Calcium Takes Concentrated Solar Power Storage to the Next Level

Southern Research Institute TCES shows sustainable operation up to 900 degrees 350 degrees above current systems.
Published: Wed 11 Jun 2014

The Southern Research Institute has signed a jointly funded cooperative agreement with the US Department of Energy (DOE) as part of the Department’s new Concentrating Solar Power: Efficiently Leveraging Equilibrium Mechanisms for Engineering New Thermochemical Storage (CSP:ELEMENTS) funding program.

The US$1.05 million research effort falls under the SunShot Initiative which is a collaborative national effort that aggressively drives innovation to make solar energy fully cost-competitive with traditional energy sources before the end of the decade. Through SunShot, the Department supports efforts by private companies, academia, and national laboratories to drive down the cost of solar electricity to US$0.06 per kilowatt-hour.

Supporting the thermo-chemical energy storage system

The CSP:ELEMENTS program supports the development of high-temperature thermo-chemical energy storage (TCES) systems that enable concentrating solar power plants to produce electricity in the evenings and even overnight when the sun is no longer shining.

Concentrating Solar Power technology employs mirrors that concentrate reflected sunlight onto receivers containing heat transfer fluids. From there, the fluids are used to heat water, which in turn generates steam that is used to power turbines and produce electricity.

By adding thermal storage to these facilities they are able to operate at significantly higher capacity factors and produce approximately double the energy for the same size power facility. Furthermore, the production of electricity can be shifted to occur at the same time as peak power demand, making the electricity even more valuable.

The Southern Research Institute project will develop a thermo-chemical energy storage system that uses a low-cost calcium-based sorbent in a reversible closed-loop endothermic-exothermic chemical reaction cycle.

The system stores energy during mid-day when sunlight is plentiful in the endothermic step, and then releases energy when the sun is no longer shining during the exothermic step, allowing for electricity to be produced in a more stable and consistent fashion.

Cost-effective and efficient

This thermo-chemical energy storage system is projected to cost about one-quarter as much as current state-of-the-art molten salt storage systems, and will be able to store the same amount of energy in a system about one-sixth the size.

“Utilizing these low-cost regenerative calcium-based sorbents, researched for carbon dioxide capture in coal-based power generation facilities, leverages existing knowledge bases and is an innovative transfer of technology,” said Dr. Santosh Gangwal, project Principal Investigator. “Through rigorous material development we can refine these sorbents to perform successfully in this environment throughout the entire 30 year life of a CSP plant.”

Furthermore, while molten salt storage systems can only operate up to about 550 degrees Celsius, the Southern Research Institute TCES system can operate sustainably up to 900 degrees.

“As the next generation of CSP plants moves towards higher operating temperatures to achieve higher conversion efficiencies, a new generation of high-temperature storage needs to be developed to allow these facilities to continue to provide power in a cost-effective and dispatchable manner,” said Ryan Melsert, co-Principal Investigator of the project.

Further reading

Southern Research Institute-U.S. Department of Energy Signs $1.05 Million Cooperative Agreement With Southern Research Institute To Develop Advanced High-Temperature Solar Thermal Storage System