Geothermal Energy Power Plants and How They Produce Green Electricity

Geothermal energy is created far below the earth’s surface, in the form of hot molten rock or magna, being generated by the action of decaying radioactive materials such as uranium. This energy becomes accessible at the boundaries of tectonic plates, where through rubbing together and one sliding under the other, columns of magma break up from the edges pushing them nearer to the surface of the earth forming a geothermal reservoir.

This is an article on renewable energy and in particular the use of geothermal energy to produce electrical power.

Here we shall examine what geothermal energy is and how geothermal energy is used to generate electricity. We begin then with a look at how geothermal energy is used to generate electricity.

A geothermal reservoir can be exploited to raise steam to power steam turbines much like the conventional steam turbine power plants. The world’s first geothermal power plant, a dry steam type, was built in 1904 at Larderello in Italy. Since then wherever there are tectonic plate boundaries or where the reservoirs are near enough to the surface to facilitate drilling, a variety of geothermal power plants have been built close to them. These include plants which are located in Iceland, California USA,(currently the largest), Costa-Rica, New Zealand, and the Philippines.

Geothermal energy is considered renewable energy because it is sustainable and, although some pollutants are released to the atmosphere during production, these emissions are much less than those from conventional power stations. Therefore, geothermal energy could mitigate global warming if used in place of fossil fuels in power plants.

When a geothermal reservoir has been located, two wells are drilled down into it; an injection well which is used to inject water and to re-inject condensate and gasses into the reservoir, circulating around the cracks in the hot rocks and replenishing the steam/hot water. This is forced up through a second well; the production well, where it flashes off to steam as it reaches the lower pressure of the earth’s surface.

There are three types of geothermal power plants;

• Dry Steam Power Plant
• Flash Steam Power Plant
• Binary Cycle Power Plant

• Dry Steam Power Plant

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This was the original, and the least common type of geothermal power plant, utilizing the dry steam straight from the production well, drilled into the geothermal reservoir. The high pressure dry steam passes up the production well and through a rock catcher; a series of mesh filters which catch any rocks, stones or other debris, which would damage the turbine blades. The steam then passes through a steam turbine that drives an electrical generator, which produces electricity for the grid.

The steam exits the LP stage of the turbine and into the turbine condenser, that is under a vacuum. From here the condensate is pumped through a series of scrubbing towers that remove any residual non-condensable gasses. The condensate is then pumped to the water cooling towers, where it is cooled, with any remaining incondensable gasses re-circulated to the scrubbers before being re-injected with the cooled condensate down the injection well into the geothermal reservoir.

• Flash Steam Power Plant

• Binary Cycle Power Plant

Reference Webs:

1. Oregon Gov

2. Darvill Clara