Alternative energy sources are being researched and developed to improve efficiency and reduce costs. Fluctuating costs of oil, coal and natural gas, along with their possible negative effects on the environment, has made energy sources such as wind and solar more cost-competitive with fossil fuels. More energy strikes the Earth in an hour than humans need in a year. We are now hard at work developing a variety of technologies to convert its power into energy that we can use to heat, cool and light our homes and businesses. This program sheds some light on photovoltaic cells and concentrated solar power as well as how they are able to convert the suns energy into electricity.