This week's wintry weather (lows in the 50s F., showers predicted well into next week) nearly scotched my plans to try out my new solar cooker, which I got for $18 at a company called Sun Toys.
My conundrum: because I live in a city where it's cloudy more often than it is sunny, solar cookers are of limited use. Even if it's sunny early in the day, there's no guarantee it will stay that way long enough to keep solar-cooked food from becoming botulism stew. There are some hybrid versions, which solve this problem by including a regular electrical heating element that kicks in when the sun fails to shine. The tradeoff: you lose a lot of the environmental benefits of a true solar cooker. And they cost far too much to be a practical option in less affluent countries, where solar cooking carries its own challenges.
Fortunately, mercurial weather doesn't have to be an intractable problem. The secret to successful solar cooking in variable climates is choosing foods that don't take long to cook through--things like nachos (about as simple as it sounds), fish and shrimp (simple recipe: wrap shrimp in basil and prosciutto; marinate in white wine, vinegar, and olive oil, and bake in solar oven for an hour) that take just minutes to cook in a conventional oven.
Of course, if you live in a place with ample, year-round sunshine, you won't have my problems with cloudy weather (lucky!). All you'll need, then, is a solar cooker, a sunny spot, and plenty of time to monitor your meal and move the oven around for maximum exposure.
My solar cooker looks a lot like one of those sun visors you put behind your windshield to keep the heat out on sunny days. The body of the cooker is made of aluminum wrapped around a thin layer of foam; it folds out into a six-sided box with a large floor (and, obviously, an open top). The cooker came with a small black pot and an enormous plastic bag for heat retention and to make foods cook more quickly.
My first experiment with solar cooking was, to put it mildly, an abysmal failure; the aluminum visor, which was supposed to concentrate the sun's rays on the top of the pot, blew over almost immediately, shading the food from the sun and leaving it barely warm after four hours on the third-story roof of my office. I attribute this to poor design; anything shaped like a sail is going to act like one. Cook's Illustrated recently tested three different types of solar ovens, including a "hot pot" model similar to (but more expensive than) my own, and concluded that "solar cookers are surprisingly good at cooking certain things, but overall they’re unreliable." They recommended the Solar Oven Society Sport Oven--but at $140, it's definitely a luxury item.
A better alternative, for those with access to a few basic materials (essentially, foil and a cardboard box), is to make your own. The Ethicurean recently ran a helpful, step-by-step guide to building a solar box cooker using newspaper, boxes, cardboard, glue, and foil. Their model takes five or six hours to build, but there are many other, simpler alternatives available; an excellent, multi-language guide to numerous solar cooker models of varying complexity can be found at the Solar Cooking Archive.
