost solar air heaters. Choudhury et al. (1995), Sfeir and Guarracino (1981) said it is impossible to predict the performance of a plastic covered solar collector using the classical models which assume that the transparent cover is totally opaque to infrared radiation. The hypothesis is quite correct for a glass cover but is unacceptable for some plastic covers as polyethylene which transmissivity to infrared radiations. However, Njomo (1991) stressed heat transfer model taking into account. This partial transparency of a solar collector covers towards infrared radiation. Solar collector considered by Njomo (1991), the air is passing between the plastic cover and the absorber plate in the air. There are two disadvantages of solar heater operators are the collector performance. First, highly sensitive to air leakage and it is quite difficult to obtain perfect air tightness with plastic cover which the small accidental perforations that can occur.
On the other hand, considering the high dust content of atmosphere during the dry season in tropical countries, materials used must be carefully chosen. Das and Chakraverty (1991) reported dry climate lead to the dust deposits both on the lower face of the plastic cover which is by electrostatic forces and on the lowering of the plastic cover transmittance as well as the absorber plate’s absorbance towards solar radiation. For these reasons, it seems that plastic is the best configuration to get sustainable performances to solar air cooker in tropical countries that with a confined and immobile air layer between the cover and the absorber plate and their air flow to be heated passing between the absorber plate and the bottom of the collector. Njomo (1991) neglected that the infrared absorbance of the plastic cover is no approximation has been done. So, the established radiation balances can be used for any type of transparent cover such as plastic, glass or other.
One or more reflectors are employed to bounce additional light into the solar box to increase cooking temperature. While mirrors are more reflective than simpler such as aluminium foil, the added gain is probably not worth the increased cost and fragility involved with using a mirror. The reflectors had an excellent spectacular characteristic. For example, if the aluminium foil reflectors weathered, winkle and collector dust, the reflectance will substantial reduce. The total potential design space is largely unexplored when a flat plate, concentrating and box type in approach and large variety of inventions and products (Grupp, 1922).
5.0.0 Development of Project:
5.1.0 Resources need:
The materials needed to construct solar cookers are easily available. The materials and tools are listed below:
* Unused boxes
* Old newspaper & magazine
* Microwave wrap
* Aluminium foil
* Paint
* Wasted wood
* Nail
* String * Aluminium soft drink can
* Used food container/ pot
* Scissors
* Masking tape
* Double-sided tape
* Glue
* Hammer
* Meat thermometer
5.2.0 Rationale for materials chosen:
5.2.1 The “GLAD Microwave Wrap”
The top part must be transparent allowing sunlight to goes in, easy to observe the cooking process and easy visual confirmation of when the food is cooked (colour changed). Although Tan (2008) has proven glass lid works better than oven bags, I still use microwave as it is easily available, light weight, water resistance, safe and able to stand for high temperature but not durable. I found a large piece of abandoned glass sheet but I do not use it for “My Portable Multipurpose Solar Cooker” because I could not find a way to cut it. Moreover, it should be portable (easy to carry) and glass is fragile. It breaks easily when knocked or dropped. “GLAD Microwave Wrap” is chosen from the range of microwave wraps because it is the cheapest.
5.2.2 Boxes and old news paper
Boxes and newspaper are easily obtained from the environment. Boxes are sturdy enough and easy to shape.
5.2.3 The “DIAMOND Aluminium foil”
I found unused aluminium sheet from the neighbourhood’s recycle center but aluminium foil is chosen because it is easier to be cut and shape compared to aluminium sheets as planned. Moreover, it is more suitable and easier to be fixed on the solar cooker. It is highly reflective but the reflective level will reduce as it oxidized (although it is wrapped or covered with a layer of microwave wrap). This can easily solved by adding or replacing a new piece of aluminium foil.
5.2.4 Spray paint
I have decided to paint my solar cooker by spay paint as it is easy to apply and cheaper than the Dulux Gloss Finish which I initially planned to use. I made the decision considering the cost factor.
5.3.0 Cost:
* Please come back for updates.
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