An exhaust heat recovery apparatus includes a first piston; a second piston; a first cylinder in which the first piston reciprocates; a second cylinder in which the second piston reciprocates; and a heat exchanger. The heat exchanger includes a heater that is independently shiftable with respect to at least one of the first cylinder and the second cylinder, and has one end portion arranged at a side of the first cylinder and receiving heat from heat medium, a regenerator that is arranged at a side of another end portion of the heater, and a cooler that has one end portion arranged at a side of the regenerator and another end portion arranged at a side of the second cylinder.

Stirling engine which may be used as a heat pump, which consists of a hot half and a cold half. Both halves are connected by two lines which constitute a counterflow heat exahnger or in which a counterflow heat exchanger is mounted. Moreover, a mutual shaft, to which in the hot half a large and a small piston are mounted and to which in the cold half a large and a small piston are mounted, connects both parts. For every up or down going movement of the shaft, a complete Stirling cycle is performed. If desired, the shaft may be replaced by a hydraulic interconnection.

An exhaust heat recovery apparatus (functioning as a Stirling engine), which is installed in, for example, an exhaust passage of an internal combustion engine and an exhaust passage of factory exhaust heat as restraining reduction in exhaust heat recovery efficiency, is installed in a device installing surface formed in the heat medium passage so that the device installing surface and a heater connecting side end surface of a high temperature side cylinder become parallel and the device installing surface and a cooler connecting side end surface of a low temperature side cylinder become parallel. The high temperature side cylinder is arranged at an upstream side of a direction of exhaust flow. The low temperature side cylinder is arranged at a downstream side of the high temperature side cylinder.

Systems and methods capable of producing electrical power from solar energy through the use of air cycles without fossil fuel combustion. The system includes a solar receiver, a generator, a compressor, and an expander. The expander is coupled to the generator to drive the generator and coupled to the compressor to drive the compressor. The system uses solar generated heat from the solar receiver to heat compressed air from the compressor. The solar generated heat can be directly transferred from the solar receiver to the compressed air as the compressed air flows through receiver tubes of the solar receiver, or the solar receiver can transfer the solar generated heat to a liquid metal, with the liquid metal transferring thermal energy to the compressed air. The expander receives and expands the heated compressed air to drive the generator to produce electricity, and to drive the compressor to compress air.

An external combustion engine comprises a mass of compressible working fluid; a fluidic piston in fluid communication with the working fluid; and a second piston in hydraulic communication with the fluidic piston and in fluid communication with the working fluid.