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ELSEV IER E c o l o g i c a l E c o n o m i c s 1 7 ( 1 9 9 6 ) 7 3 - 8 1

E C O L O G I C A LE C O N O M I C S

S o l ar c o o k e r sCommentary

c h e a p t e c h n o l o g y w i t h h i g h e c o l o g i c a l b e n e f i t s 1: 42Shyam S. Nandwani

L a b o r a t o r i o d e E n e r g l a S o l a r , D e p a r t a m e n t o d e F i s i c a, U n i c e r s i d a d N a c i o n a l , H e r e d i a , C o s t a R i e aR e c e i v e d I 1 S e p t e m b e r 1 9 95 : a c c e p t e d 2 3 J a n u a r y 1 9 9 6

AbstractT h i s s t u d y d i s c u s s e s t h e q u a li t y a n d q u a n t i t y o f e n e r g y u s e d f o r c o o k i n g i n C o s t a R i c a a n d i n th e w o r l d a s a w h o l e , a n d

t h e n c o m p a r e s t h e a d v a n t a g e s a n d l i m i t a t i o n s o f s o la r o v e n s w i t h c o n v e n t i o n a l f i r e w o o d a n d e l e ct r ic s t o v e s . T h e p a y b a c kp e r i o d o f a c o m m o n h o t b o x t y p e s o l a r o v e n , e v e n i f u s e d 6 - 8 m o n t h s a y e a r , is a r o u n d 1 2 - 1 4 m o n t h s . E v e n i f o n ly 5per cent o f pe r sons f ac ing f ue l shor tages in the yea r 2005 use so la r ovens , r oughly 16 .8 mi l l ion tons of f i r ew ood w i l l besaved and the e miss ion o f 38 .4 m i l l ion tons of ca r bon d io xide pe r yea r w i l l be pr evented .K e y w o r d s : S o l a r o v e n s ; S o l a r c o o k e r s : E c o n o m i c s ; D e f o r e s t a t io n : P o l l u t io n ; E n e r g y c o n s u m p t i o n i n c o o k i n g

1 . In tr od u c t i onA f t e r f o o d i s c u l t i v a t e d a n d p r o d u c e d , i t s t i l l

c a n n o t b e c o n s u m e d u n l e s s i t i s p r o p e r l y c o o k e d .F u e l w o o d a n d a g r i c u l t u r a l r e s i d u e s a r e t h e m a j o re n e r g y s o u r c e s f o r c o o k i n g i n d e v e l o p i n g c o u n t r ie s ,n o r m a l l y a c c o u n t i n g fo r 5 0 - 9 0 % o r m o r e o f al le n e r g y c o n s u m p t i o n i n t h o s e c o u n t r i e s . H o w e v e r , t h er a te o f f u e l w o o d c o n s u m p t i o n e x c e e d s i t s r e p l a c e -m e n t , c o n t r i b u t i n g t o d e f o r e s t a t i o n , s o i l e r o s i o n a n dw o r s e n i n g o f t h e w e l f a r e o f m i l l i o n s o f p e o p l e a l lo v e r t h e w o r l d .

A l t h o u g h e l e c tr i c c o o k i n g i s c o m p a r a t i v e l y c o n -v e n i e n t , i t s p r o d u c t i o n f r o m f o s s i l f u e l s i s v e r y e x -p e n s i v e a n d r e s u l t s i n t h e e m i s s i o n o f h i g h q u a n t i t i e so f ca r b o n d i o x i d e a n d / o r s u lf u r d i o x i d e i n t h e a tm o -s p h e r e . G e n e r a t i o n o f e l e c t r ic i t y f r o m h y d r o p l a n t sh a s i t s o w n s p r o b l e m s a s w e l l , i n c l u d i n g h a b i t a td e s t r u c t i o n a n d d i s r u p t i o n o f s t r e a m f l o w .

T h e a u t h o r , w h o h a s w o r k e d o n v a r i o u s t h e r m a la p p l i c a t i o n s o f s o l a r e n e r g y f o r 1 8 y e a r s a n d e v e nu s e s s o m e o f t h e s e d e v i c e s i n c l u d i n g a s o l a r o v e n a th i s h o m e , w o u l d l i k e t o s h a r e p a r t o f h i s e x p e r i e n c ei n t h i s a r e a .

F a x : ( + 5 0 6 ) 2 6 0 1 1 9 7 , 2 6 0 2 5 4 6 : e - m a i l :s n a n d w a n @ i r a z u . u n a .a c . c r

i P r e l i m i n a r y r e p o r t w a s p r e s e n t e d a s P o s t e r a t T h i r d B i e n n i a lM e e t i n g o f T h e I n t e r n a ti o n a l S o c i e t y f o r E c o l o g i c a lE c o n o m i c s - - D o w n t o E a r th : P r a c ti c al A p p l i c a ti o n s o f E c ol o g ic a lE c o n o m i c s h e l d a t H o te l H e r r a d u r a , C o s t a R i c a , d u r i n g O c t o b e r24- 28 . 1994 .

2 M e m b e r . S o l a r C o o k e r s I n t e r n a t i o n a l (S C I ) , S a c r a m e n t o , C A .U S A : I n t e r n a t i o n a l S o l a r E n e r g y S o c i e t y ( I S E S ) , G e r m a n y a n dA s o c i a c i r n C o s t a r r i c e n s e d e E n e r g ~ a S o l a r ( A C E S ) , C o s t a R i c a .

2 . C o o k i n g - - f u e l a n d e n e r g y r e q u ir e d2.1. General

E x p e r i m e n t s w i th f i r e w o o d h a v e s h o w n t h at a b o u t0 . 7 - 1 . 5 k g o f d ri e d w o o d i s n e e d e d t o c o o k f o r as i ng l e p e r s o n / d a y ( o r o n t h e a v e ra g e o f 6 80 k g p e rp e r s o n p e r y ea r ). T a k i n g 4 3 0 0 k c a l / k g a s t h e c a lo r i c

0 9 2 1 - 8 0 0 9 / 9 6 / $ 1 5 , 0 0 1 9 96 E l s e v i e r S c i e n ce B . V . A ll ri g h ts r e s e rv e dP II S 0 9 2 1 - 8 0 0 9 ( 9 6 ) 0 0 0 2 1 - 3

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74 s.s. Nandwani Ecological Economics 17 (1996) 73- 81v a l u e o f f i r e w o o d , e n e r g y f o r c o o k i n g w i ll b e b e -t w e e n 3 0 1 0 a n d 6 4 5 0 k c a l / p e r s o n / d a y .2.2. Costa Rica

I n th e c a s e o f C o s t a R i c a , t h e f u e l s c o n s u m e d a r eb i o m a s s a n d e le c t r i ci t y ( 7 0 - 8 0 % f r o m h y d r o a n dr e s t f r o m i m p o r t e d o i l a n d g a s) . T h e c o n s u m p t i o n i n1 9 9 2 f o r a l l f u e l s i n a ll s e c t o r s i s s h o w n i n T a b l e l a

( D i r e c c i 6 n S e c t o r i a l d e E n e r g i a , 1 9 94 ) . O f th i s t o t ale n e r g y , 3 6 % i s u s e d i n t h e d o m e s t i c s e c t o r ( T a b l el b ). F r o m t h i s w e w i l l e s t i m a t e w h a t p a r t o f t h i sd o m e s t i c e n e r g y g o e s i n to c o o k i n g . B a s e d o n t h eo f f i c i a l d a t a ( D i r e c c i 6 n S e c t o r i a l d e E n e r g [ a , 1 9 9 4)t h e f o l l o w i n g a r e th e p e r c e n t a g e s o f t h e p o p u l a t i o nu s i n g d i f f e r e n t c o o k i n g f u e l s :7 8 . 9 % u s e e l e c t r i c i t y , 2 6 . 4 % u s e f i r e w o o d ,

Table 1a. Total energy consumption in Costa Rica, by various sources (in1992)Sources Bio- Elec- O il/ ga s Totalmass tricityAbsolute PJ 28.11 13 .2 41.44 82.75Relative cA 33.97 15.9 5 50 .08 100b. Total energy consumption in domestic sector in Costa RicaSources Bio- Elect. Gas Kero- Total

mass (~) seneAbsolute PJ 23 .1 5.6 0.53 0.52 29.75Rela tive % 78 18.7 1.7 1.6 100

c. Total energy consumption tbr cooking in domestic sector (DS}in Costa Rica

1 8 . 6 % u s e L . P . G . ,3 . 3 % u s e s o f t c o a l ,1 . 0 % u s e k e r o s e n e , e t c ,

I t m a y b e n o t e d t h a t s o m e f a m i l i e s u s e a s m a n y a s2 o r 3 c o o k i n g f u e l s , e i t h e r f o r d i f f e r e n t c o o k i n gp r o c e s s e s o r f o r e m e r g e n c y p u r p o s e s . A l t h o u g h n or e a l d a t a a r e a v a i l a b l e t o s h o w t h e a b s o l u t e c o n s u m p -t i o n i n t h e c o o k i n g s e c t o r , as d i s c u s s e d w i t h I n g .A l l a n C h i n W o o f D i r e c c i 6 n S e c t o r i al d e E n e r g i a ,o n e c a n c o n s t r u c t t h e s e n u m b e r s w i t h o u t a n y a p p r e -c i a b l e e r r o r ( T a b l e l c ) . W e f i n d t h a t 2 9 . 4 % o f t h et o t al e n e r g y c o n s u m e d i n C o s t a R i c a is s p e n t o nc o o k i n g .

2.3. Some other countriesI n A f r i ca , f o r e x a m p l e , 9 0 % o f th e p o p u l a t i o n

u s e s f i r e w o o d f o r c o o k i n g . I n I n d i a 1 5 0 m i l l i o n t o n so f f ir e w o o d , 5 2 m i l l i o n t o n s o f c o w d u n g , a n d 3 6m i l l i o n t o n s o f o t h e r w a s t e b i o m a s s a r e u s e d o n l y f o rc o o k i n g . T h e s e h u g e a m o u n t s o f n o n - c o m m e r c i a ls o u r c e s a r e e q u i v a l e n t t o a b o u t 4 5 % o f t h e t o t a le n e r g y a v a i l a b l e i n th e c o u n t r y . O n t h e o t h e r h a n d ,i n t h e U n i t e d S t a t e s o n l y 2 0 % o f t he t o ta l e n e r g yp r o d u c e d i s c o n s u m e d i n t h e d o m e s t i c s e ct o r , o fw h i c h o n l y 5 % ( o r 1 % o f th e t o t a l) i s u s e d f o rc o o k i n g .

SourcesBiom ass 90CA, of biomass used in DS ~ 20.79 PJElectricity 45% of the electricity used in DS h 2.52 PJNatural gas 100CA f the gas used in DS 0.53 PJKerosene 50% of the kerosene used in the DS c 0.26 PJT o t a l / 2 4 . 3 6 P JyearPJ = pent ajou les = 1015 J .:" Mainly firewood.a Rest o f the biomass is used for heating water.b ICE, Co sta R ican Electricity Institute, official data.

Rest of kerosene is used for lamps, etc.

2.4. International levelF u e l w o o d i s t h e m a j o r e n e r g y s o u r c e i n d e v e l o p -

i n g c o u n t r i e s b e c a u s e o t h e r f u e l s a r e e i t h e r n o t a v a i l -a b l e o r ar e e x p e n s i v e . T w o b i l li o n p e o p l e c o o k w i t hf i r e w o o d o r a n i m a l d u n g . I n o t h e r w o r d s , h a l f t h em e a l s f o r E a r t h ' s 6 b i ll i o n p e o p l e a r e c o o k e d w i t hw o o d f i re s ea c h d a y .

3 . C o n v e n t i o n a l m e a n s o f c o o k i n g a n d t h e i r c o n -s e q u e n c e s

3.1. Fuel wood / a gricultural residuesA s e x p l a i n e d a b o v e , f i r e w o o d a n d o t h e r t y p e s o f

b i o m a s s a r e t h e m a j o r f u e l so u r c e s f o r c o o k i n g . T h ev a r i o u s s t e p s i n v o l v e d i n th i s p r o c e s s a r e :

S U N - p l a n t i n g t r e e s - g ro w i n g t r e e s - c u t t i n g / b u y -

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s.s. Nandwani Ecological Economics 17 (1996) 73 81 75i ng t r e e s - t r a ns po r t i ng / w a l k i ng - C O O K I N GRANGE (STOVE).

Firewood has advantages, such as ease of storage,with the result that it can be used at any time andanywhere. However, the excessive burning of thesefuels for cooking has the following drawbacks whichaffect the welfare of millions of people all over theworld:3.1.1. Shortage of fir ewo od

According to the United Nations Food and Agri-cultural Organization, some 2400 million people areexpected to face acute fuelwood shortages by the endof the century with serious nutritional and healthconsequences.3.1.2. Cost

Due to a shortage of fuelwood in many places,users must pay high prices. In rural areas of China, afamily may spend up to 25% of its income onfirewood.3.1.3. Transport

In many places children walk many miles tocollect fuelwood. Afghan refugees in Pakistan usedto spend 99 man-hours per month collecting fuel forcooking (Magney, 1988).3.1.4. EO'iciency

Firewood and agricultural wastes have very lowburning efficiency.3.1.5. Health / social

The firewood stove is a major source of concen-trated indoor air pollution. The World Bank's Devel-opment Report 1993, reports that eliminating indoorsmoke caused by cooking and heating could cutchildhood pneumonia by half and reduce the burdenof other diseases by 5% (Solar Box Joumal, 1994a).3.1.6. D~q'orestation

It has been estimated that at present more than 15million hectares (150 000 km 2) of forests are lost peryear in developing countries, mainly due to theconsumption of firewood. This area is equivalent toabout 3 times that of Costa Rica. Unfortunately, therate of deforestation is more than the reforestationrate in many parts of the world.

3.1.7. Fertil izer and erosion o f soilThe use of cow dung as a fuel for cooking

(common in India) is extremely unfortunate, as thisfuel is a good fertilizer. About 400 million tons ofwet cow dung (equivalent to about 80 million tons ofdried dung) are burned annually in India alone,which wastes nutrients and organic material. Thisrepresents enough fertilizer to grow 20 million tonsof grain, enough to feed 100 million people for ayear (Kammen and Lankford, 1990).3.2. Electricity

Next to firewood stoves, electricity is the mostimportant fuel source used for cooking. In the caseof hydroelectricity, the different steps involved are:SUN-reservoir-dam-flow of water- turbine-generator- distribution-transmission of electricity-COOKING RANGE.

Hydroelectric plants have a number of negativeenvironmental effects, such as the high initial cost ofhydroelectric dams, cost of transmission of electric-ity, floods, sedimentation, displacement of personsliving at the site, decrease in hydro potential espe-cially in summer, habitat loss, etc.

At the world level, programs countering fuelscarcity so far have concentrated on planting trees,teaching better charcoal-making techniques, and pro-moting more efficient wood stoves. But these pro-grams can have only limited effects on overall woodconsumption, as growing populations depend socompletely on wood.

4 . A l t e r n a t i v e m e a n s - - s o l a r c o o k i n gSolar cookers, using the sun's free energy, offer

tremendous potential for aiding in the solution of thefuel 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 worlddiscussed above have a high water content, cooking

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76 S.S. Nandu'ani / E{'olo~ical Economi~"l~]17 (1996) 73 - 81

\\

Fig. I. Scheme for conventionalsolar oven. (I) Transparent glasspanes. (2) Galvanised iron plate. (3) Glass wool as heat insulator.(4) Reflector. (5) Door to introduce he food. (6) Rod with variousholes to adjust the reflector. (8) Outer case of the solar oven.

requires temperatures only in the order of 90-100C(except for frying). Higher temperatures of course,have the advantage of reducing the cooking time.Solar ovens can easily attain these temperatures.4 .2 . T e c h n i c a l a s p e c t s

There are two types of solar stoves: the hot boxsolar oven and the concentrating solar cooker. F o rvarious reasons, the first type of stove is commonlyaccepted at the world level. A detailed design can beseen in Fig. 1 (Nan dwan i, 1980; Nand wani , 1993).In brief, a solar cooker is a highly insulated box witha black metal plate kept in the box for absorption ofsolar radiation. The top is glass, and often exteriorreflector(s) are used to concentrate the sun's raysinto 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. Adouble -pane glass top also helps in insulation.

The box can be opened either at the front or fromthe top. Fig. 2 shows one of the models designed,studied, and used by the author for last 16 years.

4 . 3 . I n i t i a l c o s tAs will be seen in the next section, there are

various models (Ku hnk e et al., 1990) made withdifferent materials, and hence different thermal per-formances, durability, and different costs (US$ 5-1500). Howeve r, a fami ly-si ze oven (0.25 m e) withreasonable durability and efficiency (outer box madeof wood, two window panes, etc.) may cost aroundUS$40-50 (materials cost), and it can be made athome using only hand tools.4 . 4. V a r i o u s m o d e l s

Listed below are the various models made by theauthor, and also some of the 100 models made at theinternational level.4 . 4. I . A u t h o r ' s m o d e l s ( s h o w n i n Fig ,, 3 ) a r e :I. Simple hot box (The Tico Times, 1979),2. Impro ved hot box (Nan dwan i, 1993),3. Sola r-electric oven (Nandwa ni, 1989),4. Heat storage oven, (Nan dwan i, 1990),5. Solar oven integrated with water heater (Nan dwan i

and Fernandez, 1995),6. Solar oven integrated with drier (Nandwani and

Fernandez, 1995),7. Solar-powered microwave oven (Currin et al.,

1995),8. Parabol ic cooker

Details of these models can be obtained in thereferences listed.

Fig. 2. Actual conventional olar oven.

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S.S. N a m t w a , i / E c o l o . q , ic a l E c o m , , i c ~ 1 7 ( 19961 73 ~, '1 77

F i g . 3 . V a r i o u s s o l a r o x c n s d e s i g n e d b y t h c a u l h o r .

i

F ig . 4 . S o m e o f t h e i n l e r n a t l o n a l m o d e l s o f s o l a r o v e n s / c o o k e r s .

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7 8 S . S . N a l M w a . i / E co lo ,g , i c a l E c o . o m i c s 1 7 ( 1 9 96 ~ 7 3 - 8 1

4 . 4 . 2 . h T t e r n a t i o n a l m o d e l s . "F i g . 4 s h o w s s o m e o f t h e 1 00 l a b o r a t o r y a n d

c o m m e r c i a l m o d e l s o f s ol ar c o o k e r s / o v e n s f ro mI n d i a , U S A , F r a n c e , G e r m a n y , a n d S w i t z e r l a n d .T h e s e c a n b e c l a s s i f i e d in f o u r c a t e g o r i e s ( K u h n k e e ta l . , 1 9 9 0 ; P e j a c k , 1 9 9 2 ) . h o t b o x o v e n , w i t h o u t o r w i t h 1 - 8 r e f l e c t o r s,

s o l a r c o o k e r , w i t h p a r a b o l i c c o n c e n t r a t o r ,s o l a r o v e n , w i t h v a p o r c o o k i n g ,

h e a t st o r a g e s o l a r o v e n s4 .5 . M e a l s c o o k e d i , t h e s o l a r o c e n

T h e s i m p l e h o t b o x m o d e l c a n b e a n d h a s b e enu s e d t o c o o k , b a k e , a n d r o a s t p r a c t i c a l l y al l ty p e s o fm e a l s ( N a n d w a n i , 1 9 93 ) , w h e r e a s f o r f r y in g t h ec o n c e n t r a t o r c o o k e r i s r e q u i r e d .4 .6 . N u m b e r o f m e a l s c o o k e d w i t h so l a r o v e n / c o o k e r

O b v i o u s l y i t d e p e n d s o n t h e d e s i g n o f t h e c o o k e r ,c l i m a t i c c o n d i t i o n s , a n d t h e c h a r a c t e r o f t h e u s e r .H o w e v e r , i n C o s t a R i c a , b e t w e e n 3 0 0 a n d 4 5 0 m e a l sc a n b e c o o k e d p e r y e a r f o r a f a m i l y o f 4 - 5 p e r s o n s .4 . Z O t h e r a d l ' a n t a g e s

B e s i d e s c o o k i n g , t h e s o l a r o v e n c a n d o a v a r i e tyo f j o b s - - i t c a n d r y a g r i c u l t u r a l p r o d u c t s , h e a t an dp a s t e u r i z e w a t e r , m a k e t e a a n d c o f f e e , a n d h e a t i r o n sf o r ir o n i n g c l o t h e s ( M e t c a l f , 1 9 95 : N a n d w a n i a n dF e r n a n d e z , 1 9 9 5 ) .4 . 8 . F u e l s a t i n g ,

F o r a c o n s u m e r w h o h a s p u r c h a s e d a s o l a r c o o k e r ,f i n a n c i a l g a i n w o u l d d e p e n d o n t h e f o l l o w i n g f a c -t o r s : n u m b e r a n d ty p e o f m e a l s c o o k e d ,

t y p e o f c o n v e n t i o n a l f u e l u s e d b y t h e c o n s u m e rb e f o r e t h e u s e o f a s o l a r o v e n . i t s e f f i c i e n c y a n dc o s t i n c l u d i n g t r a n s p o r t a t io n . H o w e v e r , s o m er o u g h e s t i m a t e s c a n b e m a d e o f s a v i n g s a t d i f f e r -e n t l e v e l s .

4 . 8 .1 . F a m i l y l e c e lW i t h a n a v e r a g e s o l a r i nt e n si t y o f 3. 5 k W h / m 2

p e r d a y , n o r m a l l y t w o m e a l s c a n b e c o o k e d . B a s e do n t h e s e d a t a a n d a k n o w l e d g e o f c l i m a t i c c o n d i -

t i o n s , a s i n g l e f a m i l y i n C o s t a R i c a c a n u s e a s o l a ro v e n f o r 7 - 8 m o n t h s a n d c a n c o o k a b o u t 3 5 0 m e a l si n a y e a r . w h i c h c a n s a v e :

1 0 00 k W h o f e l e c t r i c i ty p e r y e a r.2 4 0 l i te r s o f p r o p a n e g a s .2 4 2 l i t e r s o f k e r o s e n e , o r7 2 5 k g o f f i r e w o o d p e r y e a r .W i t h t he p r e s en t c o s t o f e l e c tr i c it y ( $ 0 . 0 6 / k W h ) ,

s a v i n g s w o u l d b e a r o u n d U S $ 6 0 p e r y e ar . I n o t h e rw o r d s , t h e i n i t i al c o s t o f a g o o d s o l a r c o o k e r ( w i t h ad u r a b i l i t y o f a b o u t 5 - 6 y e a r s ) ca n b e r e c o v e r e d i n1 2 - 1 4 m o n t h s ( w i t h o u t c o n s i d e r i n g f u t u re i n c r e a se si n e l e c t r i c i t y p r i c e s ) .4 . 8 .2 . N a t i o n a l l e c e l ( C o s t a R i c a )

B a s e d o n t h e s a v i n g o f d i f f e r e n t f u e l s b y e a c hf a m i l y , m e n t i o n e d a b o v e , o n e c a n c a l c u l a t e t h e t o t a ls a v i n g s b y t h e c o u n t r y a c c o r d i n g t o t h e n u m b e r o ff a m i l i e s w h o u s e s o l a r c o o k e r s . A s a n e x a m p l e , w ec a n c a l c u l a t e t h e p o s s i b l e s a v i n g s o f e l e c t r i c i t y i nC o s t a R i c a d u e t o th e u s e o f s o l a r o v e n s . A c c o r d i n gt o 1 9 9 2 d at a , 7 9 % o f a l l C o s t a R i c a ' s 7 0 0 0 0 0 f a m i -l i es w e r e u s i n g e l e c t r i c r a n g e s f o r c o o k i n g . B a s e d o n1 0 00 k W h o f e l e c tr i c e n e r g y s a v e d p e r f a m i l y ( u s in gs o l a r o v e n s 6 - 8 m o n t h s ) p e r y e a r , to t a l s a v i n g s ine l e c t r i c e n e r g y o n a n a t i o n a l l e v e l w o u l d b e :7 0 0 0 0 0 * 0 . 7 9 * 1 0 00 = 5 5 3 m i l l i o n k W h / y e a r s a v e d( in a d d i t i o n to t h e s a v i n g o f a b o u t 6 5 0 - 7 5 0 k g o ff i r e w o o d p e r y e a r p e r f a m i l y ) . C o r r e s p o n d i n g l o s se sf o r t h e n a t i o n a l e l e c t r i c u t i li t y c o m p a n y ( I n s t i tu t oC o s t a r r i c e n s e d e E l e c t r i c i d a d ) d u e t o l o w e r s a l e s o fe l e c tr i c it y ( $ 0 . 0 6 / k W h ) w o u l d b e U S $ 3 3 .2 m i l -l i o n / y e a r .4 . 8 .3 . h z t e r , a t i o n a l l e c e l ( a n e s t i m a t e .f t, " t h e y e a r2 0 0 0 )

T h e n u m b e r o f f a m i l i e s c o o k i n g w i th f i r e w o o d ind e v e l o p i n g c o u n t r i e s i s 4 0 0 m i l l i o n ( 2 0 0 0 m i l l i o np e o p l e / ~ 5 p e r f a m il y ).

A t t h e p r e s e n t t i m e a b o u t 5 3 0 0 0 0 s o l a rc o o k e r s / o v e n s h a v e b ee n m a n u f a c t u r e d i n d i f fe r e n tc o u n t r i e s a n d m o r e a r e b e i n g c o n s t r u c t e d e a c h d a y .l , e t u s s u p p o s e t h a t b y t h e y e a r 2 0 0 0 t h a t o n l y I % o ff a m i l i e s c o o k i n g w i t h f i r e w o o d u s e s o l a r c o o k e r s( i. e ., j u s t 4 m i l l io n ) . T h e f i r e w o o d s a v e d w o u l d b e :0 .7 0 t o n / f a m i l y / y e a r * 4 m i l li o n

= 2 . 8 m i l l i o n t o n s / y e a r

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s.s. N and wa ni/ Ecological Economics 17 (1996) 73-81 79(plus electricity and gas saved, by the users of thesefuels).4 . 9 . P o l l u t a n t s s a t i n g ( e n t : i r o n m e n t a l e f f e c t s) , i n t h ey e a r 2 0 0 5

Use of solar cookers in addition will reduce emis-sion of pol lutan ts such as SO 2, fly-ash, smoke, andthe main greenhouse gas, CO.-.

Solar Cookers International, a non-profit organi-zation (Sacramento, CA, USA), believes that 2400million people will be aware of Solar Cookers by theyear 2005 if the cookers are properly developed andpromoted. If we assume only 5% of them (120million or around 24 million families) use solarcookers, there would be a savings of 16.8 milliontons of firewood per year.

Let us calculate approximately the reduction ofCO~ emission due to this saving of firewood.4 . 9 .1 . D i r e c t e m i s si o n o f C O ,

Assum ing 35% of carb on (C) content in firewood,the total C of the firewood saved would be 5.88million tons. According to the chemical reaction,C + O.- ---, CO 2, total CO 2 not emit ted 3 wou ld be(a):= 5.88 )4 (4 4/ 12 ) = 21.6 mill iont ons/ year ,

4 . 9 .2 . I n d i r e c t e m i s s i o n o f C O ~Trees, if not cut, absorb carbon dioxide and pro-

vide oxygen for all of us. If burnt, in addition toemit ting CO 2, they will not be able to ab sorb thisCO,. Thus there is indirect emission of CO 2 fromnot cutting the trees. Assuming trees were cut to getfirewood for cooking and each tree provides roughly300 kg (0.3 ton) of dry wood, the num be r of treessaved, due to the use of solar ovens, per year wouldbe:= 16.8 million to ns /0 .3 ton = 56 million

On average each hectare of forest (~ 100 trees)has the c apacity to absorb 30 tons o f CO 2 per year.

Molecular weight of carbon and CO, are 12 and 44 atomicmass units, respectively.

Thus, the quantity of CO 2 not absorbed would be(b):= 56M * 30ton s /100 = 16.8mil l iontons /yearTherefore the total reduction in emissi on of CO 2 peryear (a + b) = 38.4 mill ion tons.

In addition, there will be some reduction in theemiss ion of CH 4, smoke and ash, etc., due to lessburning of firewood.

Although the literature gives various costs forremoving carbon dioxide from the atmosphere, wecan take as an average US$ 100-200/ton. Thus,cleaning of 38.4 million tons of CO. may require$3840-7680 M/year .

The total i nvestme nt (material and labor costs) toc o n s t r u c t 24 million reasonably durable solar ovenswill be US$2000-2400 million. This is the invest-ment to be made only once in 5-6 years. Thus, solarovens are economically and ecologically viable.4 . 1 0 . L i m i t a t i o n s o f s o l a r o t 'e n s / c o o k e r

Some of the limitations of solar ovens include(Nandwani, 1995):1. irregular avail ability of solar radiation,2. inabi lity to store and transport heat energy,3. unsui tabil ity at high latitudes,4. traditional cooking and eating habits,5. longer cooking time.

This explains in part why solar cookers have notbeen used on a large scale (Blum, 1995).

Table 2Approximate number of solar cookers constructed and or dis-tributed in different countriesIndia 340028 (Garg, 1995)China 140000 (Hongpeng, 1995)Tibet 20000 (Hongpeng. 1995)Pakistan (Afghan refugees) 10000Switzerland 60 00 (SustainableEnergy News,1994)United States of America 3000South Africa 2720 (SolarBox Journal,1994b)Kenya 1250Ladakh, Mexico. Nicaragua. CostaRica, Ecuador, Chile, Nepal 2 100Total 525000

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80 S .S. Na n d wa n i . / Eco l o c, i ca l Eco mm l i c~ 1 7 ( 1 9 9 6J 7 .? 8 15 . N u m b e r o f s o la r c o o k e r s a t t h e w o r l d l ev e l

I t i s v e r y d i f f i c u l t t o e s t i m a t e t h i s n u m b e r . H o w -e v e r , s o m e d a t a b a s e d o n a l i te r a t u re s u r v e y w e r ec o m p i l e d a n d a r e s h o w n i n T a b l e 2 ( i n c l u d e d i n t h el i st a r e o n l y c o u n t r i e s h a v i n g a t l e a s t 1 0 0 0 c o o k e r s ) .T o t a l s o l a r c o o k e r s , a s s u r v e y e d b y t h e a u t h o r , a r ea b o u t 5 2 5 0 0 0 .

L . P .G . o r k e r o s e n e . I n 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 R i c a , C h i l e , I n d i a , T i b e t , K e n y a , C u b a ) t h e r ea r e s o m e s m a l l r e s t a u r a n t s , c o m m u n i t i e s , p r i s o n s ,u n i v e r s i t i e s , e t c ., t h a t u s e s o l a r c o o k e r s a l o n g w i t hc o n v e n t i o n a l f u e l s .

A c k n o w l e d g e m e n t s

6 . C o n c l u s i o n s6 .1 . S u m m a # w

P r o p o s e d n u m b e r o f s o l ar o v e n s / c o o k e r sI n t h e y e a r 2 0 0 5I n i t i a l c o s t ( d u r a t i o n 5 y e a r s )I n i t i a l c o s t ( p e t " y e a r )F i r e w o o d s a v i n g p er y e a rC O e s a v i n g p er y e a rC o s t o f c l e a n i n g t h i s g a sp e r y e a r

2 4 0 0 0 0 0 0 .U S $ 2 4 0 0 m i l l i o nU S $ 4 8 0 m i l l i o n1 6 . 8 m i l l i o n t o n s3 8 . 4 m i l l i o n t o n sU S $ 3 8 4 0 - 7 6 8 0m i l l i o n .

" T h i s f i g u r e i s v e r y h i g h . H o w e v e r , t h e S 50b i l l io n r a i s e d i n a m a t t e r o f m o n t h s t o f i n a n c e / h eG u l f W a r i s e v i d e n c e o f w h a t c a n b e a c c o m p l i s h e dw h e n t h e n e e d i s j u s t i f i e d ( H e r a l d , 1 9 9 2 ).

7 . C l e a r e x a m p l e o f e c o l o g ic a l a n d l o g ic a l e c o -n o m i c s7 .1 . F i n a l r e m a r k s

S o l a r e n e r g y i s f r ee a n d a b u n d a n t ( o n t h e g l o b a ll e v e l ) . H o w e v e r , i n a n y p a r t i c u l a r p l a c e i t i s n o ta v a i l a b l e 2 4 h o u r s a d a y a n d c a n n o t b e s to r e d a n dt r a n s p o r t e d ( a s w i t h c o n v e n t i o n a l f u e ls ) . T h u s t h eu s e o f s o l a r o v e n s c a n n o t c o m p l e t e l y r e p l a c e c o n v e n -t i o n a l f u e l s . B u t t o t h e e x t e n t t h a t s o l a r o v e n s c a n b eu s e d , t h e y w i l l g r e a t l y r e d u c e d e f o r e s t a t i o n , a i r p o l-l u t io n , 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 w i l l c o n s e r v ec o n v e n t i o n a l f u e l s .

S o l a r c o o k e r s h a v e a l r e a d y b e g u n t o g a i n t h ei m a g e o f a n e f f e c ti v e f u e l s a v e r , p a r t i c u l a r l y a s as u p p l e m e n t a r y o p t i o n t o c o m m e r c i a l f u e ls s u c h a s

T h e a u t h o r i s t h a n k f u l t o M r . 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 , f o r c o n -s t r u c t i n g v a r i o u s s o l a r c o o k e r s , t o M r . M a r v i nA l p i z a r , e l e c t r i c a l t e c h n i c i a n , f o r h e l p i n g w i t h e l e c -t r i ca l c o m p o n e n t s , a n d t o P r o f. O t o n i e l F e r n a n d e z ,a l s o f o r h e l p i n g w i t h m e a s u r e m e n t s . T h e a u t h o r i sa l s o g r at e f u l t o M r . M a r t i n O g l e , t h e r e v i e w e r o f t h em a n u s c r i p t , f o r m a k i n g v a r i o u s u s e f u l s u g g e s t i o n s .

R e f e r e n c e sBhnn, B.L.. 1995 . Sola r cooking prom ot ion : recomendal ions f romgrass roots organizations. In: S.S . Nandw ani. E . Pejack and B.Blum (Editors) , Dexelopments in Solar Cookers, Proc eedingsof the Second Wor ld Conference on Solar Cookers - -Use andTechnology,. 12-1 5 July, 199 4, Univ ersidad Naciomd. Costa

Rica, pp. 228 235.Currin C. , Nandwani. S.S . and A lpizar, M . , 199 5. Prel iminarystudy of solar powered microwave oven. In: S.S. Nandwani.E. Pejack and B. Blum (Editors) , Developments in SolarCookers. Proceedings of the Second W orld Conference onSolar Co oke rs - -U se and Technology , 12-15 J u l y . 1994, Uni -versidad Nacional. Costa Rica, pp. 149 158.

Dircccidn Scctorial de Energfa, 1994 . In: Diagnostico del SectorEnergfa. Periodo 1970 -1993, M inisterio de Recursos N atu-rales. Encrgfa y Minas, Republica de Costa Rica. September1994, 159 pp.Garg, H .P, , 19 95 . Solar cooking technolo gy and promotionalprogram in India. In: S.S . Nandw ani, E. Pejack and B. Blum(Editors), Dev elopm ents in Solar Cookers, Proceedings of theSecond Wor ld Con/ ie rence on Solar Cookers - -Use and Tech-nology, 12 15 July, 199 4, Univ ersidad Nation al , Costa Rica.pp . 27-43 .Herald. R.N. 1992. The Sun shine Revolution. SU N-LA B Publishers. Norway. 187 pp.Hongpeng. L . 199 5. Dev elopm ents in solar cookers. In: S.S.Nand,,~,ani. E. Pejack an d B. Bln m (Editors). P roceedings ofthe Second World Con ference on Solar Cookers Use andTechnology. 12-15 , July 1994 , Universidud N acional . CostaRica. pp. 330 335.Kammen, D.M. and Lankford. W .M.. 19 90 . Cook ing in thesunshine. Nature, 348: 385-386.

8/22/2019 69959847 Sola

9/9

S.S. Nandw~mi / Ecological Ecommlics / 7 (/996) 73 81 81Kuhnke K.. Reuber, M. and Schwefel, D., 1990. Solar Cookers in

the Third World. Fr iedr . Vicweg und SohnBraunschwei g/Wiesbad en. Germany, 228 pp.

Mugney, G., 1988. Providing solar cookers to Afghan refugees.In: W,H. BIoss and F. Pfisterer (Editors), Advances in SolarEnergy Technology, Proceedings ISES, Solar World Congress,Hamburg, Germany, Vol. 3, Pergamon Press, pp. 2688-2692.

Metcalf, R., 1995. Solar water pasteuri zation and other non cook-ing applications of solar cookers. In: S.S, Nandwani, E. Pejackand B. Blum (Editors), Developments in Solar Cookers, Pro-ceedings 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 climateof San Jose, Costa Rica. In: International Symposium on theSolar Energy Utilization, University of Western Ontario,Canada, August 10-24. 1980. Published in Solar EnergyConversion II, Pergamon Press, 488 pp.

Nandwani, S,S.. 1989. Design, construction and experimentalstudy of electric cum solar oven. Solar Wind Technol., 6 (2):149-158. Pergamon Press.

Nandwani, S.S., 1990. Cheap Sola r 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 /Ho rno Solar-Hagala Usted

mismo!. Fundacion Univcrsidad Nacional, Heredia, Costa Rica,98 pp.

Nandwani, S.S., 1995. From cheap /si mpl e three stones to expen-siv e/Adva nced convective cookers. Ill : S.S. Nandwani, E.Pejack and B. Blum (Editors) , De','elopments in Solar Cook-ers, Proceedings of the Second World Conference on SolarCoo ker s- -Us e and Technology, 12~15 July, 1994. Universi-dad National, Costa Rica, pp. 17-26.

Nandwani, S.S. and Fernandez, O., 1995. Experimental study ofsolar oven cure water heater and solar oven cmn drier. I1. In:S,S. Nandwani , E. Pejack and B. Blum (Editors), Develop-ments in Solar Cookers. Proceedings of the Second WorldConference on Solar Cookers--Use and Technology, 12-15July. 1994, Universidad National, Costa Rica, pp. 273-284.

Pejack, E. (Editor), 1992. Proceedings of First World ConDrenccon Solar Cooking, 19-20 June, Stockton, CA, USA, 158 pp,

The Tico Times, 1979. Sunny vision s--g ett ing a charge from OldSol. 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 CookersNorthwest, Seattle. WA. USA, 5(I), February 1994.

Solar Box Journal, 1994b. The Newsletter of Solar Box CookersNorthwest, Seattle, WA. USA, 5(3), October, 1994. p. 2.

Sustainable Energy News. 1994. Denmark. No. 6, September,1994,