Publication
Green hydrogen production via electrochemical water splitting is a promising approach for future sustainable energy and industry. Among the existing water electrolysis technologies, solid oxide steam electrolysis exhibits the highest electrical efficiency, and hence potentially considerable cost-effectiveness. Moreover, from thermodynamic considerations, the efficiency can be increased further by integrating external high temperature heat to reduce the electrical energy required for the water splitting reaction. Therefore, this paper proposes an innovative system for cost-competitive solar hydrogen production by integrating concentrated solar heat into the solid oxide electrolysis steam generation process. Economic viability of such solar-driven solid oxide electrolysis hydrogen production system is assessed over the long term (from current status to 2030) by taking into account the cost reduction of essential components and the expansion of the solid oxide electrolysis load range. Heat cascade utilization in each time step is optimized using multi-time heat and mass integration technology to maximize cost savings. The results showed that, for a hydrogen yield of 200 kg/day, levelized cost of hydrogen production has a significant amount of space to fall from its current 4.6 Euro/kg to 1.7 Euro/kg in 2030, achieving cost-competitiveness with hydrogen produced by traditional non-renewable energy sources, and the main drivers of this decrease are cost reductions of SOE unit and PV. To achieve hydrogen production cost below 2.7 Euro/kg and even 2 Euro/kg, the investment costs of SOE unit should be decreased by at least to 1000 Euro/kWe and 500 Euro/kWe respectively. Compared with the system using photovoltaic battery to provide electricity and heat for hydrogen production, the system coupling concentrated solar heat-thermal energy storage-steam generation subsystem with photovoltaic-battery subsystem showed higher economic viability. Employing 134 kWth concentrated solar heat with 420 kWhth thermal storage allows for maximum 3.2 Euro/kg hydrogen production cost reduction via significantly saving capacities of battery and solid oxide electrolyzer.