Optimal Unit Sizing of Biogas-Fuelled Micro Gas Turbine Cogeneration Systems in a Sewage Treatment Plant

This paper investigates the optimum size of Micro Gas Turbine Cogeneration Systems (MGT-CGSs) in a sewage treatment plant in relation to its economic performance. A sewage treatment plant in a cold region was adopted as a model, and three units of MGT-CGS with power output capacity of 30, 65 and 200kW were simulated to utilize biogas produced in-house in the plant. The energy balance of the system was first studied, and economic performance using Net Present Value method was carried out. It was found that a configuration with optimum combination of 3 types of MGTs (MGT-Combined) stated above had the highest power generation efficiency. However, MGTCombined needed more units of MGT resulting in higher capital investment. Although all configurations of MGTCGSs studied can generate Net Present Value (NPV) in the range of US$2,640,000-3,100,00, MGT-200 had the highest NPV. MGT-200 had 15% higher NPV compared to the lowest one, MGT-30. MGT-200 can generate the highest NPV because it had the lowest capital investment cost, while having high power cost savings. (C) 2015 The Authors. Published by Elsevier Ltd.