Design and optimization of a combined heat and power system with a fluidized-bed combustor and stirling engine

In this study, a fluidized-bed biofuel system was integrated with a Stirling engine (SE) to create a combined heat and power (CHP) system with high energy efficiency. Methods for ensuring the stability of the SE and fluidized-bed combustion were investigated and implemented. The proposed design was tested experimentally, and the system successfully produced electricity from the heat of the flue gas generated during biomass combustion. The Taguchi method was employed to maximize the temperature of the fluidized bed by modifying three parameters: the sand height, air flow rate, and biomass feed rate. The biomass used in this study was discarded mushroom sawdust waste. The biomass feed rate was varied from 9.5 to 17 g/min, and the air flow rate was varied from 50 to 60 L/min. The integrated CHP system was found to yield 90−100 W of electric power and 1077.3 W of heat energy for producing hot water. The oxygen, carbon dioxide, carbon monoxide, and nitric oxide concentrations of the flue gas produced under the optimized system parameters were analyzed, and minimal emissions of carbon monoxide and nitric oxides, which are harmful gases, were discovered. In most experiments on SEs in the literature, liquid or gaseous fuels have been used to power the engine. However, this study successfully used solid biomass fuel to power a practical SE, thus widening the knowledge on the utilization of this renewable energy source for electricity generation. The results of this study indicate that the proposed CHP system is stable, clean, and efficient. This system potentially provides a solution for two problems, namely the disposal of mushroom sawdust waste and the eco-friendly generation of heat and electricity. Therefore, the proposed system is promising for green and sustainable power generation in the future.