A thermoacoustic energy conversion system includes a closed circumferential encasing filled with a working fluid through which an acoustic wave can propagate in a propagation direction in use of the system, and at least one assembly of two heat exchangers with a regenerator sandwiched there-between arranged in said encasing. The at least one assembly is arranged substantially parallel to a local longitudinal axis of the encasing.

A thermoacoustic energy conversion system includes a closed circumferential encasing filled with a working fluid through which an acoustic wave can propagate in a propagation direction in use of the system, and at least one assembly of two heat exchangers with a regenerator sandwiched there-between arranged in said encasing. The at least one assembly is arranged substantially parallel to a local longitudinal axis of the encasing.

A device for compressing a gaseous fluid includes a first chamber thermally coupled with a hot source, a second chamber thermally coupled with a cold source, a movable piston moved by a rod, and a regenerating exchanger establishing fluid communication between the first and second chambers. The rod is arranged in a cylindrical socket and guided in axial translation by a linear guiding system such as to guide the piston without contact relative to the sleeve. A sealing ring attached to the cylindrical socket surrounds the rod with a very low radial clearance, in order to limit the passage of the gaseous fluid along the mobile rod. Also disclosed is an integral cold casing having machined boreholes, a thermal screen in the hot casing, and a self-driving system with a resilient return means.

A device for compressing a gaseous fluid includes a first chamber thermally coupled with a hot source, a second chamber thermally coupled with a cold source, a movable piston moved by a rod, and a regenerating exchanger establishing fluid communication between the first and second chambers. The rod is arranged in a cylindrical socket and guided in axial translation by a linear guiding system such as to guide the piston without contact relative to the sleeve. A sealing ring attached to the cylindrical socket surrounds the rod with a very low radial clearance, in order to limit the passage of the gaseous fluid along the mobile rod. Also disclosed is an integral cold casing having machined boreholes, a thermal screen in the hot casing, and a self-driving system with a resilient return means.

A thermal regenerator apparatus is disclosed including a regenerator medium having a plurality of flow passages extending between first and second ports, the flow passages facilitating back and forth fluid flow in a generally transverse direction between the first and second ports while the medium alternatively receives thermal energy from and delivers thermal energy to the fluid. The regenerator medium includes a plurality of overlying foils, each foil having a plurality of channels extending through the foil, the channels having beveled sidewalls. The channels have a width and spacing in the transverse direction and channels in each adjacent overlying foil are transversely offset such that each channel spans between and is in fluid communication with a pair of channels in the adjacent foils and the beveled sidewalls of the channels redirect fluid flow between channels in adjacent foils to form the flow passages. The channels are elongated along the foil in a longitudinal direction orthogonal to the transverse direction and divided by foil bridges extending transversely, the foil bridges being sized to reduce thermal conduction through the medium in the transverse direction.

A thermal regenerator apparatus is disclosed including a regenerator medium having a plurality of flow passages extending between first and second ports, the flow passages facilitating back and forth fluid flow in a generally transverse direction between the first and second ports while the medium alternatively receives thermal energy from and delivers thermal energy to the fluid. The regenerator medium includes a plurality of overlying foils, each foil having a plurality of channels extending through the foil, the channels having beveled sidewalls. The channels have a width and spacing in the transverse direction and channels in each adjacent overlying foil are transversely offset such that each channel spans between and is in fluid communication with a pair of channels in the adjacent foils and the beveled sidewalls of the channels redirect fluid flow between channels in adjacent foils to form the flow passages. The channels are elongated along the foil in a longitudinal direction orthogonal to the transverse direction and divided by foil bridges extending transversely, the foil bridges being sized to reduce thermal conduction through the medium in the transverse direction.

Multiple free-piston stirling-cycle machine modules are connected together in double-acting configurations that may be used as engines or heat pumps and scaled to any power level by varying the number of modules. Reciprocating piston assemblies oriented in balanced pairs reduce vibration forces. There are no buffer spaces. Linear motors or generators are packaged inside piston cavities entirely within the module working spaces. The external heat-accepting and heat-rejecting surfaces in one embodiment are directed along inward-facing and outward facing cylinders, and in another embodiment along parallel planes, simplifying thermal connections to the external heat source and sink.

A system for energy conversion, the system including a closed cycle engine containing a volume of working fluid, the engine comprising a first chamber defining an expansion chamber and a second chamber defining a compression chamber each separated by a piston attached to a connection member of a piston assembly, and wherein the engine comprises a heater body in thermal communication with the first chamber, and further wherein the engine comprises a cold side heat exchanger in thermal communication with the second chamber, and wherein a third chamber is defined within the piston, wherein the third chamber is in selective flow communication with the first chamber, the second chamber, or both.

A system for energy conversion, the system including a closed cycle engine containing a volume of working fluid, the engine comprising a first chamber defining an expansion chamber and a second chamber defining a compression chamber each separated by a piston attached to a connection member of a piston assembly, and wherein the engine comprises a heater body in thermal communication with the first chamber, and further wherein the engine comprises a cold side heat exchanger in thermal communication with the second chamber, and wherein a third chamber is defined within the piston, wherein the third chamber is in selective flow communication with the first chamber, the second chamber, or both.

An improvement is provided to a pressurized close-cycle machine that has a cold-end pressure vessel and is of the type having a piston undergoing reciprocating linear motion within a cylinder containing a working fluid heated by conduction through a heater head by heat from an external thermal source. The improvement includes a heat exchanger for cooling the working fluid, where the heat exchanger is disposed within the cold-end pressure vessel. The heater head may be directly coupled to the cold-end pressure vessel by welding or other methods. A coolant tube is used to convey coolant through the heat exchanger.