Thermodynamic Study of Advanced Supercritical Carbon Dioxide Power Cycles for High Performance Concentrating Solar Power Systems

In 2011, the U.S. Department of Energy (DOE) initiated a “SunShot Concentrating Solar Power R&D” program to develop technologies that have the potential for much higher efficiency, lower cost, and/or more reliable performance than existing CSP systems. The DOE seeks to develop highly disruptive Concentrating Solar Power (CSP) technologies that will meet 6¢/kWh cost targets by the end of the decade, and a high-efficiency, low-cost thermal power cycle is one of the important components to achieve the goal. Supercritical CO₂ (s-CO₂) operated in a closed-loop Brayton cycle offers the potential of equivalent or higher cycle efficiency versus superheated or supercritical steam cycles at temperatures relevant for CSP applications. Brayton-cycle systems using s-CO₂ have a smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine cycles due to the higher density of the fluid and simpler cycle design. The simpler machinery and compact size of the s-CO₂ process may also reduce the installation, maintenance and operation cost of the system.