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The National Renewable Energy Laboratory (NREL) and its partners, under the 2012 SunShot Concentrating Solar Power (CSP) R&D funding opportunity announcement (FOA), aim to demonstrate a multi-megawatt power cycle using supercritical carbon dioxide (s-CO2) as the working fluid. The use of carbon dioxide instead of steam allows higher power-cycle efficiency and cycle components that are more compact.


The research team intends to showcase the turbomachinery for a new cycle—the s-CO2 Brayton cycle. During the past decade, researchers have modeled the basic thermodynamics of the cycle and tested it to explore the behavior of s-CO2 turbomachinery and operational/control characteristics of a closed Brayton cycle. However, to establish the true potential of this power cycle, the industry needs validation via the operation of a larger-scale prototype at temperatures relevant to CSP systems.

The goals of this project are to:

  • Design, fabricate, and validate a closed-loop, s-CO2 power cycle of nominally 10 megawatts electric (MWe) that can operate at up to 700°C and under dry-cooling conditions
  • Validate the turbomachinery and control strategies for a power cycle that can fundamentally transform the CSP industry.

Illustration of the internal view of a turbine with tubes, wires, and parts that are different colors. 


The proposed s-CO2 system uses no water, which is significant given that CSP plants are typically located in hot, dry climates where water is scarce. Researchers plan to demonstrate the inherent efficiencies of the s-CO2 power turbine and associated turbomachinery at a scale relevant to commercial CSP projects. Success in this endeavor will provide a foundation for solar applications that exceed the SunShot Initiative's goal of 50% net thermal-to-electric conversion efficiency.

Publications, Patents, and Awards

Final Report

Project Fact Sheet

The SunShot CSP R&D program seeks to accelerate progress toward the cost target of $0.06 per kilowatt-hour through novel and revolutionary research into CSP technologies. Learn about other concentrating solar power research.