Exergy and economic analyses of a novel hybrid structure for simultaneous production of liquid hydrogen and carbon dioxide using photovoltaic and electrolyzer systems

Power-to-X technology that converts renewable electricity to chemicals and liquid fuels will be a key component of the energy turnaround. However, for a successful transition toward fossil-free energy alternatives, serious issues associated with renewable energy storage have to be addressed. Here, we report an innovative power-to-liquid hydrogen and carbon dioxide plant. The proposed integrated plant is composed of five subsystems: power generation using grid-connected solar photovoltaic (PV) subsystem, hydrogen and oxygen gas production using an electrolyzer, oxyfuel power plant for power and heat generation, carbon dioxide liquefaction using an absorption-compression refrigeration subsystem, and a hydrogen liquefaction subsystem. This hybrid structure produces 3.359 kg/s (similar to 300 ton/day) liquid hydrogen and 10.04 kg/s liquid carbon dioxide. The total exergy efficiency and specific energy consumption of the hydrogen liquefaction system are 94.87% and 3.368 kWh/kg(LH2), respectively. Exergy analysis of this integrated structure shows that the largest contribution of exergy destruction (30.58%) is associated with the photovoltaic system and the lowest exergy efficiency (25.28%) belongs to the Turbine in an oxy-fuel subsystem where it, interestingly produces over 70% of the total energy consumption of the plant. Furthermore, the economic analysis of the plant indicates that the time required for the return of capital is 4.794 years, where the prime price of the product and the value added are 0.1921 US$/kg(LH2) and 0.5433 US$/kg(LH2), respectively. This work can certainly provide a new approach to producing liquid hydrogen and carbon dioxide for long-distance transportation and CO2 reduction using solar as the renewable energy source. (C) 2020 Elsevier Ltd. All rights reserved.