The reuse of the (waste) heat generated in heat engines or other industrial processes can make a significant contribution to increasing the efficiency of such processes and plants. One concept by which the conversion of process heat into high-level forms of energy can be represented is the Organic Rankine Cycle (steam turbine cycle) with embedded expander, with the aid of which process heat is converted into electrical energy via a generator. In this project, a wing piston expansion engine is used; the aim of the STEAM, together with the partner Mahle König, is a new development of the expansion engine for the 30-60 kW power class and operation with water as the working medium.

Within the Mahle König wing piston expander two wing-type pistons are rotating with cyclically changing rotation speed relative to one another in one single housing. This way, the four resulting working chambers are changing their volume, leading to expansion and compression of the working medium. This technical solution allows the partial conversion of the enthalpy stored in the working medium into mechanical work. The conversion of the even rotation speed into a cyclically changing rotation is realized via a non-circular gear. This leads to a relative movement of the two rotors.