Use of Particle Heat Carriers in the Stirling Engine Concept

The Stirling engine has drawn new attention for its high efficiency and flexibility towards the application of different heat sources. A new Stirling engine application in a renewable energy combined heat and power (CHP) concept will be presented, in which powders are used as the heat carrier between the hot storage and the ultimate Stirling reuse. A fluidized bed of small particles (50-150m) is examined in this study. The outside heat transfer coefficient to the finned Stirling heat exchanger largely exceeds 1500Wm(-2)K(-1) at very low fluidization velocities, which is, therefore, not the heat transfer limitation. Positron emission particle tracking experiments demonstrated that the particle movement and mixing in the fluidized bed are not hampered by the presence of the finned heat transfer tube. As the Stirling engine can reach efficiencies in excess of 30% and has the potential to be integrated in a CHP mode of operation, it should be considered as a hot research topic in the renewable energy sector.