Techno-economic assessment of a novel power-to-liquid system for synthesis of formic acid and ammonia, based on CO2 electroreduction and alkaline water electrolysis cells

The power-to-liquid concept is a promising strategy to convert the power plants' flue gas to value-added liquid fuels using renewable energy. This technology could potentially reduce global greenhouse gases emissions and mitigate the environmental problems associated with the fossil fuels industry. In this regard, the main objective of the present study is to propose a novel power-to-liquid plant for the synthesis of formic acid and ammonia from power plants' flue gas, emphasizing the role of electrochemical technologies and renewable energy. The system's basis is developed by the integration of CO2 electroreduction cell, alkaline water electrolysis cell, and photovoltaic panel technologies. The plant performance is evaluated by a techno-economic analysis by considering the operating conditions of the electrochemical cells as operating variables. The results show that the Power-to-liquid energy efficiency is continuously reduced with the CO2 electroreduction cell's current density, while it reaches a peak at the alkaline electrolysis cell's current density of 0.2 A/cm2. Also, the study of the effect of alkaline electrolysis cell's operating temperature and pressure on the Power-to-liquid energy efficiency shows that the plant is more efficient at higher temperatures and lower pressures. From an economic aspect, the plant's cost of the product decreases with cells' current densities. Moreover, the plant's cost of the product is reduced by the increase in the alkaline electrolysis cell's operating temperature while it increases with the operating pressure. At design conditions, the alkaline electrolysis and CO2 electroreduction cells' energy efficiencies were calculated as 60.80% and 33.80%, respectively. Also, the Power-to-liquid energy efficiency and plant's cost of the product were obtained 37.60% and 22.676 $/kg, respectively.