Science Energy What Are Solar Ovens – and Why Are They Heating Up? By Meghan Holmes Updated December 11, 2020 stockstudioX / Getty Images Share Twitter Pinterest Email Energy Renewable Energy Fossil Fuels Solar ovens are devices that gather sunlight and create heat to cook food without other fuel sources. Popular with homesteaders, off-the-grid enthusiasts, and environmentalists, solar ovens are also an affordable and sustainable cooking method that can be used in isolated communities and rural areas in the developing world. Among its many benefits, solar energy is a clean, renewable source, which also helps prevent deforestation, fossil fuel usage, and greenhouse gas emissions. There are many different designs, but solar ovens typically fall into three primary categories: box ovens, panel ovens, and parabolic ovens. Box ovens reflect sunlight directly into an enclosed container; panel ovens create heat through strategically positioned surfaces and direct it to a separate container; and parabolic ovens use a curved surface to concentrate sunlight to a single point. Most ovens can be moved easily, set up anywhere with sunlight, and DIY versions can be made at a very low cost. How Solar Ovens Work Solar ovens gather sunlight and direct it into an enclosed surface, where the trapped heat gathers. The exact process varies depending on the design, but all solar ovens require highly reflective materials (such as mirrors, polished metal, or aluminum foil) set at particular angles to gather light. They also need to retain heat well, separating outside air from the air inside the cooking vessel. Box ovens often have a glass lid (DIY versions might even use clear plastic wrap) to allow sunlight into the oven and, in a process similar to the greenhouse effect, retaining heat inside. Solar cooker in Tengboche Monastery, Khumbu, Nepal. John Elk III / Getty Images While there are dual electric/solar ovens available, with an electric hot plate at the base for overcast days, the majority of solar ovens won't function at night or when it's too cloudy. Reasons to Choose a Solar Oven There are many different reasons people choose solar ovens, including their safety, sustainability, and reliability. Health Benefits Scientific evidence suggests that eating foods grilled using fire and indoor wood-burning stoves can increase cancer risk, which may be the only option for many rural people around the world who don't have access to electricity. Many thermal ovens also cook with a relatively low internal temperature, which increases the amount of nutrients that will ultimately be retained in the food we eat. Economic Benefits Some high-end solar ovens aren't cheap, but DIY options can be made with items people have at home, like aluminum foil, plastic wrap, and pizza boxes. After the initial purchase cost, even expensive solar ovens remove the cost of cooking fuel, meaning there are long-term cost reductions. Safety Benefits Solar ovens work without electricity, making them a great option for hurricane preparedness kits and situations when areas could be without power for an extended period of time. Because they also don't require a fire, they're considered safer than burning wood or other materials. That doesn't mean there are no risks, however. In particular, parabolic ovens reaching intense temperatures frequently need close supervision, and it's important not to seal cooking jars too tightly or they could explode. Environmental Benefits Solar energy is a renewable resource; it is less environmentally harmful to cook food with this energy source when compared to non-renewable sources like wood and fossil fuels. Using sunlight to produce heat means less air pollution, as wood isn't burned and petrochemicals aren't being processed for fuel. Less wood for fuel also means less deforestation. Using sunlight exclusively is the solar oven's greatest asset as well as its biggest drawback — reaching cooking times comparable to conventional ovens requires significant sun exposure, which isn't possible in many cases. Tips for Using Your Solar Oven Selecting the right solar oven first requires determining what you'd primarily like to cook. The most basic DIY varieties are great for S'mores, but they won't sear a steak. For all types of ovens, it's ideal to have a thermometer, if one isn't integrated into the oven's design. It's also important to consider if you plan to travel with your solar oven, as some types are much lighter and easily broken-down for transport than others. Until you become confident using your solar cooker, it's best to prepare vegetarian foods. Here are some important tips for different types of solar ovens. Box Ovens Bread and rice cooked in a solar oven with an average temperature of 250-300 degrees in Borrego Springs, in Southern California. Corbis via Getty Images / Getty Images Box ovens typically contain the most space for cooking and can often allow multiple pots of food to be prepared at once. The clear surface on top of the box should always be kept clean to allow the maximum amount of light to enter the container. Try to avoid opening it, as that will release heat. That said, if steam obscures the top of the box it could reduce how much sunlight can enter, and it will need to be released. Use dark, shallow, pans, as that will help absorb optimal sunlight. These solar ovens are great for baking, cooking beans, or foods that require a longer cooking time. You can place a dark brick or stone inside and place the box in the sun to preheat. Panel Ovens Panel ovens are ideal for people on the go, typically lightweight and easy to transport. That said, they don't reach the temperatures that box and parabolic ovens can. When using these ovens, work with a dark pan or glass jars that have been painted black. These containers are then often placed in a sealed oven bag or some sort of clear, oven-safe enclosure to further concentrate the heat. zianlob / Getty Images Parabolic Ovens Because these ovens concentrate heat to a single point, they can reach a high temperature quickly; however, maintaining that temperature requires turning as the sun changes positions. Dark-colored, tightly sealed vessels are ideal for this method, commonly used of rural Chinese provinces to boil water for purification. Parabolic ovens require a closer eye than box or panel ovens because they can reach higher temperatures much more quickly. View Article Sources Suharta, Herliyani, et al. "The solar oven: development and field-testing of user-made designs in Indonesia." Solar Energy 64.4-6, 1998, pp 121-132, doi: 10.1016/S0038-092X(98)00096-6 Hernández-Luna, G., et al. “A Solar Oven for Intertropical Zones: Evaluation of the Cooking Process.” Energy Conversion and Management, vol. 49, no. 12, Dec. 2008, pp. 3622–3626, doi:10.1016/j.enconman.2008.07.012 Sinha, Rashmi, et al. "Role of well-done, grilled red meat, heterocyclic amines (HCAs) in the etiology of human cancer." Cancer Letters 143.2, 1999, pp 189-194, doi:10.1016/S0304-3835(99)00123-8 Fabbri, Adriana DT, and Guy A. Crosby. "A review of the impact of preparation and cooking on the nutritional quality of vegetables and legumes." International Journal of Gastronomy and Food Science 3, 2016, pp: 2-11, doi: 10.1016/j.ijgfs.2015.11.001 Shahzad, Aamir, et al. "Design and development of efficient domestic electric cum solar oven." Journal of Basic and Applied Sciences 9, 2013, pp: 296-301. Clarke-Sather, Abigail R., et al. "Analysis of a Rural Northwestern China Household Energy Use Survey Focusing on Parabolic Solar Cooker Use for Water Purification." Journal of Sustainability Research 1.2, 2019.