In science, the term renewable refers to renewable sources of energy, meaning sources of energy that naturally replace themselves at a rate near or equal to human consumption. Examples of renewable energies include geothermal, hydropower, solar and wind. Today, many nations are increasing their use of renewable energies in lieu of fossil fuels, including oil, coal, and natural gas, which renew only over thousands and sometimes millions of years. Because humans use fossil fuels at a much faster rate than it can replace itself, these fuels are considered non-renewable resources.
Types
Renewable energy comes from five main sources. Biomass is the conversion of the energy within plants that perform photosynthesis. Geothermal energy is the use of Earth's internal heat. Solar energy is harnessed from the sun's light and radiation. Hydropower is the conversion of water flow into usable energy. Wind power is the conversion of airflow into usable energy. These are all renewable because they all self-sustain through Earth's natural processes.
Considerations
Most types of renewable energies are readily available. Hydropower and wind energy, for example, are very available as water flow and airflow occur naturally from Earth's weather patterns. Wind power is especially accessible because it can be captured onshore or offshore. Geothermal energy, however, has been historically limited to tectonic plate boundaries along which Earth's heat is most easily captured.
Benefits
There are two major factors that make renewable energies very beneficial. One, their use and conversion is much cleaner than that of fossil fuels, which release harmful greenhouse gases into the atmosphere. Two, renewable energies are self-sustaining, meaning they will naturally replace themselves at a rate similar to or even greater than human use.
Cellulosic Ethanol
Cellulosic ethanol is a biofuel produced from the structural matter of plants (cellulose). It is renewable in that its source, plants, naturally regrow on their own. A 2007 report by Environmental California states that cellulosic ethanol gives off nearly 80 percent less pollution than gasoline, making it much cleaner than fossil fuels.
Potential
Renewable energies, especially wind and solar power, are not used to their full potential. According to National Atlas, solar power provides less than 1 percent of total U.S. energy needs. The sun, however, provides Earth with enough energy in one hour to meet annual global energy use.
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