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Geothermal Plants

A typical geothermal plant can generate as much as one billion kWh per year.1 Incredibly, that is enough energy to power more than 53,000 homes.2 However, is there enough geothermal energy available to replace our existing fossil fuel power plants?

What Are Geothermal Plants?

Geothermal plants are medium-sized power plants that are not too dissimilar in appearance to fossil fuel power plants. However, unlike fossil fuel power plants, geothermal plants don’t burn a fuel source to generate electricity. Instead, they use heat that’s naturally generated beneath the earth’s surface. The heat is primarily produced from tiny quantities of decaying thorium, uranium and potassium that create temperatures in excess of 7,000°C within the earth’s core.3 While the majority of the heat is too far beneath the earth’s surface for us to use, there are a few locations around the world where we can access it cost-effectively. This is most commonly done by drilling into reservoirs of high-pressure hot water created by the earth’s heat.4 The hot water flows up through wells in the ground under its own pressure.5 As it flows upward, the pressure decreases and some of the hot water boils into steam.6 The steam is then separated from the water and used to generate substantial amounts of electricity.7 In fact, by using geothermal plants, we could generate some 60% of the world’s current electrical demand.8 Furthermore, geothermal has the potential to provide an incredible 1,400 PWh of low-level heat energy.9 That’s around fourteen times the world’s current energy demand. Sadly, the usefulness of this heat is limited as it is very difficult to distribute.10

What’s Good About Them?

  • They provide a reliable and consistent source of energy.11
  • They are incredibly cheap to run.12
  • They generally require small amounts of land.13

What’s Bad About Them?

  • Despite their potential, there are a limited number of viable sites around the world.14

How Much Area Do We Need?

If geothermal energy were widely available in the United States, less than 1% of the landmass would be required to meet the country’s energy demand.15 In fact, even for the United Kingdom which, as we know, has eight times as many people per kilometre,16 only 3% of the landmass would be required to meet the country’s energy demand.17 This, of course, assumes that geothermal energy is widely available in the UK which, unfortunately, it isn’t.18

What Impact Do They Have on the Landscape?

Modern geothermal plants generally consist of a modest set of buildings that primarily house the generators needed to produce the electricity and the condensers required to turn the steam into a liquid so that it can be returned to the ground.19 Most geothermal plants also emit a visible plume of steam into the air,20 however, this can now be avoided at the expense of an increased capital spend and a reduction in energy production.21 As well as the buildings, geothermal plants also require a significant area for the pipes that both collect the steam and return it to the ground. In fact, the Geysers Geothermal Complex in the USA, which consists of 15 geothermal plants,22 uses some 116 square kilometres of land.23 Despite this, geothermal plants take up less space than most other renewable energy devices. Furthermore, the buildings can be designed to blend in with the surrounding context and much of the pipework can be buried.24 As such, any visual impact due to geothermal energy production is likely be minimal.

The Nesjavellir Power Plant in Iceland not only used to generate electricity, but also to provide hot water for Iceland’s capital city – Reykjavik.25

Where Are Geothermal Plants Best Located?

Good locations for geothermal occur where underground temperatures are highest.26 This can generally be found in regions where there are active or geologically young volcanoes.27 As such, geothermal energy has most potential in western United States, eastern Africa, India, parts of the Middle East and a handful of other smaller nations.

How Do They Perform?

Energy PriceLife SpanEnergy per KM²
¢5/KWH2830 YRS29200 GWH/YR30

Economic OffsetEnergy OffsetWorld Potential
12 YRS312 YRS3212 PWH33

How Do They Rate?

Value for Money|★ ★ ★ ★ ★ ★
Reliability|★ ★ ★ ★ ★ ★
Eco-friendliness|★ ★ ★ ★ ★ ★
Global Potential|★ ★ ★ ★ ★
Overall|★ ★ ★ ★ ★

Geothermal Plants in a Nutshell

To summarise, geothermal plants can provide a very affordable, reliable and consistent source of energy. Furthermore, geothermal plants require very little land. Unfortunately though, there are a limited number of viable sites around the world and, as such, geothermal will only be able to supply a small percentage of our future energy demand.

Which Renewable Should We Opt For?

Now you have a good understanding about geothermal plants, why not find out which renewable devices are best placed to meet our future energy demand by clicking the link below. Alternatively, find out about other renewable devices by checking out The Renewable Solution.

Image Credit

Title image taken by Gretar Ívarsson and released into the public domain.

United States map created by SUPER RADICAL.

Aerial image of Nesjavellir Power Plant taken by javarman and reproduced under license from Shutterstock.

World map created by SUPER RADICAL. World map loosely based on all onshore locations that hold high geothermal potential. World map data sourced from Islandsbanki Geothermal Energy Team – ‘United States Geothermal Energy Market Report’ – Page 11.

General Notes

All figures presented in this section are estimates based on best available data, assume optimum locations, and, wherever possible, are based on comparable studies. That said, many of the studies assume different economic conditions, climatic conditions, time frames and locations. Furthermore, the technologies discussed in this section are in a constant state of development. As a result, the figures presented within this section provide a rough guide only and should not be viewed as a definitive performance level.

For the total world energy demand, a figure of 104.4 million GWh has been used. The figure is based on 2012 data and sourced from International Energy Agency – 'World Balances for 2012' – www.iea.org.

All UK to USA currency conversions have been set at $1.656 USD for each £1 GBP. The figure is based on the conversion rate as of the 1st January 2014 and sourced from XE – 'XECurrency Table: USD - U.S. Dollar' – www.xe.com.

Article Endnotes

  1. Verkís – ‘Nesjavellir Power Plant’ – www.verkis.com
  2. Based on a UK home using an average 18,738 kWh of energy in 2014. Sourced from UK Department of Energy and Climate Change – ‘Energy Consumption in the UK’ – Page 7.
  3. Boyle, Godfrey – ‘Renewable Energy: Power for a Sustainable Future’ – Oxford University Press – Page 344.
  4. National Renewable Energy Laboratory – ‘Geothermal Electricity Production Basics’ – www.nrel.gov.
  5. National Renewable Energy Laboratory – ‘Geothermal Electricity Production Basics’ – www.nrel.gov.
  6. National Renewable Energy Laboratory – ‘Geothermal Electricity Production Basics’ – www.nrel.gov.
  7. National Renewable Energy Laboratory – ‘Geothermal Electricity Production Basics’ – www.nrel.gov.
  8. Based on a current global electrical demand of 18.9 PWh and geothermal having the potential to generate some 12 PWh of energy. Global electrical demand based on 2012 data sourced from International Energy Agency – ‘World: Balances for 2012’ – www.iea.org. Geothermal potential sourced from Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 39. Please note, geothermal potential does not include power conditioning, distribution and transmission losses.
  9. Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 39. Figure rounded up to the nearest one hundred.
  10. Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 28.
  11. Watson, Stephanie – ‘How Geothermal Energy Works’ – howstuffworks.com.
  12. Based on a cost of ¢5 per kWh making it the cheapest renewable option available.
  13. Based on 200 GWh being generated per spare kilometre. Only offshore wind, photovoltaics and nearshore waves provide more energy per square kilometre.
  14. Based on geothermal energy being limited to areas identified on the location map.
  15. Based on the United States of America having a total land area of 9,147,420 square kilometres, the United States of America demanding 16.8 million GWh of energy per year, geothermal plants generating 200 GWh per hectare, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Land area sourced from The World Bank – ‘Land Area (SQ. KM)’ – data.worldbank.org. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United States: Balances for 2012’ – www.iea.org. Energy generated by geothermal plants based on 1 TWh of energy being generated per five square kilometres of land. Sourced from Trieb et al. – ‘Concentrating Solar Power for the Mediterranean Region’ – Page 166. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from U.S. Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  16. Based on the United States of America having 35 people per square kilometre of land area and the United Kingdom having 267 people per square kilometre of land area. Figures based on 2014 data sourced from The World Bank – ‘Population Density (People Per SQ. KM of Land Area)’ – data.worldbank.org.
  17. Based on the United Kingdom having a total land area of 248,532 square kilometres, the United Kingdom demanding 1.48 million GWh of energy per year, geothermal plants generating 200 GWh per hectare, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Land area sourced from The World Bank – ‘Land Area (SQ. KM)’ – data.worldbank.org. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United Kingdom: Balances for 2012’ – www.iea.org. Energy generated by geothermal plants based on 1 TWh of energy being generated per five square kilometres of land. Sourced from Trieb et al. – ‘Concentrating Solar Power for the Mediterranean Region’ – Page 166. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from U.S. Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  18. Based on map data sourced from Islandsbanki Geothermal Energy Team – ‘United States Geothermal Energy Market Report’ – Page 11.
  19. Union of Concerned Scientists – ‘How Geothermal Energy Works’ – www.ucsusa.org.
  20. Manzella, A. et al. – ‘Report on Mitigation Measures’ – Page 28.
  21. United States Energy Information Administration – ‘Some U.S. Electricity Generating Plants Use Dry Cooling’ – www.eia.gov.
  22. Future Power Technology – ‘The Top 10 Biggest Geothermal Power Projects in the World’ – www.power-technology.com.
  23. Calpine Corporation – ‘About Geothermal Energy’ – geysers.com.
  24. Hidden pipework sourced from VSO Consulting – ‘Hverahlid Power Station, 90 MWe, Environmental Impact Statement, Summary’ – Page 4.
  25. Mannvit– ‘Nesjavellir Combined Heat and Power Plant’ – www.mannvit.com.
  26. Union of Concerned Scientists – ‘How Geothermal Energy Works’ – www.ucsusa.org.
  27. Geothermal locations sourced from Union of Concerned Scientists – ‘How Geothermal Energy Works’ – www.ucsusa.org. Map loosely based on all onshore locations that hold high geothermal potential except for any areas that have undergone urban development, or that are covered with forests, mountains or significant quantities of ice. Areas of geothermal potential sourced from Islandsbanki Geothermal Energy Team – ‘United States Geothermal Energy Market Report’ – Page 11. Areas covered by urban development based on satellite images sourced from Mayhew, Craig and Simmon, Robert – ‘Earth’s City Lights’ – visibleearth.nasa.gov. Areas of forest cover sourced Food and Agriculture Organization of the United Nations – ‘Global Forest Resources Assessment 2005, Progress Towards Sustainable Forest Management’ – Page 15. Areas of mountain and ice cover sourced from Koistinen, Ville – ‘The Main Biomes in the World’ – commons.wikimedia.org.
  28. Based on projected costs for 2020 sourced from United States Energy Information Administration – ‘Levelized Cost and Levelized Avoided Cost of New Generation Resources in the Annual Energy Outlook 2015’ – Page 6.
  29. Matek, Benjamin – ‘The Manageable Risks of Conventional Hydrothermal Geothermal Power Systems: A Factbook on Geothermal Power’s Risks and Methods to Mitigate Them’ – Page 17.
  30. Figure calculated based on 1 TWh being generated per five square kilometres of land. Sourced from Trieb et al. – ‘Concentrating Solar Power for the Mediterranean Region’ – Page 166.
  31. Calculation undertaken within the ‘Renewable Solution’ section of the ‘ZERO-FIFTY World Energy Database’ and based on a lifespan of 30 years. Lifespan sourced from U.S. Energy Information Administration – ‘Levelized Cost and Levelized Avoided Cost of New Generation Resources in the Annual Energy Outlook 2015’ – Page 2.
  32. No carbon offset data available so substituted with energy offset period. Average figure based on two case studies. Sourced from Southon, Michael and Krunmdieck, Susan – ‘Energy Return on Investment (EROI) for Distributed Power Generation from Low-Temperature Heat Sources Using the Organic Rankine Cycle’ – Page 5.
  33. Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 39. Please note, power conditioning, distribution and transmission losses have not been considered.

For further information about any of the above sources, please visit the ZERO EMISSION WORLD Works Cited page.

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