Abstract
An efficient configuration method of a biogas-fuelled cogeneration system (CGS) in a sewage treatment center was investigated in this study. The efficient configuration was clarified by classifying a relationship between exhaust heat recovery efficiency (η_<ehr>) of the micro gas turbine COS, and the ratio of average heat demand to average biogas production of the facility (Q_<h.d/Q_<b.p>). It was found that the CGS can cover the total heat demand of the facility by only using biogas produced in any conditions, but on the point of view of reduction of unutilized biogas efficiency, biogas energy recovery efficiency and reduction of electrical power demand efficiency, the most efficient CGS was obtained under Q_<h.d>/Q_<b.p> 〓 η_<ehr> condition. If a CGS with lower η_<ehr> such as a fuel cell is used under Q_<h.d/Q_<b.p> < η_<ehr> condition, or a CGS with higher η_<ehr> such as a steam turbine is used under Q_<h.d/Q_<b.p> < η_<ehr> condition, more efficient system can be obtained. On the other hand, if η_<ehr> cannot be conformed with the Q_<h.d/Q_<b.p> value of the facility, more efficient energy system can be obtained if other heat supplier equipment such as a heat pump is used under the Q_<h.d/Q_<b.p> > η_<ehr> condition, and other biogas or heat utilization pathways are used under the Q_<h.d/Q_<b.p> < η_<ehr> condition.
