How Are Electricity and Heat Produced?

Solar cells are a kind of battery that change sunlight into electricity. The batteries we use most often are the lithium batteries found in cameras and computers and the alkaline batteries people put in their portable CD players and TV remote controls.

A solar cell contains two sheets of different materials. When light from the sun hits the cell, electricity begins to flow. Ordinary families can produce electricity to use in their homes by placing solar panels on their roofs or some other place that gets a lot of sunlight. Also, heat from the sun can be used to warm up water or the house itself. Solar panels are not used just to light homes and supply them with hot water; they are also fitted to satellites, powering the satellites with electricity while they are in space.

Japan produced 43% of the world's solar cells in 2001, and recently there have been a number of technological advances that have made solar cells more practical. For example, some solar cells can store electricity produced in the daytime in a secondary battery so that it can be used at night. Some local governments and foundations keen to promote new forms of energy provide financial assistance when people equip their homes with solar cells.

Solar cookers work by storing heat and reflected light from the sun. You can use a solar cooker to cook rice or make pancakes by putting it outside on the veranda or in the yard on a clear day. In Japan, many people air their futons and hang their laundry out to dry on their verandas, and most verandas receive a lot of sunlight. This makes them an ideal place to put a solar cooker. A solar cooker has a black pot with a lid that reflects sunlight inward; the pot absorbs heat from the sun, and this heat is trapped in a tightly sealed box. While simple kits for putting together a solar cooker are sold in stores, it is also possible to make one on your own. Solar cookers are a great example of clean energy in action.

Wind power is another source of clean energy. The energy created from a spinning windmill can be used as mechanical energy for such tasks as scooping up water from a lake or river. If the windmill can spin fast enough, the energy can be used to produce electricity.

The ocean can also be used as a source of energy. For example, electricity can be produced by taking advantage of the differences in temperature between the warm water at the ocean's surface and the cold water about 800 meters (half a mile) below. Also, the flow of air caused by the up-and-down motion of waves can be converted into electricity.

When producing electricity from wind or ocean power, a machine called a turbine is used. Turbines have blades much the same as a fan. The blades turn when steam or gas pushes against them; as they turn, they produce mechanical energy. Turbines can also be spun by falling water or by the movement of steam or air caused by differences in temperature. In other words, water, steam, and air can all be made to work as sources of energy.

Photos: Sharp Corp. (top); PANA (second); Yasuko Torii (third, fourth, and bottom)