Is Geothermal Power Limited?

Geothermal power harnesses heat from within the earth to generate clean, renewable energy. Heat from the earth’s core, mantle, and crust can be captured through geothermal resources like hot springs, geysers, and steam vents. The high temperature of these geothermal reservoirs allows their inherent heat energy to be converted into electricity.

Geothermal power works by piping hot water or steam from geothermal reservoirs up to power plants at the surface. The high pressure and temperature of the geothermal fluid spins turbine generators to produce electricity. Geothermal power plants generally have low emissions and a small environmental footprint compared to conventional power plants.

As a renewable baseload resource, geothermal power has the potential to provide consistent and reliable electricity generation. Only a small fraction of the earth’s vast geothermal energy potential is currently being utilized. Expanding geothermal power can help nations reduce their dependence on fossil fuels and increase the share of renewables in their energy mix.

Geothermal Resources

There are several types of geothermal resources that can be used for power generation:

Hydrothermal resources involve natural reservoirs of steam or hot water that can be tapped directly to run geothermal power plants. This is the most common type of geothermal resource currently used. According to the California Energy Commission, hydrothermal resources provide the hottest and most productive geothermal wells.

Enhanced Geothermal Systems (EGS) involve injecting fluid into hot rock reservoirs to create an artificial geothermal resource. EGS has the potential to greatly expand geothermal capacity by accessing untapped heat underground.

Geopressured resources contain hot water and methane gas trapped under high pressure. This type of geothermal resource has not yet been widely utilized.

Magma resources involve extremely high temperature molten rock which has not yet been successfully harnessed for energy production.

Total Potential Capacity

Though geothermal energy currently accounts for only a small fraction of global electricity production, estimates show the total global potential capacity is massive. According to a report by the International Renewable Energy Agency (IRENA), the theoretical geothermal resource potential is estimated to be 5,000 times the world’s annual primary energy use. However, the technically feasible and economically viable potential is lower at around 7,000 GW for heat and power generation.

The installed global geothermal capacity for electricity production is only around 17 GW as of 2022. This indicates only a fraction of the total technical potential is currently utilized. With technology improvements, increased investment, and supportive policies, significant growth in geothermal capacity can be achieved to tap into the immense untapped potential.

Current Utilization

According to Our World in Data, the installed geothermal capacity worldwide was approximately 16,127 megawatts (MW) at the end of 2022. This represents a small but steady increase from around 12,000 MW in 2010. The countries with the most installed geothermal capacity are the United States (3,987 MW), Indonesia (2,105 MW), Turkey (1,500 MW), New Zealand (1,135 MW), and Kenya (1,090 MW) according to Think GeoEnergy. While geothermal power capacity has grown globally, it still only accounts for around 0.4% of total electricity generation worldwide.

Growth Trends

Global geothermal power capacity grew at an average annual rate of 5% between 2015-2020, reaching just over 17 gigawatts (GW) in 2020 (1). While the growth rate for electricity generation has been more modest, growth for direct use applications like heating and cooling has been stronger. Geothermal heating and cooling capacity grew at around 9% annually between 2015-2020, reaching 107 gigawatt thermal (GWth) in 2020.

The International Renewable Energy Agency (IRENA) projects global geothermal power capacity could reach almost 60 GW by 2030 in their planned energy scenario, representing an average annual growth rate of 10%. The geothermal heating and cooling market is projected to reach about 200 GWth by 2027, growing at over 8% annually (2).

The United States, a leader in geothermal energy, is projected to increase geothermal electricity generation from 17 billion kWh in 2022 to 37.2 billion kWh in 2050. This implies a growth rate of around 3% annually (3).

Sources:
(1) https://www.irena.org/News/articles/2023/May/Boosting-the-Global-Geothermal-Market-Requires-Increased-Awareness-and-Greater-Collaboration
(2) https://www.marketsandmarkets.com/Market-Reports/geothermal-energy-market-205152720.html
(3) https://css.umich.edu/publications/factsheets/energy/geothermal-energy-factsheet

Limiting Factors

Adoption of geothermal power faces several key limiting factors that have constrained its growth.
According to research by a geothermal
expert
highlighted at California Energy Commission, political factors could become major roadblocks if geothermal threatens current agricultural businesses.
This presents a challenge since many sources are located in agricultural areas.
Quora contributors note financing and risk as primary obstacles, since drilling is capital intensive but success is uncertain.

Further analysis in the Geothermal Energy journal found climate is a major variable influencing how effectively resources can be utilized. Areas with more favorable temperatures and geologic formations will see higher productivity and capacity factors from geothermal plants.

Technology Improvements

Recent technological advances could significantly expand viable geothermal resources and accessibility. According to the U.S. Department of Energy, next-generation geothermal technologies could provide up to 120 gigawatts of capacity in the U.S. by 2050. These include enhanced geothermal systems (EGS) that can extract heat from harder-to-reach subsurface rock through hydraulic fracturing, potentially expanding geothermal beyond conventional hydrothermal resources.

Ultra-deep drilling techniques like those used in the petroleum industry can also enable accessing deeper, hotter rock formations several miles underground. Supercritical geothermal systems utilize fluids above 374°C to produce power more efficiently. Advancedbinary cycles, nanofluids, and hybrid solar-geothermal plants are other innovations that can maximize output and viability in more areas.

While these technologies are still emerging, steady improvements could substantially boost global geothermal capacity. With sufficient investment and research, next-gen geothermal may transition from niche to mainstream, providing an abundant, renewable baseload power source.

Policy Support

Government incentives and regulation could help accelerate the adoption of geothermal power. The Department of Energy’s GeoPowering the West program provided grant funding between 2001-2008 to identify and develop geothermal resources in the western United States, resulting in 182 new geothermal projects [1]. Tax incentives like the federal renewable electricity production tax credit have boosted geothermal development, but the tax credits keep expiring and needing renewal from Congress [2]. Some analysts recommend long-term extensions of tax credits to provide market certainty. Streamlining federal permitting processes could also accelerate geothermal projects. At the state level, renewable portfolio standards that classify geothermal as renewable energy can incentivize development by requiring utilities to supply a percentage of power from renewable sources.

Environmental Impact

Geothermal energy is considered a renewable and sustainable energy source. Unlike fossil fuels, geothermal energy does not directly produce greenhouse gas emissions or other air pollutants (according to ucsusa.org). The emissions from geothermal power plants are minimal – 99% lower per kWh than coal plants and 75-90% lower than natural gas plants (UCSUSA). This makes geothermal a clean alternative for power generation.

However, geothermal plants can impact water resources. Hot geothermal fluids brought to the surface contain hazardous materials like mercury, arsenic, and boron. These can pollute groundwater if not properly disposed of (UCSUSA). Plants use cooling towers which emit water vapor plumes. There is also a risk of subsidence from over-pumping underground reservoirs. Proper siting, fluid injection, and disposal techniques can mitigate these risks and make geothermal energy highly sustainable.

Conclusion

Overall, while geothermal power does face some limitations, there remains significant untapped potential for future growth globally. Geothermal resources are available across large swathes of the planet, with technical estimates of several hundred gigawatts of undiscovered hydrothermal resources. However, only about 14 GWe of geothermal capacity is installed worldwide as of 2019. While geothermal suffers from high upfront capital costs and geological constraints, next-generation technologies such as EGS, co-production, and hybrid systems are expanding viable sites and improving project economics. With supportive policy frameworks and research investments to improve technologies and reduce costs, geothermal power capacity could grow substantially to provide clean, renewable baseload power. Much depends on whether geothermal energy can overcome its key limitations through innovation and secure adequate policy support. But with vast undiscovered resources available, geothermal remains far from reaching its full potential.