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James Dulley: Getting familiar with solar ovens

Dear Jim: I like to do things the natural way when cooking. Since my kitchen gets really hot when I cook, I would like to try a solar oven.

Is it really possible to cook with solar and how can I make an oven? – Pat C.

Dear Pat: It is possible to cook almost anything in a solar oven.

Millions, if not billions, of people around the world use solar ovens exclusively because they have no other fuel source.

I used my solar oven today to steam brown rice in about 90 minutes. The inside temperature of the solar oven gets hot enough to bake bread, roast meats, etc. By not having your kitchen oven hot for hours, your air-conditioning cost will also be lower.

There are several designs of solar ovens you can make yourself. There also are many commercially available solar ovens with insulated glass tops, extra reflector panels and special solar-absorbing paints which cook faster.

The simplest design of solar oven consists of two cardboard boxes, one large and one small, without tops. The larger box is lined with crumpled up newspaper for insulation and the smaller box is placed in it. Line the inside of the smaller box with aluminum foil and paint the bottom flat black.

Cover the top of the box with a sheet of clear acrylic plastic. Use foil duct tape on one edge of the top to function as a hinge. This simple oven will probably not get hot enough to roast meat or bake bread, but it will be adequate to steam rice and vegetables. Use a covered black pot.

To attain higher temperatures, use wood to make the boxes and stuff fiberglass insulation between them. Make them deep enough so a shelf inside can be tilted on an angle. This allows you to tilt the box so the clear top faces the sun more directly.

To improve efficiency, use two layers of acrylic separated by a small edge spacer for the top. This creates an air gap similar to double-pane windows. This slightly reduces the amount of solar energy that gets into the oven, but greatly reduces the amount of heat lost back out through the top.

Also, add reflective side and back panels to increase the effective solar energy collection area. Cardboard covered with shiny aluminum foil is effective. Don’t use a standard glass mirror. Mirrors reflect visible light, but not heat energy, so little additional heat will be gained.

For some serious solar cooking, select one of the professional solar ovens. I use a hybrid model, SunFocus, by Sun BD Corp. It includes an adjustable mirrored top and side panels and can cook anything you like.

It has a thermometer and backup electric heater in case it becomes cloudy. All of the various solar oven designs collapse for easy mobility and storage.

The following companies offer solar cookers, kits and plans: Clear Dome Solar, (619) 990-7977,; Reflections, (530) 273-9378,; Solar Cookers International, (916) 455-4499,; Sun BD Corp., (315) 651-8821,; and Sun Ovens International, (800) 408-7919,


Dear Jim: Our central air conditioner seems to be running fine, but there is some liquid leaking out from the bottom on the floor. I think it might be freon. Is this a dangerous problem? – Sandi H.

Dear Sandi: A freon leak would not appear as a wet spot on the floor.

Also, if freon were leaking, the working pressures would be incorrect and it would not cool properly. It probably is a clogged drain tube from the pan under the evaporator coils.

Mold can grow in the pan and clog the opening to the tube. Try running a straightened coat hanger or a flexible wire up from the drain tube outlet. This should dislodge the clog.