Solar cookers are devices that are used to prepare food by harnessing solar radiation as their energy source. Cooking with freely available solar energy is a healthy and environmentally friendly alternative or addition to using wood fuel, gas or electrical energy. The technology is most appropriate in sunny and dry regions with sufficient levels of solar radiation (but it has his followers in less sunny countries as well); however, in order to ensure the successful implementation of this technology, local needs, cooking habits and social conditions must also be taken into account.
Solar cookers have the potential to make a significant contribution to reducing the use of unsustainable cooking fuels in the developing world. They are highly suitable for decentralised applications where people currently depend on firewood (that they must collect) or imported LPG for cooking. About 85% of countries in Africa, the Americas and Oceania have the appropriate conditions for solar cooking1. As well in Asia a lot of regions are most suitable. Solar Cookers International compiled a list of the 20 most suitable countries for solar cooking, where around 500 million people could benefit from appropriate annual average sunshine hours and currently depend on firewood or LPG for cooking. First five listed countries are India, China, Pakistan, Ethiopia and Nigeria.
There is no country where solar cookers can be used as a stand-alone system without any alternative energy source, therefore experts recommend their use as part of an integrated cooking system, e.g. in combination with fuel-efficient stoves or biogas.
Solar cookers can contribute to the reduction of harmful carbon emissions associated with global warming. It is estimated that 80% of fuel wood consumption in developing countries is used for cooking and that most of the wood is harvested non-sustainably. Optimistic assessments assume that the adoption of solar cookers could save more than 35% of this fuel wood. Estimations on net GHG emission savings vary between 690 kt to 140,000 kt CO2 per year2. How much a solar cooker can save depends on the local conditions and frequency of use. The figures per parabolic cooker (K14) vary between 3-4 t CO2 saved. In a SEPS project in Peru (see case study), an average annual saving of 3.8 t CO2 was achieved.
The use of solar cookers can contribute to almost all the United Nations Millennium Development Goals (MDGs). They offer access to a clean and free energy source to meet the basic need of food preparation. As a consequence, they reduce indoor air pollution, energy costs and time spent on the collection of fuel wood.
However the technology can hardly be applied as a single solution, but rather as a complement to other cooking technologies. Thus, thorough assessment of current cooking practices and actual requirements of potential users are recommendable before designing strategies for the diffusion of solar cookers.
Using solar cookers does not cause any form of environmental pollution. On the contrary, solar cookers can help people to improve their lives while, at the same time, protecting their environment. Because there is much less wood required as cooking fuel, there is less pressure on the local vegetation meaning that deforestation, soil degradation and desertification are less likely. At the same time the use of solar cookers on a large scale could help to reduce carbon emissions and the associated global warming.
Like any other apparatus, the production of a solar cooker has an environmental impact. Some parabolic cookers use a considerable amount of aluminium for instance. Care has to be taken that the elements likely to be recycled can be separated easily at the end of life of the cooker.
In areas with sufficient solar radiation the use of solar cookers can help to make significant improvements to the living conditions of energy poor households. However, the benefits can only be achieved if the potential user accepts the new cooker technology and uses it regularly. To ensure successful implementation of the technology, local needs, cooking habits and social conditions must be taken into account. It is advisable to adapt the technology to the local conditions in a way that cooking habits have to be changed the least possible.
Using solar cookers can have a positive impact on health. Cooking with pollution-free solar power can significantly reduce indoor air pollution which, according to WHO, is responsible for two million deaths per year. Furthermore, solar cookers can reach temperatures that are high enough to sterilise drinking water. Because there are no additional fuel costs involved, water can be boiled on a regular basis, helping to reduce the spread of waterborne diseases. However, working with direct solar concentrators does present the possible danger of sunburn or eye damage.
In particular women and children, who mainly collect the firewood and do the cooking, can benefit. They can save time and use if for education, income generation or other activities. However, saved time does not always have a recognised value if no cash income is saved. The decision to buy a cooker is often in the hands of the men who might be reluctant to spend extra money without "saving“ cash. On the other hand, men also might be attracted by a more technical model of cooker, while women tend to choose the most practical one. Cleaner air, more time and better living conditions can help to convince women to use solar cookers, but these are not the only aspects to be considered.
Despite all these advantages the social acceptance of solar cookers is still one of the main barriers to change. A number of past distribution programmes have not been successful for a variety of factors. One reason that is often pinpointed is that adopting the new technology requires a change in traditional cooking habits.
Solar cooking might have a reputation problem due to the fact that most NGOs promote low-cost solar cookers for poor rural people. If rich people in the cities accept solar cooking as well, this might be a convincing argument for the poor. For the same purpose, solar cooking practised industrialized countries gives the technology an enviable reputation.
The maximum cooking temperature of economical models is often low and the cookers can only be used when the sun is shining, ideally around noon. This is problematic in regions where the main warm meal is in the evening, or where the clouds gather around noon, such as in the tropics. Additionally, cooking outdoors, exposed to the sun, wind and dust is not a common practice. In India, for example, cooking is viewed as a private activity - not something to be done outdoors. One requirement for solar cooker technology is a sunny space to set up the reflectors. This is often a problem in urban environments where many families live in apartments and do not have access to open sunny yards or to rooftops for solar cooking. Furthermore, in areas with access to electricity solar cookers have to compete with modern applications3.
Generally speaking, solar cookers cannot be used all year round. This means that the users need alternative appliances or a hybrid system - a fact that can discourage potential users from investing in solar cookers. However, studies of previous projects show that improvements in both equipment design and the training of users can significantly increase the acceptance of the technology4.
As well as being used as household appliances, solar cookers are also suitable for business use. In this context, the positive economic aspects of using solar cookers is more apparent and a convincing argument for the users as they reduce their running costs for the purchase of cooking fuels. In addition to their large-scale application in institutional kitchens, e.g. school canteens, or in restaurants, solar cookers can also be used for food processing. One example of this is in Sheabutter production in Burkina Faso, where the Shea nuts are boiled and sterilised using solar parabolic cookers and later roasted in solar ovens or solar parabolic cookers.
Over the last few decades a number of solar cooker designs have been created and modified, often by committed individuals who are personally motivated to improve the technology. The performance of the different types varies widely and only a few high quality products exist as private companies have not yet made a significant investment into developing the technology.
Poor quality of the cookers have often been a barrier to the
acceptance of the technology and has even created an associated negative
image, therefore the introduction of quality standards is regarded as
essential for the successful broader dissemination of the technology in
the future. On the other hand the promotion of very low-cost models has
to be put into question.
As solar cookers can generally not
be used as a stand-alone system, experts recommend their use as part of
an integrated cooking system, e.g. in combination with fuel-efficient
stoves. Experts also recommend the further development of hybrid systems4.
As well as improving the quality of the technology, appropriate after-sales service to overcome teething problems (not only for technical aspects but also for helping the cooks to overcome their first difficulties) and appropriate maintenance are also crucial for the successful marketing of solar cookers. The future success of the technology will also depend greatly on awareness-raising and the education of potential users, which has been a severe problem in African countries.
Harnessing solar energy for cooking purposes is an attractive solution for replacing unsustainable fuels. However, most attempts to introduce solar cookers around the world have been made by NGOs and have not been particularly successful. Donor-based promotion programmes, offering free cookers but without appropriate training courses, have even been counterproductive in establishing local production and markets.
However, in regions with no alternative energy source and where solar cooking fits in with local cooking habits, e.g. in the highlands of Tibet or the Altiplano in South America, solar cookers have become widely accepted and are now widely used by the local population3. In areas where solar cookers are not easily compatible with cultural cooking practices, such as in India and many regions of Africa, they do not, as yet, compete with traditional cooking methods. This is also the case in countries with high subsidies for fossil cooking fuels.
The number of solar cookers currently in operation worldwide is estimated to be around 1.5 million. Most of the cookers in use are located in rural China and Tibet, where state-controlled dissemination programmes, at heavily subsidised prices, are in place3. These examples show that financial schemes must be developed to make solar cookers affordable to the poor population.
However it can also be argued that to focus on the very poor might not be the right way of introducing high quality and relatively expensive technology to the market. Targeting groups that can afford to invest a share of their income in the new cooker technology and, by doing so, reduce their fuel costs in the long run would be more appropriate. At the same time, they give the technology a modern and enviable reputation, like solar cooker use in industrialized countries.
Solar cooking offers an economically viable energy alternative in the domestic sector. At household level savings in terms of cost and time can be made by using solar energy instead of traditional biomass or commercial fuels for cooking. However, the investment costs for high-quality solar cookers are often not affordable for low-income households without appropriate funding schemes.
The cost of the solar cookers depends on the locally available material and varies from region to region. In general, most production is small scale and sometimes parts need to be imported, resulting in higher production costs. Simple solar cookers, such as a panel or cardboard box cookers, can be produced for about US$ 5-10 (2009). Solid box cookers start at US$ 40 and parabolic solar cookers at US$ 55 (2010) for the cheapest design. In East Africa simple solar cookers are even manufactured for US$ 3-5 (2006)5. The payback period depends on the amount of fuel replaced and whether the fuel was bought or collected for free. The payback period in areas where fuel was bought is between 1.3 and 4.8 years for a parabolic solar cooker. Most households use the money that they save by using solar cookers to buy food6.
Although many funding schemes are in place throughout the world, high-performance solar cookers are still too expensive for many poor households. Box cookers, although simple and inexpensive, are less efficient and usually unable to compete with traditional stoves3.
A number of different state-driven or commercial dissemination strategies have been implemented, but the only successful programmes have been those introduced in Tibet and Bolivia, where the local climate and cooking conditions are supportive. In Tibet locally produced solar cookers were bought by the state and sold at a subsidised cost to the population. In addition, quality standards were also established. Now the local market is independent and subsidies are only offered to low-income families.
One way of improving the affordability of solar cookers could be the establishment of sustainable financing through carbon credits. Wisions funded one of the first projects that developed a device to monitor the usage levels of solar cookers and calculate the association emissions reduction. The project took place in the Andean region and consisted of carrying out a baseline study to officially validate and verify the emission reductions. The results of this process prove that carbon credits can be used as a financing mechanism for solar cookers.
As well as being used as household appliances, solar cookers are also suitable for business use. In this case the cookers are used in a very efficient way (many hours per day) and they replace energy which is bought; they pay back the investment in shorter time. In addition to their large-scale application in institutional kitchens, e.g. school canteens, or in restaurants, solar cookers can also be used for food processing. Two examples: