Heat from the Earth: Clean and Inexhaustible
December 12, 2012
Geothermal energy is heat from the Earth. It is a clean, renewable resource that provides energy in the U.S. and around the world in a variety of applications and resources. Although areas with telltale signs of the earth's inner heat, like hot springs, are more obvious and are often the first places geothermal resources are used, the heat of the earth is available everywhere, and we are learning to use it in a broader diversity of circumstances.
Geothermal is considered a renewable resource because the heat emanating from the interior of the Earth is essentially limitless. The heat continuously flowing from the Earth’s interior, which travels primarily by conduction, is estimated to be equivalent to 42 million megawatts (MW) of power, and is expected to remain so for billions of years to come, ensuring an inexhaustible supply of energy. Geothermal energy can be used for electricity production, for commercial, industrial, and residential direct heating purposes, and for efficient home heating and cooling through geothermal heat pumps.
The geothermal power production in the U.S. today provides enough electricity to meet the electricity needs of about 3 million California households. This does not include contributions from geothermal heat pumps and direct heating uses. Geothermal is the largest renewable power source in California, supplying roughly 5% of the state's total electricity. Worldwide, the U.S. continues to produce more geothermal electricity than any other country, comprising approximately 30 percent of the world total.
As of April 2012, over 3,000 MW of geothermal power capacity was online in the United States. Geothermal power was being produced in California, Nevada, Hawaii, Utah, Idaho, Alaska, Oregon and Wyoming. New geothermal power plants were under development in 15 states which would nearly double US production. The states with projects under development included all 8 states with production plus New Mexico, Colorado, Arizona, Louisiana, North Dakota, Texas and Washington.
Unlike fossil fuel power plants, geothermal power plants emit no smoke, because no burning takes place; only steam is emitted. Emissions of nitrous oxide, hydrogen sulfide, sulfur dioxide, particulate matter, and carbon dioxide are extremely low, especially when compared to fossil fuel emissions. The binary geothermal plant, which currently represents around 15% of all geothermal plant capacity, along with the flash/binary plant, produce nearly zero air emissions. Even dry steam plants, which are considered to have the highest levels of air emissions, are considered environmentally benign compared with fossil fuels.
Using geothermal power instead of conventional power plants reduces air and water missions and enhances both the environment and public health. Because geothermal use offsets emissions of nitrogen and sulfur produced by fossil fuel power plant, for example, geothermal can help reduce healthcare effects and related costs. An analysis by Abt Associates assessing the health impacts related to power plant emissions concluded that reducing power plant nitrogen emissions by one million tons and sulfur emissions by four million tons as of 2010 would mean:
- The number of related deaths would be reduced by 8,714 annually, with an associated healthcare savings of almost 53 million dollars.
- The number of related cases of chronic bronchitis would be reduced by 5,997 annually, with an associated healthcare savings of almost two million dollars.
- The number of related heart attacks would be reduced by 13,924 each year, with an associated healthcare savings of almost two million dollars.
According to the U.S. Department of Energy, geothermal energy uses less land than other energy sources, both fossil fuel and renewable. No transportation of geothermal resources is necessary, because the resource is tapped directly at its source. Over 30 years, the period of time commonly used to compare the life cycle impacts from different power sources, a geothermal facility uses 404 m2 of land per gigawatt hour, while a coal facility uses 3632 m2 per gigawatt hour.
Both in the US and worldwide, geothermal resources have barely been tapped. Even with several thousand megawatts of geothermal power on-line and under development, we are using only a fraction of what is available. According to the US Geological Survey there are 9,057 Megawatts (MW) of undeveloped geothermal power sites in the 13 western states, and that is only the beginning. Much more has yet to be discovered. And with development of new technology, the USGS estimates that over 500,000 MW of geothermal power could be put on-line in the Western US!
A 2007 report by the Massachusetts Institute of Technology looked at the future potential of geothermal energy. To quote from the MIT release, their study found that “the huge amounts of heat that reside as stored thermal energy in the Earth's hard rock crust could supply a substantial portion of the electricity the United States will need in the future, probably at competitive prices and with minimal environmental impact.” Such an investment would benefit America’s health, environment, and energy independence.
The views expressed in these essays are those of their respective authors and do not necessarily reflect the views of Physicians for Social Responsibility.