Geothermal Energy in the US: A Comprehensive Exploration

Geothermal energy in the United States has been steadily growing, with a total installed capacity of 3.673 GW as of 2019. Over the past five years, the US has brought seven new geothermal power plants online, adding 186 MW of nameplate capacity. However, eleven plants were retired or classified as non-operational, subtracting 103 MW of nameplate capacity. As of February 2022, nine new geothermal Power Purchase Agreements (PPA) have been signed across four states, including plans for the first two geothermal power plants to be built in California in a decade.

Geothermal Power Plant Development in the US

Geothermal companies operating in the US have a combined 58 active developing projects and prospects across nine states, with five of these projects in the phase immediately preceding project completion. These projects are located in various regions, each with its unique geological characteristics and resource potential.

Geothermal Resource Potential in the US

The United States is blessed with a vast and diverse geothermal resource base, with the potential for both electricity generation and direct use applications. According to the US Geological Survey (USGS), the total identified geothermal resource base in the US is estimated to be around 9,057 exajoules (EJ), with the technically recoverable resource estimated at 2,379 EJ. [1] This vast resource potential can be attributed to the country’s diverse geological settings, including volcanic, tectonic, and sedimentary basins, each with its unique characteristics and energy potential.

Geothermal Power Plant Technologies

Geothermal power plants in the US utilize a variety of technologies to harness the Earth’s heat for electricity generation. The most common technologies include:

1. Dry Steam Power Plants: These plants use steam directly from underground reservoirs to drive turbines and generate electricity. The Geysers in California is the largest dry steam field in the world, with a total installed capacity of over 900 MW. [2]

2. Flash Steam Power Plants: These plants use high-pressure, high-temperature geothermal fluids that are “flashed” into steam to drive turbines. The Salton Sea Geothermal Field in California is a prime example of a flash steam power plant, with a total installed capacity of over 400 MW. [3]

3. Binary Cycle Power Plants: These plants use a secondary working fluid, such as isobutane or pentane, to drive the turbines. The secondary fluid is heated by the geothermal fluid, which is then reinjected back into the reservoir. Binary cycle plants can utilize lower-temperature geothermal resources, making them suitable for a wider range of geothermal resources. [4]

4. Hybrid Power Plants: These plants combine geothermal energy with other energy sources, such as solar or natural gas, to optimize power generation and improve overall efficiency. The Stillwater Hybrid Power Plant in Nevada is an example of a hybrid geothermal-solar power plant. [5]

Geothermal District Heating Systems in the US

In addition to electricity generation, geothermal energy is also used for direct-use applications, such as district heating systems. There are 23 geothermal district heating (GDH) systems in the US, with the oldest installation dating from 1892 and the most recent installation completed in 2017. [6] These GDH systems tend to be smaller in size (average of 4 MWth) compared to their European counterparts (continent-wide average of ~17 MWth) and orders of magnitude smaller than the average GDH system in China (~1,000 MWth).

Geothermal Research and Development in the US

The National Renewable Energy Laboratory (NREL) plays a crucial role in advancing geothermal research and development in the US. NREL’s research efforts focus on data collection, analysis, and stakeholder engagement to further the role of geothermal energy in the country’s energy mix.

NREL’s Geothermal Research Initiatives

1. 3 Year Portfolio: NREL Kicks Off Modeling and Analysis Projects to Understand Geothermal Value and Improve Geothermal Representation: This initiative aims to improve the representation of geothermal energy in energy models and tools, enabling better decision-making and policy support for geothermal development. [7]

2. Geothermal Data and Analysis: NREL collects and analyzes geothermal data from various sources, including the Geothermal Data Repository, to support research, development, and deployment of geothermal technologies. [8]

3. Stakeholder Engagement: NREL actively engages with geothermal industry stakeholders, policymakers, and other relevant parties to identify and address barriers to geothermal development, as well as to promote the adoption of geothermal technologies. [9]

Barriers to Geothermal Development in the US

Despite the significant potential of geothermal energy in the US, there are several barriers that hinder its widespread adoption. A report released by NREL in FY23 highlighted non-technical barriers at the federal, state, and local levels that may influence geothermal project development timelines in California and Nevada, the largest producers of geothermal energy in the US. [10]

Non-Technical Barriers to Geothermal Development

1. Lengthy Permitting and Regulatory Processes: The report found that delays in project implementation due to lengthy permitting and regulatory processes are a major barrier to geothermal development in California and Nevada. This includes obtaining necessary permits, navigating complex regulatory frameworks, and addressing environmental concerns.

2. Land Access and Leasing Challenges: Securing access to land and obtaining appropriate leases for geothermal development can be a significant challenge, particularly on federal lands, where the Bureau of Land Management (BLM) plays a crucial role in the leasing process.

3. Lack of Incentives and Policy Support: Compared to other renewable energy sources, geothermal energy has historically received less policy support and financial incentives, making it less competitive in the energy market.

4. Limited Public Awareness and Acceptance: There is a general lack of public awareness and understanding of the benefits and potential of geothermal energy, which can hinder its widespread adoption.

To address these barriers and unlock the full potential of geothermal energy in the US, a concerted effort is needed from policymakers, industry stakeholders, and research institutions to streamline regulatory processes, provide targeted incentives, and raise public awareness.

Conclusion

Geothermal energy in the United States has been steadily growing, with a total installed capacity of 3.673 GW as of 2019. The country’s diverse geological settings offer a vast and untapped geothermal resource potential, which can be harnessed through a variety of power plant technologies, including dry steam, flash steam, binary cycle, and hybrid systems. Additionally, geothermal district heating systems play a role in direct-use applications of geothermal energy.

The National Renewable Energy Laboratory (NREL) is at the forefront of geothermal research and development in the US, focusing on data collection, analysis, and stakeholder engagement to further the role of geothermal energy in the country’s energy mix. However, non-technical barriers, such as lengthy permitting and regulatory processes, land access challenges, and limited policy support, continue to hinder the widespread adoption of geothermal energy in the US.

To unlock the full potential of geothermal energy, a collaborative effort is needed to address these barriers and create a more favorable environment for geothermal development. By overcoming these challenges, the US can harness its vast geothermal resources and contribute to a more sustainable and diversified energy future.

References

1. U.S. Geological Survey. (2008). Assessment of Moderate- and High-Temperature Geothermal Resources of the United States. Link
2. Geothermal Energy Association. (2016). U.S. Geothermal Power Production and Development Update. Link
3. Geothermal Energy Association. (2016). U.S. Geothermal Power Production and Development Update. Link
4. U.S. Department of Energy. (n.d.). Geothermal Technologies Office: Binary Cycle Power Plants. Link
5. U.S. Department of Energy. (n.d.). Stillwater Hybrid Power Plant. Link
6. Lund, J. W., & Boyd, T. L. (2016). Direct utilization of geothermal energy 2015 worldwide review. Geothermics, 60, 66-93. Link
7. National Renewable Energy Laboratory. (2022). 3 Year Portfolio: NREL Kicks Off Modeling and Analysis Projects to Understand Geothermal Value and Improve Geothermal Representation. Link
8. National Renewable Energy Laboratory. (n.d.). Geothermal Data Repository. Link
9. National Renewable Energy Laboratory. (n.d.). Geothermal Research. Link
10. National Renewable Energy Laboratory. (2023). Barriers to Geothermal Development in California and Nevada. Link