Supercritical carbon dioxide (sCO₂) power cycles have the potential to reduce the cost of concentrating solar power (CSP) by far more efficiently converting high-temperature solar heat into electricity. 

The Solar Energy Technologies Office pursues dramatic cost reductions in technologies to make solar electricity available to all Americans. Next-generation CSP system designs use sCO₂ turbine power cycles to more efficiently convert solar thermal energy to electricity and reduce the cost of CSP technology.

Because sCO₂ power cycles work best at very high temperatures and under intense pressure, a CSP system needs receivers and heat exchangers that can withstand these conditions. Heat exchangers contribute up to 60%−70% of the total cost of a CSP sCO₂ turbine system, so low-cost, highly efficient exchangers are necessary to help make CSP cost-competitive.

Applications for Concentrating Solar Power

• Direct Solar to sCO₂ power tower: The power cycle working fluid also serves as the power tower heat transfer fluid.
• Indirect sCO₂ power tower: A high-temperature stable material is heated with sunlight, then a heat exchanger transfers the thermal energy into the power cycle. (see schematic below)

• Potential to increase maximum temperature of the heat transfer media to <1,000^oC 
• Well-suited for scalability to 10-100 MWe power tower systems

Benefits Uniquely Valuable to CSP

• Reduces water consumption compared to current Rankine process
• Makes smaller, more dispatchable power plants cost viable
• Reduces capital costs by increasing the efficiency of converting sunlight into energy.

Research Focus Areas (also see References)

• Lifetime performance of sCO₂-compatible materials
• Turbomachinery design, manufacturing, and testing sCO₂ regenerators
• Integration of CSP heat transfer media with sCO₂ cycle
• CSP subsystems compatible with >720°C sCO₂ cycle inlet temperature