Energy from the Earth What could be more natural or plentiful? The source of geothermal power is the heat contained inside the Earth; heat so intense that it creates molten magma. There are a few different types of geothermal energy that can be tapped. "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 outward toward the surface, manifesting as 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. "Other geothermal systems are formed even when no magma is nearby as 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 facilities will often fracture the hot rocks and pump water into and from them in order to use the heated water to generate electricity.
The concentration of geothermal energy at any given location must be quite high in order to make heat extraction feasible, and not all geothermal sites are created equally. Regions that have well-developed geothermal systems are located in geologically active areas. These regions have continuous, concentrated heat flow to the surface. The western United States has the best geothermal regions in the country, while Iceland , New Zealand , the Philippines , and South America , are some of the more prominent global "hot spots." 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 a non-renewable renewable. "The Geysers," the world's largest geothermal facility, is a working model on how not to approach a so-called "renewable" geothermal resource. Built in the 1950s on a steam field in Northern California , the facility was established on the apparent assumption that geothermal resources were infinite at that locatio. However, by the late 1980s, steam decline became noticeable and sustained. Depletion occurred because steam was being extracted faster than it could be naturally replaced. According to a report by Pacific Gas and Electric, "because of declining geothermal steam supplies, the Company's geothermal units at The Geysers Power Plant are forecast to operate at reduced capacities." In response, "plant operators and steam suppliers continually seek new operating strategies to maximize future power generation coupled with daily injection of millions of gallons of reclaimed municipal wastewater." Even though improvements in efficiency and conservation are being implemented and in 1996 The Geysers was still producing enough electricity to supply the power demand of a city like San Francisco , it is projected that the steam field will be defunct in 50 years or so. To prevent this sort of thing from happening elsewhere, geothermal facilities can use a closed-loop system at all times, or the re-injection of water back into the system for constant steam generation, as PG&E is now implementing at The Geysers.
Despite the fact that geothermal energy is abundant renewable, and able to reduce our dependence on imported fuels, the fact remains that fields of sufficient quality to produce economic electricity are rare. In addition, many of those that are known are located in protected wilderness areas that environmentalists want to preserve. 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.
Environmental concerns also taint the issue of geothermal energy. 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.
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 since the temperature inside the ground tends to stay at the yearly average. Therefore, in the winter the ground is warmer than the air and can be used to heat a building, and in the summer the ground is cooler than the air and can act as an air conditioner. Researchers know that "no active technology for home cooling is more efficient than the geothermal heat pump." This technique reduces the reliance on other resources and can be utilized anywhere, resulting in significant environmental benefits and reduced energy costs.
Hydrothermal Reserves: Geothermal energy is found in many places on the earth. Its use contributes to the development of important third-world countries including the Philippines, Indonesia, Mexico, countries of Central and South America, and countries in eastern Africa and in eastern Europe. Italy, Iceland, New Zealand, Japan and France, along with the United States, are developed countries using geothermal energy.
There is a very large geothermal resource base in the U.S. and in the world, much of which can not yet be economically used. In fact, the resource base for the renewable energies- geothermal, solar, biomass and wind -- is much larger than the total resource base in coal, oil, gas, and uranium (nuclear power).
There are also other problems that prevent us from taking full advantage of this form of energy. Even though there are geothermal resources throughout the world, our current technology is not sufficient or economical enough to warrant its widespread use. Funding for energy extraction that involves the penetration of magma is not available because we do not yet know how to prevent a high-temperature, high-pressure blowout. When heat pumps are considered, which tap local sources of heat and can help to reduce a family's electricity bill by about $1 per day, the system is not economically viable. It "may have a payback period in excess of 5 years," which will increase with decreased electricity rates "unless equipment and installation costs drop dramatically." In addition, Earth energy is not "intense" enough to produce power for the electrical distribution grid; it is only sufficient to reduce the draw from the grid.
There are definite obstacles to be overcome before geothermal energy can be easily and economically harnessed for everyday, worldwide use. Case in point: "Construction of new domestic electricity-producing geothermal facilities in the Western United States during 1996 was limited to one site, due to the availability of cheap, plentiful natural-gas-fired electricity in the West."