Renewable energy is sustainable as it is obtained from sources that are inexhaustible. Renewable energy sources include wind, solar, biomass, geothermal and hydro, all of which occur naturally. Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV), indirectly using concentrated solar power, or a combination. Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaic cells convert light into an electric current using the photovoltaic effect. Creating electricity from sunlight instead of fossil fuels avoids the emission of greenhouse gases and other air pollutants and stimulates the economy. Solar energy is one of the most important sources of renewable energy currently available. It is tremendously abundant and is the most abundant natural energy resource on the planet. More solar energy is produced in one hour than the entire Earth uses in a year. Non-renewable resources like fossil fuels can skyrocket in price based on availability and solar energy is green and safe for the environment. It will not produce polluting emissions, like greenhouse gasses or toxic waste, while generating power.