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Geothermal Energy

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Fast Facts About
Geothermal Energy

Principal Energy Uses: Heat, Electricity
Form of Energy: Thermal

Geothermal energy makes use of abundant natural heat deep below the Earth’s surface. Geothermal resources are accessible where the Earth’s crust is thin or faulted or near volcanic activity, which often occurs near tectonic plate boundaries.

Geothermal has two main uses:

  1. Direct Use Heat: High-temperature water or steam is used to provide heat for buildings, agriculture, aquaculture, industrial processes, and recreation (e.g., hot springs)
  2. Electricity: High-temperature water or steam is used to run a steam cycle power plant and generate electricity

There are three things needed in a traditional geothermal resource–permeability, heat, and water. Finding these conditions requires significant up-front capital expenditures. The exploration begins with geophysical assessments but eventually actual drilling and testing must be done to ensure that these conditions are present. These similarities with the oil and gas exploration process enable the transfer of knowledge, technology, and jobs from the fossil fuel industry to geothermal.

Geothermal power plants are a source of 24/7 renewable electricity, unlike wind and solar which are variable and dependent on weather conditions. Geothermal energy has traditionally been limited to places with suitable geology and the natural existence of water or steam in the reservoir, but new technologies ("Enhanced Geothermal Systems" or "EGS") are making geothermal resources available and easier to find in more locations. We categorize the geothermal resource as semi-renewable. Although the Earth’s heat is non-depletable, the use of geothermal energy must be carefully managed in each location to prevent water or steam depletion.

Note: Ground source heat pumps are often referred to as geothermal heat pumps, but they are an energy efficiency measure and do not use the geothermal resource. Instead of using the Earth’s heat, these heat pumps use the ground, which maintains a constant temperature (warmer than the winter air and cooler than the summer air), as a heat source or sink, allowing them to be more efficient than air source heat pumps. See our Energy Efficiency and Buildings pages for more information.


Significance

Energy Mix

<1% of world 🌎
<1% of U.S. 🇺🇸

Electricity Generation

<1% of world 🌎
<1% of U.S. 🇺🇸

Global Uses

Direct use heat: 59%
Electricity: 41%

Changes in Global Demand

Direct Use Heat
Increase:
⬆78%
(2016-2021)

Electricity
Increase:
⬆25%
(2016-2021)


Direct Heat (World)

Largest User of Direct Heat

China 57% 🇨🇳
of global geothermal direct heat use

Direct Heat Uses

Swimming and Bathing: 44%
Space Heating: 39%
Greenhouse Heating: 9%
Industrial Applications: 4%
Other: 4%

Highest Direct Heat Penetration

Iceland 90% 🇮🇸
of country’s heating demand is met by geothermal


Electricity (World)

Most Geothermal Electricity Capacity

US 18% 🇺🇸
Indonesia 16% 🇮🇩
of global geothermal electricity capacity

Most Geothermal Electricity Generation

US 20% 🇺🇸
Indonesia 17% 🇮🇩
of global geothermal electricity generation

Highest Geothermal Electricity Penetration

Kenya 44% 🇰🇪
of country’s electricity comes from geothermal


Electricity (US)

Most Geothermal Electricity Generation

California 70%
of US geothermal electricity generation

Highest Geothermal Electricity Penetration

Nevada 10%
of state’s electricity comes from geothermal


Expansion of Geothermal Resources and Technological Improvements

Almost all new geothermal plant additions in the US since 2000 have been binary cycle, which require lower temperature geothermal reservoirs (allowing geothermal to be used in more locations) and emit no greenhouse gasses or air pollution. Binary cycle plants are also being deployed around the world.

US Geothermal Capacity by Plant Technology

 Area graph showing geothermal capacity in the US by plant type from the 1970s to 2020.
Dry steam and flash technology provided the foundation of US geothermal production capacity. However, all new US geothermal capacity additions between 2000 and 2020, other than one triple-flash plant in 2011, have been binary cycle plants.

Enhanced Geothermal Systems (EGS) are being explored and developed:

  • The combination of heat, permeability, and naturally occurring water exists in limited locations
  • EGS expands the geographic availability of the geothermal resource by creating permeability and/or adding water in locations where those don’t occur naturally

There are opportunities for geothermal projects to be co-located with other high energy need systems:

  • Direct Air Capture (carbon removal) - energy intensive and can be located almost anywhere. With co-location, the geothermal resource can provide lots of 24/7 energy for the Direct Air Capture process
  • Lithium Extraction - geothermal brines often contain dissolved lithium
  • Data centers - energy intensive and can be located near geothermal plants that provide the 24/7 baseload power they need

Costs of US Geothermal

Unsubsidized LCOE*: $61 - $102/MWh
Subsidized LCOE: $37 - $87/MWh

Geothermal is subsidized in the Inflation Reduction Act and other policies.

*LCOE (levelized cost of electricity) - price for which a unit of electricity must be sold for system to break even

Compare costs with subsidies and for other resources on the Introduction to Renewable Energy Fast Facts

 

Unlike wind and solar which have been getting increasingly cheaper, geothermal’s costs have remained relatively steady over the last 10 years. Geothermal is just starting to apply technological advances from the oil and gas industry, so is in the early stages, and costs are expected to decline in the coming years.

The costs of the power plant infrastructure and exploration and drilling are the vast majority of geothermal costs, with actual production costs being low.


Drivers

  • Abundant resource: heat from the Earth
  • Baseload source of energy: can run day and night regardless of weather
  • High capacity factor compared to other renewable energy systems (90-95% for new geothermal plants, 78% for all geothermal plants)
  • Relatively low climate and environmental impacts
  • Technology and practices can be leveraged from oil and gas industry, such as drilling methods
  • New EGS* technologies are expanding places where geothermal can be used

Barriers

  • Tapping a subsurface resource is inherently risky and very capital intensive
  • Site-specific resource (conventional methods require the presence of heat, permeable rock, and water)
  • Potential siting challenges, such as NIMBY/BANANA** or insufficient electricity transmission infrastructure
  • Resource must be managed to be sustainable: geothermal reservoirs naturally recharge, but can be depleted if over-exploited
  • Potential seismicity risk for EGS projects
  • Some air emissions possible, including H2S
  • Some systems (such as EGS) may require additional water supply
  • Weak policy support compared to other technologies, but improving

*EGS (Enhanced Geothermal Systems) - geothermal plants using new technologies to make geothermal electricity economically viable in more locations
**NIMBY - not in my backyard; BANANA - build absolutely nothing anywhere near anything


Climate Impact: Low

Low gradient
  • Small amounts of CO2 can be released in some geothermal processes
  • New binary systems have zero GHG emissions

Environmental Impact: Low

Low gradient
  • Small amounts of air pollution (primarily H2S)  can be released in some geothermal processes
  • Some EGS projects can pose a low risk of seismicity and require additional water supply
  • Can have land and habitat impacts

Updated April 2024

Before You Watch Our Lecture on
Geothermal Energy

We assign videos and readings to our Stanford students as pre-work for each lecture to help contextualize the lecture content. We strongly encourage you to review the Essential readings and videos before our lecture on Geothermal Energy. Include selections from the Optional and Useful list based on your interests and available time.

Essential

Optional and Useful

Our Lecture on
Geothermal Energy

This is our Stanford University Understand Energy course lecture on geothermal energy. We strongly encourage you to watch the full lecture to understand geothermal as an energy system and to be able to put this complex topic into context. For a complete learning experience, we also encourage you to watch / read the Essential videos and readings we assign to our students before watching the lecture.

Presented by: Dawn Owens, Adjunct Lecturer, Civil and Environmental Engineering, Stanford University; Head of Development and Commercial Markets, Fervo Energy
Recorded on: December 1, 2023  Duration: 63 minutes

Table of Contents

(Clicking on a timestamp will take you to YouTube.)
00:00 Introduction, Importance & Background 
07:57 Understanding the Fundamentals 
15:39 Exploration, Development & Technology 
31:31 Market & Economics 
45:06 Growth & Promising Technology 
56:57 Q & A/Case Studies & Success Stories

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Additional Resources About
Geothermal Energy

Government and International Organizations

Fast Facts Sources

More details available on request.
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