Integrated model of a biomass boiler coupled with a Stirling engine

Integration of a Stirling engine in a biomass boiler can be an interesting renewable alternative for the supply of heat and electricity in isolated homes located in areas where local biomass is available and during months when sunlight is low. Since this integration requires a careful coupling of the engine and boiler, an integrated model of these two devices is a relevant issue. In this case, a modular integrated model of a 25 kWth biomass pellet boiler, fire-tube with a cylindrical water jacket, coupled to a 1 kWe free piston Stirling engine is presented. To model the boiler, and take into account the location of the Stirling head, the zonal method was chosen, which allows estimating this temperature from an additional set of surrounding temperatures. For the Stirling engin, a model widely used to evaluate those engines was used. Various software tools have been used to integrate the model sequentially. The integrated model predicts the thermal and electrical production based on different opera-tion parameters, such as the boiler load in 5% fractions of its load from 50 to 100%. The obtained results, which will be validated with the experimental setup, show a maximum output of approximately 600 W for the engine and a decreasing tem-perature profile in the combustion chamber, as a function of the partial load.