Using anaerobic digestion of organic wastes to biochemically store solar thermal energy

Solar energy is the most abundant energy resource with the potential to become a major component of a sustainable global energy solution. However, unsteady energy flow and low energy density make it difficult to collect, convert, and store solar energy, which is why current solar power generation technologies have limited applications. This paper comprehensively studied the integration of solar thermal collection with different anaerobic digestion operations to form solar-bioreactor systems in order to realize biological storage of solar energy and solve the issues that solar energy generation encounters. The experimental comparison of manure digestion and co-digestion concluded that co-digestion had a better methane yields with a minimum difference between mesophilic and thermophilic conditions. The energy analysis of solar-bioreactor systems with both manure digestion and co-digestion at different bioreactor sizes further concluded that solar-bioreactor systems with mesophilic co-digestion was the preferred system to store solar energy into methane biogas. The optimal solar-storage efficiencies for the three systems of 10, 100, 1000 m3 were 67%, 68% and 70%, respectively. The corresponding solar-bioreactor system efficiencies were 82%, 88%, and 89%.