Supercritical carbon dioxide (sCO₂) power cycles are Brayton cycles that utilize supercritical CO₂ as working fluid to convert heat into power. They offer the potential for higher system efficiencies compared to other energy conversion technologies such as steam Rankine cycles which are used in conventional power plants, especially when operating at elevated temperatures. It is the unique properties of supercritical CO₂ that offer intrinsic benefits over steam as a working fluid to absorb thermal energy, to be compressed, and to impart momentum to a turbine. This higher efficiency results in lower cost and lower emissions for the same amount of power produced.

sCO₂ power cycles are being considered for a wide range of applications including fossil-fired systems, waste heat recovery, concentrated solar power, and nuclear. It is expected that the STEP Demo project will achieve a 50% cycle efficiency.