Conceptual design of a novel sustainable hybrid renewable energy system based on biogas/molten carbonate fuel cell/water desalination for a building energy supply

To ensure an independent and sustainable energy supply, including electricity, drinking water, hot water, heating, and cooling for a 4-floor building in Bandar Dayyer, located in the south of Iran, a novel hybrid renewable energy system consisting of biogas/molten carbonate fuel cell/water desalination was proposed. With a hydraulic retention time of 15 days and a temperature of 55 °C in the digester section, the daily methane production reached 16,000 L. A power output of 98 kW was achieved with the fuel cell operation at a temperature of 650 °C. Additionally, 1137.4 kg of fresh water was produced daily to meet the consumption needs and the reformer's water requirements. The amounts of CO2 produced in the combustion chamber and the fuel cell were 43.93 and 23.3 kg/h, respectively. The gas composition analysis indicated a CO2 output of 4 %. The hybrid system's overall energy and exergy efficiency were 54 % and 52.58 %, respectively. This system demonstrates outstanding performance as a sustainable renewable energy system, providing reduced waste production and electricity, drinking water, hot water, heating, and cooling while exhibiting favorable environmental impacts with limited greenhouse gas emissions.