Closed loop scroll expander engine

An engine for converting heat into mechanical output using a working fluid in a closed circulating system, the engine comprising:

• at least one pump for pressurizing the fluid from a first pressure to a second pressure, wherein the second pressure is higher than the first pressure;
• a heat receiving portion of a regenerative heat exchanger;
• said heat receiving portion configured to receive the fluid from said pump said regenerative heat exchanger configured to add heat to the fluid;
• a heating device to supply additional heat to the fluid to raise the fluid to a desired working temperature substantially above its critical temperature;
• at least one expansion device, having an inlet connected to the heating device, to generate the mechanical output through the expansion of the working fluid from the inlet to an outlet of the expansion device;
• a heat transmitting portion of said regenerative heat exchanger configured to receive the expanded working fluid from the outlet of said expansion device and pass it therethrough;
• a condenser connected between an outlet of said heat transmitting portion of said regenerative heat exchanger and said at least one pump to reduce said fluid temperature to a low cycle temperature;
• and
• a power control valve to adjust the mechanical output of the engine by adjusting a mass flow of the working fluid in the closed circulating system;
• wherein the at least one pump is adapted to compensate for the adjustment of the mass flow rate by maintaining the second pressure in a specified range.

A method of converting heat into mechanical output using a working fluid in a closed circulating system, comprising:

• supplying said fluid at a low cycle temperature;
• raising the pressure of said fluid with a pump from a first pressure to a second pressure;
• adding heat to said fluid at substantially its second pressure to raise said fluid to a high cycle temperature substantially above its critical temperature;
• expanding said fluid in at least one expansion device to generate the mechanical output and reduce said fluid pressure;
• cooling said fluid substantially down to its low cycle temperature;
• transferring a major portion of the heat contained in the expanded fluid to the pressurized fluid using a regenerative heat exchanger during the cooling process;
• controlling the mechanical output of the engine by regulating a mass flow rate of the working fluid;
• and
• maintaining the second pressure in a specified range wherein said pump is able to compensate for adjustments to the mass flow rate of said fluid by maintaining the second pressure in a specified range.