A free piston apparatus includes a piston receptacle in which a piston device having a piston is reciprocable along an axis. The piston receptacle includes or forms a chamber delimited by a wall arrangement forming an inlet opening and an outlet opening. A cooling device is arranged on the piston receptacle for cooling the wall arrangement. The cooling device includes or forms a cooling channel arranged radially outside on the wall arrangement. The cooling channel has first and second cooling regions axially on opposing sides of the outlet opening. The piston receptacle includes or forms an outlet chamber, arranged outside on the wall arrangement, for exhaust gas exiting via the outlet opening. The cooling channel has a third cooling region which flow-connects the first cooling region and the second cooling region along the outlet chamber and is positioned at least in sections radially outside of the outlet chamber.

A fluid cylinder includes an outer cylinder surrounding expandable intermediate and inner cylinders. A first sealed volume is defined between the outer cylinder and the intermediate cylinder, a second sealed volume is defined between the intermediate cylinder and the inner cylinder and a third volume defined within the inner cylinder. The first sealed volume is held at a lower pressure than the second and third volumes. At upper heights of the intermediate and inner cylinders, the pressures of the second and third volumes are approximately equal. Exerting a downward force on a linkage connected to a top end of the inner cylinder results in changes in pressure-volume relationships, causing the intermediate cylinder to fall and, upon release of the downward force, causing the intermediate and inner cylinders to rise again to their upper heights. The reciprocal motion generated can be harnessed for various purposes.

A combined heat and power microgrid system is provided that stores energy in the form of compressed air that can then be utilized as needed in the form of electricity. The compressed air may be generated with energy from multiple electrical energy sources, such as renewable energy sources. The energy stored as compressed air/heat is used to charge a battery by utilizing a pulley system and a barrel housing that transfers kinetic energy generated by the release of the compressed air to an array of piezoelectric generators that can produce electricity, which is stored in the second battery. In addition, water may be extracted from the compressed air storage tank. In this way, energy produced by the renewable sources can be accessed during periods of high need or low production and water may be collected.

A homogeneous charge compression ignition free-piston linear generator is disclosed. The linear generator includes a housing having cylinders at opposite ends. A double-ended piston assembly is to move linearly in the housing to convert kinetic energy of the piston assembly into electrical energy, and to enable conversion of electrical energy into kinetic energy of the piston assembly. Sensors measure one or more states of the cylinders and/or piston assembly, and a controller controls the linear generator based on the sensor data.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a first stroke from one end to another. The first stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion. The non-expansion stroke portion may include a scavenging phase. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

Provided is a power generation system with which it is possible to perform efficient power generation. The power generation system comprises: an evaporation chamber; a reciprocal heat-insulating cylinder provided with a forward-side expansion chamber and a backward-side expansion chamber; an operating fluid supply/ejection means which performs a supply flow passageway forming operation and an ejection flow passageway forming operation in an alternating and reciprocal manner; a heat-insulating expansion chamber; a liquefied operating fluid recirculating means; and a compression/liquefaction recirculating means. The heat-insulating expansion chamber may be provided separately on both the ejection flow passage downstream side of the forward-side expansion chamber and on the ejection flow passage downstream side of the backward-side expansion chamber.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a method and system are provided for displacing a free-piston assembly to achieve a desired engine performance by repeatedly determining position-force trajectories over the course of a propagation path and effecting the displacement of the free-piston assembly based, at least in part, on the position-force trajectory. In a dual-piston assembly free-piston engine, synchronization of the two piston assemblies is provided.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a method and system are provided for displacing a free-piston assembly to achieve a desired engine performance by repeatedly determining position-force trajectories over the course of a propagation path and effecting the displacement of the free-piston assembly based, at least in part, on the position-force trajectory. In a dual-piston assembly free-piston engine, synchronization of the two piston assemblies is provided.

Provided is a power generation system with which it is possible to perform efficient power generation. The power generation system comprises: an evaporation chamber; a reciprocal heat-insulating cylinder provided with a forward-side expansion chamber and a backward-side expansion chamber; an operating fluid supply/ejection means which performs a supply flow passageway forming operation and an ejection flow passageway forming operation in an alternating and reciprocal manner; a heat-insulating expansion chamber; a liquefied operating fluid recirculating means; and a compression/liquefaction recirculating means. The heat-insulating expansion chamber may be provided separately on both the ejection flow passage downstream side of the forward-side expansion chamber and on the ejection flow passage downstream side of the backward-side expansion chamber.

A fluid cylinder includes an outer cylinder surrounding expandable intermediate and inner cylinders. A first sealed volume is defined between the outer cylinder and the intermediate cylinder, a second sealed volume is defined between the intermediate cylinder and the inner cylinder and a third volume defined within the inner cylinder. The first sealed volume is held at a lower pressure than the second and third volumes. At upper heights of the intermediate and inner cylinders, the pressures of the second and third volumes are approximately equal. Exerting a downward force on a linkage connected to a top end of the inner cylinder results in changes in pressure-volume relationships, causing the intermediate cylinder to fall and, upon release of the downward force, causing the intermediate and inner cylinders to rise again to their upper heights. The reciprocal motion generated can be harnessed for various purposes.