Combined heat and power generation from a stirling engine coupled with a fluidzed bed combustor

This work investigates the advantages of placing the hot side heat exchanger of a Stirling engine (SE) immersed in a Fluidized Bed Combustor (FBC). This choice is primarily suggested by the more efficient heat transfer between the multiphase fluidized bed medium and the heat exchanger, as compared with immersion in the flue gases. Moreover, the mechanical action of the solid particles reduces fouling, a typical problem of biomass combustion. In the model, the heat dissipated by the cooler of the SE and the exhaust gases heat are recovered to produce domestic hot water (DHW). A mathematical model, which couples the FBC and the SE, is developed and used to optimize design and operating conditions, with specific attention to the SE hot side heat exchanger. It is shown that placing the heat exchanger in direct contact with the fluidized bed can lead to an improvement of performance in terms of fuel utilization efficiency (FUE) and shaft power output.