Experimental study on a 3 kWe free-piston Stirling engine-based combined heat and power system using a clean coal burner

• A combined heat and power system with high exergy effiency is proposed. • Based on a free-piston Stirling engine , the experimental facility is developed. • The effects of using coal as a fuel are studied for the first time in a field test . • The payback period of the system is significantly reduced. • The system’s CO 2 emissions are reduced by 16.8% versus conventional setup. Distributed energy systems have gained increased attention in recent years, due to their technical and economic benefits. Among them, the free-piston Stirling engine offers remarkable advantages such as compactness, high efficiency, and reliability. In this work, a distributed energy system comprising a 3 kWe free-piston Stirling generator and utilizing a clean coal burner as a heat source is proposed. The system is optimized based on one-dimensional steady state thermodynamic calculations using the software package of Engineering Equation Solver. Experiments are carried out to investigate the operational performance of the coal-fired free-piston Stirling engine based combined heat and power system. The field test results demonstrate a maximum power of 3200 We and a thermal efficiency of 67%. Overall, the maximum thermal-to-electric of the system is 16%. Additionally, the analysis of the internal energy flow showed that the maximum exergy efficiency of the system is 20%, revealing a potential for further optimization. The findings of this study demonstrate the feasibility of developing a cost-effective and efficient off-grid energy supply system based on free-piston Stirling engine technology while employing clean coal burners as the heat source.