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 piston 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.

An energy storage system is disclosed. The energy storage system includes a turbo train drive, a hot heat sink, and a reservoir. The turbo train drive is in mechanical communication with a compressor and an expander. The hot heat sink is in thermal communication between an output of the compressor and an input of the expander. The reservoir is in thermal communication between an output of the expander and an input of the compressor. The compressor and the expander, via the turbo train drive, are operable between a charging function for charging the hot heat sink and a discharging function for discharging the hot heat sink.

A system includes a combustion power plant for generating power and an electrolysis unit for producing hydrogen. The combustion power plant has a combustion chamber for combustion of a fuel and an offgas conduit for leading off hot offgases formed in the combustion of the fuel. The offgas conduit is thermally coupled to the electrolysis unit. A method for operating the system includes burning the fuel in the combustion power plant, forming the hot offgases in the combustion of the fuel, removing the hot offgases through the offgas conduit, feeding the thermal energy of the hot offgases from the offgas conduit to the electrolysis unit, and producing hydrogen in the electrolysis unit by using the thermal energy from the hot offgases.

An assembly with a piston reciprocated with the aid of a floating head in fluid communication with the piston. The assembly may utilize a floating head that is shifted in position to promote reciprocation of the piston through the aid of pressure supplied to the floating head from a pressure volume regulator. Alternatively, the floating head may be in fluid communication with the piston at one side of the head and isolated at the other side. In this manner changing volume and pressure at this other side of the head during reciprocation may ultimately lead to floating head movement toward the piston, thereby promoting the continued reciprocation. Additional efficiencies may also be realized through unique hydraulic layouts for both operating and working fluid circulations.

An assembly with a piston reciprocated with the aid of a floating head in fluid communication with the piston. The assembly may utilize a floating head that is shifted in position to promote reciprocation of the piston through the aid of pressure supplied to the floating head from a pressure volume regulator. Alternatively, the floating head may be in fluid communication with the piston at one side of the head and isolated at the other side. In this manner changing volume and pressure at this other side of the head during reciprocation may ultimately lead to floating head movement toward the piston, thereby promoting the continued reciprocation. Additional efficiencies may also be realized through unique hydraulic layouts for both operating and working fluid circulations.

A heat recovery system that includes at least one an engine, a radiator, an Organic Rankine Cycle (ORC) and a thermo-electric generator (TEG). The radiator may be coupled to the reciprocating engine, and the ORC may be coupled to the reciprocating engine and to the TEG. A control module in the system is configured to divert reciprocating engine jacket water fluid through any of the radiator, ORC and TEG to increase the energy efficiency of the reciprocating engine through heat recovery caused by the diverted fluid.

A heat recovery system that includes at least one an engine, a radiator, an Organic Rankine Cycle (ORC) and a thermo-electric generator (TEG). The radiator may be coupled to the reciprocating engine, and the ORC may be coupled to the reciprocating engine and to the TEG. A control module in the system is configured to divert reciprocating engine jacket water fluid through any of the radiator, ORC and TEG to increase the energy efficiency of the reciprocating engine through heat recovery caused by the diverted fluid.

An energy storage system is disclosed. The energy storage system includes a turbo train drive, a hot heat sink, and a reservoir. The turbo train drive is in mechanical communication with a compressor and an expander. The hot heat sink is in thermal communication between an output of the compressor and an input of the expander. The reservoir is in thermal communication between an output of the expander and an input of the compressor. The compressor and the expander, via the turbo train drive, are operable between a charging function for charging the hot heat sink and a discharging function for discharging the hot heat sink.

A power recovery system for recovering power from a working fluid, comprising a heat exchanger that is configured to receive a first stream of the working fluid, one or more expansion stages for expanding the working fluid to recover power from the working fluid, wherein one or more of the expansion stages is in fluid communication with the heat exchanger, wherein the heat exchanger is configured to transfer heat between the first stream of the working fluid and another stream of the working fluid that is received from one or more of the expansion stages.

The boiler using a liquid metal as a working medium according to the present invention is comprises: a combustion furnace, in which the working medium is supplied and heated; a heat exchange part, which is connected to the combustion furnace and to which the working medium heated in the combustion furnace is supplied; a heat medium injection part, which is positioned in the heat exchange part; and a supply part, which is connected to the heat exchange part and supplies the heat medium to the heat medium injection part. In the heat exchange part, the heat exchange between the heat medium supplied to the heat medium injection part and the heated working medium is performed. The heat medium reaches high temperature and high pressure states at a threshold point or higher by means of the heat exchange. In addition, the working medium is a liquid metal.