Optimization of an SOC green hydrogen production storage and transportation system based on electricity-heat-gas multi-energy coupling

Considering the randomness and fluctuating characteristics of wind and light resources, there are major challenges associated with the production and supply of green electricity. On the other hand, conventional hydrogen production employing the electrolysis of water has a generally low efficiency, with complex hydrogen storage and transportation processes. Through examining the characteristics of solid oxide cell (SOC), this paper proposes a synergistic optimization model for an integrated cycle of SOC hydrogen storage electricity-heat-gas multi-energy system with a hydrogen-doped natural gas pipeline network. First, an overall optimization model of the electricity-heat-gas multi-energy coupling system is established, including wind power, photovoltaic units, heating system, SOC battery, hydrogen transmission and transportation system, and auxiliary equipment, in addition to harnessing the efficient use of waste heat. Then, an analysis is conducted to study the green power output uncertainty constraints and the energy conservation constraints of the electricity, heat, and gas system. Also, the operational constraints for H₂ production, storage, and transport are examined. On this basis, the optimal solution is derived through integration and optimization. Finally, a simulation experiment is performed, considering an electricity-heat-gas multi-energy flow system in an industrial park in Xinjiang, China. The results showed that SOC hydrogen storage improves green power consumption and capacity compared to conventional storage. It also reduces the economic operating costs of the system and accelerates the near-zero carbonization of the investigated industrial park. Additionally, an evaluation is carried out to examine the electrical heat ratio coefficients of the regulated combined heat and power (CHP) system, the tunable hydrogen production efficiency, and the heat consumption efficiency of SOC systems. This allows for optimizing comprehensive hydrogen production efficiency. Also, a study is presented to quantify the impacts of different proportions of hydrogen-doped natural gas on compressor performance, gas network nodes, pipeline transportation characteristics, and gas consumption load. The findings provide a solid theoretical basis for large-scale harnessing of renewable energy, along with efficient, economic, and safe long-distance transportation of massive amounts of H₂.