Solar ovens are devices that use solar radiation as their energy source for baking (and cooking); they are a sub-category of solar cookers. The food is placed in a box, which has, preferably, an even heat distribution. The box can be heated by direct sunlight entering through one or two windows (as in the case of box cookers) or by sunlight concentrated by a parabolic reflector. Some are appropriate for household use, others for commercial purposes. The term solar oven is often used synonymously with Solar Cooker and Solar Box Cooker.
Most of the energy consumed by households in the developing world is used for food preparation and heating. Using solar energy for cooking and baking can reduce the unsustainable use of fuels such as charcoal and fossil fuels or firewood that is harvested non-sustainably. With increasing deforestation and a growing population, by 2050 firewood will become an even scarcer resource. Solar ovens are, therefore, a highly suitable technology for using in remote areas with wood fuel shortages.
The use of solar ovens can reduce the consumption of unsustainable firewood and fossil fuels, avoiding harmful carbon emissions that trigger global warming. According to one producer, one large-scale commercially used solar oven could save about 150 tonnes of wood annually1.
Solar ovens offer an urgently needed clean and cheap alternative to traditional fuels (which are in diminishing supply) for baking. The technology is particularly appropriate for remote areas where no baking is possible with simple cookers, such as the 3-stone model, and where bread needs to be purchased from urban settlements. For these reasons, dissemination of the technology on both a small and large scale can contribute towards reaching the MDGs, making fresh bread affordable for poor households and preventing the unhealthy use of firewood.
Solar ovens use a pollution and cost free renewable resource: sunshine. Bakery produce can be provided cost-effectively with solar power while, at the same time, the destructive forces of deforestation and desertification can be reduced.
As is the case for any other appliance, the production of a solar oven has an environmental impact. For instance, some parabolic cookers use a considerable amount of aluminium. Care has to be taken to ensure that the elements that are likely to be recycled can be easily separated at the end of the cooker's life.
One of the biggest environmental threats to many developing countries is deforestation. Massive population growth and the inefficient conversion of wood to charcoal have led to the unsustainable use of forest resources. As a result, forests are unable to regenerate, leading to land degradation in arid, semi-arid, and sub-humid areas, climatic variations, loss of biodiversity and numerous social effects for the local population2. Currently, much of the baking in the developing world is done in ovens fuelled by charcoal or LPG. Replacing charcoal fuelled ovens with solar powered ovens will allow bakery goods to be produced without further damage to the already fragile environment1.
When asked what cooking device they would most wish to have and use, the majority of rural cooks in developing countries (35% of the sample interviewed) responded that they wanted an oven for baking.34 The solar oven is suitable for baking and can provide an option for local bread making or for the production of cakes and biscuits. As well as providing baked goods, solar ovens also offer an opportunity for local entrepreneurs to open micro-businesses. Solar bakeries can provide employment and income in both rural and urban areas.
Women especially, who are traditionally in charge of cooking and baking, can benefit from replacing wood fuels by solar energy for cooking and baking in various ways:
In general, the acceptance of new technologies for household use is a sensitive issue. One reason that is often pinpointed in the case of solar cookers is that adopting the new technology requires a change in traditional cooking habits.
Solar ovens that are solely used for baking encounter fewer problems with user acceptance than solar cookers that are intended to be used for the preparation of the daily meals.
The former are an "add-on“ for households and offer the possibility to bake - at least while the sun is shining. As the ovens do not have to be regularly adjusted to track the sun, the goods are baked with little input from the user. However, in order to promote the adoption of the ovens for every day use, they must be seen to be attractive and competitive in terms of cost. Users must also have access to appropriate information and training, and good quality devices must be available.
Solar ovens are used in numerous countries but, unfortunately, there are no statistics available that relate solely to solar baking. Solar cookers and solar ovens are usually accounted for in one category. The number of solar cookers (including solar ovens) in use globally is estimated to be around 1.5 million.5
Most commercially produced solar ovens have been developed in industrialised countries, where they are also purchased and used by a "niche target group“, e.g. in the South of the USA or in Europe. For the developing world, low-cost and easy to construct solar ovens can be appropriate and affordable for households, whereas high-quality solar ovens would only be economically feasible for communities or small-scale businesses.
While the use of box cookers for slow baking is commonplace, large-scale commercial solar bakeries are still limited to a small number of pilot projects. The next stage is to analyse the experiences gained in order to develop a long lasting, efficient and user-friendly oven, which has the option to use a second energy source on cloudy days or during the rainy season. The alternative energy source should also be, preferably, environmentally friendly.
Baking bread in a solar oven increases self-sufficiency. The time and/or money previously spent on acquiring fuel can be saved or at least reduced if solar radiation is used as an energy source. However, the investment costs for commercially available ovens are often not affordable for low-income households without the support of appropriate funding schemes. Especially when fuel wood is collected and used freely, the cost saving potential of using solar power for baking is quite low.
Therefore, solar baking is mainly suitable for business applications. The investment needed to set up a solar bakery can be paid back within 2 to 5 years, depending on the particular circumstances.
In rural areas in developing countries bread must frequently be delivered from larger settlements. The reason for this is that there are often no bakeries in the remote areas and most households do not possess an oven for baking their own bread. The transport distances involved mean that the price of baked goods is higher in rural areas than in the larger settlements.1, 6 In addition, bread is often not delivered on a regular basis meaning that, typically, it is not fresh by the time it is sold in the rural areas. Solar ovens, either family-sized or bakery-sized, would reduce expense and allow for fresher baked goods to be provided to the local population. The use of solar energy and the avoidance of transport costs can reduce the prices of bakery goods in rural areas by about 25%. However, family-sized solar ovens can cost from US$ 40 upwards (in 2001), which is already a sizable investment in developing countries.7
In cities electricity and gas are usually used as the power source to run ovens. Baking and cooking with solar powered ovens can help to reduce energy use and decrease the need to import fossil fuels such as cooking gas. The limiting factors are space and the supply of sunshine.
Solar ovens are not only applicable for micro-businesses but can also be used on a larger commercial scale. However, large-scale solar ovens are expensive and need a lot of space. A commercially available solar oven was purchased to establish a pilot solar bakery in a community in Cameroon. The bakery is successfully managed by a women's group (see example).
In Ougadougou (Burkina Faso) a solar bakery is due to be opened in July 2011. A Scheffler Reflector of 16 sqm is equipped with a stove that has space for up to a hundred small baguettes. The baguettes can be baked within 30 minutes, meaning that one oven can bake up to 1200 loaves in a day. The bakery will be extended by a further 3 units so that the production can be increased to up to 4800 loaves per day.
(See video on www.solarfood.org)