This disclosure relates to the unique integration of a plurality of thermodynamic cycles comprised of a supercritical carbon dioxide thermodynamic cycle, one or more other thermodynamic cycles with multiple heat sources derived from nuclear fuel, solar energy, hydrogen, and fossil fuels, with the energy production systems configured to noticeably improve power plant efficiency, cost and performance.

Systems and methods for variable pressure inventory control of a closed thermodynamic cycle power generation system or energy storage system, such as a reversible Brayton cycle system, with at least a high pressure tank and an intermediate pressure tank are disclosed. Operational parameters of the system such as working fluid pressure, turbine torque, turbine RPM, generator torque, generator RPM, and current, voltage, phase, frequency, and/or quantity of electrical power generated and/or distributed by the generator may be the basis for controlling a quantity of working fluid that circulates through a closed cycle fluid path of the system.

Systems and methods for variable pressure inventory control of a closed thermodynamic cycle power generation system or energy storage system, such as a reversible Brayton cycle system, with at least a high pressure tank and an intermediate pressure tank are disclosed. Operational parameters of the system such as working fluid pressure, turbine torque, turbine RPM, generator torque, generator RPM, and current, voltage, phase, frequency, and/or quantity of electrical power generated and/or distributed by the generator may be the basis for controlling a quantity of working fluid that circulates through a closed cycle fluid path of the system.

Systems and methods are provided for charging a pumped thermal energy storage (“PTES”) system. A system may include a compressor or pump configured to circulate a working fluid within a fluid circuit, wherein the working fluid enters the pump at a first pressure and exits at a second pressure; a first heat exchanger through which the working fluid circulates in use; a second heat exchanger through which the working fluid circulates in use; a third heat exchanger through which the working fluid circulates in use, a turbine positioned between the first heat exchanger and the second heat exchanger, configured to expand the working fluid to the first pressure; a high temperature reservoir connected to the first heat exchanger; a low temperature reservoir connected to the second heat exchanger, and a waste heat reservoir connected to the third heat exchanger.

Systems and methods are provided for charging a pumped thermal energy storage (“PTES”) system. A system may include a compressor or pump configured to circulate a working fluid within a fluid circuit, wherein the working fluid enters the pump at a first pressure and exits at a second pressure; a first heat exchanger through which the working fluid circulates in use; a second heat exchanger through which the working fluid circulates in use; a third heat exchanger through which the working fluid circulates in use, a turbine positioned between the first heat exchanger and the second heat exchanger, configured to expand the working fluid to the first pressure; a high temperature reservoir connected to the first heat exchanger; a low temperature reservoir connected to the second heat exchanger, and a waste heat reservoir connected to the third heat exchanger.

A method including: (i) receiving a first amount of electricity into a pumped-heat energy storage system (“PHES system”) from a power generation plant supplying a second amount of electricity to an electrical grid; (ii) operating the PHES system in a charge mode, converting at least a portion of the received first amount of electricity to stored thermal energy; and (iii) increasing a power level of the PHES system such that the first amount of electricity that the PHES system receives from the power generation plant is increased such that the second amount of electricity supplied to the electrical grid by the power generation plant is a reduced amount of electricity less than the second amount of electricity.

Aircraft power plants including combustion engines, and associated methods for recuperating waste heat from such aircraft power plants are described. A method includes transferring the heat rejected by the internal combustion engine to supercritical CO.sub.2 (sCO.sub.2) used as a working fluid in a heat engine. The heat engine converts at least some the heat transferred to the sCO.sub.2 to mechanical energy to perform useful work onboard the aircraft.

Power is produced by operating first and second nested cycles utilising CO.sub.2 as working fluid without mixing of working fluid between the nested cycles. The first cycle comprises a semi-open loop operating under low pressure conditions in which CO.sub.2 is sub-critical. The second cycle comprises a closed loop operating under higher pressure conditions in which CO.sub.2 is supercritical. The first cycle operates in a Brayton cycle including oxycombustion of hydrocarbons, preferably LNG, in a combustion chamber under low pressure conditions, expansion for power production to provide a first power source, cooling in a recuperator, compression, reheating by counter-current passage via the recuperator, and return of working fluid heated by the recuperator back to the combustion chamber. Water and excess CO.sub.2 resulting from the oxycombustion step are separated from the first cycle. The first cycle serves as a source of heat for the second cycle by gas/gas heat exchange in a gas/gas heat exchanger which results in cooling of the products of combustion and circulating working fluid in the first cycle and heating of working fluid in the second cycle. The second cycle is operated in a Brayton cycle including heating of working fluid in the second cycle by the gas/gas heat exchanger, expansion for power generation to provide a second power source, cooling in two-stages by first and second recuperator steps, compression, reheating by counter-current passage via the first recuperator step, and return of working fluid heated by the first recuperator step back to the gas/gas heat exchanger. Working fluid in the first cycle following the compression step is heated by working fluid in the second cycle by counter-current passage via the second recuperator step.

Power is produced by operating first and second nested cycles utilising CO.sub.2 as working fluid without mixing of working fluid between the nested cycles. The first cycle comprises a semi-open loop operating under low pressure conditions in which CO.sub.2 is sub-critical. The second cycle comprises a closed loop operating under higher pressure conditions in which CO.sub.2 is supercritical. The first cycle operates in a Brayton cycle including oxycombustion of hydrocarbons, preferably LNG, in a combustion chamber under low pressure conditions, expansion for power production to provide a first power source, cooling in a recuperator, compression, reheating by counter-current passage via the recuperator, and return of working fluid heated by the recuperator back to the combustion chamber. Water and excess CO.sub.2 resulting from the oxycombustion step are separated from the first cycle. The first cycle serves as a source of heat for the second cycle by gas/gas heat exchange in a gas/gas heat exchanger which results in cooling of the products of combustion and circulating working fluid in the first cycle and heating of working fluid in the second cycle. The second cycle is operated in a Brayton cycle including heating of working fluid in the second cycle by the gas/gas heat exchanger, expansion for power generation to provide a second power source, cooling in two-stages by first and second recuperator steps, compression, reheating by counter-current passage via the first recuperator step, and return of working fluid heated by the first recuperator step back to the gas/gas heat exchanger. Working fluid in the first cycle following the compression step is heated by working fluid in the second cycle by counter-current passage via the second recuperator step.

In a thermodynamic cycle with at least one first heat exchanger for creating a first heated or partially evaporated working medium flow by heating or partially evaporating a liquid working medium flow by heat transmission from an expanded working medium flow; a second heat exchanger for creating a second at least partially evaporated working medium flow; a separator for separating a liquid from a vaporous phase of the second flow; and an expansion device for creating an expanded vaporous phase, pressure pulsations are prevented during the start-up of the cycle in that the vaporous phase separated by the separator is conducted past the expansion device and the first heat exchanger. The liquid phase separated by the separator is cooled in the first heat exchanger by heat transfer to the liquid flow. After the first heat exchanger, the cooled, separated, liquid phase and the separated vaporous phase are brought together.