A constant density heat exchanger and method of operating are provided. The constant density heat exchanger includes a housing extending between a first end and a second end and defining a chamber having an inlet and an outlet. A first plate is positioned at the first end of the housing and rotatable about an axis of rotation such that the first plate selectively allows a working fluid to flow into the inlet of the chamber. A second plate is positioned at the second end of the housing and rotatable about the axis of rotation such that the second plate selectively allows the working fluid to flow out of the outlet of the chamber. The first plate and the second plate are rotatable about the axis of rotation so as to hold a volume of the working fluid at constant density as a heat source imparts thermal energy thereto.

Systems and methods are disclosed to recover waste heat from an engine fluid with a heat exchanger subsystem that includes a heat exchanger. The heat exchanger subsystem is thermally coupled to a working fluid and the engine fluid, so the waste heat from the engine fluid is transferred to the working fluid. The engine fluid is bypassed from the heat exchanger in response to a heat exchanger bypass condition.

Systems and methods are disclosed to recover waste heat from an engine fluid with a heat exchanger subsystem that includes a heat exchanger. The heat exchanger subsystem is thermally coupled to a working fluid and the engine fluid, so the waste heat from the engine fluid is transferred to the working fluid. The engine fluid is bypassed from the heat exchanger in response to a heat exchanger bypass condition.

The present invention provides a heat medium circulation structure for a micro-combined heat and power (micro-CHP) generator in which a heat medium that primarily looses heat by undergoing heat exchange with water in a hot-water tank and thus has a low temperature further performs heat exchange with low-temperature direct water supplied through a direct water line, thereby further loosing heat, in a return line heat exchanger, and then returns to a stirling engine through a heat medium return line, thereby effectively cooling a low temperature portion of the stirling engine. Thus, the heat medium circulation structure enables high electricity production efficiency. Further provided is a hot water temperature control method for a micro-CHP generator in which the consumption of hot water is detected by a flow sensor. First and second predetermined temperatures are defined to operate a stirling engine in the case of temperature droppings of hot water respectively due to natural radiation and consumption of hot water.

The present invention provides a heat medium circulation structure for a micro-combined heat and power (micro-CHP) generator in which a heat medium that primarily looses heat by undergoing heat exchange with water in a hot-water tank and thus has a low temperature further performs heat exchange with low-temperature direct water supplied through a direct water line, thereby further loosing heat, in a return line heat exchanger, and then returns to a stirling engine through a heat medium return line, thereby effectively cooling a low temperature portion of the stirling engine. Thus, the heat medium circulation structure enables high electricity production efficiency. Further provided is a hot water temperature control method for a micro-CHP generator in which the consumption of hot water is detected by a flow sensor. First and second predetermined temperatures are defined to operate a stirling engine in the case of temperature droppings of hot water respectively due to natural radiation and consumption of hot water.

A radiation thermal absorber based on characteristic absorption spectrum, a Stirling engine and an operation method thereof. The radiation thermal absorber allows working gas in the Stirling engine to absorb radiation heat quickly, and help the Stirling engine adopt assistant heating to ensure steady operation when solar power is not enough. The radiation thermal absorber includes a heater base, a radiation energy conversion device, heating tubes, a combustion chamber and valves of the heating tubes. The radiation energy conversion device converts the solar energy into radiation energy near a characteristic absorption peak of the working gas, and the working gas absorbs the radiation directly in depth.

A radiation thermal absorber based on characteristic absorption spectrum, a Stirling engine and an operation method thereof. The radiation thermal absorber allows working gas in the Stirling engine to absorb radiation heat quickly, and help the Stirling engine adopt assistant heating to ensure steady operation when solar power is not enough. The radiation thermal absorber includes a heater base, a radiation energy conversion device, heating tubes, a combustion chamber and valves of the heating tubes. The radiation energy conversion device converts the solar energy into radiation energy near a characteristic absorption peak of the working gas, and the working gas absorbs the radiation directly in depth.

A near isothermal machine for compressing or expanding gas having a piston in a main cylinder with a heat absorbing and releasing structure attached thereto. The main cylinder contains a substantially constant volume of liquid maintained at a substantially constant temperature and a variable volume of gas, the gas temperature being controlled to substantially the same temperature as the liquid by the movement with the piston of the heat absorbing and releasing structure. A compensator is provided to compensate for variations in the level of liquid as the piston moves in the main cylinder.

A near isothermal machine for compressing or expanding gas having a piston in a main cylinder with a heat absorbing and releasing structure attached thereto. The main cylinder contains a substantially constant volume of liquid maintained at a substantially constant temperature and a variable volume of gas, the gas temperature being controlled to substantially the same temperature as the liquid by the movement with the piston of the heat absorbing and releasing structure. A compensator is provided to compensate for variations in the level of liquid as the piston moves in the main cylinder.

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.