Techno-economic optimization of a coupled electricity-heat-hydrogen energy system considering seasonal hydrogen storage and demand response

Hydrogen is increasingly recognized as a key energy carrier for achieving deep decarbonization across sectors. Coupled electricity-heat-hydrogen systems (EHHSs) provide a suitable framework for its widespread deployment and practical application. However, ensuring reliable and flexible operation of the system requires addressing both long-term seasonal imbalances and short-term load fluctuations, where seasonal hydrogen storage (SHS) and demand response (DR) emerge as two promising solutions. In this study, a bi-level stochastic optimization framework is proposed for the techno-economic planning and operation of an industrial-park-scale EHHS. The proposed framework couples long-term capacity sizing with short-term stochastic operation, enabling coordinated evaluation of SHS and DR. The lower-level model optimizes energy dispatch under uncertainty, informing upper-level sizing decisions to ensure system balance and minimize costs. The system integrates renewable generation and hybrid energy storage technologies to coordinate electricity, heating, and hydrogen demands across multiple time scales. Then, three classic scenarios are constructed to investigate the respective and combined contributions of SHS and DR to system performance: DR-only for short-term load flexibility; SHS-only for seasonal energy shifting; and SHS–DR for coordinated multi-scale optimization. Results reveal that DR improves short-term flexibility but increases grid reliance, while SHS enables seasonal balancing yet underutilizes hydrogen for power generation. Their integration achieves the lowest energy cost, reducing COE by 25 % and 34 % compared to DR-only and SHS-only cases, respectively, while raising renewable penetration to 87.5 % and significantly improving system coordination and flexibility.