Low- Cost Thermal Energy Storage for Dispatchable CSP

Demonstrating an innovative and low-cost approach to utility-scale thermal energy storage

The Regents of the University of California on behalf of the Los Angeles Campus


Los Angeles, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

The project performed detailed heat transfer modeling and simulation, laboratory-scale material compatibility experiments, and laboratory-scale thermal battery testing. Results from the laboratory-scale (10 kWh capacity) system were very promising. The system was successfully operated at high temperature (600 degrees Centigrade) over multiple thermal cycles and demonstrated higher energy density and faster dynamic response (speed of charge and discharge) compared to conventional molten salt technology. A pilot-scale (30 kWh capacity) thermal battery system was designed, built, and field tested with CSP in December 2018. Testing the system in a real-world environment validated performance with actual solar energy input and provided valuable validation of system-level analysis and heat transfer tools. Researchers are now scaling up the technology.

The Issue

With an increasing share of electricity generation coming from variable renewable energy resources such as wind and solar, new strategies are needed to ensure that electricity supplies can effectively match demand. One such strategy is to use thermal energy storage (TES) with concentrating solar power (CSP). However, this technology is currently prohibitively expensive and difficult to dispatch.

Project Innovation

The purpose of this project was the development and demonstration of a robust, low-cost thermal energy storage (TES) fluid -- elemental sulfur. Use of sulfur as a TES fluid will enable overall low system costs, long lifetime, and scalability for a wide range of concentrating solar power (CSP) applications and temperatures.

Project Benefits

This project will develop a low-cost thermal storage fluid, elemental sulfur, which enables overall low system costs, long lifetime, and scalability for a wide range of concentrating solar power applications.

Lower Costs


This project aims to reduce the cost of TES to $15/kWh. Compared to current state-of-the-art, this leads to a decrease in LCOE from 3 cents/kWh to 0.4 cents/kWh, providing $0.66 billion to $1.32 billion in annual savings depending on CSP penetration.

Economic Development

Economic Development

Assuming 5% to 10% penetration of CSP and deployment beginning in 2017, the 10-year net present value of this technology is estimated to be between $680 and $906 million.

Environmental & Public Health

Environmental Sustainability

Assuming 5% to 10% penetration of CSP and 1010 MWh of TES by 2020, significant greenhouse gas and criteria air pollutant reductions would be achieved: 2791 ton/MW of CO2, 37 ton/MW of SO2, 5 ton/MW of NOx, and 2.4 ton/MW of CO.

Greater Reliability


Use of TES allows excess harvested solar energy to be stored during the day to be used during peak or non-solar hours, which increases dispatchability of renewable resources and provides load shifting.

Key Project Members

Project Member

Richard Wirz

Associate Professor



Thermal Storage Systems


Match Partners


Southern California Gas Company (SoCalGas)


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