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Concentrated Solar Power (CSP) Energy Storage

Concentrated solar power uses large arrays of mirrors or lenses to concentrate sunlight onto a small fixed point. The heat from this fixed point is then transferred to a conventional steam generator for conversion into electricity. Unlike photovoltaic solar energy storage, which often use batteries to store energy, CSP energy storage uses mechanical systems to manage thermal energy.

Southwest Research Institute is working to advance CSP energy storage through development of supercritical carbon dioxide (sCO2) power cycles and other thermal energy storage systems for concentrated solar power plants, including:

Supercritical CO2 for CSP

This 10 MWe sCO2 four-stage axial flow turbine generates 15 MW gross power at inlet conditions of 715 degrees C and 250 bar. It was developed by SwRI under DOE’s Sunshot Program in collaboration with General Electric.

Supercritical CO2 (sCO2) power cycle technology could increase the thermal efficiency of CSP plants from 42% to 50% or more with reduced turbomachinery size and compatibility with dry cooling. SwRI is home to the world’s highest temperature sCO2 turbine for CSP applications. Developed with the support of the U.S. Department of Energy Solar Energy Technologies Office, the 10-megawatt turbine is the size of a desk and yields the highest power density of any industrial turbine, rivaled only by the turbopumps used on the space shuttle engines. This small but powerful turbine can withstand the tough operating conditions of concentrated solar power (CSP) plants and is scalable up to 100 megawatts or more for utility-scale CSP. SwRI is also performing component development for sCO2 cycles including advanced turbine seals and heat exchangers and is also the host site for the STEP pilot plant that will demonstrate sCO2 cycles at CSP-relevant conditions.

CSP Thermal Storage

SwRI is exploring the development and application of molten salt, solid media, and encapsulated phase change materials for thermal energy storage in CSP cycles, as well as advanced heat exchangers including packed bed concepts and thermoclines. SwRI is also developing pumped thermal energy storage technology with potential application to hybridize CSP systems by charging the thermal store using excess renewable power from solar photovoltaic or wind generators.

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