Two-Phase Anaerobic Digester Combined with Solar Thermal and Phase Change Thermal Storage System in Winter

Using solar energy as the heat source for biogas improvement of the anaerobic digester is an effective method. However, intermittent solar radiation and low ambient temperature in-the winter make it, difficult,to maintain a steady fermentation temperature. In this study, a pilot-scale two-phase anaerobic digester combined-with solar thermal and phase change thermal storage (PCTS) system has been constructed, A set of comparative field studies were carried out during the winter in Maanshan City, Anhui Province, China; these periods of study,included,no heating mode (P1), heated with solar thermal and PCTS system (P2), and conventional solar heating Mode (P3). The comparison shows that Methane yields and the energy conversion rate of the substrates of P2 were 12.33 m(3) and 48.6%, respectively, both of which increased by 5.65 and 1.01 times, compared with that of P1 and P3, respectively. The statistical coefficients of variation for the fermentation-temperature were 2.5% in P2 and 6.6% in P3, which means that the PCTS system supplied heat with less temperature fluctuation when solar radiation was weak.