Cook with the Sun
Thinking of buying a solar cooker, but confused about how they work? There are four popular designs. Each has its strengths and weaknesses.
Sponsored by Haines Solar Cookers LLC
Parabolic Solar Cookers
Advantages: For fast cooking and frying, you can’t beat a parabolic or “dish” solar cooker! Parabolics concentrate the sun on a tight focal point, and can reach temperatures hot enough to fry chicken or bacon and to sear meat. Cooking times can be similar to cooking times for a gas or electric stove.
Disadvantages: As the sun moves, parabolics require constant turning during cooking in order to keep the focal point focused on the bottom of the cooking pot. Be careful not to put your hand or arm near the tight focal point. Most parabolics are bulky and difficult to transport or store. Cost? Around $300 to $600.
Vacuum Tube Cookers
Advantages: A vacuum tube solar cooker works like a thermos bottle. The food is placed on a semicircular tray, and inserted into a black vacuum tube. Sunlight is reflected onto a black glass tube inside a clear glass tube, and a vacuum prevents the heat from escaping. Vacuum tube cookers can cook quite fast, and they are especially good for cooking meat or vegetables. They are also quite portable, especially smaller models.
Disadvantages: The tube is glass, so it’s breakable. The food must be cut to fit the semicircular tray, so you can’t cook large items. It’s not recommended to boil water in the horizontal tube, because the water can easily spill, causing thermal shock that can break the glass tube. For making coffee, special vertical tubes are available. Cost is $150 to $600, depending on model.
Advantages: Box ovens perform and feel like conventional ovens. They consist of an insulated box with a glass or plastic cover and a reflector to direct sunlight into the box. Because they’re insulated, they’ll work in cold weather, even when there’s snow on the ground. You can roast a chicken or bake casseroles, potatoes, cakes, pies, or cookies.
Disadvantages: Because the insulation needs to heat up, box ovens should be preheated in the sun before cooking. In northern latitudes, or in the afternoon or evening when the sun is low, they may have to be tilted toward the sun. However, tilting can spill the food, so some box cookers come with a swinging tray, though this can limit the space inside. Box ovens are bulky and heavy, so they’re more difficult to transport and store. Cost is $200 to $600, depending on size and quality.
Advantages: Panel cookers work like box ovens, but instead of insulation, they have foldable panels that reflect sunlight onto the pot. To prevent heat loss, the pot is usually enclosed in a transparent “greenhouse” like the plastic oven bag shown in the diagram at left. Panel cookers can boil rice; steam vegetables; roast chicken or stew; and bake potatoes, bread, cakes and even cheese soufflé. Because they’re lightweight and fold flat, they’re perfect for camping, boating, and emergency preparedness. Cost is $60 to $200, depending on quality, performance, and extras.
Disadvantages: Panel cookers aren’t well-insulated, so they don’t work well when it’s cold or windy.
The Haines 2 Panel Solar Cooker
Roger Haines has designed, built, and tested all types of solar cookers, and founded Haines Solar Cookers LLC in 2013. More than 2,500 Haines Solar Cookers have been sold in the United States, with more than 1,800 distributed in refugee camps and developing countries, in partnership with nonprofit organizations. The cookers reduce the use of smoky cooking fires, and thereby improve respiratory health, reduce deforestation, and help save the environment.
Less expensive cookers use reflectors made of cardboard and foil. But when the cardboard gets wet, the foil separates and the cardboard turns to mush. Better reflectors are made of “fluteboard” (plastic cardboard) or vinyl bonded to foil. Polished aluminum reflectors require complicated hinges for folding, and can oxidize over time. Haines solar cookers use Mylar bonded to polyester (PET) foam with a strong polyester plastic backing. Polyester (PET) is food-safe, and it’s the most desired plastic for recycling. Mylar doesn’t scratch or oxidize and should last 10 years or more in normal use.
“Greenhouse.” Plastic oven bags, like those in the diagram above, are awkward to use and bad for the environment. One alternative is to put the pot inside a glass mixing bowl, with another glass bowl upside-down on top, to form a “clamshell.” But glass bowls are expensive, breakable, and not very portable. Haines solar cookers use a transparent plastic cooking sleeve that’s adjustable to fit any size pot. The sleeve elevates the pot so sunlight can be reflected onto the pot’s bottom. This allows the lid to remain accessible during cooking — like cooking on a gas or electric stove
Cooking pot. The cooking pot itself must be black on outside, to absorb the heat of the sun. A glass lid is recommended, so the cook can see the cooking process without lifting the lid, which loses heat. Glass also retains more heat than a metal lid. The Haines Dutch oven is stainless steel and holds 4½ quarts — big enough to roast a whole chicken or cook a gallon of stew.
Performance testing. Using an international standard for testing solar cookers, an independent organization, Solar Cookers International, found that the Haines 2 Solar Cooker produces the equivalent of 82 watts of cooking power — more than any other commercially available panel or box cooker tested.
Heat water for camp shower. Set a 5-gallon black jerrycan of water in the Haines 2 Solar Cooker in the sun for 2 to 3 hours, for a hot (125 degrees Fahrenheit) refreshing camp shower to wash off the grime from a day of hiking.
Bottom line: If you want to fry food, or cook food fast, buy a parabolic or vacuum tube solar cooker. If you want an oven that will bake food year-round, buy a box oven. If you want an inexpensive, portable cooker to use in warm weather, buy a panel solar cooker. Solar cookers work. They’re convenient and fun to use. The food is healthy and delicious. You can reduce your fuel bills, and save the planet. What’s not to like?
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