Proposal and assessment of a novel integrated CCHP system with biogas steam reforming using solar energy

The conventional way to utilize biogas either is energy-intensive due to biogas upgrading or causes huge waste of energy grade and environmental pollution by direct burning. This paper proposes a biogas and solar energy-assisted combined cooling, heating and power (BSCCHP) system that upgrades the caloric value of biogas before combustion by introducing a thermochemical conversion process that is driven by solar heat. Adopting commercially established technologies including steam reforming and parabolic dish concentrators, the system exhibits an enhanced system exergy efficiency, and the technology considerably reduces the direct CO2 footprint and saves depletable fossil fuel. With a solar thermal share of 22.2%, the proposed system not only has a high net solar-to-product thermal and exergy efficiency of 46.80% and 26.49%, respectively, but also results in a commensurate 18.27% reduction of the direct CO2 footprint compared with the reference individual systems. The effect of critical parameters in the biogas steam reforming process on the system performance was studied. A proper selection of the steam/carbon ratio leads to the optimal direct CO2 footprint and system exergy efficiency. Pursuing a very high conversion of biogas by improving the reforming temperature is not a wise choice from a system perspective. Finally, a typical-day dynamic simulation was conducted to preliminarily explore the general operation features. This study may provide a new way to efficiently use the renewable energy in the distributed energy system.