Multi-objective optimization of a novel offshore CHP plant based on a 3E analysis

Abstract

Abstract Recovering waste heat of gas turbines in order to power production and heat supply is one of the effective approaches in energy and environment management in offshore installations. In the present study, a gas turbine in the Draugen offshore platform was modeled and its exhaust waste heat was utilized to generate power through an ammonia-water cycle and supply the heat demand of the offshore facility. In order to optimize the combined heat and power system, pressure ratio, maximum temperature of gas turbine, heat source temperature of bottoming cycle, ammonia mass fraction, and boiler pressure were considered as the effective decision variables. At first, based on each of the objective functions including exergy efficiency, rate of carbon emissions, and payback period, the operating conditions were optimized by a genetic algorithm. Finally, the results of a multi-objective GA optimization were presented in which all three objective functions were simultaneously optimized. Based on the multi-objective function, the optimum values of pressure ratio, maximum temperature of gas turbine, heat source temperature of bottoming cycle, ammonia mass fraction, and boiler pressure were 21.94, 1359K, 605K, 37.73 bar, and 88.2%, respectively.