Thermodynamic analysis of a near-zero carbon emissions hydrogen-electricity cogeneration system coupled with solar driven chemical looping fuel conversion and energy storage

Conventional fossil fuel-based hydrogen production and power generation face challenges of high energy consumption, complex CO2 capture, and reliance on non-renewable resources. Furthermore, the inherent intermittency of solar energy can lead to a mismatch between energy supply and user demand. To address these issues, this study proposes a novel near-zero carbon emissions hydrogen-electricity cogeneration system. The system integrates solar energy utilization with chemical looping technology enabling inherent CO2 capture, and innovatively employs Fe-Ni mixed oxygen carriers (OCs) for energy storage to achieve output regulation and supply-demand matching. Solar energy drives the endothermic reduction of OCs in the fuel reactor, converting intermittent solar energy into storable chemical energy in solid OCs. The reduced OC is subsequently oxidized by steam to produce high-purity hydrogen and further oxidized by air to release heat for power generation. By regulating the steam input and OC storage/release rate, the hydrogen-electricity output can be flexibly adjusted to achieve output matching. Thermodynamic analysis reveals that under the design condition, the system achieves a solar thermochemical efficiency of 65.08% and a CO2 capture rate of 99.67%. The reduced OC exhibits high hydrogen and heat storage densities of 155.60 Nm3/m3 and 3062.03 MJ/m3, respectively. Compared with the reference system, the proposed system increases the solar energy contribution ratio from 23.17% to 35.04%, achieves an 11.47% fuel saving rate, and reduces the LCOE from 84.77 to 78.91 $/MWh, demonstrating a clear economic advantage. Furthermore, under typical daily variable-load conditions, the system realizes electricity supply-demand matching through coordinated OC storage/release and electricity-to‑hydrogen ratio regulation (1.27–5.06 kWh/Nm3), achieving an overall energy efficiency of 62.87%. This study proposes a novel thermodynamic framework that integrates solar energy utilization, inherent CO2 capture, hydrogen-electricity cogeneration, and OC energy storage, offering a promising pathway for solar-fuel hybridization.