Parametric thermodynamic analysis and economic assessment of a novel solar heliostat-molten carbonate fuel cell system for electricity and fresh water production.

With the ever-rising paces of fuel consumption and CO emission, the urge for renewable energy resources is becoming a challenge in today's world; especially for Iran that has started to reduce its fuel subsidies. The need for electricity and fresh water in the southern coastal regions of the country is increasing with the increase in the population. The high solar radiation level in the region is a promising alternative to mitigate the fuel consumption of the conventional power or desalination plants by the solar thermal source through the concentrated solar technology. In addition, the CO emission of the aforementioned plants significantly diminishes by using the molten carbonate fuel cell that is suitable for the CO capture. Furthermore, the combination of different power and water technologies, which are operating at different temperatures and pressures, leads to enhance the overall efficiency of the integrated systems. To this end, a novel integrated power/water plant comprising a solar tower, a molten carbonate fuel cell, a gas turbine, a solar Rankine cycle, an organic Rankine cycle, a multi-effect distillation, and reverse osmosis desalination was techno-economically investigated. The multi-objective genetic algorithm was used to find the optimum configuration of the system with the low amount of CO emissions, and low unit costs of the electricity and fresh water. The results showed that the most effective parameter on system performance is the operating pressure of the molten carbonate fuel cell. For the optimum configurations of the system, the electricity unit of the cost was found as a value between 0.022 and 0.025 $/kWh. Part of the electricity unit of the cost that is associated with the output power that is generated based on solar thermal energy was obtained as a value between 0.08 and 0.092 $/kWh. In addition, the average unit cost of fresh water was obtained as 1.21 $/m. The payback period of the system was obtained as 10.44 years if the electricity and fresh water are sold as 0.023 $/kWh and 1.21 $/m. This can be reduced to 2.88 years for the electricity and fresh water selling prices of 0.069 $/kWh and 1.40 $/m, respectively. Based on the results, the system with the solar thermal resource will be economically justifiable if the fuel price is increased.