We use a lot of energy to power our lives, from our homes and cars to our tablets and handheld games. The challenge facing us today is finding sustainable energy methods that will ensure a green future. There are seven different types of green energy and they are the only types that don't pollute our Earth. We have learned how to harness the power of the sun, wind, water, and Earth. And technological innovations have allowed us to put these alternative energies to work in our everyday lives.