Cogeneration of Heat and Electricity: A Comparison of Gas Turbine, Internal Combustion Engine, and MCFC/GT Hybrid System Alternatives

摘要

The purpose of this paper is to present the results of a feasibility study of the supply ofnelectricity and heat to a large user (i.e., a public hospital in Northern Italy) by means ofna molten carbonate fuel cell (MCFC) hybrid system in comparison with other technologies.nThe study investigated three alternative options in order to meet the user’s demand:ninternal combustion engine, gas turbine, and a hybrid system (molten carbonate fuel cellsnand gas turbine, MCFC-HS), which is currently under development by Ansaldo Fuel CellnLtd. and ENEA. The user requirement was the yearly supplies of 6.65 GWhe / year andn21.64 GWhth / year. Due to demand fluctuations over the year, integration by electric gridnand/or additional thermal boilers was also required and investigated. The approachnintegrates the usual mass balance with large scale material flow accounting, embodiednenergy analysis, exergy efficiency, and emergy synthesis, within a LCA perspective. Resultsnshow that the best performance from the point of view of energy and exergy efficiencynis shown by the MCFC-hybrid system. The latter is also characterized by thenlowest embodied energy demand and cumulative material demand as well as by thenlowest requirement for direct and indirect environmental support (emergy method). However,nthe small thermal energy supply of the MCFC-HS compared with the large thermalnneeds of the hospital calls for a larger use of the additional boiler. The latter devicenworsens the local-scale emissions of the system, compared with the other alternativesninvestigated. Results point out that a proper choice cannot only be based on the individualnperformance of an even well performing technological device, but also needs to bentailored on the system’s characteristics and dynamics, in order to adequately matchnsupply and demand.