Non-combustion non-solar deployment characterization of a free-piston Stirling engine to integrate with an exothermic reactor

Background: A small 1 kW free-piston β type Stirling engine was tested for its feasibility of integration with an exothermic reactor under the EU funded research project SOCRATCES (GA 727348). The engine’s heat receptor was minimally modified to adapt it to the reactor’s integration needs, introducing, instead of a combustion chamber, a CFD-optimized hooded enclosure. The open-loop configuration also included a small plate heat exchanger acting as a recuperator. The study attempted to investigate the performance of the Stirling engine under these non-combustion non-solar deployment conditions, focusing on conversion efficiency and thermal loss. Methods: A number of tests were run under different temperatures and flowrates to assess the engine’s response. Temperature, power, pressure and flowrate were measured at points of interest. Results: It was found that the engine is able to operate at efficiencies comparable to that of gasoline engines at much lower working fluid temperatures. It was possible to demonstrate, with the aid of a downstream recuperator, that the system in an open-loop configuration can minimize thermal loss significantly, virtually eliminating it in some cases. Conclusions: The Stirling engine appears to be a sound choice, in terms of conversion efficiency, at comparatively low temperatures, to be integrated with an exothermic reactor, at least at small-scale applications.

Thermodynamic modeling and controlling of a combined Free Piston Stirling Engine System (FPSE) with a Permanent Magnet Linear Synchronous Machine (PMLSM)

Converting thermal energy to electricity is one of the most common energy conversions in the field of electricity production. This transformation of energy is essential for both renewable and non-renewable heat sources. One of the main parameters of such a system that is responsible for this conversion is its efficiency. To have an efficient transformation, many improvements have been made to the old methods, and also new techniques were developed. One of these new methods that will be discussed here is a combined system of a Free Piston Stirling Engine (FPSE) with a Permanent Magnet Linear Synchronous Machine (PMLSM). The two purposes of presenting such a system are that firstly, the theoretical efficiency of a Stirling engine is high. Secondly, by eliminating crank-shaft from this system compared to the standard Stirling engine system, some of the losses will be removed. To study this system, a thermodynamic model of a RE-1000 FPSE was presented and validated. Then it was coupled with a PMLSM, and the combined system was controlled. The total efficiency of this system in steady-state is 14.4%.