Geothermal power is the use of geothermal heat to generate electricity.There are three types of geothermal energy used to make electricity,
Hydrothermal – uses steam and hot water
Geopressurized – uses hot water (around 350°F) and hydraulic turbines
Petrothermal – uses dry hot rocks requiring water injections to make steam.
A Clean Alternative
Geothermal energy is clean energy because no fuel is burned, so there are no harmful pollutants released into the environment.Geothermal power plants use steam from wells that reach deep in the earth into geothermal reservoirs,which are found along the earth’s major plate boundaries where volcanoes and earthquakes occur most frequently.
Estimates of exploitable worldwide geothermal energy resources vary considerably. According to a 1999 study, it was thought that this might amount to between 65 and 138 GW of electrical generation capacity ‘using enhanced technology.
The Geothermal Cycle
Geothermal energy is produced by drilling a well deep into the ground where thermal energy has been found.A well head is then attached and the steam is then seperated from water.The water is then used to turn a turbine and in turn generate electricity.The water is then returned to the source to resupply the well.
Geothermal power plants are located all over the world but can only be placed in tectonic plate locations.It is the interaction between the mantle of the earth and the earth’s crust that makes geothermal power possible. The crust of the earth traps the heat of the mantle beneath it.
Sometimes the heat of the mantle becomes so intense that it causes the mantle to break through at the thinnest areas of the crust. These areas are referred to as hot spots. The material in the mantle can escape at hot spots in the form of volcanic lava. When a volcano erupts, it is basically allowing the mantle of the earth to flow up through the crust to the surface.
A 2006 report by MIT that took into account the use of Enhanced Geothermal Systems (EGS) concluded that it would be affordable to generate 100 GWe (gigawatts of electricity) or more by 2050, just in the United States, for a maximum investment of 1 billion US dollars in research and development over 15 years.
Geothermal energy was first used to produce electricity in Italy in 1903. At the end of 2004, there were 43 power plants producing electricity from geothermal energy in the USA. Most of these are located in California and Nevada.
Iceland leading the way
Geothermal energy can be used as an efficient heat source in small end-use applications
such as greenhouses, but the consumers have to be located close to the source of heat. The capital of Iceland, Reykjavik, is heated mostly by geothermal energy.
Water Injection
In some locations, the natural supply of water producing steam from the hot underground magma deposits has been exhausted and processed waste water is injected to replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is carefully managed.
Geothermal energy has a major environmental benefit because it offsets air pollution that would have been produced if fossil fuels were the energy source. Geothermal energy has a very minor impact on the soil – the few acres used look like a small light-industry building complex. Since the slightly cooler water is reinjected into the ground, there is only a minor impact, except if there is a natural geyser field close by.
