Multiobjective Optimization of Micro-Gas Turbines Environmental Polluting Emissions Due to their Internal and External Thermal Losses

Abstract

The ever-increasing demand for energy worldwide is hurting our environment, especially global warming. This is due to the significant use of fossil fuels. Faced with this situation, research and innovation actions are directed toward reducing these emissions by various scientific solutions including the multi-objective optimization of thermal machines. Among these thermal machines, one can mention the micro-gas turbines. Indeed, internal and external heat transfers are made in these machines because of their small size. These heat transfers contribute to degrading their performances in particular their environmental discharges that increase brutally. The present study aims at applying the eco-design methodology to these machines to evaluate their actual performances according to the heat transfers and to improve them. For this study, a thermodynamic model coupled with an environmental and economic model that describes the global behavior of micro-gas turbines has been performed. This model, operating in two modes adiabatic and polytropic to appreciate the deviations, gives good results that agree with those of the literature. The model was then optimized in a multi-objective way by Genetic Algorithms (NSGA IIb) giving a set of Pareto optimal solutions. The ideal solutions’ selection was done by applying the TOPSIS multi-criteria decision-making technique and gave the following results in polytropic operation: net power: 858.4 kW; global warming potential: 0.9561 kg CO₂/kWh and the estimated production cost of US$4256/hr. This ideal solution was subsequently analyzed by OpenLCA software to evaluate the whole environmental impacts characterized mainly by HTP (kg C₆H₆/kWh): 0.356; EP (kg PO₄^3-/kWh): 0.525; PCOP (kg C₂H₄/kWh): 0.295; AP (kg SO₂/kWh): 0.356.