Dual-combustion chamber cycle utilizing biomass and geothermal energy: A comprehensive economic analysis and multi-objective optimization for enhanced multi-generation

This paper proposes a novel multi-generation system comprising a digester, a gasifier, a geothermal unit, a Kalina cycle, a multi-effect desalination, a flash desalination, and an organic flash cycle. Energy, exergy, and exergoeconomic analyses are performed for the system, yielding a second law efficiency of 31.97 %, total power generation of 5416 kW, a heating rate of 584.6 kW, cooling rate of 25.34 kW, freshwater production of 72.36 kg/ s, and total exergy destruction of 12,273.44 kW. The highest exergy destruction occurs in the multi-effect desalination subsystem at 4546 kW (37 % of the total), followed by the digester at 2798.26 kW (22.9 % of the total). The unit exergy cost of the system products is calculated as $31.88/GJ. With a freshwater price of $1.5/m3 and an electricity price of $ 0.14/kWh, the payback period is obtained as 5.44 years. Using the Gray Wolf algorithm, multi-objective optimizations are performed for two scenarios resulting in optimal values for the first scenario with 33.54 % second law efficiency, 6538 kW power generation, and 75.56 kg/s freshwater production. For the second scenario, the second law efficiency is 33.96 %, with a power output of 6398 kW and a total unit exergy cost of the products amounting to $33.59/GJ.