Another recent addition to the family of Parabolic cooker comes from the prolific inventor Mr Deris of California. The Parabola it self is simple, he seems to have discarded the interesting design of square Parabola invented by himself. The parabola he uses is held vertically, and it directs the focused rays on to a Cooking vessel kept on a reflector kept horizontally on the ground.
Interestingly way back in 1980, I had proposed that a reflector/focusing device kept outside or in a suitable position would point focus the image in the house which could then be used for cooking. This design you would see under Type ---but such a concept has already taken shape, independently at Bahai institute in India and with the help of a parabolic reflector kept out side the hut cooking even Chapathis are being cooked.
Fig 3a1 & 2 Photos from Bahai Institute, India ( Ref. their site on the web )
The following diagram shows the principle of Scheffler's reflective cooker design in detail.
The photos bellow shows Scheffler's reflective cooker, a 2.7 m dia cooker, just out side an Indian Home, The photos are from ecosolar.com. The second photo shows a lady cooking in a small kitchen.
The parabolic cookers are being uses in Africa as well and the photo below confirms it further.
Attempt are on worldwide to form parabolas from other materials. In India it is being made from mud. The photo included, taken form Solarcooking.org site, confirms this.
Many interesting variations have been reported, and some of the following photos, taken from Solar cooking.org, are self explanatory.
Note the light but stable stand arrangement, looks like it could be easily tucked in a corner and easily transported as well. ( Ref. solracooking.org site )
Monday, December 31, 2007
Wednesday, December 19, 2007
Know About Solar Power
The Bernard Solar Panel Cooker
A simple, portable model that may open new horizons
It is generally assumed that a solar cooker should have some minimal capacity in order to work properly. For instance, in the booklet Your Own Solar Box, Solar Cookers International (SCI) recommends an inner box at least 45 cm X 55 cm (18" x 22"). The result is a rather large box, well suited to family use, but which can prove unnecessarily cumbersome in some cases
Smaller cookers would be appreciated by the following:
* people living or traveling alone,
* people living with their family but needing a special diet,
* elderly people who feel reluctant to carry a heavy box,
* teenagers wishing to build and experiment their own first cooker.
If you belong to one of these categories, here is how you can build a cheap and fairly efficient small cooker.
Choose a cardboard box (figure 1) with the height BC greater than the width DC. For example, in my own cooker BC = 30 cm (about 12"), DC = 23 cm (9") and CG = 25 cm (10").
Cut the flaps off the box. Then cut the seams along FG and GC. Do the same on the other side along EH and HD. The carton folds out to a flat assembly of five rectangles as shown in figure 2 (Letters appearing twice on this figure indicate two points which were the same point before cutting). If the cardboard is thin, reinforce the rectangle CDHG by gluing another rectangular piece of cardboard onto it to better insulate the bottom of the pot. Then glue aluminum foil to one side of the five rectangles (the inside of the original box).
Now, keeping the rectangle CDHG horizontal on a table or on level ground, position the other rectangles as shown in figure 3. The front "mirror" EFGH is tilted about 30 degrees above the horizontal plane (Put a rock or other object under it). The "wing mirrors" BFGC and AEHD are vertical, the angles GCG and HDH being about 45 degrees. A few rocks as shown in figure 4 will be helpful, especially in windy weather.
The black cooking pot is put on the horizontal base CDHG and covered with a colorless glass salad-bowl [or oven cooking bag, see next article, ed.] replacing the glass window of a classical box cooker. To avoid convective heat losses, the diameter of the salad-bowl should not exceed the width CD.
A more convenient way of keeping the reflective system in good shape is to mount the panels on a wooden board in which you will drive a few nails on each side of GC and HD to maintain the wing mirrors in their correct position (see figure 5).
Although this cooker uses (slightly) concentrated sunlight, it is not necessary to worry about a constant tracking of the sun. A big vertical nail at the front of the board can act as an "orientation indicator". Its shadow should be seen on the white triangular piece of paper glued on the board (figure ) and whose 30 degree angle roughly corresponded to 2 hours of absentee cooking in my experiments. Most of the following results have been obtained without any readjustment of the cooker orientation.
All cooking was done in an aluminum pot painted black. Scrounged glass jars may be used, even without the salad-bowl, but cooking times are increased.
The latitude of Paris is about 45 degrees. When cooking at lower latitudes the vertical reflectors become less effective; it remains to be tested whether this design will work as well there. On the other hand, people living at latitudes above 40 degrees could find it more efficient than a simple, one-reflector box cooker. I'm interested in knowing the results obtained by readers who live in other parts of the world.
Roger Bernard can be contacted at
La Association Lyonnaise pour l'Etude et le Developpement de l'Energie Solaire. A.L.E.D.E.S.
Université de Lyon
Bat. 721,
69 622 - Villeurbanne
France
Barbara Kerr Tests The Solar Panel Cooker
I am really excited by the opportunities opened up by Roger Bernard's panel cooker design. We have known that multiple reflectors can be used to concentrate solar radiation, but until I watched my lentil stew bubbling under the glass salad bowl, I did not see this as a serious cooker. Suddenly, I realized that an oven cooking bag could be used in place of the salad bowl. This would provide a very abbreviated solar "box." All we have learned over the years with box-type cookers could be helpful in utilizing Solar Panel Cookers (SPCs). Now we may have both our "oven" and our "hot plate."
By limiting ourselves to flat foil-covered panels, the danger of eye damage is greatly reduced but remains a problem. Retinal damage, which can occur when sunlight shines into the eyes, is not painful. You cannot tell it is happening, but a retinal burn produces permanent damage and can result in blindness. Be extremely careful if using anything that concentrates the light or reflects the sunlight directly into your eyes.
The first cooker I made based on Roger Bernard's specifications would not fold neatly. The illustrations show a slight modification of Roger's design. Since the panels are all the same size, they fold to form a flat packet which is so small and light-weight that it can be used by backpackers and others who do not have space for much storage. The extra cuts and folds also provide areas where rocks can be placed to anchor the panels without blocking any sunshine. Our winds are fierce and unpredictable! I have found that a cardboard SPC in this configuration tolerates the wind very well.
Place the cooking pot in an oven cooking bag with the opening at the top so you can open the bag, check the food and seal it again without disturbing the cooking. And that part of the bag is usually dry. This is important because food in a panel cooker usually does need to be stirred and checked, since the heat is not as even.
First I closed the baking bags with clothes pins--too heavy and bulky. Then with paper clips tore up the baking bag which otherwise was good for many uses. Then with a thin piece of wire worked well but the twisted wire broke after several uses. Now I am using wire but simply wrapping it tightly around the baking bag top, without twisting. Since there is no pressure, it works fine and the twist ties last a long time.
Too often I have found jars or pots have vigorously boiled over, spilling juice and making a mess. Got to remember to allow more space at the top to contain a boil, at least until I get a handle on when this is going to happen. A delightful problem. Food does not have the delicately enhanced flavor of SBC cooked food, probably because of the higher temperatures.
Then I noticed a cold spot on the foiled reflector directly under a pot and remembered the advantage the University of Washington engineers found through elevating the SBC tray off the cardboard bottom. I looked around the kitchen for an "elevator" and seized on canning rings. It is clear that pots heat faster when sitting on a canning ring than when sitting on the foiled cardboard. Darkened canning rings work better than shiny, of course. But the center is dark and I wondered if it would help to get light to shine under the pot. I put three little pebbles, dark and oiled, under a pot. That seems to work even better. I like that . . . three little pebbles used in memory of the historic three stone fire that has served humanity for thousands of years. Women, nostalgic for the wood fire where there is no more wood, might even take tiny pieces of wood and form a little "fire" within the pebbles under the pot. It would keep us from feeling so torn away from roots.
Solar cooking continues to get simpler. I have put major attention on simple solar cooker designs for 20 years, working to have them easier and more accessible to everyone. Today, I held a Solar Panel Cooker and realized our 20 year mountain of work had truly brought forth a mouse. A mighty mouse! Simplicity is so difficult...difficult to see, not difficult to do, once the idea forms. I think that box-style cookers will remain part of the solar kitchen where time, material and circumstances dictate, but the SPC has opened up a new level of simplicity.
We are doing pretty well with reducing the materials needed to solar cook. If only we could eliminate the need for oven cooking bags of heat-resistant nylon. I used regular kitchen plastic bags and they seemed to hold up under the heat for several cooking times. But January 12 was brighter, the air was warmer, and three different kinds of regular plastic bags melted. I guess we will have to stick with baking bags . . . too bad. But the baking bags I started with two months ago are still in good shape, having cooked many dishes and been washed and dried many times. Perhaps they can be obtained wholesale and distributed one or two at a time where they are not available in stores. We should be able to get them wholesale if someone puts a little effort into it.
It seems that "open-box" cookers will now be an integral part of serious solar cooking. It will just take finding out specifically how to use them.
A simple, portable model that may open new horizons
It is generally assumed that a solar cooker should have some minimal capacity in order to work properly. For instance, in the booklet Your Own Solar Box, Solar Cookers International (SCI) recommends an inner box at least 45 cm X 55 cm (18" x 22"). The result is a rather large box, well suited to family use, but which can prove unnecessarily cumbersome in some cases
Smaller cookers would be appreciated by the following:
* people living or traveling alone,
* people living with their family but needing a special diet,
* elderly people who feel reluctant to carry a heavy box,
* teenagers wishing to build and experiment their own first cooker.
If you belong to one of these categories, here is how you can build a cheap and fairly efficient small cooker.
Choose a cardboard box (figure 1) with the height BC greater than the width DC. For example, in my own cooker BC = 30 cm (about 12"), DC = 23 cm (9") and CG = 25 cm (10").
Cut the flaps off the box. Then cut the seams along FG and GC. Do the same on the other side along EH and HD. The carton folds out to a flat assembly of five rectangles as shown in figure 2 (Letters appearing twice on this figure indicate two points which were the same point before cutting). If the cardboard is thin, reinforce the rectangle CDHG by gluing another rectangular piece of cardboard onto it to better insulate the bottom of the pot. Then glue aluminum foil to one side of the five rectangles (the inside of the original box).
Now, keeping the rectangle CDHG horizontal on a table or on level ground, position the other rectangles as shown in figure 3. The front "mirror" EFGH is tilted about 30 degrees above the horizontal plane (Put a rock or other object under it). The "wing mirrors" BFGC and AEHD are vertical, the angles GCG and HDH being about 45 degrees. A few rocks as shown in figure 4 will be helpful, especially in windy weather.
The black cooking pot is put on the horizontal base CDHG and covered with a colorless glass salad-bowl [or oven cooking bag, see next article, ed.] replacing the glass window of a classical box cooker. To avoid convective heat losses, the diameter of the salad-bowl should not exceed the width CD.
A more convenient way of keeping the reflective system in good shape is to mount the panels on a wooden board in which you will drive a few nails on each side of GC and HD to maintain the wing mirrors in their correct position (see figure 5).
Although this cooker uses (slightly) concentrated sunlight, it is not necessary to worry about a constant tracking of the sun. A big vertical nail at the front of the board can act as an "orientation indicator". Its shadow should be seen on the white triangular piece of paper glued on the board (figure ) and whose 30 degree angle roughly corresponded to 2 hours of absentee cooking in my experiments. Most of the following results have been obtained without any readjustment of the cooker orientation.
All cooking was done in an aluminum pot painted black. Scrounged glass jars may be used, even without the salad-bowl, but cooking times are increased.
The latitude of Paris is about 45 degrees. When cooking at lower latitudes the vertical reflectors become less effective; it remains to be tested whether this design will work as well there. On the other hand, people living at latitudes above 40 degrees could find it more efficient than a simple, one-reflector box cooker. I'm interested in knowing the results obtained by readers who live in other parts of the world.
Roger Bernard can be contacted at
La Association Lyonnaise pour l'Etude et le Developpement de l'Energie Solaire. A.L.E.D.E.S.
Université de Lyon
Bat. 721,
69 622 - Villeurbanne
France
Barbara Kerr Tests The Solar Panel Cooker
I am really excited by the opportunities opened up by Roger Bernard's panel cooker design. We have known that multiple reflectors can be used to concentrate solar radiation, but until I watched my lentil stew bubbling under the glass salad bowl, I did not see this as a serious cooker. Suddenly, I realized that an oven cooking bag could be used in place of the salad bowl. This would provide a very abbreviated solar "box." All we have learned over the years with box-type cookers could be helpful in utilizing Solar Panel Cookers (SPCs). Now we may have both our "oven" and our "hot plate."
By limiting ourselves to flat foil-covered panels, the danger of eye damage is greatly reduced but remains a problem. Retinal damage, which can occur when sunlight shines into the eyes, is not painful. You cannot tell it is happening, but a retinal burn produces permanent damage and can result in blindness. Be extremely careful if using anything that concentrates the light or reflects the sunlight directly into your eyes.
The first cooker I made based on Roger Bernard's specifications would not fold neatly. The illustrations show a slight modification of Roger's design. Since the panels are all the same size, they fold to form a flat packet which is so small and light-weight that it can be used by backpackers and others who do not have space for much storage. The extra cuts and folds also provide areas where rocks can be placed to anchor the panels without blocking any sunshine. Our winds are fierce and unpredictable! I have found that a cardboard SPC in this configuration tolerates the wind very well.
Place the cooking pot in an oven cooking bag with the opening at the top so you can open the bag, check the food and seal it again without disturbing the cooking. And that part of the bag is usually dry. This is important because food in a panel cooker usually does need to be stirred and checked, since the heat is not as even.
First I closed the baking bags with clothes pins--too heavy and bulky. Then with paper clips tore up the baking bag which otherwise was good for many uses. Then with a thin piece of wire worked well but the twisted wire broke after several uses. Now I am using wire but simply wrapping it tightly around the baking bag top, without twisting. Since there is no pressure, it works fine and the twist ties last a long time.
Too often I have found jars or pots have vigorously boiled over, spilling juice and making a mess. Got to remember to allow more space at the top to contain a boil, at least until I get a handle on when this is going to happen. A delightful problem. Food does not have the delicately enhanced flavor of SBC cooked food, probably because of the higher temperatures.
Then I noticed a cold spot on the foiled reflector directly under a pot and remembered the advantage the University of Washington engineers found through elevating the SBC tray off the cardboard bottom. I looked around the kitchen for an "elevator" and seized on canning rings. It is clear that pots heat faster when sitting on a canning ring than when sitting on the foiled cardboard. Darkened canning rings work better than shiny, of course. But the center is dark and I wondered if it would help to get light to shine under the pot. I put three little pebbles, dark and oiled, under a pot. That seems to work even better. I like that . . . three little pebbles used in memory of the historic three stone fire that has served humanity for thousands of years. Women, nostalgic for the wood fire where there is no more wood, might even take tiny pieces of wood and form a little "fire" within the pebbles under the pot. It would keep us from feeling so torn away from roots.
Solar cooking continues to get simpler. I have put major attention on simple solar cooker designs for 20 years, working to have them easier and more accessible to everyone. Today, I held a Solar Panel Cooker and realized our 20 year mountain of work had truly brought forth a mouse. A mighty mouse! Simplicity is so difficult...difficult to see, not difficult to do, once the idea forms. I think that box-style cookers will remain part of the solar kitchen where time, material and circumstances dictate, but the SPC has opened up a new level of simplicity.
We are doing pretty well with reducing the materials needed to solar cook. If only we could eliminate the need for oven cooking bags of heat-resistant nylon. I used regular kitchen plastic bags and they seemed to hold up under the heat for several cooking times. But January 12 was brighter, the air was warmer, and three different kinds of regular plastic bags melted. I guess we will have to stick with baking bags . . . too bad. But the baking bags I started with two months ago are still in good shape, having cooked many dishes and been washed and dried many times. Perhaps they can be obtained wholesale and distributed one or two at a time where they are not available in stores. We should be able to get them wholesale if someone puts a little effort into it.
It seems that "open-box" cookers will now be an integral part of serious solar cooking. It will just take finding out specifically how to use them.
Tuesday, December 18, 2007
Know About Solar Power
Panel solar cookers are the first solar cookers that are truly affordable to the world’s neediest. In 1994, a volunteer group of engineers and solar cooks associated with Solar Cookers International developed and produced the first “panel” cooker, the CooKit. Elegant and deceptively simple looking, it is an affordable, effective and convenient solar cooker. It requires a dark, covered pot and one plastic bag per day or one high-temperature plastic bag per month. With a few hours of sunshine, the CooKit makes tasty meals for 5-6 people at gentle temperatures, cooking food and preserving nutrients without burning or drying out. Larger families use two or more cookers. The CooKit weighs half a kilogram, folds to the size of a big book for easy transport. CooKits are now produced independently in 25 countries from a wide variety of materials at a wholesale cost of $3-7 US. We expect that the new hand-assembled CooKits will outlast the manufactured CooKits which last for two years.
CooKits complement other cooking methods needed at night and on cloudy days. Coming about twenty years after the first efforts to replace open fires with improved cooking stoves, the CooKit uses no fuel at all. The CooKit is both user-friendly and environmentally friendly. Families can save scarce, expensive for when they cannot solar cook and when economically capable, add other, higher cost cooking improvements such as modern biomass, smoke hoods, biogas, or liquefied petroleum gas.
The CooKit folds to be about the size of a large notebook when not in use.
The CooKit folds to be about the size of a large notebook when not in use.
The value of CooKits is outlined in the following manner:
Addressing fuelwood scarcities:
* Solar cooking one meal a day, three times a week has been proven to reduce fuelwood consumption and related smoke by one third.
* The CooKit saves more than four times its value in fuelwood each year. With careful use and storage, a CooKit can be used for two years, reducing fuelwood consumption by two tonnes.
Improving health:
* The CooKit can pasteurize household drinking water, making it safe to drink.
* The solar cooking process is smokeless, reducing respiratory diseases and eye irritation
* Solar cooked foods retain vitamins, nutrients and their natural flavors; there is no smoky taste; the foods cook slowly in their own juices. Nutritious, slow-cooking traditional foods (beans, root crops, and some grains) are restored to the family diet
* Clean up is easy as the food never burns or sticks to the cooking pot.
* Solar cooks frequently report that the money they save on cooking fuel purchases is used to for many essentials, such as extra food, school supplies, and medical care.
* Without having to gather wood or dung, breathe smoke, and tend a fire – all associated with traditional cooking – solar cooking is easy and safe for people with AIDS and other illnesses, the elderly, disabled and young orphans.
Rocks can be used to allow the CooKit to be used under windy conditions.
Rocks can be used to allow the CooKit to be used under windy conditions.
Enhancing household and women’s economic status:
* The CooKit represents a new opportunity for women to capitalize on an underserved market and better meet their own cooking energy needs
* Solar cooking saves time as there is less need to tend a fire or collect firewood. A person can cook while at work, at the market, or tending crops. Young girls can attend school instead of searching for fuelwood.
* Solar energy is free and abundant in many areas of Kenya, providing a safe, clean, healthy supplement to traditional fuels.
Co-developers are Roger Bernard of France and Barbara Kerr of the USA, with work also by Ed Pejack, Jay Campbell, and Bev Blum of Solar Cookers International. Extensive field tests in the USA and in many developing countries confirm its performance, convenience, low cost, acceptance, and adaptability to diverse needs.
CooKits complement other cooking methods needed at night and on cloudy days. Coming about twenty years after the first efforts to replace open fires with improved cooking stoves, the CooKit uses no fuel at all. The CooKit is both user-friendly and environmentally friendly. Families can save scarce, expensive for when they cannot solar cook and when economically capable, add other, higher cost cooking improvements such as modern biomass, smoke hoods, biogas, or liquefied petroleum gas.
The CooKit folds to be about the size of a large notebook when not in use.
The CooKit folds to be about the size of a large notebook when not in use.
The value of CooKits is outlined in the following manner:
Addressing fuelwood scarcities:
* Solar cooking one meal a day, three times a week has been proven to reduce fuelwood consumption and related smoke by one third.
* The CooKit saves more than four times its value in fuelwood each year. With careful use and storage, a CooKit can be used for two years, reducing fuelwood consumption by two tonnes.
Improving health:
* The CooKit can pasteurize household drinking water, making it safe to drink.
* The solar cooking process is smokeless, reducing respiratory diseases and eye irritation
* Solar cooked foods retain vitamins, nutrients and their natural flavors; there is no smoky taste; the foods cook slowly in their own juices. Nutritious, slow-cooking traditional foods (beans, root crops, and some grains) are restored to the family diet
* Clean up is easy as the food never burns or sticks to the cooking pot.
* Solar cooks frequently report that the money they save on cooking fuel purchases is used to for many essentials, such as extra food, school supplies, and medical care.
* Without having to gather wood or dung, breathe smoke, and tend a fire – all associated with traditional cooking – solar cooking is easy and safe for people with AIDS and other illnesses, the elderly, disabled and young orphans.
Rocks can be used to allow the CooKit to be used under windy conditions.
Rocks can be used to allow the CooKit to be used under windy conditions.
Enhancing household and women’s economic status:
* The CooKit represents a new opportunity for women to capitalize on an underserved market and better meet their own cooking energy needs
* Solar cooking saves time as there is less need to tend a fire or collect firewood. A person can cook while at work, at the market, or tending crops. Young girls can attend school instead of searching for fuelwood.
* Solar energy is free and abundant in many areas of Kenya, providing a safe, clean, healthy supplement to traditional fuels.
Co-developers are Roger Bernard of France and Barbara Kerr of the USA, with work also by Ed Pejack, Jay Campbell, and Bev Blum of Solar Cookers International. Extensive field tests in the USA and in many developing countries confirm its performance, convenience, low cost, acceptance, and adaptability to diverse needs.
Monday, December 17, 2007
Know About Solar Power
Prof. Ghai’s (Anon. 1970) parabolic concentrator was of a different type (PRS2, Figure 6). Evolved in the 1950s, the reflector was made from spun Aluminium sheet. It had a hole at the centre through which projected an arm of the stand to hold the cooking vessel. Part of the reflector was cut out to enable easy access to the vessel. The entire unit had to be turned to face the sun.
These types of cookers did not become very popular, but The German News, 38 (June-July): 5-6, 1997, informs that 180 sq. m, parabolic concentrators have been installed at an institute at Mount Abu, to generate 600 kg. of steam at 16 bar pressure and cook food for 1200 people (Herms 1977).
Fig 3a. Parabolic Mirror array form Mt. Abu ( Source SCI site )
Recently Sintex Plastics of India seems to have entered the Solar Market in a big way. They had been manufacturing Solar Water Heaters of Plastic, but now they are trying their hand at Solar Cookers, the Parabolic as well as Box type Cookers. I am yet to receive the samples for evaluation. The photo presented here has been copied from their site, though it does not display any innovations, the price is very competitive at just Rs. 2500. Of course, much depends on the reflective coating too, and again I am yet to receive details regarding the same. With a long lasting Reflective material, and at the price, this Parabolic Cooker should steel the market.
Another recent addition to the family of Parabolic cooker comes from the prolific inventor Mr Deris of California. The Parabola it self is simple, he seems to have discarded the interesting design of square Parabola invented by himself. The parabola he uses is held vertically, and it directs the focused rays on to a Cooking vessel kept on a reflector kept horizontally on the ground.
Interestingly way back in 1980, I had proposed that a reflector/focusing device kept outside or in a suitable position would point focus the image in the house which could then be used for cooking. This design you would see under Type ---but such a concept has already taken shape, independently at Bahai institute in India and with the help of a parabolic reflector kept out side the hut cooking even Chapathis are being cooked.
Fig 3a1 & 2 Photos from Bahai Institute, India ( Ref. their site on the web )
The following diagram shows the principle of Scheffler's reflective cooker design in detail.
The photos bellow shows Scheffler's reflective cooker, a 2.7 m dia cooker, just out side an Indian Home, The photos are from ecosolar.com. The second photo shows a lady cooking in a small kitchen.
The parabolic cookers are being uses in Africa as well and the photo below confirms it further.
These types of cookers did not become very popular, but The German News, 38 (June-July): 5-6, 1997, informs that 180 sq. m, parabolic concentrators have been installed at an institute at Mount Abu, to generate 600 kg. of steam at 16 bar pressure and cook food for 1200 people (Herms 1977).
Fig 3a. Parabolic Mirror array form Mt. Abu ( Source SCI site )
Recently Sintex Plastics of India seems to have entered the Solar Market in a big way. They had been manufacturing Solar Water Heaters of Plastic, but now they are trying their hand at Solar Cookers, the Parabolic as well as Box type Cookers. I am yet to receive the samples for evaluation. The photo presented here has been copied from their site, though it does not display any innovations, the price is very competitive at just Rs. 2500. Of course, much depends on the reflective coating too, and again I am yet to receive details regarding the same. With a long lasting Reflective material, and at the price, this Parabolic Cooker should steel the market.
Another recent addition to the family of Parabolic cooker comes from the prolific inventor Mr Deris of California. The Parabola it self is simple, he seems to have discarded the interesting design of square Parabola invented by himself. The parabola he uses is held vertically, and it directs the focused rays on to a Cooking vessel kept on a reflector kept horizontally on the ground.
Interestingly way back in 1980, I had proposed that a reflector/focusing device kept outside or in a suitable position would point focus the image in the house which could then be used for cooking. This design you would see under Type ---but such a concept has already taken shape, independently at Bahai institute in India and with the help of a parabolic reflector kept out side the hut cooking even Chapathis are being cooked.
Fig 3a1 & 2 Photos from Bahai Institute, India ( Ref. their site on the web )
The following diagram shows the principle of Scheffler's reflective cooker design in detail.
The photos bellow shows Scheffler's reflective cooker, a 2.7 m dia cooker, just out side an Indian Home, The photos are from ecosolar.com. The second photo shows a lady cooking in a small kitchen.
The parabolic cookers are being uses in Africa as well and the photo below confirms it further.
Friday, December 14, 2007
Know About Solar Power
LIGHT CONCENTRATED FROM BELOW
Spherical Mirrors/Parabolic mirror/Rigid Parabola/Shallow Parabola/
Deep Parabola/Asymmetrical Parabola
Concentrator Type
Being a pioneering design, this type of cooker has seen maximum variations, Besides, the design offers several advantages. One of the most important is that the mode of cooking is very much identical to day to day cooking. There are two major types of concentrator solar cookers: (I) cookers which concentrate the light from below, and (ii) cookers which concentrate the light from above.
Heat coming from below is most convenient for routine cooking, hence, many designers have concentrated on this type of cookers. There are a lot of designs in this category, and they are classified on the basis of the type of reflectors used (I) Spherical reflector (S), (ii) Parabolic reflectors (P), (iii) Fresnel types (F), (iv) Cylindro parabolic (CP), and (v) Mirrors plane (MP).
Spherical Mirrors
Spherical mirrors are the simplest type of reflectors, very easy to build and use. Focusssing sun rays are also easy, and if one opts for a moving vessel to meet the focus, cooking can also be done very easily. Such a design was suggested for the first time in the year 1961 by Stam (1961) (Type S1, Figure 1). He suggested a large reflector of 4.0 m diameter made of local material which could even include mud, and the reflector surface suitably smoothed with fine mud/cement and coated with aluminized polyester. An appropriate technology handbook describes a simple method of construction of the spherical mirror in the ground (a tall tripod with a long string to which a stone is attached at the tip, will act as a guide for excavating a hollow in the ground) and after finishing and stabilizing the interior, the reflector material could be stuck to make it into a spherical mirror. Such a mirror, of about 2.0 m in diameter, would do useful work for at least five to six hrs a day.
The cooking vessel could be hung from the tripod or a suitable stand and positioned to cooking vessel could be hung from the tripod or a suitable stand and positioned to meet the focus (Type S 1a). Dr. Halacy 91974) suggests a similar design (Type S 1b, Figure 2). He uses two full and several half cardboard ribs to fabricate the base with a mylar film as a reflector. This device was meant mainly for campers. Bamboo and/or other locally available materials could be used to fabricate such hemispherical baskets (Type S1).
Spherical Mirrors/Parabolic mirror/Rigid Parabola/Shallow Parabola/
Deep Parabola/Asymmetrical Parabola
Concentrator Type
Being a pioneering design, this type of cooker has seen maximum variations, Besides, the design offers several advantages. One of the most important is that the mode of cooking is very much identical to day to day cooking. There are two major types of concentrator solar cookers: (I) cookers which concentrate the light from below, and (ii) cookers which concentrate the light from above.
Heat coming from below is most convenient for routine cooking, hence, many designers have concentrated on this type of cookers. There are a lot of designs in this category, and they are classified on the basis of the type of reflectors used (I) Spherical reflector (S), (ii) Parabolic reflectors (P), (iii) Fresnel types (F), (iv) Cylindro parabolic (CP), and (v) Mirrors plane (MP).
Spherical Mirrors
Spherical mirrors are the simplest type of reflectors, very easy to build and use. Focusssing sun rays are also easy, and if one opts for a moving vessel to meet the focus, cooking can also be done very easily. Such a design was suggested for the first time in the year 1961 by Stam (1961) (Type S1, Figure 1). He suggested a large reflector of 4.0 m diameter made of local material which could even include mud, and the reflector surface suitably smoothed with fine mud/cement and coated with aluminized polyester. An appropriate technology handbook describes a simple method of construction of the spherical mirror in the ground (a tall tripod with a long string to which a stone is attached at the tip, will act as a guide for excavating a hollow in the ground) and after finishing and stabilizing the interior, the reflector material could be stuck to make it into a spherical mirror. Such a mirror, of about 2.0 m in diameter, would do useful work for at least five to six hrs a day.
The cooking vessel could be hung from the tripod or a suitable stand and positioned to cooking vessel could be hung from the tripod or a suitable stand and positioned to meet the focus (Type S 1a). Dr. Halacy 91974) suggests a similar design (Type S 1b, Figure 2). He uses two full and several half cardboard ribs to fabricate the base with a mylar film as a reflector. This device was meant mainly for campers. Bamboo and/or other locally available materials could be used to fabricate such hemispherical baskets (Type S1).
Thursday, December 13, 2007
Know About Solar Power
STEAM COOKER
This appliance is build with a large surface area for collecting sunshine which is transformed into steam.
The steam produced spreads upwards into the uppermost space where the cooking pot is placed on a highly insulated container.
The construction allows maximum solar energy collection because the collector is quite open. However the energy absorption of this appliance is relatively low and its maximum temperature is 100 degrees centigrade.
FIXED-FOCUS SOLAR COOKER
Fixed-focus solar cookers have fixed parabolic mirrors placed parallel to the earth’s axis. The focal length lies out of the mirror and when the curve is well calculated the focal point will fall on the area where the pot is placed.
The metabolic lies on a particular system and will adjust automatically to the sunshine. The pot space is protruding such that some other fuel can be used to heat the cooking pot incase the sun fails. Here the power produced is directly dependent on the size of the mirror.
This appliance is build with a large surface area for collecting sunshine which is transformed into steam.
The steam produced spreads upwards into the uppermost space where the cooking pot is placed on a highly insulated container.
The construction allows maximum solar energy collection because the collector is quite open. However the energy absorption of this appliance is relatively low and its maximum temperature is 100 degrees centigrade.
FIXED-FOCUS SOLAR COOKER
Fixed-focus solar cookers have fixed parabolic mirrors placed parallel to the earth’s axis. The focal length lies out of the mirror and when the curve is well calculated the focal point will fall on the area where the pot is placed.
The metabolic lies on a particular system and will adjust automatically to the sunshine. The pot space is protruding such that some other fuel can be used to heat the cooking pot incase the sun fails. Here the power produced is directly dependent on the size of the mirror.
Wednesday, December 12, 2007
Know About Solar Power
RESERVOIR COOKER
Reservoir cooker is an appliance which collects solar energy during the day and is able to store it in a medium like crude oil (petroleum) for later use. The oil is kept in a highly insulated container for it to store the heat energy for a long time, normally 24 hours. This makes it possible for the system to be used even at night in the rooms.
When cooking, the isolation plate should be removed so as to place the cooking pot on an iron plate lying below it. It can be built with at least three reservoirs and three pot spaces at disposal. These appliances are so far better with only one disadvantage of a high cost of production.
STEAM COOKER
This appliance is build with a large surface area for collecting sunshine which is transformed into steam.
The steam produced spreads upwards into the uppermost space where the cooking pot is placed on a highly insulated container.
The construction allows maximum solar energy collection because the collector is quite open. However the energy absorption of this appliance is relatively low and its maximum temperature is 100 degrees centigrade.
Reservoir cooker is an appliance which collects solar energy during the day and is able to store it in a medium like crude oil (petroleum) for later use. The oil is kept in a highly insulated container for it to store the heat energy for a long time, normally 24 hours. This makes it possible for the system to be used even at night in the rooms.
When cooking, the isolation plate should be removed so as to place the cooking pot on an iron plate lying below it. It can be built with at least three reservoirs and three pot spaces at disposal. These appliances are so far better with only one disadvantage of a high cost of production.
STEAM COOKER
This appliance is build with a large surface area for collecting sunshine which is transformed into steam.
The steam produced spreads upwards into the uppermost space where the cooking pot is placed on a highly insulated container.
The construction allows maximum solar energy collection because the collector is quite open. However the energy absorption of this appliance is relatively low and its maximum temperature is 100 degrees centigrade.
Tuesday, December 11, 2007
Know About Solar Power
Types of solar cookers
.
Use of ecologically friedly and readily availible solar energy is a good substitute for the fossil fuel.
.
. REFLECTOR COOKERS
.
THE PAPILLON (Butterfly)
How does our Papillon work?
The Papillon is a concentrating solar system which works with direct solar radiation. The radiation entering the mirrors is concentrated in a point (Focus) where the cooking equipment stands.
In order to keep the focus, the mirrors are followed up the sun.
This happens by swinging the frame with the 2 wings and turning the hole cooking rack.
.
Use of ecologically friedly and readily availible solar energy is a good substitute for the fossil fuel.
.
. REFLECTOR COOKERS
.
THE PAPILLON (Butterfly)
How does our Papillon work?
The Papillon is a concentrating solar system which works with direct solar radiation. The radiation entering the mirrors is concentrated in a point (Focus) where the cooking equipment stands.
In order to keep the focus, the mirrors are followed up the sun.
This happens by swinging the frame with the 2 wings and turning the hole cooking rack.
Sunday, December 9, 2007
Know About Solar Power
AN ENORMOUS ENVIRONMENTAL DESTRUCTION
In the modern industrialized countries 100 slaves are available to every citizen daily on the average in form of vigour. In the poorest countries of the world this energy is replaced by human physical strength, which does not suffice by far to increase the standard of living of these people. This missing energy is replaced in the poor countries by manpower of the children, what leads to a continuous growth of the population and impairs the situation of the people.
The population growth in these countries lies between 2,5 % and 3 %. That means, that the number of inhabitants duplicates every 25 years in these countries and therefore also misery and poverty. The demand for energy increases.
.... The other source of energy is wood. Did you know that every month deserts increase around half a million hectares?Even today we find with unfavorable wind circumstances the dust of Sahara on our garden furniture, cars and houses.
Countries as for example Mali, Mauritania, Chad or Burkina Faso lost in the last 15 years 60 % of their tree population. Soon there will no more trees be left!
Wood is there in the meantime more expensive than the prepared food, as far as it is still available anyway.
.
Our chairman Willi Heinzen with Tuareg:
no firewood in Sahara
STOPPING DESERT WITH THE SUN?
Every minute 30 hectares rainforest on the earth were destroyed, every month deserts extend around half a million hectares. Every year the Wild Sahara spreads about 1 - 2 km. That applies also the entire Sudan belt which has a boundary of about 12.000 km. All countries which border on Sahara are affected in the end.
What are the causes? Every human being has to cook and eat. Also in Burkina. In order to prepare for example the national food To (millet mash), they mainly use wood in the Sahel. About 95 % of the used energy for cooking and preparing hot water is made by firewood, which decimates the stock of trees every year. The advance of Sahara is sped up by that.
... Pessimistic calculations of the UN predict, that Burkina Faso with 10 Mio. inhabitants will be a desert landscape in the next 25 years, where no more tree will be found
But there is also another problem: "Pas d'argent" is called the most needed sentence in Burkina Faso "I do not have any money". No wonder with some average income of less than 500 U$ in the year. And such a stove costs 400 DM after all, even in case of local manufacturing. As firewood is very expensive, the stove would be paid by saving firewood within 18 months at the latest. After that one can cook for the nought rate.
.
Therefore we support cooking with the sun !
In the modern industrialized countries 100 slaves are available to every citizen daily on the average in form of vigour. In the poorest countries of the world this energy is replaced by human physical strength, which does not suffice by far to increase the standard of living of these people. This missing energy is replaced in the poor countries by manpower of the children, what leads to a continuous growth of the population and impairs the situation of the people.
The population growth in these countries lies between 2,5 % and 3 %. That means, that the number of inhabitants duplicates every 25 years in these countries and therefore also misery and poverty. The demand for energy increases.
.... The other source of energy is wood. Did you know that every month deserts increase around half a million hectares?Even today we find with unfavorable wind circumstances the dust of Sahara on our garden furniture, cars and houses.
Countries as for example Mali, Mauritania, Chad or Burkina Faso lost in the last 15 years 60 % of their tree population. Soon there will no more trees be left!
Wood is there in the meantime more expensive than the prepared food, as far as it is still available anyway.
.
Our chairman Willi Heinzen with Tuareg:
no firewood in Sahara
STOPPING DESERT WITH THE SUN?
Every minute 30 hectares rainforest on the earth were destroyed, every month deserts extend around half a million hectares. Every year the Wild Sahara spreads about 1 - 2 km. That applies also the entire Sudan belt which has a boundary of about 12.000 km. All countries which border on Sahara are affected in the end.
What are the causes? Every human being has to cook and eat. Also in Burkina. In order to prepare for example the national food To (millet mash), they mainly use wood in the Sahel. About 95 % of the used energy for cooking and preparing hot water is made by firewood, which decimates the stock of trees every year. The advance of Sahara is sped up by that.
... Pessimistic calculations of the UN predict, that Burkina Faso with 10 Mio. inhabitants will be a desert landscape in the next 25 years, where no more tree will be found
But there is also another problem: "Pas d'argent" is called the most needed sentence in Burkina Faso "I do not have any money". No wonder with some average income of less than 500 U$ in the year. And such a stove costs 400 DM after all, even in case of local manufacturing. As firewood is very expensive, the stove would be paid by saving firewood within 18 months at the latest. After that one can cook for the nought rate.
.
Therefore we support cooking with the sun !
Friday, December 7, 2007
Know About Solar Power
Pros of the solar cooker
.
Business
* Pays back all the initial costs in only 18 months
* Works for many years without any operational costs.
* Has no operational costs as sunshine is always free.
Reducing fatigue
* Doesn't make exterior of the pot dirty, hence no much cleaning.
* Eliminates use of firewood which is cumbersome especially during rainy seasons.
Health
* No smoke realted infections
* No eye imflammation
* No exposure to lung cancer
Availability
* No long journeys in search of firewood from forests.
* Minimal running costs as in the traditional heating where firewood must be constantly acquired.
Security
* No burking dangers, especially for children
* No injury as may occur while splitting firewood.
* No burning down of huts.
Economy
* Production of solar cookers will provide employment opportunities.
Ecology
* No carbon dioxide emission.
* No more trees felled for firewood.
* Exhaust fumes during timber transportation eliminated.
* Biomass cannot be used for cooking and should instead be used to fertilize the fields.
* Fights deforestation and desertification.
* Protects animals
Global
* Self protection against environmental destruction and climatic catastrophe.
. This is a typical 3-stones cooking place, standard in many developing countries.
The smoke emission in a kitchen is equivalent to the daily inhaling of 40 cigarettes.
.
Business
* Pays back all the initial costs in only 18 months
* Works for many years without any operational costs.
* Has no operational costs as sunshine is always free.
Reducing fatigue
* Doesn't make exterior of the pot dirty, hence no much cleaning.
* Eliminates use of firewood which is cumbersome especially during rainy seasons.
Health
* No smoke realted infections
* No eye imflammation
* No exposure to lung cancer
Availability
* No long journeys in search of firewood from forests.
* Minimal running costs as in the traditional heating where firewood must be constantly acquired.
Security
* No burking dangers, especially for children
* No injury as may occur while splitting firewood.
* No burning down of huts.
Economy
* Production of solar cookers will provide employment opportunities.
Ecology
* No carbon dioxide emission.
* No more trees felled for firewood.
* Exhaust fumes during timber transportation eliminated.
* Biomass cannot be used for cooking and should instead be used to fertilize the fields.
* Fights deforestation and desertification.
* Protects animals
Global
* Self protection against environmental destruction and climatic catastrophe.
. This is a typical 3-stones cooking place, standard in many developing countries.
The smoke emission in a kitchen is equivalent to the daily inhaling of 40 cigarettes.
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