Solar Cooker Research Starts: 1980

Land Research Institute (LRI), a not-for-profit organisation started research in solar cooker design.

At that time, 40% of India’s energy was consumed in cooking.

That figure has not changed significantly since.

Solar Cooker Models Then Available

These were

• The box-type cooker. Its disadvantage was that it did not cook two meals a day in winter.
• The concentrating cooker with a sharp focus. The disadvantage was that it needed too-frequent adjustments to track the sun. It also required the cook to stand in the sun throughout the cooking process.

Both types were unacceptably bulky for most households.

LRI’s Suryakund

Combining the box and concentrating principlies, LRI developed Suryakund, a light, compact 2-litre solar cooker.

• Food was kept in a tall cylindrical cooking vessel, in 2 compartments if desired.
• This was enclosed in an inverted glass jar, making these the equivalent of the “box”.
• A separate compound parabolic reflector provided a soft focus through the glass jar onto the cooking vessel.
• Tracking adjustment was required after one hour.
• It took 2 hours to cook a full load, and could be used twice a day in winter.

Solar Reflector Material

The early reflector * was a compound parabolic concentrator * made of ABS plastic, * with vacuum-deposited aluminum as the reflecting surface, * protected by a film of clear lacquer.

The lacquer degraded within a year under ultra-violet light.

If left empty outdoors, at certain sun angles this reflector also burned a hole in itself.

A later model had a reflector of sheet aluminum spun to make a regular parabolic concentrator. The cooking pot and glass jar remained unchanged.

Suryakund Sales

Between 1982 and 1989 LRI sold about 1,000 pieces of this cooker.

Its selling price, on a no-profit no-loss basis, was the same as that of subsidized box-cookers in the market, where manufacturers were given a 50% subsidy by Government. Suryakund had no subsidy, and sold competitively.

Experience showed that sales were brisk in times of kerosene shortage, but slowed down otherwise.

A paper written during this period was Mathematical Modelling Leading to a Solar Cooker Design, Shirish B Patel, National Solar Energy Convention 1981, Solar Energy Society of India.

A variation of this paper with the same title was also presented at the International Solar Energy Conference in Perth in 1983.

Ford Foundation Grant For Making Dies For The Reflector

In May 1987 Ford Foundation gave LRI a grant of $48,000 to manufacture reflector dies. Stamping dies was cheaper than spinning. Stamped surfaces would be more precise and improve performance.

Soon after LRI had received this grant, Government announced major subsidies in the prices of kerosene and cooking gas.

Grant Returned, Manufacturing Discontinued

LRI decided that in these changed economic circumstances Suryakund could not sell.

Ford Foundation’s grant was returned to them, together with the interest earned since the grant was received. Further manufacture of Suryakund was discontinued, although sales continued while stocks lasted.

UNCHS Grant To Develop 5- Litre Cooker

In July 1993 LRI received $12,000 from UNCHS (Habitat), Nairobi, Kenya.

The grant for LRI was secured by Women for Sustainable Development, a Nairobi-based organisation that wanted a 5-litre solar cooker developed for use in Africa. They found the 2-litre model too small for African conditions.

It was not possible to simply scale up the 2-litre model to 5 litres. The reflector’s collecting area would go up as the square of the linear dimension, but the volume of the cooking container would go up as the cube.

The larger model would therefore have a smaller container relative to the reflector, and too many reflected rays would miss the target.

Research for the larger model would have to be started afresh.

UDCT Powers The New Research Effort

In July 1993 LRI was lucky in persuading Mumbai’s University Department of Chemical Technology (UDCT) to help with the research programme. UDCT is now autonomous and has been renamed Institute of Chemical Technology (ICT).

LRI argued that, with 40% of India’s energy consumed in cooking, any savings would be of national significance. Also, many of the problems in solar cooking related to chemical engineering such as:

• the development of UV-resistant transparent films to protect mirror surfaces,
• development of black paints that are differential absorber-radiators,
• the mechanics of heat transfer,
• the fact that cooking itself is a chemical process.

The Research Team And Early Guidelines

A Research Team was set up comprising two professors from UDCT, and other members from LRI. Since late 1993 the Research Team has met regularly about once every fortnight.

Research on a 5-litre solar cooker began with the appointment of a full-time Master’s degree graduate student.

Self-imposed constraints in developing the design were:

• that the reflector should require adjustment not more often than once an hour,
• that cooking should take not more than 2 hours, and
• that it should be possible to cook twice a day in winter.

5-Litre Solar Cooker Design Ready Late 1996

By the end of 1996 design of a 5-litre model was complete. Various aspects of its performance had been investigated in careful trials. The new design proved to be significantly more efficient that the original 2-litre Suryakund.

It was also becoming apparent that the gains in efficiency were

• partly from the design of the cooking pot, and
• partly from the design of the reflector surface.

Third International Conference on Solar Cooking, Coimbatore, January 1997

The Research Team attended this Conference. Papers read included the following:

• Development of High Efficiency Concentrating Solar Cookers, J B Joshi et al.
• Computer Simulation of Solar Cooker Reflectors, Shirish B Patel

Meeting other participants, and taking part in the Exhibition of solar cooker products that accompanied the Conference was an invaluable learning experience.

We realised that some further improvements could be made in the design. With this, we felt we were finally ready to go into large-scale production.

A Marketing Guru’s Input

At this point, we had a meeting with Shunu Sen, one of India’s leading marketing men, to decide on a strategy by which this solar cooker could be sold in the millions.

We emphasised that we were not interested in the romantic users of solar energy, who would buy our cooker anyway. We wanted to reach a mass market.

Analysing the problem together, we concluded that there are two major points of resistance to solar cooking:

• the food cooks slowly, and although it needs no attention during that time, this is a negative attribute in the mind of the customer; and
• the food is no longer cooked in the kitchen, it has to be taken outside and placed in the sun.

On the marketing guru’s advice it was decided to split our problem’s solution into two, to be tackled successively:

• First, introduce a cooking pot in the kitchen that saves fuel on a normal flame.
• Later, take the same pot and place it in the sun, add a reflector, and save all the fuel.

Work on the reflector was put aside, for the moment.

It was decided to focus further research exclusively on the cooking pot.

Research Focus Now Exclusively On The Cooking Pot

Work on the cooking pot began in February 1997.

One by one the features that bring about significant fuel savings were uncovered. Cost implications and simplicity of manufacture were constantly kept in mind during development. There are other features, such as pressure, which were investigated and discarded as being valuable, but not central, to improved performance, particularly when cost and simple manufacture are guiding considerations.

75% Fuel Saving Over Normal Cooking

What emerged eventually was a remarkably simple device, cheap and easy to fabricate, that promised 75% fuel savings as compared to normal cooking.

Does This Kill The Solar Cooker Project?

When you have already saved 75%, do you really care about the remaining 25%, for which you need added investment in a reflector and sunny days?

Our research continues even now.

How The Ecocooker Is Manufactured

LRI has no manufacturing facilities. The cooker parts are fabricated in small workshops in Mumbai, using facilities that already exist or else could be easily replicated in workshops around the country. LRI co-ordinates the fabrication, assembly and despatch, and works essentially on a not-for-profit basis while recovering all out-of-pocket costs.

LRI members cannot be remunerated, as this is prohibited by LRI’s charter. UDCT professors similarly receive no separate remuneration for work on this project.

Acknowledgments

Research has been generously supported and made possible by grants from

• Mahindra & Mahindra Limited, and
• Excel Industries Limited

both of Mumbai.

We are also grateful to the Industrial Design Centre of the Indian Institute of Technology, Mumbai, for working with us, without charge, in the final stages of product design.

EcoCooker was jointly developed by Mumbai University’s autonomous Institute of Chemical Technology (ICT, formerly University Deparment of Chemical Technology, UDCT) and Land Research Institute (LRI).

In the mid 1990s, the Georgia Institute of Technology conducted a survey and rated UDCT the best chemical engineering school in the world outside the USA.

LRI is a not-for-profit Trust engaged in solar energy research and work on energy conservation.

As far as we know, ours is the first sustained Institutional research effort to develop a fuel-efficient cooking pot.

Part of our future work will be concerned with how to combine our cooker with a fuel-efficient wood stove to obtain overall an especially fuel-efficient wood-burning cooking system.