KEYWORDS: Parabolic cooker, absolute poverty, Nepal
People who collect their cooking fuel themselves are a difficult target group for solar cooker dissemination because they do not save money by using SCs, i.e. the payback time of a SC is infinite. Use of SCs saves time of family members with collection duties but it does not directly benefit the persons with cooking duties. Thus, from the SC acceptance point of view the validity of the fuel collection timesaving argument is questionable.
a) ALIEN TECHNOLOGY: While women take good care of their houses and men take good care of their tools and machines, say micro hydro mills [3], transferred technology frequently suffers from a lack of maintenance, even as simple as wiping dust off cooker's glass. People consider SCs alien technology and request continuous support from outside.
b) LOW PERFORMANCE: The overwhelming main reason for disacceptance in our project, a fact that women always mention, is the slowness of the box SC compared to their traditional 3 stone biomass stoves. As Table 1 shows this is a very natural reaction, especially when not considering the wood collection timesaving an advantage, as mentioned earlier. Also, although many local dishes can be prepared, with low nutrient losses [4], and water pasteurized [5], baking and frying can not be done.
| Cooker type | Boiling time, 2 l water [min] |
|---|---|
|
|
c) HIGH PRICE: Affordability is a crucial requirement of SCs offered for people who do not pay money for their fuel and who are extremely poor moneywise. The price should be of the same order of magnitude with utensils people find important enough to purchase. Appropriate targets are the price ranges $1-$3 of metal cooking pots and $0-$6 of improved biomass stoves.
The most popular of cooker types, box cooker, may reach the performance requirement, but with a price tag of over $1000. Most existing models that cost $30-$50 are slow (Table 1 and [6]). Due to the requirement of many factory made parts (glass, metal tray and pot, reflecting material) it is very difficult to build, or produce in series, a box SC for under $10, even if the box itself can be made in villages where useful materials like clay, dung, wood, bamboo and grass are available. The use of factory made parts also raises a difficult maintenance problem.
Panel cookers used successfully in refugee camp conditions are cheap but have lower performance than box cookers. They also require many factory made parts: plastic bag or cover, metal pot and reflector material. These cookers have a good potential for upsizing with low price increase. However, to reach our performance target the reflector would need to be very large.
Parabolic cookers are popular in Tibet where 140,000 have been sold [7]. The Chinese steel cookers are faster than 3 stone ovens and they can match electric oven in performance. Later we show that parabolic SC can be made almost with skills and materials available in Southern Nepal. The only required factory made component is reflecting material (2 m2 of Al foil costs about $1). Even the metal pot can be avoided because if the mirrors are made well enough a clay pot will do. Also, baking and frying are possible and food can be stirred during cooking.
BSCs were made of cardboard, clay-dung, cement and plywood. Both vertical and tilted tops, single and double glass, with or without reflectors, were built using paper balls, peddy husk, plant leafs, peddy straw and corn sheath as insulation. Tilted double glass plywood box with reflector and paper ball or peddy husk insulation ($22) performed the best but only marginally better than the corresponding clay-dung box ($15). The most indigenous and the cheapest design, a single glass clay-dung box ($11) cooked a meal of 0.5 kg of potatoes, 0.5 kg of rice and 5-6 eggs in 2.5 h. This is a meal for 1/3 of family.
The BSC project (except in Kathmandu and in the first Hawpur course) was organized the same way as the other subprojects of the integrated rural development program of PFL [10,11] (which is in Saptari and in Siraha a part of GTZ Churia Hills Forest Development Project). First, in the awareness creation phase, PFL staff members told about and demonstrated SCs in villages. Second, interest groups were formed by villagers or SC interest was born in existing women's interest groups (women's committees). Third, workshops were applied by the interest group. Fourth, workshops were delivered by PFL staff to couples chosen by the interest groups. And finally, follow-up and SC user support was conducted by PFL (and TFL, to a lesser extent).
Most of the workshop participants used their cookers at least for a few weeks. In Saptari where people were the most motivated they cooked within 4 months in average 10% of their food with SCs, i.e. saving 10% of fuel, because space heating is rarely needed in Terai. For those buying their firewood this means saving a bundle of firewood per month, costing $1 in countryside. Thus, the SBC payback time is 1-2 years. In Kathmandu where firewood costs 4 times more the payback time would be 3-6 months with 10% usage. The most motivated family in the city of Hetauda, Makwanpur, reported 30% savings of kerosin.
Now, very few continue using their SBC for reasons described earlier (and due to disturbances by children, animals, rain and clouds but, surprizingly, no religious impediments have been given). Moreover, no independent SBC fabrication, i.e. self-spreading of the technology has been noticed. So far none has applied for funds for purchasing the factory made parts for self-constructed SBC. And, none has applied for micro loan within the PFL income generation program for establishing an artisan workshop for commercial manufacturing of SBCs.
Due to the unsatisfactory SBC dissemination results among adult population we continue the program only in two elementary schools (in Makwanpur and in Saptari) where SBC workshops were conducted in 1996. Since fall 1995 we have concentrated more on parabolic cooker (PT-LIFE) development.
A cooker design workshop was conducted (spring 1995) with interested villagers in Saptari. The villagers with PFL staff members as facilitators designed and built a clone of the Chinese PSC out of large traditional bamboo baskets covered by clay-dung mixture, as in their buildings, Al foil and bamboo support structure, imitating their building architecture. Description of the prototype construction process of the PT- LIFE cooker is given in [12] and [13]. The cost of the prototype was 18 person-hours of work and $3. The only required factory made material is the Al foil costing about $1.
The cooker technology has not yet matured to a level acceptable to villagers. The performance is 2-3 times lower than 3 stones, although by about the same amount higher than SBCs. The main reasons for low performance are too small reflector area, the quality of dish surfaces and the shape of the dishes.
In addition, the prototype was very heavy and horizontal tracking required moving the whole system. These problems have been addressed during further development when total of 11 PT- LIFE cooker variants have been built. The latest variants include horizontal and vertical bamboo axels for easier tracking, and lighter bamboo dishes.
The performance problems are currently being dealt with, the dish shaping being the main concern. The parabolic shape for the mold can be plotted using a simple tool that can be made of wood and strings. With deep focus mirrors the shape would not be so critical.
The PT-LIFE cooker concept, i.e. technology designed and manufactured by target group members, has a potential to become accepted and spread without external contributions. The main components of this design, i.e. a parabolic basket and a dish support system, can be done everywhere. At this moment the technology is not yet mature and accepted.
Our alternative approach is commercial artisan manufacturing, a strategy behind the breaktrough of many improved cooking stove programs. We are offering income generation loans for this purpose for various SC models, including SBCs and metallic SPCs.