Geothermal energy

The source of geothermal power is the heat contained inside the Earth. There are a few different types of geothermal energy that can be tapped.

1) "Some geothermal systems are formed when hot magma near the surface (1,500 to 10,000 meters deep) directly heats groundwater." The heat generated from these hot spots flows toward the surface (volcanoes, geysers, and hot springs). Naturally-occurring hot water and steam can be tapped by energy conversion technology to generate electricity or to produce hot water for direct use.

2) "Other geothermal systems are formed when magma heats rocks which in turn heat deeply-circulating groundwater." In order to maximize the energy gleaned from these so-called "hot dry rocks," geothermal facilitieswill often fracture the hot rocks and pump water into and from them in order to use the heated water to generate electricity.

Iceland, New Zealand, the Philippines, and South America are some of the more prominent global "hot spots" in the world. In Iceland, geothermal energy, caused by the constant movement of geologic plates coupled with the volcanic nature of the island, is used to heat 95% of all homes.

Unfortunately even good geothermal areas are non-renewable. "The Geysers," the world's largest geothermal facility, built in the 1950s on a steam field in Northern California, was established on the assumption that geothermal resources were infinite. However, by the late 1980s, steam decline became noticeable. Depletion occurred because steam was being extracted faster than it could be naturally replaced. The Geysers was still producing enough electricity to supply the power demand of a city like San Francisco, the steam field can be defunct in 50 years or so. To prevent this sort of thing, geothermal facilities can use a closed-loop system, or the re-injection of water back into the system for constant steam generation.

Despite the fact that geothermal energy is abundant, fields of sufficient quality to produce economic electricity are rare. In addition, many of them are located in protected wilderness areas. Although no combustion occurs, some applications produce carbon dioxide and hydrogen sulfide emissions, require the cooling of as much as 100,000 gallons of water per megawatt per day, and dispose of toxic waste and dissolved solids. Unless research and technology join forces to "harvest" geothermal power through non-traditional means, such as deep-crustal drilling or the acquisition of heat from magma, the tapping of geothermal energy is limited to a handful of locations.

Another type of geothermal energy being used commercially is Earth energy, extracted through heat pumps. Heat contained in shallow ground is used to directly heat or cool houses. In winter the ground is warmer than the air and can be used to heat a building, and in summer the ground is cooler than the air and can act as an air conditioner. This technique reduces the reliance on other resources and can be utilized anywhere, resulting in significant environmental benefits and reduced energy costs.