Another type of solar energy, known as light solar energy or photovoltaic energy, has only been used since the 1950s. This type of solar power comes from changing sunlight into actual electrical current. Very thin photovoltaic cells, which contain layers of different chemicals, absorb light from the sun and change it into electricity. The photovoltaic electricity is then stored in large batteries for later use, or it is actually sent back through the power lines to the electric company, which pays you for making electricity. Photovoltaic energy is growing in popularity every year. New types of photovoltaic cells, called “thin films”, are making solar electrical systems easier to put into homes, and less expensive than they were before.