A fluid expander is disclosed as used in conjunction with an air compressor that is driven by a prime mover. The fluid expander is structured to extract useful work from a fluid stream and add that work to the work provided by the prime mover to the compressor. In some embodiments a clutch can be used to decouple the expander from the compressor if insufficient work is developed by the expander. A gear train can also be used to change the rotational speed prior to work being delivered to the compressor.

Disclosed herein is a supercritical carbon dioxide power generation system utilizing a plurality of heat sources, comprising: a pump for circulating a working fluid; a plurality of heat exchangers for heating the working fluid through an external heat source; a plurality of turbines driven by the working fluid heated through the heat exchangers; and a plurality of recuperators that allow the working fluid passed through the turbines and the working fluid passed through the pump to heat exchange with each other to cool the working fluid passed through the turbine, wherein the plurality of heat exchangers are sequentially disposed from a high temperature region at an inlet end into which waste heat gas stream is introduced up to a low temperature region at an outlet end through which the waste heat gas stream is discharged via a mediate temperature region.

An oxy-combustion combined cycle power plant that includes a gas turbine engine configured to combust natural gas and pure oxygen to generate power, and configured to discharge exhaust gas consisting essentially of carbon dioxide and water therefrom. A heat recovery system of the power plant includes a fluid path that is a closed loop, the fluid path channeling a working fluid that is carbon dioxide therethrough. A first heat exchanger is coupled along the fluid path, and a turbine is coupled downstream from the first heat exchanger along the fluid path. The first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid, and the turbine is configured to use the heated working fluid, received from the first heat exchanger, to generate power.

An oxy-combustion combined cycle power plant that includes a gas turbine engine configured to combust natural gas and pure oxygen to generate power, and configured to discharge exhaust gas consisting essentially of carbon dioxide and water therefrom. A heat recovery system of the power plant includes a fluid path that is a closed loop, the fluid path channeling a working fluid that is carbon dioxide therethrough. A first heat exchanger is coupled along the fluid path, and a turbine is coupled downstream from the first heat exchanger along the fluid path. The first heat exchanger is configured to transfer heat from the exhaust gas to the working fluid, and the turbine is configured to use the heated working fluid, received from the first heat exchanger, to generate power.