WHAT IS WIND ENERGY? Wind is a form of solar energy, caused by the uneven warming of the earth's surface. This is why air masses have different temperatures and pressures, and are constantly moving to find a balance. The greater the difference in pressure, the swifter the air moves and the stronger the wind. People have used wind energy for thousands of years, using it to pump water, grind flour, press olives, and even to explore the world in wind-driven sailing ships. Wind farms use turbines to generate electricity, converting the kinetic energy of the wind into mechanical energy. The wind's force causes the long blades of the turbine to rotate. This rotation starts a generator, which produces low-voltage electric energy.
ABOUT SOLAR CELLS: In the future, more homes will most likely incorporate solar cells, also known as photovoltaics. Solar cells are made of semiconductor materials (usually silicon), which absorb sunlight's energy and stores it until it is needed to power something. Unfortunately, present solar cells can only absorb between 15-25 percent of sunlight's energy. This is because it only absorbs visible light; other kinds of light pass right through the cell as if it were transparent.