The United States primarily uses fossil fuels, like coal, oil, and natural gas, for its energy. You may think that we just use fossil fuels to run our cars, but many electric power plants burn coal, oil, or natural gas to generate electricity. Fossil fuels are considered non-renewable, meaning that Earth holds a limited supply of them and they cannot be replenished in a short period of time. Non-renewable energy sources come out of the ground as liquids (oil), gases (propane and natural gas), and solids (coal). They form from the buried remains of plants and animals that lived millions of years ago. Eventually it will be too expensive or environmentally damaging to tap these diminishing resources.
On the other hand, renewable energy sources are replenished by nature. Renewable sources include biomass (organic matter composed of plants and animals), water (hydropower), wind, geothermal energy (from heat in layers of rock below Earth's surface), and the Sun.
Solar technologies, for example, provide an alternate energy supply, reduce our dependence on fuels, and, unlike fossil fuels, do not add carbon dioxide to the atmosphere. Energy from the Sun can be converted to thermal (or heat) energy and used to heat water or spaces in homes, buildings, greenhouses, and swimming pools. It can also be changed into electricity using photovoltaic cells (also known as PV devices), which are cells made from silicon alloys. At the regional level, solar energy can be turned into electricity by solar power plants that collect heat in solar panels. Once inside the power plant, the collected heat is used to boil water and create steam, which then powers generators that create electricity.
Solar and environmental engineers, like those working at the National Renewable Energy Lab, are figuring out how to make renewable energy efficient and cost-effective. Currently, the machines used to manufacture solar cells cost tens of millions of dollars, and the materials used to make the cells are expensive. The solar-energy market has been plagued by the shortage of refined silicon, but scientists are researching alternate materials. In addition, in order to capture the most sunlight possible, solar installations generally take up a large amount of land, which makes them costly as they occupy valuable real estate.
The growth of the solar industry is creating many new jobs in the area of solar manufacturing and installation of solar technologies. Someday, systems that convert solar energy into electricity may replace the non-renewable energy sources we are so heavily dependent on today.