Evaluation of the Performance of a Micro Gas Turbine Cogeneration System in a Sewage Treatment Facility: Optimized Configuration of a Cogeneration System

In this study, efficient configuration of a biogas-fuelled cogeneration system (CGS) in a sewage treatment facility was investigated. The efficient configuration of the CGS was clarified on the basis of the relationship between exhaust heat recovery efficiency (eta(ehr)) of the CGS and the ratio of yearly average heat demand to yearly average biogas production of the facility (Q(h.d) /Q(b.p)). The CGS was assumed to be used under Q(h.d) /Q(b.p) < eta(ehr), Q(h.d) /Q(b.p) approximate to eta(ehr), and Q(h.d) /Q(b.p) >eta(ehr) conditions. It was found that although the CGS was able to cover total heat demand of the facility by only consuming biogas produced, from the point of view of energy utilization, reduction of unutilized biogas and reduction of electricity demand efficiencies, the most efficient CGS was obtained under the Q(h.d) /Q(b.p) approximate to eta(ehr) condition. Under the Q(h.d) /Q(b.p) approximate to eta(ehr) condition, energy utilization, reduction of unutilized biogas, and reduction of electrical demand efficiencies were 0.64, 0.99, and 0.32, respectively, whereas under the Q(h.d) /Q(b.p) <eta(ehr) and Q(h.d) /Q(b.p) >eta(ehr) conditions, energy utilization, reduction of unutilized biogas, and reduction of electrical demand efficiencies were in ranges of 0.56-0.64, 0.43-0.99, and 0.16-0.20, respectively. A more efficient system can be obtained if a CGS with lower.ehr such as a fuel cell is used under the Q(h.d) /Q(b.p) <eta(ehr) condition and if a CGS with higher eta(ehr) such as a steam turbine is used under the Q(h.d) /Q(b.p) >eta(ehr) condition. (C) 2011 Wiley Periodicals, Inc.