Thermodynamic Optimization of a Biogas Engine Powered Cogeneration System with Using Genetic Algorithm

In this study a genetic algorithm based thermodynamic optimization of biogas engine powered cogeneration system that is active in GASK？ WWTP and produce electricity from biogas which is produced in plant will be presented. In this purpose, we will develop our own code that is suitable to characteristics of system, by using MATLAB software. Biogas engine powered cogeneration system produces 1000 kW electricity and supplies heat for anaerobic digestion. The focus of optimization will be on exergetic efficiencies of heat exchangers and overall system. Optimization variables are selected as output temperature of water that flow from digestion throught engine-side heat exchanger, its mass flow rate and temperature of water that transfer heat from engine to heat exchanger. Optimization is applied with using elitism and roulette wheel methods seperately, also single point mutation is applied. By using elitism and roulette wheel, exergetic efficiency of heat exchanger-1 found respectively 32,2 % and 39,1 %. Exergetic efficiency of heat exchanger-2 for both two methods found 59,5%. By using elitism and roulette wheel, exergetic efficiency of exhaust gas heat exchanger found respectively 47,7 % and 41%. Exergetic efficiency of overall cogeneration system obtained 26,4 % by using elitism and 26,1 % by using roulette wheel. These results discussed according to effects of variables by using graphs