Heating, Cooling, and Storage Technologies
Through research, NREL is exploring geothermal heating, cooling, and storage technologies including heat pumps and thermal energy networks.
Geothermal Heat Pumps
The ground temperature at about 30 feet below the Earth's surface remains a constant 40°F to 70°F in the United States. The relatively constant ground temperature throughout the year provides an excellent mechanism for heating and cooling applications, as excess heat can be transferred underground or vice versa with the Earth's shallow subsurface acting as a heat source or heat sink depending on the season. NREL researchers are analyzing various aspects of geothermal heat pumps, including the potential benefits to the grid that would come from incorporating geothermal heat pumps and other geothermal heating and cooling applications into everyday uses.
Geothermal heat pumps, also referred to as ground-source heat pumps or geo-exchange, can reduce energy use and peak electricity demand in buildings compared to traditional HVAC systems while satisfying space heating, space cooling, and domestic water heating needs. A GHP system consists of one or more water-source heat pump(s), ground heat exchanger(s), circulating pump(s), and systems for air and water distribution. Fluid is circulated through the ground heat exchanger, installed in the relatively shallow subsurface to use the ground as a heat sink or source.
Leveraging high level analysis on heating and cooling demands, especially in residential and commercial buildings, NREL researchers are working to improve the widespread use of geothermal heat pump technologies for heating and cooling buildings to the benefit of the economy and society. NREL capacities in techno-economic analysis, market modeling, and barriers analysis are contributing to the characterization and proliferation of geothermal heat pump technologies.
Contact
Thermal Energy Networks Using Geothermal Heat Pumps
Connecting buildings through a thermal energy network (TEN) or a district heating and cooling (DHC) system create economies of scale that allow for the deployment of energy sources that are resilient as well as energy and cost efficient. Geothermal DHC systems and TENs typically use geothermal heat pumps to provide heating and cooling from a geothermal resource to buildings connected through a network of pipes. Geothermal DHC systems and TENs come in different configurations and designs and offer the potential to integrate with various other energy sources.
NREL is actively engaged in research on different aspects of geothermal TENs and DHC systems, including thermal, hydraulic, and control modeling; techno-economic analysis; integration of energy sources; performance evaluation and optimization strategies; and the potential benefits to the grid, among others.
Contact
Geothermal Direct Use
Earth's naturally occurring heat exists everywhere beneath the surface, and it has been used for centuries for everything from cooking to space heating. District heating systems for schools, hospitals, and other facilities are one potential effective way of utilizing medium to low enthalpy resources, especially where such facilities are collocated and within reach. Using direct geothermal cooling for data centers and other institutional, commercial, and industrial applications in cold to moderate climates is another potential way of utilizing low enthalpy geothermal resources. Geothermal direct use deployment has huge benefits for the grid in ensuring efficiency in energy utilization.
NREL is exploring the potential in the United States for specific types of resources especially in sedimentary basins and developing new, innovative ways to incorporate this heat into everyday uses across commercial, residential, industrial, and manufacturing sectors. Repurposing oil and gas wells for producing heat for district heating for schools or commercial area is one key area NREL researchers are focusing on.
Contact
Energy Storage
NREL researchers are exploring ways to use the Earth to store energy, including geothermal compressed air energy storage, borehole thermal energy storage, high-temperature storage, and reservoir thermal energy storage. Using national laboratory capabilities and leveraging geothermal technology as a large-scale thermal energy in boreholes and underground reservoirs, researchers are exploring ways to scale up and engineer subsurface heat energy storage, which can offer substantial cost savings compared to other energy storage technologies like batteries and molten salt. Once identified and developed, geothermal deployment can be flexible over a range of storage hours, making it especially suitable for long-term energy storage.
Contact
Featured Projects
Through support from the state of Massachusetts, members of the NREL geothermal team are partnering with the nonproft HEET on the Learning from the Ground Up project, studying the first utility-led networked geothermal installations in Massachusetts as a pathway to large-scale heating and cooling. The project consortium includes national labs, universities, and industry partners. The installations will include a thermal network that links each building, water-source heat pumps connected to the loop for meeting user heating and cooling loads, and geothermal borehole fields. NREL is performing system-level modeling of the thermal loop, connected buildings, and borehole fields for improved understanding of the system control and operation.
Impact
NREL's strategic public-private partnerships develop high-impact, multiyear, multisector collaborations that drive energy innovation.
The Cold Underground Thermal Energy Storage project aims to address data center cooling-system challenges by incorporating geothermal underground thermal energy storage technology into data centers.
Cold underground thermal energy storage
uses off-peak power to create a cold energy reserve underground, which can be incorporated into existing data center cooling technologies and used during grid peak load hours. It can also achieve long-duration energy storage at seasonal
time scales.
Impact
Reduce strain on the grid from data centers, reduce the energy cost to data centers, and reduce the cost of data center cooling systems
Partners
Lawrence Berkeley National Laboratory, Princeton University, and the University of Chicago
FLXenabler (Flexible Heating and Cooling and Geothermal Energy Storage as an Enabler for Integrated Energy Systems), a transnational collaborative project through Geothermica, seeks to evaluate and quantify the impact of the flexibility that geothermal heating, cooling, and storage can bring to integrated energy systems.
This project investigated geothermal heating and cooling technology integration with other energy sources and thermal energy storage as well as impacts on sector coupling.
NREL grid modeling identified which U.S. states could benefit the most in terms of fuel costs and grid savings from grid flexibility provided by geothermal heating, cooling, and storage technology deployment.
Impact
Evaluates how geothermal heating, cooling, and seasonal energy storage can reduce stress on the grid and provide flexibility
Partners
SINTEF (Norway), Technical University of Vienna, and USGS
NREL is conducting comprehensive performance modeling and evaluation of a geothermal heat pump (GHP) system providing heating and cooling at NREL's Mesa Top Campus in Golden, Colorado. Performance modeling, coupled with performance evaluation
using long-term measurement data, plays a crucial role in enhancing system efficiency, minimizing energy consumption and predicting future performance. Through detailed modeling of the GHP system, which consists of 23 boreholes and 11 distributed
heat pumps, predictions regarding the system's heating and cooling performance are made. These models are then validated and refined using actual measurement data collected from the system. This combined approach allows for accurate assessment
of system performance, identification of any discrepancies between predicted and actual behavior, and ongoing adjustments to ensure the system operates at peak efficiency under various conditions.
Impact
This project will deliver operational data, validated modeling tools, and valuable insights that will inform and enhance the design and operation of future GHP systems. The project will also contribute to the development of an educational platform at NREL, aimed at increasing public awareness of the advantages of GHP technology.
Capabilities
NREL's geothermal capabilities run the gamut from analysis to downhole tools and sensors and from reservoir modeling to full-scale field research validation. Learn more about these Geothermal Anywhere capabilities:
NREL is modeling fluid flow and heat transport in geothermal reservoirs to tackle the biggest question in next-generation geothermal: How do we develop geothermal anywhere?
From traditional hydrothermal sites to new reservoir designs such as enhanced geothermal systems and closed-loop advanced geothermal systems, NREL scientists are advancing the science behind geothermal heat exchange. New reservoir designs could significantly reduce upfront project risk and allow for the development of geothermal anywhere in the United States.
Our reservoir modeling team uses modeling tools for 3D static (structural) and dynamic (numerical) simulation, including thermal, hydrological, mechanical, and chemical properties. We engage our high-performance computing system to gain insights into the subsurface from well targeting to reservoir operations and from optimization to design of unconventional geothermal systems.
Publications
Techno-Economic Feasibility of Geothermal Energy Production Using Inactive Oil and Gas Wells for District Heating and Cooling Systems in Tuttle, Oklahoma, Energy Conversion and Management (2024)
An Embedded 3D Fracture Modeling Approach for Simulating Fracture Dominated Fluid Flow and Heat Transfer in Geothermal Reservoirs, Geothermics (2020)
Sedimentary Geothermal Resources in Nevada, Utah, Colorado, and Texas, NREL Technical Report (2020)
Code Modifications For Modeling Chemical Tracers and Embedded Natural Fractures at EGS Collab, Stanford Geothermal Workshop (2019)
Analysis of Geothermal Reservoir and Well Operational Conditions Using Monthly Production Reports From Nevada and California, Transactions (2017)
Slender-Body Theory for Transient Heat Conduction: Theoretical Basis, Numerical Implementation, and Case Studies, Proceedings of the Royal Society A (2015)
NREL works with government, municipal, industry, and university partners to find innovative yet effective ways to apply geothermal resources to meet residential, industrial, and commercial heating and cooling demands while reducing costs.
NREL analysis—including system modeling, techno-economic analysis, life cycle impact assessment, and performance measurements—can help organizations meet their goals through demand-side analysis and management, resource assessment and optimization, storage potential evaluation and planning, and overall design and control strategy improvements.
Publications
Geospatial Characterization of Low-Temperature Heating and Cooling Demand in the United States, 48th Workshop on Geothermal Reservoir Engineering (2023)
Geothermal Deep Direct Use For Turbine Inlet Cooling in East Texas, NREL Technical Report (2020)
Desalination of Impaired Water Using Geothermal Energy, Geothermal Resources Council Transactions (2017)
Performance, Cost, and Financial Parameters of Geothermal District Heating Systems for Market Penetration Modeling Under Various Scenarios, 42nd Workshop on Geothermal Reservoir Engineering (2017)
Update on Geothermal Direct-Use Installations in the United States, 42nd Workshop on Geothermal Reservoir Engineering (2017)
Characterizing U.S. Heat Demand for Potential Application of Geothermal Direct Use, Transactions (2016)
Use of Low-Temperature Geothermal Energy for Desalination in the Western United States, NREL Technical Report (2015)
NREL possesses unique capabilities in the performance modeling and design of geothermal heating and cooling systems, leveraging advanced tools such as GHEDesigner and URBANopt to model entire geothermal systems, including buildings, distribution systems,
and ground heat exchangers.
NREL has extensive expertise in modeling a range of geothermal systems, from individual buildings to large-scale community projects. Whether horizontal or vertical, centralized or distributed, NREL's
advanced capabilities in performance modeling and design enable the creation of customized, efficient heating and cooling solutions tailored to diverse project needs. NREL's capabilities also include life cycle cost analysis to optimize the efficiency
and long-term viability of geothermal heating and cooling systems.
Contact
Industry Applications
NREL scientists work with industry partners to identify ways geothermal can meet their heat demands in economic ways. Industry applications use a large amount of energy each year for process heating and facility heating, ventilating, and air conditioning. With geothermal heat available throughout the U.S. and new closed-loop geothermal systems becoming more common, geothermal can help the United States meet its large heating demands reliably. Integration with ground-source heat pumps or absorption chillers provides opportunity for cooling as well.
Share
Last Updated Sept. 9, 2025