Tuesday, November 6, 2012

Guide to geothermal power plants

Geothermal power plants use earth's heat (geothermal energy) to generate power. They have more than century old history of use since the first geothermal power plant was built in Landarello, Italy in 1904. This facility became commercial in 1911. Despite the long history of use, geothermal energy is still far from being widely used as in 2010 all the world's geothermal power plants supplied only 0.3% of global electricity demand

There are three main types of technologies used in geothermal power plants: 

1. Dry steam plants – these facilities use steam piped directly from a geothermal reservoir to turn the generator turbines.
2. Flash steam plants - these facilities operate by taking high-pressure hot water from deep inside the Earth and convert it to steam to turn the generator turbines.
3. Binary cycle power plants – these facilities operate by transferring the heat from geothermal hot water to another liquid, and afterward this second liquid is turned into the steam that drives turbines.

Geothermal power plants are predominantly built on the edges of tectonic plates because these areas ensure the best possible economics of new geothermal energy projects. However, with the development of new technologies, such as EGS (enhanced geothermal systems) technology, new geothermal power plants should spread to many new areas.

With the further technological and scientific advancement geothermal power plants could soon spread to many new areas.

Geothermal power plants are connected with high upfront costs (exploration and drilling) but once built have very low maintenance and operational costs.

In terms of greenhouse gas emissions, geothermal power plants emit an average of 122 kg of CO2 per megawatt-hour of electricity. This amount is almost negligible compared to greenhouse gas emissions coming from fossil fuel fired power plants. However, the construction of geothermal power plant, if not done properly, can lead to significant environmental damage- it can affect the stability of the land, and sometimes even trigger earthquakes.

Geothermal power plants have minimal land requirements, which isn't the case with many other energy sources. In average, geothermal power plants use 3.5 square kilometres per gigawatt of electrical production in comparison to 32 square kilometres for coal power plants. Geothermal power plants aren't too demanding of water as they use only around 20 litres of freshwater per MWh compared to more than 1000 litres per MWh for coal power plants.

The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California, United States. This complex includes 22 geothermal power plants that draw steam from more than 350 wells accounting for more than 1500 MW of total geothermal capacity.