Provided herein are heat engine systems and methods for transforming energy, such as generating mechanical energy and/or electrical energy from thermal energy. The heat engine systems may have one of several different configurations of a working fluid circuit. One configuration of the heat engine system contains at least four heat exchangers and at least three recuperators sequentially disposed on a high pressure side of the working fluid circuit between a system pump and an expander. Another configuration of the heat engine system contains a low-temperature heat exchanger and a recuperator disposed upstream of a split flowpath and downstream of a recombined flowpath in the high pressure side of the working fluid circuit.

A combined cooling, heating and power system is formed by integrating a CO.sub.2 and ORC cycle systems, and an LNG cold energy utilization system on the basis of an SOFC/GT hybrid power generation system. The combined systems provide utilization of energy and low carbon dioxide emission. The SOFC/GT is used as a prime mover, high-temperature, medium-temperature, and low-temperature waste heat of the system are recovered through a CO.sub.2 and ORC cycles, cold energy (for air conditioning and refrigeration), heat, power, natural gas, ice, and dry ice is provided by using LNG as a cold source of the CO.sub.2 cycle and the ORC cycle, and low carbon dioxide emission of the system is achieved by condensation and separation of CO.sub.2 from flue gas, so energy losses of the combined system is reduced, and efficient and cascade utilization of energy is achieved, thereby providing energy conservation and emission reduction effect.

A carbon dioxide cycle power generation system includes a first carbon dioxide storage configured to store a first portion of carbon dioxide and a second carbon dioxide storage configured to store a second portion of the carbon dioxide. The carbon dioxide cycle power generation system also includes a generator configured to generate electrical power based on a flow of at least part of the carbon dioxide between the first and second carbon dioxide storages. The carbon dioxide cycle power generation system is configured to cycle between different underwater depths in order to employ water pressure and/or water temperature in creating the flow of the at least part of the carbon dioxide through the generator. The second carbon dioxide storage includes an annular region surrounding a central region, where the annular region has a variable internal volume configured to receive at least part of the second portion of the carbon dioxide.

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.

The present disclosure relates to systems and methods for power production utilizing a recirculating working fluid. In particular, a portion of the recirculating working fluid can be separated from the main stream of recirculating working fluid as a bypass stream that can be compressed for adding heat to the system.

A method for producing work is disclosed. The method includes increasing the pressure of a working fluid including carbon dioxide from a first pressure at least equal to a triple point pressure to a second pressure above the triple point pressure. The method also includes heating the working fluid, extracting mechanical work by expanding a first portion of the heated working fluid to a third pressure, supplying a second portion of the heated working fluid as a motive fluid to an ejector, increasing the pressure of the expanded working fluid by supplying the expanded working fluid to the ejector to combine with the motive fluid and form an output fluid at the fourth pressure, the fourth pressure at least equal to the triple point pressure of the working fluid. The method also includes refrigerating the output fluid to condense a vapor phase into a liquid phase.

An apparatus with a first pathway configured to circulate a first substance and a second pathway configured to circulate a second substance between a plurality of plates. The first pathway includes: a plurality of plates with a plurality of flow channels; a first inlet configured to receive the first substance and provide the first substance to the first plurality of flow channels; and a first outlet configured to receive the first substance from the first plurality of flow channels. The second pathway includes: a second inlet configured to receive the second substance; and a second outlet configured to output the second substance.

An aeronautical gas turbine engine includes a turbomachine including a compressor section, a combustion section, a turbine section, and an exhaust section in serial flow order. The aeronautical gas turbine engine additionally includes a closed cycle heat engine including a compressor configured to compress a working fluid; a primary heat exchanger in thermal communication with the turbomachine and the working fluid, the primary heat exchanger configured to transfer heat from the turbomachine to the working fluid; an expander coupled to the compressor for expanding the working fluid; and an output shaft driven by the expander.

In some embodiments the disclosure is directed to a closed-loop piston engine system using a recirculating carbon dioxide (CO.sub.2) system with supercritical carbon dioxide (scCO.sub.2) as a working fluid. The closed-loop piston engine system may include a scCO.sub.2 injector; a superheating nozzle region; a first valve; a second valve; a piston moving in the cylinder and coupled with a crankshaft, the piston being driven toward a centerline of the crankshaft during a power stroke using a connecting rod and causing the crankshaft to rotate thereby causing one power stroke per crankshaft rotation and thereby producing two power strokes for every single power stroke that a similar engine would produce if run as a hydrocarbon fuel powered internal combustion engine. The recirculating CO.sub.2 system recirculates the used carbon dioxide and there are no carbon dioxide emissions from the system.

A process for energy storage comprises carrying out a cyclic thermodynamic transformation wherein, in a charge phase, a condensation of a working fluid is executed by means of heat absorption by a heat carrier in order to store the working fluid in the liquid or supercritical phase; in a discharge phase, an evaporation of the working fluid is executed starting from the liquid or supercritical phase and by transfer of heat from the heat carrier; provision is made for actively adjusting at least one parameter of the working fluid related to the condensation and/or to the evaporation, in order to control at least one temperature of the heat carrier and uncouple it from the ambient temperature without the aid of systems outside the cyclic thermodynamic transformation.