While wind and water can be used to generate power through movement, the sun provides a significant amount of energy in the forms of heat and light. Solar cell technology, called photovoltaic (PV) cells, convert that light into electricity. These PV cells contain semiconductor materials such as silicon. Electrons in the semiconductor move when the material absorbs the light.
Unlike the water and wind power technologies we've covered, solar cells are versatile in size and portability. Large solar panels with hundreds of cells can be built in a factory then sold to stretch out across land or mount on a rooftop. These large panels are used to power homes and businesses and must be replaced after about 30 years. Small solar panels with only a few cells gather enough energy to power standalone devices, like calculators and outdoor lighting.
Despite being a clean, renewable energy source, sunlight alone isn't sufficient for those who want to use electricity at night or on cloudy days. In most cases, solar panels are a supplemental power source for a building that's already attached to the electric grid. A few people, though, choose to go "off the grid" entirely and use rechargeable batteries to store solar-generated electricity when the sun's not shining.
So far, we've looked at innovations that make the most of renewable energy sources. Next, we'll look at an innovation making use of the most efficient non-renewable source of energy known today.