Energy, exergy, and economic analysis of a centralized solar and biogas hybrid heating system for rural areas

Abstract

Although solar energy and biogas have the advantages of clean and sustainable supply when used to drive heating systems, they still face major issues of intermittency, unstable fluctuations, and vulnerability to the environment. To make use of the advantages of solar energy and biogas and to improve the stability and economy of the system, a centralized solar and biogas hybrid heating system is proposed in this study to satisfy the demands in rural areas. First, the energy and exergy analysis mathematical model of the solar and biogas hybrid heating system was established. Then, the developed dynamic simulation model was compiled and constructed in the MATLAB/Simulink platform. The corresponding operation control strategy of the solar and biogas hybrid heating system is proposed. In addition, the energy and exergy performance of the solar and biogas hybrid heating system are calculated and analyzed by using the simulation model. Furthermore, the influence of system component capacity parameters on its thermodynamic performance is analyzed. Finally, the energy conservation and economy of the hybrid system and the single solar or biogas system are compared and discussed. The results show that the energy efficiency of the hybrid heating system is much higher than the exergy efficiency, reporting an energy efficiency of 29.7% and an exergy efficiency of 4.5%. In terms of the exergy losses in the system, the solar collector, the biogas digester, and the biogas boiler are the major contributors to such losses. In the case of limited biomass raw materials, the heating growth rate of the hybrid system is larger compared to a single solar or biogas system, where the proportion of renewable energy exceeds 95% in the hybrid system case. It was shown that the economic feasibility of the hybrid heating system is better than that of the conventional single solar heating system, with a reduction of around 50% in the payback period.