The unique properties of Supercritical CO₂ (sCO₂) present advantages for closed-loop power generation and can be applied to various power generation applications. Power generation systems that use traditional air Brayton and steam Rankine cycles can be upgraded to sCO₂ to increase efficiency and power output.
The relatively new Allam power cycle uses sCO₂ as the working fluid in combination with fuel and pure oxygen. The CO₂ produced by combustion mixes with the sCO₂ working fluid and a corresponding amount of pure CO₂ must be removed from the process (for industrial use or sequestration). This process reduces atmospheric emissions to zero.
It presents interesting properties that promise substantial improvements in system efficiency. Due to its high fluid density, sCO₂ enables extremely compact and highly efficient turbomachinery. It can use simpler, single casing body designs while steam turbines require multiple turbine stages and associated casings, as well as additional inlet and outlet piping. The high density allows for highly compact, microchannel-based heat exchanger technology.