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Where are solar electric panels used? Have you seen those big orange signs along the highway with flashing messages about an exit being closed or a traffic jam ahead? Ever look on top of those signs? Yup, there are big solar panels up there. Those solar panels are attached to batteries, so the signs stay lit at night. Little solar panels are used on solar calculators (the panel is usually in a little strip across the top). You might have seen solar panels on people's roofs or on poles in front of their houses. And how about in space? You know those flat, black "wings" that stick off satellites and space stations? Yeah, solar panels! Can you think of other places you?ve seen a solar panel, or that would be a smart place for one?
Solar electric panels are made up of something called silicon, the same thing that makes up sand. There is more silicon on the planet than almost anything else. Even though you can find silicon almost everywhere, making a solar panel is difficult and expensive. The silicon has to be heated to super high temperatures in a big factory, and then formed into very thin wafers. When sunlight hits a solar panel, it makes electrons in the silicon move around. (Electrons are teeny tiny specks--they?re way too small for us to see, even under a microscope.) The electrons flow through wires that were built into the solar panel. And presto! We have electricity! We can do whatever we want with this electricity, run a calculator, a CD player, or, if we have big enough solar panels, a satellite! [Solar panels are also called photovoltaic panels. "Photo" means light and "voltaic" means electricity.]
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What is solar cooking? In the United States, the stoves in our houses run on electricity or gas. In other parts of the world, many people still cook over campfires. One of the many cool things about solar ovens is that they don't need electricity, gas, or wood to work--they cook food using only sunlight! Basically, you put food in a box and trap the sun's heat by covering the box with glass or plastic. (Solar cooking is an example of using solar thermal energy.) And they're easy to make! You can make one with two cardboard boxes, one inside the other, covered with glass or plastic. You can put crumpled-up newspaper between the two boxes to help trap the sun's heat, paint the inside black, and put aluminum foil outside to help reflect more sun into the cooker. Even a simple solar cooker like this one can reach temperatures over 250? F. Solar cookers are great because they save money and energy, and produce no pollution. People don't have to cut down trees for firewood, and they make no nasty smoke to hurt people's lungs, things that are big problems in countries that don't have as much money as we do. Solar cookers can also be used to make water safe to drink, make doctor's tools safe to use, and heat water for laundry.
