The energy of the sun can be harnessed, very simply, to cook food. There is no need for large, complex systems of lenses and mirrors to achieve this task. When sunshine falls on a dark surface it is absorbed and transformed into heat. Glass has the property of letting in light but not heat. If a shallow glass covered chamber coated black inside and insulated all around is exposed to sun for a time the temperature inside soon exceeds 100 degree C. This is sufficient to cook food. Some more heat input can be achieved by having a reflector outside the box. There can be more than one reflector also, even as many as four sloping reflectors enclosing the box on all four sides, to funnel in the solar radiation. A box-like device incorporating these principles is the solar box cooker. On a hot summer day the temperature inside the solar box cooker will easily touch 140o C.
The solar box cooker made in India has a single reflector. The box looks like a square shaped suitcase measuring 0.6 metre square and weighs about 12 kg. Usually it has four cooking pots of aluminium or stainless steel. The cooker has castor wheels for easy movement. The outer case of the cooker is made of aluminium or fibreglass reinforced plastic (FRP) which is a light, tough and can be fabricated in different colours pleasing to the eye. Such box cookers are available in India for Rs.1500 – Rs.2500 depending on the finish.
The solar cooker takes 2-3 hours to cook food. The cooker has to be moved occasionally, say, at hourly intervals, to face the sun as it moves across the sky. Even this would not be necessary if the solar cooker is directed at the sun’s ‘average’ position as the sun transits during this time. It can cook food only during the day when the sun is shining – not in early mornings or late evenings or when it is cloudy or raining. Passing clouds do not matter. If there is a clear shadow behind the cooker the sunshine can be considered good enough to cook. It is good practice to wheel out the cooker as soon as the sun is up on the horizon. The preheating reduces the cooking time. If there is good sun for an hour at start, even intermittent clouding thereafter, will not matter except delaying the cooking time somewhat. On a clear day one can even do two rounds of cooking – say between 9 am and noon and again between noon and 3 pm.
The solar cooker can also perform the role of a ‘Thermal’ cooker – as a heat retention cooker — if the sunshine at starting time is weak. You can then bring the food to boil on the regular oven and transfer the pots into the solar cooker. The weak sunshine will be sufficient to cook the food fully.
Solar cookers are also made with electrical back-up. These are useful when the weather which was good at start suddenly turns bad and forces you to switch to the regular stove. This saves you from the let-down feeling which is demotivating for a beginner. The electrical circuit is automatically initiated when the temperature build up is insufficient.
The great advantage of solar cooking is its convenience. You do not have to be on your legs in constant attendance. This is because the food never gets overcooked or burnt. The housewife can attend to other chores while the solar cooker is doing its job. There is a trade off here. Apart from its “load-and-forget” quality, the food cooked in the solar cooker is also more tender and retains more of the nutritive values. But this comes at a cost — slow cooking.
A typical load for the cooker would be rice, in double its volume of water in one pot (it can take 200 gms of rice), ‘dal'( lentil) in a similar volume of water in another pot, cut vegetables ( or whatever) with a small amount of water in the two other pots. After 2-3 hours when you revisit the cooker you will find all the items cooked. All that remains is for you to take them out and do the “tadka’ or tempering with herbs or spices, on the regular oven, to convert them into complete dishes. You have then made a meal at zero cost in terms of fuel and in terms of the environment.
One can cook not only food, but also roast nuts, dry vegetables and fruits (taking care to keep the glass lid slightly open, to the extent necessary, to control the heat input), pasteurize water, bake fruits, and even bake bread or cake on a clear day at noon. One can make jams and do fruit canning. One can use the cooker to get rid of insect infestations from cereals and condiments. I have used the cooker even to do repair jobs like restoring the crisp quality to soggy biscuits and banana and other chips especially during humid weather. The solar cooker is a truly versatile and multipurpose device. It is more than a cooker. A solar cooker kept out in the sun is like an oven kept permanently switched on. You can place anything in it anytime and take it out when done. Can anyone ask for more?
What is important for solar cooking is not how hot the sun is but how clear the sunshine is. In most places in India one can cook for 70-80 % of the days in a year. One can thus solar cook in all seasons. You can cook on the Himalayas on a clear day. In fact, our jawans in Kargil are using the solar cooker. The solar cookers were put to good use in the aftermath of the Gujarat earthquake, thanks to the initiative of Professor Sharan of the Indian Institute of Management, Ahmedabad.
There is no other oven or stove which is as cost effective and convenient as the solar cooker. Yet solar cooking has not caught on. Why? I suspect it is because most people do not know about it. People may find it strange or odd to cook in the open and may not really be aware that solar cooking is a perfectly feasible proposition. Or they may be under the impression that it is a hassle requiring one to be out in the open all the time which is not the case. The fact is that unless you are introduced to it and see things for yourself you will not realize its extraordinary potential
It is but true that the solar cooker has certain drawbacks which makes people say it is not an ‘efficient’ energy source. It is slow the cook, it cannot cook on some days when the sunshine is obscured. (This is true of photovoltaic devices also, except that the battery in the PV system can take the lag for a time.) The solar cooker cannot also make chapatis or for frying in oil – just as an electric oven cannot ideally be used for such purposes. But these drawbacks are really not very serious. An effort should be made to convince people that these drawbacks are worth living with. One gets used to it in course of time. Our world is not perfect in all respects and we have to make sensible compromises. At any rate those that cannot adjust to it could be left out and those that can should be persisted with and an effort should be made to reach them. This requires a sustained effort lasting over several years which has been lacking so far.
The solar cooker is a lifetime asset. Handled with care it can last 15 years or more. There is no moving part in it to go wrong. The only maintenance required is an occasional coat of black paint on the inside of the cooker and on the outer surfaces of the cooking pots. The solar cooker can be used both in the rural and urban sector. In the rural sector it saves village woman from having to trudge for miles in search of scraps of firewood and spending her lifetime in smoke-filled kitchens to the great detriment to their health and also saves the messy cleaning of smoke blackened pots and pans. In the urban sector it saves energy on kerosene and LPG and makes cooking easy. The cost of petro-based fuels is going up all the time by the gradual withdrawal of the subsidies. The price of a cylinder of LPG has already reached Rs.280, after the recent budget, and even this forbidding price has a subsidy element of 20%. This subsidy might also go away in the coming months and years.
The solar cooker is the most self sufficient and decentralized cooking instrument imaginable. If you have a place in your home where you can access sunshine you can acquire a solar cooker today and start using it immediately. You do not need any infrastructural support. It makes you energy independent. But the cost of the cooker which is around Rs.1500 is not as forbidding as it looks as this is all the cost you have to bear and you will not be regularly milked by recurring fuel cost. Even so the poorer sections may have to be helped with a subsidy or a facility of payment in instalments.
It defies logic, but it is true, that solar cookers are not being subsidized by the Indian government (they were till 1994. Some states like Gujarat and Karnataka continued the subsidy after 1994) but commercial fuels like kerosene and LPG which are imported at great cost and add to the pollution are subsidized. Even other renewable energy systems are subsidized – e.g. improved chulhas, biogas systems, PV systems etc.
There is another class of cookers called ‘concentrating cookers’ or ‘direct-focusing cookers’ which are concave mirrors (parabolic in shape) which reflect solar energy to a focal point where a cooking pot can be placed. They are available in several models (Rs. 5000, Rs.55000 and more !). These are the SK 14 cookers and the Scheffler cookers. The SK 14 requires close tracking and one has to brave the sun to operate it.. The Scheffler cooker reflects the sunshine through a hole in the kitchen wall on to a secondary reflector which reflects the sunshine upward on to the pot. Hence one can cook in the kitchen itself, but it requires all the aforesaid arrangements to be made. These cookers can do a faster job of cooking and are useful for large scale cooking. They can be used to make chapatis and for frying in oil also. The Scheffler cookers have a mechanical tracking facility. These cannot cook more than one item at a time but they can take a pressure cooker. They are large, unwieldy and have to be fixed at a place and they are prone to scratches on the reflecting surface. Since they are not cheap, compact and portable they will not be relevant to the large majority of ordinary households, especially for poor households. But may it be noted that these high-cost cooking devices are being promoted by heavy subsidies by the Indian government!
India may be justifiably proud that the world’s largest solar steam cooking system is operating in the Brahmakumaris’ ashram at Mt. Abu in India. Here the solar energy is concentrated by a battery of concentrators to convert water into superheated steam. The system can cook for 10,000 people. This is a truly a fascinating achievement of human endeavour. It cost a crore of rupees excluding the labour of love of the ashram inmates and was aided financially by the German and Indian governments. But I would rather that the same money was used instead to introduce the box cooker in 10,000 poor homes.
Another type of solar cooker is also now being made in India, the Sunstove, designed by Richard Wareham of U.S.A. It has been popularized in South Africa. It is an insulated box whose sloping sides themselves are reflecting – thus doing away with the outside reflector – and has a plexiglass window. It has two large sized pots. It is being made in Kolkata, with assistance from Rotary International. Disabled children of a Ramakrishna mission organisation assemble the cookers. I do feel it has very good prospects since it dispenses with glass components and is very light to carry and also cheap – costing around Rs.1000.
There are over two dozen manufacturers of solar cookers in India but they are languishing for want of orders. Government, the energy gurus and even the NGOs in India have no use for them as they seem more enamoured of other elitist renewable energy technologies.
One can see a lot of promotional activity, world over, for photo electricity. So much so that one would be led to think that solar energy cannot be harnessed usefully except in this manner. Photo-electricity is undoubtedly a most elegant technology ideally suited to bring electricity to people living in remote places unconnected to the grid. But to offer it as the cure-all for backwardness is a mistake. The Indian government offers subsidised solar PV even to those who are connected to the electricity grid and who are not in real need for alternative energy. This is a waste of government resources. Photo electricity cannot provide the much higher energies required for cooking. Photo-electricity does not automatically usher in the age of electricity for the poor. At its high cost it can meet only the minimal energy need of lighting. These PV enthusiasts slur over the much larger cooking-energy needs of the poor.
There are numerous websites on renewable energy world over, including those on household energy but none of these seriously broach the topic of solar cooking. They seem to chanting the photovoltaic mantra with great gusto. I suspect the publicity that PV gets is in part due to the powerful lobby of the multinationals who are dominating the manufacture of PV devices and their influence on governments and multilateral aid agencies like the World Bank. There is no such lobby to work for the solar cookers.
There is lot of interest worldover in biomass as a provider of household energy. This is understandable because biomass devices are the cooking devices used by the poor and it makes sense to improve their efficiency. But biomass depends on firewood which has to be avoided to the extent possible. Biomass systems emit smoke and not clean for handling or for the environment. They are not cheap either in the long run. However imperfect a solution, cooking with solar energy needs to be promoted seriously. But it requires patient and sustained promotional activity which is sadly lacking.
Many individuals and organizations are working in several developing countries promoting cardboard panel cookers such as the ‘Cook It’ which is simply a sheet of cardboard coated with aluminium foil cut and folded in a particular way so that it will reflect sunrays on a pot kept at its centre in a plastic bag which functions as a greenhouse. They are a good beginning because they are cheap and the people are too poor to afford anything better. But by their very nature they are not durable. I do feel that if solar cooking is to catch on durable solar cookers such as the ones being made in India are required. The ‘CookIts’ also make interesting projects for boys and girls in schools.
The Renewable Energy Policy of Government of India, which is under the consideration of the government, sets out the goals to be reached by 2012. According to the annual report of ministry of non-conventional energy sources for the year 2000-01 these goals include:
· coverage of 30 million households through improved chulhas · setting up of an additional 3million family size biogas plants · deployment of 5 million solar lanterns and 2 million solar lighting systems · electrification of renewables of at least one quarter of the villages that could not be electrified through conventional means · deployment of solar water heating systems in 1 million homes and contribution of at least 10% of the new power capacity addition projected for the period up to 2012.
The policy statement makes no mention of solar cooking or solar drying. This is proof, if proof is needed, of the neglect of the solar cooker by government. The sales of the solar cooker have come down from 50,000 in 1993-94 to 5000 in 2000-01 (up to December 2000). There is no evidence that government are interested in reversing this trend. It is tribute to the manufacturers of the solar cooker that they are persisting with their production activity in spite of the lack of encouragement from government.
The Ministry of Non-Conventional Energy puts out advertisements in newspapers for promoting the use of the solar cooker. A recent one can be seen in the New Indian Express of March 3, 2002. This was timely, considering the hike in the price of domestic LPG in the recent Budget. The advertisement says that solar cookers are available at any of the Suppliers, State Agencies and Aditya Shops listed therein. But a look at the list will show that there is no supplier in the whole of south India. The list of State Agencies does not include Karnataka and Tamil Nadu. This is indicative of the neglect of the solar cooker in south India. The list does include Kerala but it is public knowledge that the State Agency in Kerala (ANERT) has not stocked or sold solar cookers for several years now. If the Central and State governments are really keen to generate enthusiasm for solar cooking among the people they should truthfully and generously provide the necessary infrastructural support.
I have been practising solar cooking in Trivandrum in India for over 12 years on a sustained basis – an unlikely place for solar cooking because of its higher than average rainfall. The solar cooker is like a pet dog to me. I wheel it out to face the sun the first thing in the morning. If you are not immodest in your demands you will find solar cooking hugely satisfying and great fun.
I have written a book about renewable energy and the solar cooker. I am a retired officer of the Indian Administrative Service. The title of the book is “Making the Most of Sunshine – A Handbook of Solar Energy for the Common Man”. It is published by Vikas Publishing House Pvt.Ltd., New Delhi (E mail: email@example.com). Pages 204. Price: Rs.425 , hard cover. I have also authored a 42 page booklet titled “Sunshine for Cooking”, which is in Malayalam, priced Rs.18, which has been published by the Kerala Literacy Mission.
I have tried to canvass the cause of the solar cooker in my books. I hope that people everywhere recognise the importance of promoting solar energy for meeting the domestic heating needs. Solar cooking is not only clean, elegant, fuel saving and hassle free; it also makes for sustainable living and enrolls the user as a member of a world-wide environmental club. I hope that governments and NGOs working among the people will incorporate solar cooking in their agenda and promote it more vigorously.
Recently, I had occasion to write to the Govt. of Tamil Nadu to request them to take up the promotion of solar cooker. I was given a reply that solar cooking was not proving to be ‘popular’. I submit this is a defeatist approach. The Tamil Nadu Energy Development Agency and the departments of the government dealing with development, energy, women’s development and local administration should join hands to encourage NGOs and voluntary organisations to undertake door-to-door visits to conduct demonstrations and explain the usefulness of solar box cookers to the people. Ministers, MLAs, celebrities and public figures should use solar cookers in their homes and set an example. Solar cooking should be popularised through print and TV media.
The solar cooker is the poor man’s renewable energy device. It suits us in India ideally as we are blessed with good sunshine and our people are poor and find it difficult to afford the cost of commercial energy.
Let us not let the bonanza of sunshine which God has gifted us with go waste.