In a biogas power plant from waste heat power generation system using Organic Rankine Cycle and multi-criteria optimization

Increasing energy consumption, rapid population growth, and technological developments have increased the need for energy demand day by day. At the point of meeting this need, renewable energy is an important alternative resource that can replace rapidly exhaustible fossil fuels. There are many renewable energy sources such as sun, wind, hydrogen, geothermal, and biogas. Biogas, one of the most important renewable energy sources, is mainly used as fuel in combined heat-power (CHP) engines/gas engines and transformed into electrical energy. However, the efficiency of these engines is low owing to the fact that a considerable amount of the energy that enters with the combustion of biogas is thrown into the atmosphere as exhaust gas. In this context, the recovery of the waste heat of 26 gas engines with a temperature of 475–500 °C in the Silivri region of Istanbul and producing biogas from household wastes was studied. Calculate the waste heat values according to the exhaust gas flow, temperature, and pressure values to be taken from the chimney outlet of the gas engines in the facility. Subsequently, the determination of the parameters of the ORC (Organic Rankine Cycle) and the optimum consumption values of the equipment in the whole system in the loop as well as the optimum ORC mechanical power will help manage and optimize the electricity production. •ORCs are mostly preferred in low and medium-temperature areas and whose applications are fed from a single source such as geothermal heat within the earth. Accordingly, the waste heat from the exhaust gas of 26 separate gas engines in a biogas power plant. The exhaust gas can reach a high temperature up to 500 °C that can be reused to optimize the energy system.•The optimum and critical operation points for the pressure, flow rate, and temperature values measured from the exhaust gas of gas engines can be determined. Hence, conducting an optimization model utilizing DWSIM (process simulator) will show the effect of the optimum solutions on the performance of the ORC.•It will be shown that conducting a thermodynamic and energy conversion analysis is important to design an optimum system. This optimized system will help to provide more net power output and efficiency in terms of numerical values.•The energy system will also be studied regarding the following points:oEvaluating the exhaust gas released into the atmosphere in the waste heat energy production unit and the biogas facility.oCalculating the efficienc