Optimization of System Performance on a Biogas Cogeneration in a Sewage Treatment Center

An efficient configuration method of a biogas-fuelled cogeneration system (CGS) in a sewage treatment center was investigated. The efficient configuration was clarified by classifying a relationship between exhaust heat recovery efficiency (ηehr) of a micro gas turbine CGS, and the ratio of average heat demand to biogas production of the facility (Qh.d/Qb.p). It was found that on the point of view of biogas energy recovery, reduction of unutilized biogas and electrical power demand efficiencies, the most efficient CGS was obtained under Qh.d/Qb.p = ηehr condition. If a CGS with lower ηehr such as a fuel cell is used under Qh.d/Qb.p < ηehr condition, or a CGS with higher ηehr such as a steam turbine is used under Qh.d/Qb.p > ηehr condition, more efficient system can be obtained. On the other hand, suggestion for more efficient system when ηehr cannot be conformed to the Qh.d/Qb.p value was also presented