Solar Power

The sun provides the energy for 5/6 of all the electricity used in the world. But most of it is second- hand. Fossil fuels—coal, petroleum, and natural gas—are the remains of plants and animals that lived millions of years ago. The energy that is stored in them started as sunlight absorbed by the plants.

Cutting out the Middle Man That’s not very efficient. The plants and animals used a lot of the energy. We waste a lot of energy converting it to electricity. Burning fossil fuels also puts pollutants into the air. And, we’ll have to wait millions of years to get more. There must be a better way.

Solar Electricity Generation Most of our electricity is made by using steam to turn electric generators. You need heat to make steam. Burning fossil fuels is one way to get that heat. But why can’t we just use the sun’s heat?

Solar Electricity Generation Have you ever seen water boil in the sun? To boil water with sun light, we have to concentrate or focus the light from a large area into a smaller one. We can do that with lenses or mirrors.

The Photoelectric Effect Do you see any steam coming out of your calculator? Sometimes when light hits an atom, it knocks loose an electron. This turns the atom into a positive ion that is ready to accept a new electron. If this happens often enough, it creates an electric current—a flow of electricity.

Solar Heating Often, we use electricity to heat things. So why use the sun’s heat to make electricity to heat something. Why not just use the sun’s heat to heat it? Solar cookers and solar heaters do just that.

Solar Cooking The sun supplies plenty of heat, but we have to keep the food from loosing it. Heat is lost through convection, conduction and radiation. Because the Sun’s heat comes by radiation we can’t stop it. We have to stop the other two.

Solar Cooking Conduction is easy to stop. All we need is an insulator between the cooking surface and what it’s sitting on. This could be a wooden stand or just a layer of cardboard.

Solar Cooking Convection has to be stopped by trapping warm air around the food. This is often done with a clear plastic bag. Clear glass or plastic tops can also work well.

Solar Cooking Sila Sutharat has operated a solar- powered chicken roasting stall in Phetchaburi since He splits and hangs chickens vertically against a grill that faces hundreds of small concave mirrors reflecting sunlight at the grill. Sila can roast fifty 1.6kg chickens per day, taking just minutes each in good sun. Though the reflector array cost B30,000 to build, he has no fuel expenses and is able to sell the chickens for 160 baht each. If we want the food to cook quickly we need to add more heat, more sun. A lens big enough to help would be too expensive. Mirrors (or even aluminum foil) work much better.

Solar Still In emergencies, clean drinking water can be hard to find. A solar still can be build from household items and can produce pure, drinkable water.

Solar Still A solar still needs: a source of water a basin to hold dirty water some way to trap and condense water as it evaporates a basin to catch the condensation