Geothermal Energy Facts

  • Published on February 16th, 2016

If you are considering geothermal energy for a renewable energy option, you need to have all the facts you can get. Here are some key geothermal energy facts I’ve dug up.

geothermal system is built shutterstock_49961002

Basic geothermal energy facts:

  • Geothermal energy is made inside the Earth.
  • The world geothermal comes from Greek words meaning ‘Earth’ (geo) and ‘heat’ (thermos).
  • While the technology behind geothermal electricity generation has improved substantially, it still only provides a fraction of world electricity generation.
  • Geothermal power is clean, reliable, and cost-effective but its availability is often limited to areas near tectonic plate boundaries.
  • Geothermal power plants in the Philippines and Iceland contribute around 30% of electricity production for these countries. In the US it is less than 1%.
  • As of 2010, 24 countries use geothermal power to generate electricity; around 70 use it for various forms of heating.
  • Humans have enjoyed geothermal energy in the form of hot springs for thousands of years.
  • The oldest known spa fed from a hot spring is believed to be a stone pool found on Lisan Mountain in China, built in the 3rd century BC.
  • In some parts of Iceland, hot water runs from geothermal power plants under pavements and roads to help melt ice.

→ Also recommended: Geothermal Energy: What It is & How It Works

→ Also recommended: Geothermal Energy Advantages And Disadvantages

Here are the different kinds of geothermal energy being used today:

Electricity power plants

This geothermal power plant in Reykjavik, Iceland, is using their underground reservoirs of steam and hot water to generate electricity and to heat and cool buildings directly.

Iceland and the Philippines are the world’s leading geothermal producers of electricity. According to National Geographic,  Geothermal energy has been used for thousands of years in some countries for cooking and heating. It can be found from shallow ground to several miles below the surface, and even farther down to the extremely hot molten rock called magma.

These underground reservoirs of steam and hot water can be tapped to generate electricity or to heat and cool buildings directly.

To produce geothermal-generated electricity, wells, sometimes a mile (1.6 kilometers) deep or more, are drilled into underground reservoirs to tap either steam or very hot water. This can then drive turbines linked to electricity generators.

Here are some facts on geothermal electricity in the world:

  • First geothermally generated electricity was produced in Larderello, Italy, in 1904
  • There are three types of geothermal power plants: dry steam, flash, and binary.
  • Dry steam, the oldest geothermal technology, takes steam out of fractures in the ground and uses it to directly drive a turbine.
  • The United States has the largest geothermal electricity development in the world: The Geysers, north of San Francisco in California.
  • Iceland has at least 25 active volcanoes and many hot springs and geysers.
  • Geothermal fields produce only about one-sixth of the carbon dioxide which a relatively clean natural-gas-fueled power plant produces.
  • Unlike solar and wind energy, geothermal energy is always available, 365 days a year.
  • It is expensive to build a geothermal power plant for electricity.

Generating electricity from a geothermal power plant comes with some environmental problems. The main concern is the release of hydrogen sulfide, a gas that smells like rotten eggs at low concentrations. Another concern is the disposal of some geothermal fluids, which may contain low levels of toxic materials. Although geothermal sites are capable of providing heat for many decades, eventually specific energy producing locations may cool down.

Geothermal heat pumps

A geothermal heat pump system can take advantage of the Earth’s constant temperature below the surface to heat a home in the winter, while extracting heat from the building and transferring it back to the relatively cooler ground in the summer.

As far as heat pump history, Wikipedia reports:

“The heat pump was described by Lord Kelvin in 1853 and developed by Peter Ritter von Rittinger in 1855. After experimenting with a freezer, Robert C. Webber built the first direct exchange ground-source heat pump in the late 1940s. The first successful commercial project was installed in the Commonwealth Building (Portland, Oregon) in 1948, and has been designated a National Historic Mechanical Engineering Landmark by ASME.”

We learn this technology became popular in Sweden in the 1970s, and has been growing slowly in worldwide acceptance since that time. As of 2004, over a million units have been installed worldwide providing 12 GW of thermal capacity. In Finland, a geothermal heat pump was the most common heating system choice for new detached houses between 2006 and 2011 with market share exceeding 40%.

Geothermal Genius provides this information concerning geothermal heat pumps:

  • Over 60,000 geothermal heat pumps are installed in the US each year
  • Geothermal heat pumps currently being utilized have resulted in:saving 40 trillion BTUs of fossil fuels annually
  • These heat pumps have  eliminated at least 1.6 million metric tons of carbon equivalent annually
  • Heat pumps reduce electricity need by 2.6 million kW
  • Geothermal systems save up to 70% on heating bills and 40% on cooling bills. The cost-per-BTU of heating is significantly lower for geothermal heat pumps when compared to other heating options

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The US Department of Energy provides this information about heat pumps:

“For climates with moderate heating and cooling needs, heat pumps offer an energy efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to move heat from a cool space to a warm space, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house and during the cooling season, heat pumps move heat from your cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide equivalent space conditioning at as little as one-quarter of the cost of operating conventional heating or cooling appliances.

“The most common type of heat pump is the air-source heat pump, which transfers heat between your house and the outside air. If you heat with electricity, a heat pump can trim the amount of electricity you use for heating by as much as 30% to 40%. High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months. Air-source heat pumps have been used for many years in nearly all parts of the United States, but until recently they have not been used in areas that experienced extended periods of subfreezing temperatures. However, in recent years, air-source heat pump technology has advanced so that it now offers a legitimate space heating alternative in colder regions.”

Geothermal direct water

In modern direct-use systems, a well is drilled into a geothermal reservoir for creating  a steady stream of hot water. The water is brought up through the well into piping. It then enters a heat exchanger, where it directly delivers heat. A disposal system then either injects the cooled water underground or disposes of it on the surface.

Geothermal water from deeper in the Earth can be used directly for heating homes and offices, or for growing plants in greenhouses. Some US cities pipe geothermal hot water under roads and sidewalks to melt snow.

Geothermal hot water can be used for many applications requiring heat. Current uses include heating buildings (either individually or whole towns), raising plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes, such as pasteurizing milk.

Images: Geothermal heating system being built via Shutterstock; geothermal power plant in Reykjavik via National Geographic

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About the Author

is a writer, producer, and director. Meyers is editor and site director of Green Building Elements, a contributor to CleanTechnica, and founder of Green Streets MediaTrain, a communications connection and eLearning hub. As an independent producer, he's been involved in the development, production and distribution of television and distance learning programs for both the education industry and corporate sector. He also is an avid gardener and loves sustainable innovation.