The supercritical carbon dioxide power cycle operates in a manner similar to other turbine cycles, but it uses CO₂ as the working fluid in the turbomachinery. The cycle is operated above the critical point of CO₂ so that it does not change phases (from liquid to gas), but rather undergoes drastic density changes over small ranges of temperature and pressure. This allows a large amount of energy to be extracted at high temperature from equipment that is relatively small in size. SCO₂ turbines will have a nominal gas path diameter an order of magnitude smaller than utility scale combustion turbines or steam turbines.

Power cycles based on a supercritical carbon dioxide (SCO₂) working fluid have the potential for higher thermal efficiencies when compared to state of the art steam-based power cycles.

However, the cost and effectiveness of the cycle’s recuperators are currently seen as a barrier to the full-scale SCO₂ power cycle demonstration and economic viability.

The DOE Office of Fossil Energy’s Strategic Center for Coal supports research and development of SCO₂ power cycle systems technologies in light of their potential advantages over conventional steam cycles.

The selected project is designed to apply focused research and development to produce scalable, cost-effective recuperator technologies suitable for future deployment in large-scale SCO₂ power cycle applications.

Thar Energy will partner with Southwest Research Institute; Oak Ridge National Laboratory; Georgia Institute of Technology; and Knolls Atomic Power Laboratory to advance high-temperature, high-differential-pressure recuperator technologies suitable for use in SCO₂ recompression Brayton cycle, a likely candidate for the commercialization of SCO₂ power cycles.

A non-condensing closed-loop Brayton cycle with heat addition and rejection on either side of the expander. In this cycle, the CO2 is heated indirectly from a heat source through a heat exchanger, not unlike the way steam would be heated in a conventional boiler. Energy is extracted from the CO2 as it is expanded in the turbine. Remaining heat is extracted in one or more highly efficient heat recuperators to preheat the CO2 going back to the main heat source. These recuperators help increase the overall efficiency of the cycle by limiting heat rejection from the cycle. Source: DOE. Click to enlarge.

The focus of the program is to evaluate, advance, and demonstrate recuperator concepts, materials, and fabrication methods that facilitate the commercial availability of compact, low-cost recuperators for use under Brayton cycle conditions.