Reversible solid oxide cells-based hydrogen energy storage system for renewable solar power plants

The power-H₂-power system based on reversible solid oxide cell is a promising pathway for large-scale renewable energy storage but not well understood due to the absence of comprehensive system analyses. In this study, a reversible solid oxide cell-based H₂ energy storage system for a 100 % renewable solar power plant is proposed and analyzed through detailed modeling approach and optimization framework. The detailed parametric analyses and economic evaluations are performed in electrolysis (12:00 pm, sufficient solar energy) and power generation (6:30 am, insufficient solar energy) conditions. Notably, it is found that larger stack capacity (N_cell) and higher operating temperature (T_ReSOC) of the cell enhances system net H₂ production and system economics despite additional investment cost. Afterwards, the optimal system performance is obtained (V_H2,produce = 498.40 Nm³·h⁻¹, Z=263.59 $·h⁻¹ for electrolysis, and V_H2,consume = 380.33 Nm³·h⁻¹ for power generation) through multi-objective optimization by fully considering cell internal operating characteristics and system energy-exergy-economic factors. Besides, it is also found that the performance of power-H₂-power system is still limited by remarkable fuel (H₂) costs for nighttime power generation (daytime H₂ production is smaller than nighttime H₂ consumption when W_tot = 1 MW). Therefore, the critical power capacity (P_critical) is obtained, offering a convenient approach to determine the maximum output capacity (P_critical = 880 kW) to make the power-H₂-power system profitable at specific solar energy input. This study provides valuable insights between system capacity, economics, and cell operating features in solar power plants, which are useful for the design and optimization of practical power-H₂-power systems for renewable energy storage.