Use of Particle Heat Carriers in the Stirling Engine Concept

• Published in: Energy technology (Weinheim, Germany) Vol. 4; no. 3; pp. 401 - 408
• Main Authors: Zhang, Huili, Gowing, Tim, Degrève, Jan, Leadbeater, Thomas, Baeyens, Jan
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01-03-2016; Wiley Subscription Services, Inc
• Subjects: Carriers; CHP; Cogeneration; combined heat and power concept; Fluidization; Fluidized beds; heat carriers; Heat exchangers; Heat sources; Heat transfer; Heat transfer coefficients; Heat treatment; Particle tracking; Positron emission; Renewable energy; Stirling engines; Tubes
• ISSN: 2194-4288; 2194-4296
• DOI: 10.1002/ente.201500274

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 (50–150 μm) is examined in this study. The outside heat transfer coefficient to the finned Stirling heat exchanger largely exceeds 1500 W m−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.
Stirling engine rebirth: The vitality of the old Stirling engine will be restored in renewable energy recovery process. The figure illustrates the layout of the pilot‐scale Stirling engine with its hot cylinder head embedded at the bottom of the bubbling fluidized bed (BFB). Finned tubes are foreseen for heat extraction from the well‐mixed fluidized bed. The average BFB temperature is between 600 and 650 °C.