Solar Cookers Cheap Technology With High Ecological Benefits 1
ECOLOGICAL ECONOMICS ELSEVIER Ecological Economics 17 (1996) 73-81 Commentary Solar cookers cheap technology with high ecological benefits 1 Shyam S. Nandwani : 42 Laboratorio de Energla Solar, Departamento de Fisica, Unicersidad Nacional, Heredia, Costa Riea Received I 1 September 1995: accepted 23 January 1996 Abstract T h i s study d i s c u s s e s the quality and quantity o f energy used for c o o k i n g in C o s t a Rica and in the world as a whole, and then c o m p a r e s the a d v a n t a g e s and limitations of solar o v e n s with conventional firewood and electric stoves. T h e p a y b a c k period of a common hot box type solar oven, even if used 6-8 months a year, is around 12-14 months. Even if only 5 percent of persons facing fuel shortages in the year 2005 use solar ovens, roughly 16.8 million tons of firewood will be saved and the emission of 38.4 million tons of carbon dioxide per year will be prevented. Keywords: Solar ovens; Solar cookers: Economics; Deforestation: Pollution; Energy consumption in cooking 1. Introduction After food is cultivated and produced, it still cannot be consumed unless it is properly cooked. Fuelwood and agricultural residues are the major energy sources for cooking in developing countries, normally accounting for 5 0 - 9 0 % or more of all energy consumption in those countries. However, the rate of fuelwood consumption exceeds its replacement, contributing to deforestation, soil erosion and worsening of the welfare of millions of people all over the world. Fax: ( 506) 260 1197, 260 2 5 4 6 : e - m a i l : snandwan @ irazu.una.ac.cr i Preliminary report was presented as Poster at Third Biennial Meeting of The International Society for Ecological Economics--Down to Earth: Practical Applications of Ecological Economics held at Hotel Herradura, Costa Rica, during October 24-28. 1994. 2 Member. Solar Cookers International (SCI), Sacramento, CA. USA: International Solar Energy Society (ISES), Germany and Asociacirn Costarricense de Energ a Solar (ACES), Costa Rica. Although electric cooking is comparatively convenient, its production from fossil fuels is very expensive and results in the emission of high quantities of carbon dioxide a n d / o r sulfur dioxide in the atmosphere. Generation of electricity from hydro plants has its owns problems as well, including habitat destruction and disruption of stream flow. The author, who has worked on various thermal applications of solar energy for 18 years and even uses some of these devices including a solar oven at his home, would like to share part of his experience in this area. 2. Cooking--fuel and energy required 2.1. General Experiments with firewood 0 . 7 - 1 . 5 kg of dried wood is single p e r s o n / d a y (or on the person per year). Taking 4300 0921-8009/96/ 15,00 1996 Elsevier Science B.V. All rights reserved PII S 0 9 2 1 - 8 0 0 9 ( 9 6 ) 0 0 0 2 1 - 3 have shown that about needed to cook for a average of 680 kg per k c a l / k g as the caloric
s.s. Nandwani/ Ecological Economics 17 (1996) 73- 81 74 value o f firewood, energy for c o o k i n g will be between 3010 and 6450 k c a l / p e r s o n / d a y . 2.2. Costa Rica In the case o f Costa Rica, the fuels c o n s u m e d are biomass and electricity ( 7 0 - 8 0 % from hydro and rest f r o m i m p o r t e d oil and gas). The c o n s u m p t i o n in 1992 for all fuels in all sectors is s h o w n in Table l a (Direcci6n Sectorial de Energia, 1994). O f this total energy, 36% is used in the domestic sector (Table l b). F r o m this we will estimate what part of this d o m e s t i c energy goes into cooking. Based on the official data ( D i r e c c i 6 n Sectorial de Energ[a, 1994) the f o l l o w i n g are the percentages o f the population using different c o o k i n g fuels: 78.9% use electricity, 26.4% use f i r e w o o d , Table 1 a. Total energy consumption in Costa Rica, by various sources (in 1992) Sources Biomass Electricity Oil/gas Total Absolute PJ Relative cA 28.11 33.97 13.2 15.95 41.44 50.08 82.75 100 b. Total energy consumption in domestic sector in Costa Rica Sources Absolute PJ Relative % Biomass( ) Elect. 23.1 78 5.6 18.7 Gas 0.53 1.7 Kerosene Total 0.52 1.6 29.75 100 c. Total energy consumption tbr cooking in domestic sector (DS} in Costa Rica Sources Biomass Electricity Natural gas Kerosene 90CA,of biomass used in DS 45% of the electricity used in DS h 100CAof the gas used in DS 50% of the kerosene used in the DS c Total/ year PJ pentajoules 1015 J. :" Mainly firewood. a Rest of the biomass is used for heating water. b ICE, Costa Rican Electricity Institute, official data. Rest of kerosene is used for lamps, etc. 20.79 PJ 2.52 PJ 0.53 PJ 0.26 PJ 24.36 PJ 18.6% use L.P.G., 3.3% use soft coal, 1.0% use kerosene, etc, It may be noted that s o m e families use as m a n y as 2 or 3 cooking fuels, either for different c o o k i n g processes or for e m e r g e n c y purposes. A l t h o u g h no real data are available to show the absolute c o n s u m p tion in the c o o k i n g sector, as discussed with Ing. Allan Chin W o o f D i r e c c i 6 n Sectorial de Energia, one can construct these numbers without any appreciable error (Table l c). W e find that 29.4% of the total energy c o n s u m e d in Costa Rica is spent on cooking. 2.3. Some other countries In Africa, for example, 90% o f the population uses f i r e w o o d for cooking. In India 150 million tons of firewood, 52 million tons o f c o w dung, and 36 million tons o f other waste biomass are used only for cooking. These huge amounts of n o n - c o m m e r c i a l sources are e q u i v a l e n t to about 4 5 % o f the total energy available in the country. On the other hand, in the United States only 20% o f the total energy p r o d u c e d is c o n s u m e d in the d o m e s t i c sector, o f which only 5% (or 1% of the total) is used for cooking. 2.4. International level F u e l w o o d is the m a j o r energy source in d e v e l o p ing countries because other fuels are either not available or are expensive. T w o billion people c o o k with f i r e w o o d or animal dung. In other words, half the meals for E a r t h ' s 6 billion p e o p l e are c o o k e d with w o o d fires each day. 3. C o n v e n t i o n a l m e a n s of c o o k i n g and their consequences 3.1. Fuelwood / agricultural residues As explained above, f i r e w o o d and other types o f biomass are the m a j o r fuel sources for cooking. The various steps i n v o l v e d in this process are: SUN-planting trees-growing trees-cutting/buy-
s.s. Nandwani/ Ecological Economics 17 (1996) 73 81 ing t r e e s - t r a n s p o r t i n g / w a l k i n g - C O O K I N G RANGE (STOVE). Firewood has advantages, such as ease of storage, with the result that it can be used at any time and anywhere. However, the excessive burning of these fuels for cooking has the following drawbacks which affect the welfare of millions of people all over the world: 3.1.1. Shortage of firewood According to the United Nations Food and Agricultural Organization, some 2400 million people are expected to face acute fuelwood shortages by the end of the century with serious nutritional and health consequences. 3.1.2. Cost Due to a shortage of fuelwood in many places, users must pay high prices. In rural areas of China, a family may spend up to 25% of its income on firewood. 3.1.3. Transport In many places children walk many miles to collect fuelwood. Afghan refugees in Pakistan used to spend 99 man-hours per month collecting fuel for cooking (Magney, 1988). 3.1.4. EO'iciency Firewood and agricultural wastes have very low burning efficiency. 3.1.5. Health / social The firewood stove is a major source of concentrated indoor air pollution. The World Bank's Development Report 1993, reports that eliminating indoor smoke caused by cooking and heating could cut childhood pneumonia by half and reduce the burden of other diseases by 5% (Solar Box Joumal, 1994a). 3.1.6. D q'orestation It has been estimated that at present more than 15 million hectares (150 000 km 2) of forests are lost per year in developing countries, mainly due to the consumption of firewood. This area is equivalent to about 3 times that of Costa Rica. Unfortunately, the rate of deforestation is more than the reforestation rate in many parts of the world. 75 3.1.7. Fertilizer and erosion of soil The use of cow dung as a fuel for cooking (common in India) is extremely unfortunate, as this fuel is a good fertilizer. About 400 million tons of wet cow dung (equivalent to about 80 million tons of dried dung) are burned annually in India alone, which wastes nutrients and organic material. This represents enough fertilizer to grow 20 million tons of grain, enough to feed 100 million people for a year (Kammen and Lankford, 1990). 3.2. Electricity Next to firewood stoves, electricity is the most important fuel source used for cooking. In the case of hydroelectricity, the different steps involved are: S U N - r e s e r v o i r - d a m - f l o w of water-turbinegenerator- distribution-transmission of electricityCOOKING RANGE. Hydroelectric plants have a number of negative environmental effects, such as the high initial cost of hydroelectric dams, cost of transmission of electricity, floods, sedimentation, displacement of persons living at the site, decrease in hydro potential especially in summer, habitat loss, etc. At the world level, programs countering fuel scarcity so far have concentrated on planting trees, teaching better charcoal-making techniques, and promoting more efficient wood stoves. But these programs can have only limited effects on overall wood consumption, as growing populations depend so completely on wood. 4. Alternative means--solar cooking Solar cookers, using the sun's free energy, offer tremendous potential for aiding in the solution of the fuel problem. Unlike firewood and electric cooking, in solar cooking the only steps involved are: SUN-COOKING RANGE (SOLAR COOKER) Some of the characteristics and advantages of solar cookers are as follows: 4.1. Temperature required for cooking As most items cooked in the areas of the world discussed above have a high water content, cooking
76 S.S. Nandu'ani / E{'olo ical Economi "l ]17 (1996) 73- 81 4.3. Initial cost \ \ As will be seen in the next section, there are various models (Kuhnke et al., 1990) made with different materials, and hence different thermal performances, durability, and different costs (US 5 1500). However, a family-size oven (0.25 m e) with reasonable durability and efficiency (outer box made of wood, two window panes, etc.) may cost around U S 4 0 - 5 0 (materials cost), and it can be made at home using only hand tools. 4.4. Various models Listed below are the various models made by the author, and also some of the 100 models made at the international level. Fig. I. Scheme for conventionalsolar oven. (I) Transparent glass panes. (2) Galvanised iron plate. (3) Glass wool as heat insulator. (4) Reflector. (5) Door to introducethe food. (6) Rod with various holes to adjust the reflector. (8) Outer case of the solar oven. requires temperatures only in the order of 9 0 - 1 0 0 C (except for frying). Higher temperatures of course, have the advantage of reducing the cooking time. Solar ovens can easily attain these temperatures. 4.2. Technical aspects There are two types of solar stoves: the hot box solar oven and the concentrating solar cooker. For various reasons, the first type of stove is commonly accepted at the world level. A detailed design can be seen in Fig. 1 (Nandwani, 1980; Nandwani, 1993). In brief, a solar cooker is a highly insulated box with a black metal plate kept in the box for absorption of solar radiation. The top is glass, and often exterior reflector(s) are used to concentrate the sun's rays into the box. The box may be made of wood, metal, fibreglass, or cardboard and glass wool, styrafoam, or even newspaper may be used as an insulation. A double-pane glass top also helps in insulation. The box can be opened either at the front or from the top. Fig. 2 shows one of the models designed, studied, and used by the author for last 16 years. 4.4. I. A u t h o r ' s models (shown in Fig,, 3) are: I. Simple hot box (The Tico Times, 1979), 2. Improved hot box (Nandwani, 1993), 3. Solar-electric oven (Nandwani, 1989), 4. Heat storage oven, (Nandwani, 1990), 5. Solar oven integrated with water heater (Nandwani and Fernandez, 1995), 6. Solar oven integrated with drier (Nandwani and Fernandez, 1995), 7. Solar-powered microwave oven (Currin et al., 1995), 8. Parabolic cooker Details of these models can be obtained in the references listed. Fig. 2. Actual conventionalsolar oven.
S.S. Namtwa,i/Ecolo.q, ical E c o m , , i c 17 ( 19961 73 ,'1 77 Fig. 3. Various solar oxcns designed by thc aulhor. i Fig. 4. Some of the inlernatlonal models of solar ovens/cookers.
78 S.S. NalMwa.i / Ecolo,g, ical Eco.omics 17 ( 1996 73-81 4.4.2. hTternational models." Fig. 4 shows some of the 100 laboratory and commercial models of solar c o o k e r s / o v e n s from India, USA, France, Germany, and Switzerland. These can be classified in four categories (Kuhnke et al., 1990; Pejack, 1992). hot box oven, without or with 1 - 8 reflectors, solar cooker, with parabolic concentrator, solar oven, with vapor cooking, heat storage solar ovens 4.5. Meals cooked i , the solar ocen The simple hot box model can be and has been used to cook, bake, and roast practically all types of meals (Nandwani, 1993), whereas for frying the concentrator cooker is required. 4.6. Number o f meals cooked with solar oven / cooker Obviously it depends on the design of the cooker, climatic conditions, and the character of the user. However, in Costa Rica, between 300 and 450 meals can be cooked per year for a family of 4 - 5 persons. 4. Z Other adl'antages Besides cooking, the solar oven can do a variety of j o b s - - i t can dry agricultural products, heat and pasteurize water, make tea and coffee, and heat irons for ironing clothes (Metcalf, 1995: Nandwani and Fernandez, 1995). 4.8. Fuel sating, For a consumer who has purchased a solar cooker, financial gain would depend on the following factors: number and type of meals cooked, type of conventional fuel used by the consumer before the use of a solar oven. its efficiency and cost including transportation. However, some rough estimates can be made of savings at different levels. 4.8.1. Family lecel With an average solar intensity of 3.5 k W h / m 2 per day, normally two meals can be cooked. Based on these data and a knowledge of climatic condi- tions, a single family in Costa Rica can use a solar oven for 7 - 8 months and can cook about 350 meals in a year. which can save: 1000 kWh of electricity per year. 240 liters of propane gas. 242 liters of kerosene, or 725 kg of firewood per year. With the present cost of electricity ( 0 . 0 6 / k W h ) , savings would be around US 60 per year. In other words, the initial cost of a good solar cooker (with a durability of about 5 - 6 years) can be recovered in 12-14 months (without considering future increases in electricity prices). 4.8.2. National lecel (Costa Rica) Based on the saving of different fuels by each family, mentioned above, one can calculate the total savings by the country according to the number of families who use solar cookers. As an example, we can calculate the possible savings of electricity in Costa Rica due to the use of solar ovens. According to 1992 data, 79% of all Costa Rica's 700000 families were using electric ranges for cooking. Based on 1000 kWh of electric energy saved per family (using solar ovens 6 - 8 months) per year, total savings in electric energy on a national level would be: 700 000 * 0.79 * 1000 553 million k W h / y e a r saved (in addition to the saving of about 6 5 0 - 7 5 0 kg of firewood per year per family). Corresponding losses for the national electric utility company (Instituto Costarricense de Electricidad) due to lower sales of electricity ( 0 . 0 6 / k W h ) would be US 33.2 million/year. 4.8.3. hzter, ational lecel (an estimate .ft," the year 2000) The number of families cooking with firewood in developing countries is 400 million (2000 million p e o p l e / 5 per family). At the present time about 530 000 solar c o o k e r s / o v e n s have been manufactured in different countries and more are being constructed each day. l,et us suppose that by the year 2000 that only I% of families cooking with firewood use solar cookers (i.e., just 4 million). The firewood saved would be: 0.70 t o n / f a m i l y / y e a r * 4 million 2.8 million t o n s / y e a r
s.s. Nandwani/ Ecological Economics 17 (1996) 73-81 (plus electricity and gas saved, by the users of these fuels). 79 Thus, the quantity of CO 2 not absorbed would be (b): 56M * 30tons/100 16.8milliontons/year 4.9. Pollutants sating (ent:ironmental effects), in the year 2005 Use of solar cookers in addition will reduce emission of pollutants such as SO 2, fly-ash, smoke, and the main greenhouse gas, CO.-. Solar Cookers International, a non-profit organization (Sacramento, CA, USA), believes that 2400 million people will be aware of Solar Cookers by the year 2005 if the cookers are properly developed and promoted. If we assume only 5% of them (120 million or around 24 million families) use solar cookers, there would be a savings of 16.8 million tons of firewood per year. Let us calculate approximately the reduction of CO emission due to this saving of firewood. 4.9.1. Direct emission o f CO, Assuming 35% of carbon (C) content in firewood, the total C of the firewood saved would be 5.88 million tons. According to the chemical reaction, C O.- ---, CO 2, total CO 2 not emitted 3 would be (a): 5.88 )4 ( 4 4 / 1 2 ) 2 1 . 6 m i l l i o n t o n s / y e a r , 4.9.2. Indirect emission o f CO Trees, if not cut, absorb carbon dioxide and provide oxygen for all of us. If burnt, in addition to emitting CO 2, they will not be able to absorb this CO,. Thus there is indirect emission of CO 2 from not cutting the trees. Assuming trees were cut to get firewood for cooking and each tree provides roughly 300 kg (0.3 ton) of dry wood, the number of trees saved, due to the use of solar ovens, per year would be: 16.8 million t o n s / 0 . 3 ton 56 million On average each hectare of forest ( 100 trees) has the capacity to absorb 30 tons of CO 2 per year. Molecular weight of carbon and CO, are 12 and 44 atomic mass units, respectively. Therefore the total reduction in emission of CO 2 per year (a b) 38.4 million tons. In addition, there will be some reduction in the emission of CH 4, smoke and ash, etc., due to less burning of firewood. Although the literature gives various costs for removing carbon dioxide from the atmosphere, we can take as an average US 1 0 0 - 2 0 0 / t o n . Thus, cleaning of 38.4 million tons of CO. may require 3840-7680 M/year. The total investment (material and labor costs) to construct 24 million reasonably durable solar ovens will be U S 2 0 0 0 - 2 4 0 0 million. This is the investment to be made only once in 5 - 6 years. Thus, solar ovens are economically and ecologically viable. 4.10. Limitations o f solar ot'ens / cooker Some of the limitations of solar ovens include (Nandwani, 1995): 1. irregular availability of solar radiation, 2. inability to store and transport heat energy, 3. unsuitability at high latitudes, 4. traditional cooking and eating habits, 5. longer cooking time. This explains in part why solar cookers have not been used on a large scale (Blum, 1995). Table 2 Approximate number of solar cookers constructed and or distributed in differentcountries India China Tibet Pakistan (Afghan refugees) Switzerland 340028 140000 20000 10000 6000 United States of America South Africa 3000 2720 Kenya 1250 Ladakh, Mexico. Nicaragua. Costa Rica, Ecuador, Chile, Nepal 2 100 Total 525000 (Garg, 1995) (Hongpeng, 1995) (Hongpeng.1995) (Sustainable Energy News, 1994) (SolarBox Journal, 1994b)
80 S.S. Nandwani./ Ecoloc, ical Ecommlic 17 ( 1996J 7.? 81 5. Number of solar cookers at the world level It is very difficult to e s t i m a t e this n u m b e r . H o w ever, s o m e data b a s e d on a literature s u r v e y were c o m p i l e d a n d are s h o w n in T a b l e 2 ( i n c l u d e d in the list are o n l y c o u n t r i e s h a v i n g at least 1000 cookers). Total solar c o o k e r s , as s u r v e y e d by the author, are a b o u t 525 000. 6. Conclusions 6.1. S u m m a # w P r o p o s e d n u m b e r o f solar o v e n s / c o o k e r s In the y e a r 2005 Initial cost ( d u r a t i o n 5 y e a r s ) Initial cost (pet" y e a r ) Firewood saving per year C O e s a v i n g per y e a r C o s t o f c l e a n i n g this gas per year 24 0 0 0 000. U S 2 4 0 0 million US 480 million 16.8 m i l l i o n tons 38.4 m i l l i o n tons US 3840-7680 million. " T h i s figure is very high. H o w e v e r , the S50 billion r a i s e d in a m a t t e r o f m o n t h s to f i n a n c e /he G u l f W a r is e v i d e n c e o f w h a t can be a c c o m p l i s h e d w h e n the n e e d is j u s t i f i e d (Herald, 1992). 7. Clear example of ecological and logical economics 7.1. F i n a l r e m a r k s S o l a r e n e r g y is free a n d a b u n d a n t (on the global level). H o w e v e r , in a n y p a r t i c u l a r place it is not a v a i l a b l e 24 h o u r s a day a n d c a n n o t be stored a n d t r a n s p o r t e d (as with c o n v e n t i o n a l fuels). T h u s the use o f solar o v e n s c a n n o t c o m p l e t e l y replace c o n v e n tional fuels. But to the e x t e n t that solar o v e n s can be used, they will greatly r e d u c e d e f o r e s t a t i o n , air pollution, a n d f a m i l y h e a l t h p r o b l e m s , a n d will c o n s e r v e c o n v e n t i o n a l fuels. S o l a r c o o k e r s h a v e already b e g u n to gain the i m a g e o f an e f f e c t i v e fuel saver, p a r t i c u l a r l y as a s u p p l e m e n t a r y o p t i o n to c o m m e r c i a l fuels such as L.P.G. or kerosene. In m a n y c o u n t r i e s ( N i c a r a g u a , C o s t a Rica, Chile, India, Tibet, Kenya, C u b a ) there are s o m e small restaurants, c o m m u n i t i e s , prisons, universities, etc., that use s o l a r c o o k e r s a l o n g with c o n v e n t i o n a l fuels. Acknowledgements T h e a u t h o r is t h a n k f u l to Mr. C a r l o s D e l g a d o , I t u g o M a r t i n e z , m e c h a n i c a l t e c h n i c i a n s , for cons t r u c t i n g various solar c o o k e r s , to Mr. M a r v i n Alpizar, electrical t e c h n i c i a n , for h e l p i n g with electrical c o m p o n e n t s , a n d to Prof. Otoniel F e r n a n d e z , also for h e l p i n g with m e a s u r e m e n t s . T h e a u t h o r is also grateful to Mr. M a r t i n Ogle, the r e v i e w e r o f the m a n u s c r i p t , for m a k i n g v a r i o u s useful s u g g e s t i o n s . References Bhnn, B.L. 1995. Solar cooking promotion: recomendalions from grass roots organizations. In: S.S. Nandwani. E. Pejack and B. Blum (Editors), Dexelopments in Solar Cookers, Proceedings of the Second World Conference on Solar Cookers--Use and Technology,. 12-15 July, 1994, Universidad Naciomd. Costa Rica, pp. 228 235. Currin C., Nandwani. S.S. and Alpizar, M., 1995. Preliminary study of solar powered microwave oven. In: S.S. Nandwani. E. Pejack and B. Blum (Editors), Developments in Solar Cookers. Proceedings of the Second World Conference on Solar Cookers--Use and Technology, 12-15 July. 1994, Universidad Nacional. Costa Rica, pp. 149 158. Dircccidn Scctorial de Energfa, 1994. In: Diagnostico del Sector Energfa. Periodo 1970-1993, Ministerio de Recursos Naturales. Encrgfa y Minas, Republica de Costa Rica. September 1994, 159 pp. Garg, H.P,, 1995. Solar cooking technology and promotional program in India. In: S.S. Nandwani, E. Pejack and B. Blum (Editors), Developments in Solar Cookers, Proceedings of the Second World Con/ierence on Solar Cookers--Use and Technology, 12 15 July, 1994, Universidad National, Costa Rica. pp. 27-43. Herald. R.N. 1992. The Sunshine Revolution. SUN-LAB Publish ers. Norway. 187 pp. Hongpeng. L. 1995. Developments in solar cookers. In: S.S. Nand,, ,ani. E. Pejack and B. Blnm (Editors). Proceedings of the Second World Conference on Solar Cookers Use and Technology. 12-15, July 1994, Universidud Nacional. Costa Rica. pp. 330 335. Kammen, D.M. and Lankford. W.M. 1990. Cooking in the sunshine. Nature, 348: 385-386.
S.S. Nandw mi / Ecological Ecommlics / 7 (/996) 73 81 Kuhnke K. Reuber, M. and Schwefel, D., 1990. Solar Cookers in the Third World. Friedr. Vicweg und Sohn Braunschweig/Wiesbaden. Germany, 228 pp. Mugney, G., 1988. Providing solar cookers to Afghan refugees. In: W,H. BIoss and F. Pfisterer (Editors), Advances in Solar Energy Technology, Proceedings ISES, Solar World Congress, Hamburg, Germany, Vol. 3, Pergamon Press, pp. 2688-2692. Metcalf, R., 1995. Solar water pasteurization and other non cooking applications of solar cookers. In: S.S, Nandwani, E. Pejack and B. Blum (Editors), Developments in Solar Cookers, Proceedings of the Second World Conference on Solar Cookers-Use and Technology, 12-15 July. 1994, Universidad Nacional, Costa Rica, pp. 44-50. Nandwani, S.S., 1980. Study of a cheap solar oven in the climate of San Jose, Costa Rica. In: International Symposium on the Solar Energy Utilization, University of Western Ontario, Canada, August 10-24. 1980. Published in Solar Energy Conversion II, Pergamon Press, 488 pp. Nandwani, S,S. 1989. Design, construction and experimental study of electric cum solar oven. Solar Wind Technol., 6 (2): 149-158. Pergamon Press. Nandwani, S.S., 1990. Cheap Solar Oven with Heat storage, preliminary study for Costa Rica's climate. The Heliograph, Royal Institute of Technology, Sweden, 2: 27-36. Nandwani. S.S., 1993. La Cocina/Horno Solar-Hagala Usted 81 mismo!. Fundacion Univcrsidad Nacional, Heredia, Costa Rica, 98 pp. Nandwani, S.S., 1995. From cheap/simple three stones to expensive/Advanced convective cookers. Ill: S.S. Nandwani, E. Pejack and B. Blum (Editors), De','elopments in Solar Cookers, Proceedings of the Second World Conference on Solar Cookers--Use and Technology, 12 15 July, 1994. Universidad National, Costa Rica, pp. 17-26. Nandwani, S.S. and Fernandez, O., 1995. Experimental study of solar oven cure water heater and solar oven cmn drier. I1. In: S,S. Nandwani, E. Pejack and B. Blum (Editors), Developments in Solar Cookers. Proceedings of the Second World Conference on Solar Cookers--Use and Technology, 12-15 July. 1994, Universidad National, Costa Rica, pp. 273-284. Pejack, E. (Editor), 1992. Proceedings of First World ConDrencc on Solar Cooking, 19-20 June, Stockton, CA, USA, 158 pp, The Tico Times, 1979. Sunny visions--getting a charge from Old Sol. The Tico Times (weekly English newspaper), San Jos , Costa Rica, May 4, 1979. p. 21 (interview with the author). Solar Box Journal, 1994a. The Newsletter of Solar Box Cookers Northwest, Seattle. WA. USA, 5(I), February 1994. Solar Box Journal, 1994b. The Newsletter of Solar Box Cookers Northwest, Seattle, WA. USA, 5(3), October, 1994. p. 2. Sustainable Energy News. 1994. Denmark. No. 6, September, 1994,
Solar cookers Commentary cheap technology with high ecological benefits 1 Shyam S. Nandwani : 42 . period of a common hot box type solar oven, even if used 6-8 months a year, is around 12-14 months. Even if only 5 percent of persons facing fuel shortages in the year 2005 use solar ovens, roughly 16.8 million tons of firewood will be .
There are three types of solar cookers, solar box cookers or oven solar cookers, indirect solar cookers, and Concentrating solar cookers [2-10]. Figure 1 shows different types of solar cookers namely. A common solar box cooker consists of an insulated box with a transparent glass or plastic cover that allows solar radiation to pass through.
There are three common types of solar cookers which are; (1) concentrating solar cookers, (2) box solar cookers, and (3) panel solar cookers. An appealing solar cooker must be user friendly, locally available at an affordable price, and must be able to reach high cooking temperatures in a short period of time. Concentrating solar cookers are .
The literature on solar cookers is very limited and has focused mainly on household solar cookers, while solar cookers for institutional applications have been ignored. This study contributes carried by comparing application levels type of solar cooker. This paper presents a short review on different types of solar cookers.
"solar panel cooker" that can reach temperatures of between 120 and 150 C for cooking, roasting or boiling. It should be noted that there are other types of solar cookers that can reach higher tempera-tures for frying or grilling food. 1.1 Types of solar cookers There are three different types of solar cookers:
today! Cheap trackers boost solar panel and solar cooker performance. by gaiatechnician Optics experiments on the cheap (video) by gaiatechnician DIY 2 bucket dripper tracker for solar cookers and solar panels is cheap and it works! (video) by gaiatechnician Solar parabolic cooker with the
new cooking technology we are working with is called Insulated Solar Electric Cookers, or ISECs. These cookers are very efficient. At LEF, we use solar power, and that makes us 100% energy self sufficient at the residential level. But unlike other off-grid projects, 90% of our electricity never goes through a battery.
Basic Methods of Solar Water Pasteurization-Solar Cookers A simple method of pasteurizing water is to simply put blackened containers of water in a solar cooker.3 There are many types of solar cookers, but a solar box cooker is sketched in Fig. 1. REFLECTIVE LID GLAZING WATER JARS Figure 1: A solar box cooker being used to pasteurize water.
Coronavirus (COVID-19) risk assessment 11 Hazard Risk rating Control measures Additional controls Residual risk Persons at risk Non-essential contractors were stood down (where the service was not required at this time) to reduce possible transmission of the virus. All contractors that are providing a service are contacted on a daily basis to ensure they adhere to hygiene requirements .
