Paul Funk 2017-04-27 01:53:21
From the past and into the future Few Americans can imagine waking before dawn, heart pounding, anxious about finding enough fuel to prepare the day’s meal for their family. This reality affects over two billion people in parts of Africa, Asia, and Latin America where cooking fuel, primarily wood, has become increasingly scarce. The people who forage for wood in rural areas are primarily women, and the cost can be twenty hours per week. In urban centers, some families spend more money buying charcoal for cooking than they spend on food. Environmental costs include soil erosion and desertification from the decreased rainfall associated with deforestation. Even worse, the smoke from cooking fires in unventilated dwellings results in a staggering health cost: the World Health Organization estimates that over four million people, mostly women and children, die prematurely each year from heart disease, stroke, pneumonia, emphysema, and lung cancer caused by indoor air pollution. That’s twice the combined annual mortality from HIV/AIDS and malaria. But there is an elegant alternative. A brief history Before the U.S. declared its independence from England, Swiss scientist Horace-Bénédict de Saussure was using a solar hot box to demonstrate the greenhouse effect and cook food. In the 19th century, astronomer and aviation pioneer Samuel Pierpont Langley, who also served as Secretary of the Smithsonian Institution, cooked on Mt. Whitney using solar energy. French mathematics teacher Augustin Mouchot, who demonstrated industrial applications for solar energy at the 1878 Universal Exhibition in Paris, provided the Foreign Legion with solar cookers. In the 20th century, Hungarian- American scientist and inventor Mária Telkes worked on solar energy at the Massachusetts Institute of Technology, and some of her designs were featured in Popular Science during the 1960s. Mass-produced variants of her design occasionally turn up at garage sales. In the 1970s, Barbara Kerr, an inventor in Arizona, developed an inexpensive solar cooker made from cardboard boxes and later helped launch the non-profit organization now known as Solar Cookers International (SCI). SCI hosts a web site (www.solarcookers.org) with an encyclopedic collection of information about solar cooking projects, contact information for experts in 133 countries, project implementation guidelines, solar cooker designs and plans, news archives, and thousands of photos. SCI’s international conferences have been a catalyst for cooperation, and its monitored projects have been a source of sound data on adoption and use. And there are other organizations with similar goals, because solar cooking only makes sense: on most days, in most parts of the world, the energy required for a family to cook a meal arrives at their doorstep, emissions free, and at no cost! A variety of designs Sunlight is converted to heat when it is absorbed by a dark surface. There are three categories of solar cookers designed to perform this task: box-type, concentrating-type, and panel-type. The well-insulated box-type solar cooker bakes like an oven. These designs have a clear plastic or glass lid, some have one or more flat mirrors, and most only require an adjustment to face the sun every hour or two. Some versions can hold multiple cooking vessels, and most have an effective cooking power in the range of 50 to 200 W. Because they cook slowly, similar to an electric Crock-Pot®, users can attend to other tasks while the sun does their cooking. The high-power concentrating-type solar cooker is like a range top or grill. Most designs have a parabolic mirror focused on an uninsulated pot in which water can boil in as little as 20 minutes and oil can reach frying temperatures. A concentrating-type cooker requires more frequent adjustments to follow the sun, so the user must often stand in the sun to use it. Panel-type solar cookers—the third category—typically have multiple flat reflective surfaces arranged around a cooking pot. The pot may also be enclosed in a clear container to reduce heat loss. This design is favored for refugee and disaster relief because panel-type cookers can be mass produced for as little as $5 each, although more durable designs are available at higher prices. More complicated systems involve some type of heat transfer fluid, and these designs are more common in South Asia. Solar cookers that even work at night will be introduced soon. Current research is focusing on devices that extend the cooking opportunity into the evening through heat storage, in many cases using phase-change salt solutions. Today, there are hundreds of solar cooker designs all over the world. Several designs are mass-produced by the tens of thousands, and two designs each exceed half a million copies. Solar cookers are widely used in refugee camps and at disaster sites. The Delicias del Sol restaurant in Villaseca, Chile— an arid region where fuel wood is scarce—prepares all its meals with solar cookers. Large-scale commercial solar cookers are used to prepare thousands of meals a day at many ashrams and army bases in India, reducing the need for imported fossil fuels. Solar cooking can also support new businesses. Because box-type solar cookers are capable of baking, they can be the foundation for women-owned micro-enterprises, bringing baked goods to areas where such products were previously unavailable. With the lid ajar, box-type cookers can also dehydrate foods, thereby preserving perishable crops like fruit or fish for storage or for transport to distant markets. Engineering colleges at some universities have used solar cooker design competitions as a “mini capstone” in first-year courses to introduce freshmen to the challenges of balancing competing performance measures such as cost, durability, and cooking speed. Students particularly enjoy working on a project that has the potential to meet basic human needs. The future of solar cooking Given the need, history, and potential, it’s surprising that solar cooking has not become ubiquitous. Is it because not everyone has access to a sunny spot, or because the sun fails to shine at night and on cloudy days? Is it because the entry cost and risk are prohibitive, even in places where cooking fuel is costly? Is it because the people who would most benefit are mostly poor? Advocates who once hoped that major development agencies would promote solar cooking now realize that direct sales can provide the shortest route to meeting a significant portion of the world’s domestic energy needs with clean, renewable solar energy. In any case, there is still plenty of engineering work to do if 2.6 billion people are to be connected with a device that’s appropriate for their varying cuisines, customs, and climates. There is also much work to do to facilitate people’s transition to cooking with solar energy, necessitating cooperation with social scientists. Agricultural engineers are well prepared to understand the potential of solar cooking and contribute to the development of this technology, which is at the intersection of renewable energy and food preparation. Agricultural engineers are also well placed to collaborate with other disciplines to ensure that this task is done well. Since 2003, our Society has hosted a voluntary standard for solar cookers (S580.1: Testing and reporting solar cooker performance, available at www.asabe.org/media/200979/s580.1.pdf). To facilitate innovation and communication of this technology and address an important global issue, ASABE’s Board of Trustees recently made this standard available to the public at no cost. It has been exciting to watch the solar cooking industry grow over the past 25 years, and to sense that even greater growth is at hand. Solar cooking has a bright future! ASABE member Paul Funk, USDA-ARS Southwestern Cotton Ginning Research Laboratory, Mesilla Park, N.M., USA, email@example.com. Dr. Funk earned degrees in agricultural engineering at the University of Minnesota and the University of Arizona while conducting research on solar cooking. He worked on various designs, visited four continents, and participated in the development of the test standard.
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