Patent ID: 7690199

Claim:
A method for generating electrical energy using a thermal cycle of a working gas, the method comprising: using the motions of a first permanent magnet attached to a first piston in a cylinder and a second permanent magnet attached to a second piston in the cylinder, the cylinder containing the working gas performing the thermal cycle, to electromagnetically induce current in a set of windings of an electrical circuit coupled to the cylinder, the electrical circuit comprising an electronic power converter; using compression and expansion of the working gas between the first piston and the second piston to perform the thermal cycle; using the electrical circuit to store the electrical energy, produced by the current induced in the electrical circuit, in an electrical storage device; and using the electrical energy stored in the electrical storage device to electromagnetically provide motive force to the first piston and the second piston; the cyclically using the electrical circuit to store the electrical energy and using the stored energy to provide motive force to the first piston and the second piston effecting a net positive average power transfer into the electrical storage device over the course of the thermal cycle; and the thermal cycle receiving heat from an external heat source thermally coupled to the cylinder through at least one heat transfer zone of the cylinder; the at least one heat transfer zone of the cylinder comprising a heating zone of the cylinder and a cooling zone of the cylinder, the method further comprising using the motions of the first piston and the second piston to move the working gas along the cylinder to effect successive heat transfer of the working gas across the wall of the heating zone of the cylinder and across the wall of the cooling zone of the cylinder, the motions of the first piston and the second piston moving the working gas successively past and away from each of the heating zone of the cylinder and the cooling zone of the cylinder, the working gas being constrained by the motions of the first piston and the second piston from directly transferring heat between the heating zone of the cylinder and the cooling zone of the cylinder when the working gas is moved past and away from each of the heating zone of the cylinder and the cooling zone of the cylinder; and using the electronic power converter to perform closed-loop electronic control of the motions of the first piston and the second piston to constrain the working gas to follow as closely as possible any desired path in the pressure-volume plane, the electronic control of the motions of the first piston and the second piston permitting variation of the amount of time spent by the working gas in each segment of the pressure-volume cycle; the method using electrical storage of cyclical energy flow to and from the thermal cycle.