What are Thermal Energy Storage and Heat Transfer Media?
Thermal energy storage (TES) refers to heat that is stored for later use—either to generate electricity on demand or for use in industrial processes. Concentrating solar-thermal power (CSP) plants utilize TES to increase flexibility so they can be used as “peaker” plants that supply electricity when demand is high; as “baseload” power plants that provide solar electricity around the clock; or as continuous sources of solar industrial process heat, offsetting or replacing the combustion of conventional fuels.
Heat transfer media (HTM) refers to the fluid or other material that is used to transport heat from the solar receiver to TES and from TES to the turbine or industrial process. Existing state-of-the-art CSP plants use a liquid, molten nitrate salts, as both the TES and HTM materials. For next-generation, higher temperature systems, a number of other materials for TES, HTM, as well as containment materials for those components, are currently being researched. Learn more about how CSP works.
Why are Thermal Energy Storage and Heat Transfer Media Important?
TES helps address grid integration challenges related to the variability of solar energy. Storing thermal energy is less complicated and less expensive than storing electrical energy and allows CSP plants to deliver energy regardless of whether the sun is shining. In the past decade, the cost of energy produced by CSP technologies has dropped more than 50 percent, thanks to the wider use of TES and more efficient thermal transport systems. To effectively take advantage of TES, CSP plants need heat transfer components that are reliable and efficient. The Department of Energy Solar Energy Technologies Office (SETO) funds projects that work to make CSP even more affordable, with the goal of reaching $0.05 per kilowatt-hour for baseload plants with at least 12 hours of thermal energy storage. Learn more about SETO’s CSP goals.
SETO Research in Thermal Energy Storage and Heat Transfer Media
SETO research for TES and HTM primarily focuses on raising the temperature of the heat that can be stored, which will ultimately lower the cost of energy due to increased efficiency of the CSP plant. To reach temperatures higher than 700 degrees Celsius, projects are investigating the use of new heat transfer media, like molten chloride salts, solid particles, and supercritical carbon dioxide, as well as thermal transport systems and their components, such as receivers, pumps, heat exchangers, and advanced alloys and materials for containing and transporting these media. Several SETO funding programs contain projects that focus on TES:
- Solar Energy Technologies Office Fiscal Year 2020 funding program – developing, building, and operating a supercritical carbon dioxide power cycle integrated with thermal energy storage at high temperatures.
- Solar Energy Technologies Office Fiscal Year 2019 funding program – developing thermal storage technologies and components to make solar energy available on demand.
- Solar Energy Technologies Office FY2019-21 Lab Call funding program –improving the materials and components used within TES CSP systems, enabling them to cost-effectively operate high temperatures.
- Generation 3 Concentrating Solar Power Systems funding program – de-risking the next generation of CSP technologies by advancing high-temperature components and developing integrated assembly designs with TES.
To view specific thermal energy storage projects, search the Solar Energy Research Database.
- DOE Energy Storage Grand Challenge
- Concentrating Solar Power Gen3 Demonstration Roadmap
- Thermophysical Properties Database of Gen3 CSP Materials