Resource Maximization

Geothermal resources are playing an increasingly multi-faceted role by contributing to U.S. grid reliability, resilience, and security; supporting development of a robust domestic renewable energy manufacturing supply chain; and providing effective alternatives to grid-dependent heating and cooling as well as energy storage solutions for the built environment. Geothermal’s breadth of applications—as a source for both critical materials and thermal energy storage—is critical to tackling the climate crisis.

GTO has a strong history supporting RD&D across the geothermal application space, and the value of continuing to do so is clear. Focused RD&D increases the ability to accurately capture geothermal energy resource value across all types and application spaces to maximize the use of such resources, in turn helping geothermal applications meet the GeoVision analysis goals and benefit the U.S. grid and economy.

Most recently, GTO has supported RD&D to maximize geothermal resource value through technology development (i.e., physical coupling as well as modeling and strategic analyses). Since 2014, GTO has funded two competitively awarded RD&D solicitations focusing on strategic mineral recovery from geothermal brines through novel sorbent and substrate technologies, as well as better resource characterization for critical materials and rare earth elements in U.S. geothermal and oil and gas resources (Stringfellow and Dobson 2020). However, while these novel approaches show promise, these technologies as well as the broader industry’s demonstration of mineral recovery from geothermal brines remain pre-commercial. Recently, the DOE Advanced Manufacturing Office and the California Energy Commission have separately made awards to commercial geothermal operators in the Salton Sea region of California to demonstrate pre-commercial capabilities for direct lithium extraction from geothermal brines.^[5],[6] More broadly, despite providing initial promising indications, understanding the value of bringing such resources to market has yet to be fully considered. Through collaboration across EERE, GTO undertakes techno-economic assessments of geothermal brine extraction technologies to better understand this value proposition.

There is ubiquitous thermal energy storage available in the Earth to deploy for a variety of direct-use and grid applications that can enable new, more resilient energy services that provide an effective alternative to grid-dependent heating and cooling and add climate resilience to the broader energy system. GTO supports this potential in partnership with the DOE Energy Storage Grand Challenge and through standalone funding opportunities for large-scale resource assessment and feasibility research across public and private institutions pursuing campus-wide geothermal system installation. Through advanced resource characterization and optimized system designs that incorporate site supply and demand profiles and align with increasing calls for installing climate-resilient infrastructure, GTO seeks to unlock the vast potential for moving geothermal beyond the western United States to a true national energy solution.

These efforts have also resulted in a variety of analytical tools to estimate geothermal project costs and performance, model future grid-capacity expansion and dispatch of generation resources in collaboration with multiple EERE offices, visualize potential geothermal deployment forecasts for the United States, and empower state and local energy planners to choose effective mixes of renewable energy resources. These tools benefit the ability to accurately capture the value of geothermal energy resources but are informed by and complement work in other activity areas such as DMA.

Table 2.7 highlights GTO subprogram contributions in Resource Maximization RD&D toward meeting overall GTO program goals. The majority of the RD&D that will be conducted on grid valuation, thermal storage and utilization, and capturing additional geothermal value streams will be through the Low-Temperature and Coproduced Resources and DMA subprograms where there will be a primary and direct impact on achieving all three Strategic Goals.

[5] https://www.energy.gov/cmei/ammto/articles/doe-critical-materials-institute-selects-four-projects-support-critical or https://www.energy.gov/cmei/ammto/articles/energy-department-selects-15-projects-advance-critical-material-innovations 

[6] https://www.energy.ca.gov/news/2020-05/geothermal-lithium-recovery-projects-get-boost-california-energy-commission

Table 2.7. GTO Subprogram Contributions in Resource Maximization RD&D for Meeting GTO Strategic Goals

Table 2.8 outlines GTO milestones and performance goals through FY 2026 for increasing the ability to accurately capture geothermal resource value and maximize value across all applications.

Table 2.8. Resource Maximization Highlighted Performance Goals

Grid Valuation

Geothermal energy is a renewable and diverse domestic resource capable of providing reliable and flexible electricity generation. However, while there is a long recognition of geothermal’s traditional role as an “always-on,” baseload resource, the value of that primary service as well as broader recognition of geothermal’s ability to support numerous additional grid services has yet to be fully realized. While this challenge is likely the result of a combination between technology and market considerations, it is exacerbated by a lack of available, updated, and robust datasets on geothermal technology performance and cost. Additionally, there is a need to improve the representation of geothermal technologies within grid projection and energy planning models in a way that would allow geothermal’s present and future value to the U.S. grid to be evident to stakeholders. Some of these data limitations are the result of the subsurface nature of the resource. Advancements in exploration, characterization, and development technologies and methodologies discussed in Subsurface Accessibility –Resource Maximization can help mitigate uncertainties with understanding resource potential that in turn can inform cost models.

Developing analysis and modeling capabilities that maintain, update, and create new approaches for accurately representing the current and potential value and benefits of geothermal energy to the U.S. grid can help better represent geothermal on the grid, particularly when incorporating results from technical innovations. Greater representation of geothermal also enables a more secure path toward deploying the 60 GW_e by 2050 identified in the GeoVision analysis Technology Improvement scenario. To achieve this goal, it will be essential to understand the projected value of geothermal energy to the future U.S. grid. This can be achieved through a comprehensive effort that develops and implements new and improved modeling approaches and capabilities that accurately represent geothermal technology performance and costs.

Collaborating with DOE and external stakeholders is an overarching goal for all GTO Research Areas, but building close partnerships is particularly important for research in this section given the inherent interconnectedness of grid research; the importance in improving linkages between grid modeling communities, GTO, and the geothermal industry; and the need to ensure such efforts are complementary to broader DOE initiatives. Organizations and initiatives involved in these efforts could include but are not limited to EERE’s Renewable Power offices and its Strategic Analysis Office as well as DOE’s Energy Information Administration, national laboratories, Grid Modernization Initiative, and Energy Storage Grand Challenge.

The subsequent technical areas are of notable research interest through FY 2026 for grid valuation.

Enhance geothermal representation in grid and cost models. Geothermal resources are unique in the renewable power world, with inherent uncertainties that require a range of technologies for successful exploration, development, and operations. Representing and minimizing these resource uncertainties are key motivations across all technology focus areas highlighted in this document, including grid and geothermal project cost models. Geothermal representation in existing models can lack geographic or temporal resolution and contain largely deterministic input datasets that limit project representation abilities or are burdened by significant project cost uncertainties. Additionally, inputs can translate poorly between grid projection models. Given the vast number of public and private stakeholders that rely on these types of models, it is imperative to enhance geothermal representation to accurately capture its potential grid value. To do so will require exploring approaches that:

• Introduce higher-resolution geographic modeling capabilities to improve relevant representation in system-wide grid models, particularly at the sub-balancing authority area (sub-BAA) level
• Capture improved data fidelity on geothermal resource development costs by pursuing new data-collection efforts while also ensuring DOE-funded project data for initiatives such as FORGE are comprehensively captured
• Explore approaches to introduce physics-based and stochastic modeling capabilities into geothermal cost models
• Improve data-sharing ability between geothermal cost models and capacity-expansion models.

Validate models and characterize uncertainty. Accurately capturing geothermal values in grid and cost models is not accomplished solely through enhanced data collection or data-sharing capabilities; the means of applying these data for a given model must also minimize output uncertainties. For example, the Geothermal Energy Technology Economic Model (GETEM), a GTO-developed geothermal project cost model, is a robust tool for providing a variety of estimations for project costs associated with geothermal development. However, GETEM is deterministic in its calculation for a given project. While there are a variety of available inputs to describe geothermal project costs, the model lacks the flexibility to easily incorporate new datasets that can provide greater certainty in modeled cost outputs. Furthermore, GETEM is not rigorously tied to the physics or thermodynamics of the physical system, where cost-based parameters are highly interrelated and dynamically coupled. For example, stimulation costs are represented through a simplified set of inputs that do not incorporate the full spectrum of variables to consider during an operation (e.g., number of stimulation stages). Introducing physics-based capabilities can enhance model sophistication and minimize uncertainties from incorporated datasets, enhancing the ability of models such as GETEM to incorporate and expand available inputs. When accomplished in coordination with GTO initiatives such as FORGE, technical achievements can be better represented in GTO-funded models that more accurately reflect how such advancements lower geothermal levelized cost of electricity.

Improve capacity expansion and production cost modeling. Enhanced collaboration with internal and external stakeholders can move development of capacity-expansion models beyond current capabilities. Existing DOE-developed capacity-expansion models are restricted to average system behavior incorporated over a BAA, with no ability to model at a sub-BAA scale. This limits the ability of models to examine important regional- and market-based constraints and impacts on geothermal deployment, e.g., in important active development regions such as California and Nevada. Additionally, learning-by-doing improvements are represented as an assumed fixed rate or other type of manual input and are not calculated by the models. To improve the ability to accurately capture geothermal’s value to the U.S. grid, research can focus on a few different options that integrate grid services pricing into the National Renewable Energy Laboratory’s (NREL) Regional Energy Deployment System, or ReEDS. This will allow for better projections of service demand with increasing variable generation resources, as well as improve and create entirely new linkages between existing models for the spectrum of geothermal technologies that can benefit the U.S. grid.

Develop and demonstrate geothermal grid service technologies. Enhancing the value geothermal provides for the U.S. grid will require analysis to accurately capture geothermal value as well as research and demonstration of plant or facility infrastructure and operation designs to fit any number of grid services. Important analysis considerations to further define potential technology research focuses include understanding the techno-economics from integrating generation resources virtually or via on-site generation, understanding the extent for how geothermal operators participate in ancillary service markets, developing analytical capabilities that can determine optimized economic value and operational efficiencies for a range of geothermal grid services, and market and regulatory analysis.

Such analysis can inform GTO research and demonstration for understanding market participation options that maximize geothermal energy storage deployment and developing a range of potential geothermal technologies for the benefit of providing grid services, such as geothermal abilities to meet a range of ramping rates required to provide frequency regulation. Demonstrating these capabilities is closely linked with geothermal’s as-yet-untapped potential as a significant thermal energy storage option (see Section 2.5.3.2 for thermal storage and utilization technology development needs).

Thermal Storage and Utilization

In addition to the significant standalone electricity-generation potential from U.S. geothermal resources, these resources also hold significant potential to bolster climate resilience and provide numerous energy services—including energy storage as well as heating and cooling applications for the built environment. However, full demonstration of the breadth of these technology applications has yet to be realized. An established GHP industry exists across the United States supporting currently installed capacity of 20.2 GW_th (Lund et al. 2020). However, the DOE’s GeoVision analysis demonstrates the potential for this installed capacity to reach as much as 151 GW_th (GeoVision Breakthrough Scenario) with improved technologies. Additionally, despite geothermal direct-use economic resource potential in excess of 320 GW_th, only about 100 MW_th of geothermal direct-use resources have been deployed for district heating in 21 installations across the country (Snyder et al. 2017).

GTO is focused on enhancing understanding of how such systems can operate both efficiently and cost-effectively to meet evolving grid and heating/cooling needs, as well as better managing resource productivity. Such approaches will be necessary in helping to chart a path to develop geothermal as a true “anywhere” technology solution and capture the 320 GW_th in economically viable district-heating resource potential outlined in the GeoVision analysis. An overarching goal for all research activities discussed in this section is increased collaboration with federal partners to identify opportunities for deploying on-site geothermal systems that satisfy federal energy and fuel security demands while demonstrating how geothermal can significantly contribute toward advancing a low-carbon energy future, noting the significant impact potential and unique levers the federal government has in cultivating new energy technologies.

For purposes of the MYPP, hybrid technologies are defined to combine two or more energy types and/or produce two or more products to overcome limitations inherent in the respective stand-alone systems. Integrating multiple technologies can enhance performance capabilities, resource values, and/or cost savings compared to standalone geothermal power plants or conventional heating and cooling options for the built environment. These applications can contribute to the two focus areas in this section. Additionally, while district-heating systems and GHPs operate for the benefit of similar thermal storage and utilization goals, they have yet to be fully integrated for single-site installations. Given increased sophistication in building technologies, software, and geothermal resource management, an overarching goal will be examining the potential to research system designs that can incorporate both technology spaces.

The subsequent technical areas are of particular research interest through FY 2026 for thermal storage and utilization.

Identify additional roles for and increase the use of geothermal heat pumps in storage. GHPs harness the principles of constant near-surface temperatures to discharge and extract heat at advantageous times of the year, facilitating thermal storage on scales ranging from single family homes to facility-wide installations. While aspects of the U.S. GHP industry are established, continued research is needed to further understand the application’s potentially significant role in reducing campus-scale building energy use while also satisfying heating and cooling needs. Harnessing computational modeling approaches that can improve system configurations by incorporating parameters such as weather forecasting, spot electricity pricing, and occupant learning behavior can optimize system design and performance. The ability to standardize and lower the cost of system design and installation will benefit from research into novel installation geometries and improved automation.

Equally important with advancing technologies will be improving overall public awareness and increasing consumer acceptance of geothermal heating and cooling systems. These systems are existent, low-carbon energy solution that can offer additional roles, such as improved energy storage. Developing research strategies that emphasize this value with the broader public can have measurable impact in sparking vast near-term geothermal resource use potential. Increasing public awareness can reduce risk, in turn allowing for procurement options either currently available to or underutilized by the GHP industry. Analysis can help confirm where innovative approaches (e.g., vertically integrated installation companies) or third-party equipment ownership might better support full GHP market uptake.

Increase the use of geothermal district heating and cooling systems. While district-heating systems leverage the same thermal properties found in the subsurface, their use cases expand to a variety of beneficial applications, such as better meeting end-use demand profiles and providing flexible energy-storage options. Other applications in this focus area include bi-directional energy storage, direct use, deep direct use, reservoir thermal energy storage, aquifer thermal energy storage, borehole thermal energy storage, and advanced energy storage.

Delineating the effectiveness between optimal and suboptimal district heating and cooling systems will require modeling capabilities that account for reservoir and thermal saturation response for different phase fluids and use cases. This will require consideration of parameters such as expected storage time durations, energy intensity loads, and thermal recovery efficiencies to better delineate effective geothermal storage and utilization applications. Linking such modeling capabilities to surface infrastructure (e.g., commercial buildings or campuses) can incorporate the advancements of novel building energy management technologies with a geothermal district heating and cooling system to optimize a system’s demand profile response. Additionally, system designs at all subsurface depths (i.e., meters to hundreds of meters) can leverage the drilling, wellbore materials and construction, and resource development research advancements discussed in Subsurface Enhancement and Sustainability and Resource Maximization to improve project economics.

As discussed in the GeoVision roadmap, understanding the market potential of district heating and cooling systems will require a robust analysis of market adoption rates. The information available for conducting market potential-based assessments of heating and cooling applications has historically been restricted to general behavior of individual consumers, e.g., those who might install rooftop solar. However, district heating and cooling technologies tend to be deployed at the community level. The adoption behaviors of district versus individual groups differ, and community decision-making behavior related to heating and cooling technology adoption is not well understood. District heating and cooling systems are more widely adopted in Europe, where associated consumer behaviors have been studied and may serve as a general guide for understanding the potential for such systems in the U.S. Quantifying the market potential and possible roles of geothermal direct-use applications can raise awareness of the technology and encourage use of renewable, geothermal direct-use heating and cooling solutions in U.S. communities.

Value Streams

Developing new geothermal value streams can bolster the economic competitiveness of geothermal resources while also aiding U.S. energy manufacturing supply chains and water supplies. Value-stream areas of interest such as critical and strategic minerals extraction have historical roots that stretch even before development of the first U.S. geothermal resources. Other value streams, such as the opportunity to integrate with fuel manufacturing or commercial-scale desalination technology and operations are newer in their overall development. Regardless, none of these value streams have yet to be fully explored and realized. Pursuing research described in this section will require exploring both technology and analysis approaches to identify cost-effective pathways for advancing promising geothermal added-value streams and to diversify geothermal development options.

Investigate opportunities for critical materials recovery. Significant increases in market demand for critical materials such as lithium, combined with the low number of U.S. resources currently available for sourcing these materials, underscores the strategic importance for the United States to identify new upstream critical materials resources and to advance economically competitive critical and strategic material extraction from resources such as geothermal brines. Previous research has shown that critical and strategic materials exist in economic and sub-economic quantities across the western United States (Simmons et al. 2018). Within this region, California’s Salton Sea represents an outsized opportunity to diversify the domestic supply chain of minerals, particularly lithium, with an estimated 170,000 metric tons of lithium-carbonate annual production potential valued at $2.3 billion (Wendt et al. 2018). However, ongoing challenges exist in accurately characterizing brine resource constituents and production, representing brine complexities necessary for bench-scale experiments and process engineering that pretreats geothermal brine effectively. To better address these challenges and unlock materials resource potential, research efforts through FY 2026 can build on prior GTO work in resource characterization and development of technologies that selectively remove critical materials from brines. These RD&D focuses can help enhance data collection that leads to improved understanding of the co-location of lithium and other critical materials and hidden geothermal resources, while advancing extraction technology systems that integrate with geothermal power-plant configurations and operations. Additionally, underpinning analysis should continue to develop understanding of the impact potential that cultivating such technology can have on building out a robust U.S. energy manufacturing supply chain.

Assess the potential for geothermal desalination. Using geothermal energy to drive desalination operations can increase operational efficiencies in providing potable water for industrial or municipal purposes. This can be especially true for geothermal resources in regions of the United States that are experiencing increasing aridity and may provide growing opportunities as markets and policy shifts occur. The intersection opportunity of desalination and geothermal, however, remains application and location dependent. While initial analyses suggest competitiveness with alternative water-disposal methods, further analyses should build on these results to better understand market values and constrain project costs. Such project cost information is beneficial to include as input into DOE-supported geothermal project cost models such as GETEM. Additional refinement of existing thermal desalination technology—as well as development of new technology—can be explored in conjunction with DOE initiatives such as the Advanced Manufacturing Office-led National Alliance for Water Innovation.

Evaluate the value of hydrogen production from geothermal. Geothermal energy, in tandem with other energy resources, can produce hydrogen (H₂) fuels as a demand-response grid activity, in turn, diversifying the H₂fuel-supply chain. The temperatures required for hydrolysis processes fall within the operational conditions of many high-temperature geothermal resources—particularly for states such as California, where the largest U.S. H₂ market currently exists. A recent resource assessment for H₂ production potential indicated 483.8 MMT per year of H₂production potential from geothermal resources (Connelly et al. 2020). Expanding H₂ applications will require close alignment and coordination with broader DOE efforts led by the Hydrogen and Fuel Cells Program. This includes ongoing work with H₂ market economy maturation to further commercial deployment of H₂ production sites using geothermal energy.

Research priorities in the H₂ space are similar to analyses outlined for other value streams discussed in this section; that is, process engineering to ensure that these additions enhance the value of the overall operations. Additional analysis for hybridizing geothermal with complementary energy resources such as solar could be an important potential use case for H₂ production given the confluence of existing markets for geothermal and solar, abundant additional resource potential, and leading-edge domestic commercial markets in the western United States.