In order to answer whether geothermal energy is a renewable and sustainable source of energy it is necessary to characterize terms “renewable” and “sustainable”.
Renewable forms of energy constantly replenish themselves without any human participation. Regardless of how much renewable sources of energy are used their supply will not be exhausted. Examples of renewables include solar energy, hydro-energy and wind energy. The advantage of renewable energy sources is that they can free society of its reliance on non-renewable, finite energy supplies such as oil, coal and natural gas. This is due to the fact that renewable energy sources have both abundant energy flows and the ability for self-regeneration.
The distinguishing feature of sustainable energy sources—besides their renewability—is their capability to sustain the Earth’s ecosystems. By using the sustainable sources of energy the present generations will not jeopardize the ability of future generations to use their sustainable resources to the same amount that those energy sources are currently utilized.
Experts and researchers agree that geothermal energy is a renewable energy resource (U.S. Department of Energy, 2012; DeGunther, 2009; Pierce, 2011) and generation of geothermal energy can be sustained infinitely, as precipitation regularly supplies water to geothermal reservoirs. DeGunther (2009) asserts that geothermal energy is “the only completely renewable energy source from the earth itself” adding that “a well designed geothermal system is perhaps the most environmentally friendly source of energy possible.” According to Dickson and Fanelli (2004), the rate of energy renewal is the most important feature that helps categorize geothermal energy as a renewable energy source. Geothermal energy is a renewable energy source because during the utilization of natural geothermal systems, the rate of production from the resource is equal to the replenishment of thermal water.