Using photovoltaic thermal technology to enhance biomethane generation via biogas upgrading in anaerobic digestion

Highlights: • A biomethane production system based on photovoltaic thermal collectors is proposed. • The generated heat and electricity are reasonably used for digester and biogas upgrading unit. • The new design reduces the dependence on fossil fuel and electricity from power grid. • 86.08% more biomethane can be produced in the new design. Anaerobic Digestion (AD) is identified to be a promising method to address the dilemma of solid waste recycling, and biogas produced from AD has also been identified as an important alternative to fossil fuels, pertaining to energy crisis and climate change. As the applied technology of anaerobic digestion is fixed, required thermal energy for biogas production in an anaerobic digester varies dramatically with the ambient temperature. The conventional way is to combust the biogas on the spot for heat preservation in the digester, and the additional natural gas will be needed for supplement in colder area. To mitigate the consumption of fossil fuel and increase the amount of available biogas for bio-methane production, a hybrid system by integration of Concentrated PhotoVoltaic Thermal (CPVT) collectors and biogas upgrading technology is proposed. The heat produced from CPVT collectors is for heat preservation in the digester, and generated electric power is used in the biogas plant and biogas upgrading unit for bio-methane production. The annual performance analysis indicates that, comparing with the conventional design, the new design saves 2.6% amount of natural gas consumption, reduces 48.38% amount of electricity from power grid and increases 86.08% amount of biomethane production. Besides, the new design can supply 829.4 MWh electricity to the power grid in a year. This research provides a new way to utilize biogas by integration with solar utilization technologies.