Geothermal Heating & Cooling

Geothermal heating and cooling technologies, including networked geothermal, direct use, and geothermal heat pumps (GHPs), offer efficient temperature control solutions for buildings, campuses, military bases, and even entire communities. Widespread adoption of these technologies can help to reduce energy costs for families, stabilize the grid, and boost energy security.

 

Geothermal Heat Pumps

Geothermal heat pumps (GHPs), also known as ground-source heat pumps (GSHPs), take advantage of constant underground temperatures to efficiently exchange temperatures, heating homes in the winter and cooling homes in the summer. Using the constant temperature of the shallow earth (40–70°F), rocks and soils in the subsurface below a building or community can act as a heat sink—absorbing excess heat during summer, when surface temperatures are relatively higher—and as a heat source during the winter, when surface temperatures are lower. 

Learn more about GHPs: 

 

Networked Geothermal

Illustration of a thermal energy network, or TEN, where water is circulated through piping that connects buildings (e.g. hospitals, office buildings, apartment buildings) typically at the depth of the average natural gas system. Heat pumps and heat exchangers circulate the water and exchange the thermal energy needed to meet building heating and cooling needs. In winter, hot water is piped in to heat buildings and the cooled water is returned to the system for reheating, and vice-versa in the summer.
A TENs example. Heat pumps & exchangers circulate water through piping between buildings, exchanging thermal energy to provide heating and cooling. In winter, piped in hot water heats buildings and cooled water returns to the system; vice-versa in summer.

Networked geothermal systems—sometimes referred to as Thermal Energy Networks (TENs) or district-scale— are geothermal systems that serve entire neighborhoods, city blocks, campuses, and communities. Rather than powering one building at a time, these systems provide heating and/or cooling to multiple homes or businesses together in a network. These systems can comprise networked GHPs as well as other technologies, and various kinds of configurations of these systems are emerging in universities and communities all over the United States.

Learn more about the Office of Geothermal's District-Scale Geothermal Energy Pilots initiative, research on geothermal low temperature and coproduced resources, and other Office of Geothermal priorities.

 

Geothermal Direct Use

An illustration of a greenhouse sits above two pipes or wells tapping into subsurface fractures with warm ground water. In a direct use system, hot water/steam is pumped up from the heated aquifer for heating and cooling purposes at the site of delivery, and then is returned to refill the aquifer after giving up heat.

 

 

Geothermal direct use employs geothermal energy directly for heating or other applications, without first converting it to electricity. Direct-use applications tap into lower subsurface temperatures to draw up thermal energy that can be used to heat buildings or support industrial uses ranging from fish farming, to greenhouses, to food processing. 

Learn more about the Office of Geothermal’s work in direct-use research, including advances in deep direct use (DDU). 

 

Geothermal Energy Storage 

Underground thermal energy storage (UTES) is a geothermal technology where thermal energy, or heat energy, is stored in the subsurface to be extracted later for beneficial uses, including heating and cooling. UTES can be incorporated in TENs and direct-use applications or serve as a standalone system, and its benefits include low operating costs, compatibility with multiple heat sources, and the ability to help shift heating and cooling demand away from peak demands periods for the grid. 

Examples of UTES Configurations:

4 thermal energy storage (TES) types illustrated: Closed-system TES, where a piping loop in a borehole connects the heat source and power generator; Open-system TES, where separate piping descends from the heat source and power generator and connects via a fracture network; geomechanical pumped storage, where water is injected into a fracture network and discharged pressure goes to the power generator and heat exchanger; and cold UTES, where cold energy is stored in a fracture network to be drawn up later