- Renewable energy comes in many forms, such as solar, wind, hydropower, biomass/biofuel, geothermal, ocean and hydrogen energy, and can be used to produce electricity, transportation fuels and other chemicals (in the cases of biomass and hydrogen energy).
- Solar energy can be used for heating and lighting homes and other buildings, generating electricity, hot water heating and solar cooling, as well as for numerous commercial and industrial uses.
- Wind turbines can be used alone, connected to a utility power grid or combined with a solar cell system to serve a number of functions ranging from electricity production to water pumping.
- A small or micro-hydroelectric power system can produce enough electricity for a home, farm, or ranch.
- Biomass energy can be used for fuels, power production and products, which all have the potential to reduce greenhouse gas emissions.
- Biofuels are the only renewable liquid transportation fuels available, with about four percent of all motor fuel currently blended with up to 10 percent ethanol.
- Biomass energy supports the U.S. agricultural and forest-product industries by using feedstocks, such as paper mill residue, lumber mill scrap, and municipal waste for power.
- Biofuels use feedstocks, like corn (for ethanol) and soybeans (for biodiesel), which are surplus crop.
About four percent of all motor fuel is currently blended with up to 10 percent ethanol. - If the use of ethanol were extended to all motor fuel, some 630,000 barrels of oil per day could be offset.
- “Flex-fuel” vehicles can use fuel blends that contain up to 85 percent ethanol.
- Agricultural residues, such as corn stover (the stalks, leaves, and husks of the plant) and wheat straw, are planned to be used in the near-term for the production of biofuels.
- According to the U.S. Department of Energy, the use of biomass/biofuel energy strengthens rural economies, decreases America’s dependence on imported oil, avoids use of MTBE or other highly toxic fuel additives, reduces air & water pollution and reduces greenhouse gas emissions.
- Geothermal hot water is currently used to heat buildings (individually or entire towns), raise greenhouse plants, dry crops, heat water at fish farms and perform various industrial processes, such as pasteurizing milk.
- Geothermal heat pumps could replace the entire system of oil heating in homes, which currently uses 500,000 barrels of oil per day.
- Geothermal power plants use steam produced from reservoirs of hot water found a couple of miles or more below the Earth’s surface for generating electricity, rather than using fossil fuels to boil water and produce steam.
- Geothermal heat pumps use significantly less energy than conventional heating systems and are more efficient when cooling buildings, which saves energy and money while reducing air pollution.
- Oceans are considered the world’s largest solar collectors, as they cover more than 70 percent of Earth’s surface.
- The temperature difference between the heated ocean surface and the deep ocean waters creates thermal energy, of which a small portion could have the potential to power the world with electricity.
- Most hydrogen production is currently made by steam reforming natural gas. However, natural gas is becoming scarcer and more expensive. Natural gas is also a fossil fuel, so the carbon dioxide released in the reformation process adds to the greenhouse effect.
- Hydrogen has very high energy for its weight, but very low energy for its volume, so new technology is needed to store and transport it.
- Fuel cells have the ability to cleanly produce electricity from hydrogen and oxygen, making hydrogen attractive as a ‘fuel’ for transportation use in particular.
- Fuel cells could also act as a general energy carrier for homes and other uses, and for storing and transporting otherwise intermittent renewable energy.
- Fuel cells function like a battery, where external fuel is supplied rather than being stored electricity, and generates power by chemical reaction rather than combustion.
- Fuel cell technology is still in early development, needing improvements in efficiency and durability.
- Current fuel cell work at the National Renewable Energy Laboratory aims to develop durable, less-expensive materials for its necessary components.
- Platinum and other current electrode catalysts used in fuel cells are costly (particularly for low-operating-temperature fuel cells), where conditions can be highly corrosive (particularly for high-operating-temperature fuel cells) both for electrodes and membranes.
- Design options for fuel cells and their relation to other vehicle operating systems remain quite complex.
Sources: National Renewable Energy Laboratory (NREL), U.S. Department of Energy (Energy Efficiency and Renewable Energy), National Defense Council Foundation