Geothermal Energy

Geothermal energy uses the heat from the core of the Earth, and sometimes Sun, to generate electricity, provide heating and cooling, or perform other useful work. Unlike every other renewable energy source, except tidal, geothermal energy does not rely on the Sun as the ultimate source of energy.

Sources of Geothermal Energy

Grand prismatic hot spring in Yellowstone National Park. Image by US National Park Service.

Grand prismatic hot spring in Yellowstone National Park. Image by US National Park Service.

Our planet was formed from “planetoids” after the big bang. These were large molten rocks that collided creating an increasing gravitational pull that attracted more planetoids. Eventually the outer layer cooled creating the crust that we live on. Deep below the crust is a molten core that still hasn’t cooled. This core is the primary source of geothermal energy. Magma is forced upwards through cracks due to pressure and heats large underground water reservoirs.

Less important but still considerable are two other sources of geothermal heat. Friction caused by denser rock that has cooled in the core that sinks creating frictional heat with other rock and radioactive decay of certain elements.

Geothermal Power Plants

Sometimes geothermal energy is used to provide heating and cooling to buildings or homes. This is done simply by using the Earth as a heatsink where heat can be transferred when it’s warmer outside and obtained when it’s colder. However, geothermal power is primarily used to generate electricity using power plants.

Nesjavellir Geothermal Power Plant in Þingvellir, Iceland.

Nesjavellir Geothermal Power Plant in Þingvellir, Iceland.

There are three types of geothermal power plants. Dry steam, flash steam, and binary cycle. All three designs use turbines powered by steam or gas. Lifespan of geothermal water reservoirs can be increased by reinjecting used water back into the reservoir but some power plants simply release it as steam.

Dry steam geothermal power plants use geothermal vents that release steam to directly turn turbines to generate electricity. Once this steam is used it is condensed back into water and reinjected into the water reservoir.

Flash steam geothermal power plants use geothermal water that is extremely hot and convert the water to steam that powers turbines. When this water reaches the steam vessel some of it instantly becomes steam and some of it remains water that is now colder. This cooled water bypasses the power plant and is reinjected back into the water reservoir along with the condensed steam.

Binary cycle power plants can use either steam or water because they use heat exchangers. Essentially two tubes spiral around each other, one filled with the geothermal water or steam, the other filled with a thermal working fluid (water, oil, etc). Heat from the former is transferred to the later since the two tubes are touching and the working fluid is converted to a gas which turns turbines to generate electricity.

Environmental Impact of Geothermal Energy

Geothermal energy has very minimal environmental impact. There is zero carbon dioxide or other greenhouse gas emissions from operation. The only emissions come from plant material construction like concrete, steel, etc and naturally occurring pollutants that are trapped in the geothermal reservoir which leak out when the well is drilled. Although you might see smoke stacks incorporated in geothermal power plants they are for releasing steam.

Land area used is minimal but there have been reports and studies showing that geothermal power plants can be responsible for Earthquakes and Landslides. This is due to disturbances in the local geology due to drilling of the source and reinjection wells used by geothermal plants. No major incidences have been reported with mainly small tremors being the result.

Geothermal Power in the News

DOE Launches Geothermal Regulatory Roadmap For Project … – 2013-06-08
The roadmap features flowcharts addressing all potential federal and state regulatory requirements for developing new geothermal power …
N. America leads world in number of geothermal projects in … – 2013-06-08
North America and Asia Pacific lead the world in terms of geothermal projects in the final stages of development, according to Electric Light …
Geothermal power plant to be built on Hokkaido’s Okushiri Island – 2013-06-08
Planning is under way for a 500-kilowatt geothermal power plant on Okushiri Island in the Sea of Japan off Hokkaido, with the launch of …
North America and Asia Pacific Lead the Market for Geothermal … – 2013-06-08
(BUSINESS WIRE)– Conventional geothermal power exploits naturally … “More than 4 gigawatts (GW) of geothermal power capacity are …
Geothermal Plant In Saskatchewan: Deep Earth Energy Production … – 2013-06-07
According to Deep Earth Energy Production Corp., geothermal power has a number of inherent advantages over other green or renewable …
NEVADA GEOTHERMAL POWER INC : Alternative Earth Resources … – 2013-06-07
Earth” or “the Company”) (TSX-V: AER, Pink Sheets: NGLPF), today announced the following management changes: Margot Delport, Chief …
North America and Asia Pacific Lead the Market for Geothermal … – 2013-06-07
Conventional geothermal power exploits naturally occurring pockets of steam or hot water close to the Earth’s surface to generate electricity.
MRP extends option to bigger stake in US geothermal firm – 2013-06-06
EnergySource has already developed one geothermal power station in California, commissioned in 2012, and is in the pre-development …
Power plant concept could change geothermal in the Basin – 2013-06-05
A pioneering power plant concept could pave the way for a new use of geothermal resources, while saving the Oregon Institute of Technology …
Geothermal Energy Benefits ‘$278m Annually’ – 2013-06-05
The new information found the benefit of producing power using geothermal sources as opposed to fossil fuels is worth 3.5 cents for coal, …


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