Impact of heat demand integration on optimal design and operation of renewable-based electrolyzer system

Power-to-X solutions play an essential role in decarbonizing multiple energy sectors. Power-to-gas technologies, such as electrolyzers, produce hydrogen while simultaneously generating significant amounts of waste heat. As the coupling between sectors like heat and power intensifies, new opportunities for cost reduction emerge. However, fully exploiting these synergies requires an integrated, cross-sector optimization approach. In this work, we analyze a renewable energy-coupled hydrogen production system to demonstrate how heat demand shapes system design decisions under fluctuating hydrogen and heat price assumptions. We evaluate the operational implications of both including and excluding heat demand during the design phase and investigate how this affects the electrolyzer behavior. After presenting an optimization framework that jointly determines component sizing and operational scheduling within a multi-energy context, three use cases with an increasing role for the electrolyzer waste heat are examined. While the operation without heat recovery results in earnings equal to expenditures, a simple utilization of electrolyzer heat reduces expenditures by 22.1% while maintaining constant profit. Fully integrating waste-heat utilization into the design process increases expenditures by 79.8%, while increasing system profit by 86.5% – both compared to the simple heat recovery. This highlights the importance of cross-sectoral design methodologies for future energy systems. Finally, a comprehensive sensitivity analysis quantifies the influence of assumed energy prices and component capacities on the total annualized cost, identifying the parameters that most critically affect system performance and that should therefore guide system development.