Flexible Operation Strategies for Wind-Powered Energy Islands Utilizing Solid Oxide Electrolyzer

Following EU carbon neutral and net-zero policies, Danish energy islands will use offshore wind power to produce green fuel. The solid oxide electrolysis cell (SOEC) is a potential green hydrogen production technology that can be installed on energy islands. Given the inherent variability of wind power, the SOEC plant on an energy island must contend with fluctuating energy inputs. This study investigates the energy and economic performance of an SOEC-based energy island, exploring various control strategies, operating temperatures, and hydrogen storage technologies. An optimization procedure based on the energy distribution principle is proposed, characterized by a limited set of decision variables and enhanced computational efficiency. The results confirmed that this procedure could successfully illustrate the dynamic energy distribution process. Our findings indicated that the most economically viable SOEC plant for the Bornholm energy island consists of two independent SOEC systems, each with a capacity of 187.7 MW, culminating in a combined output of 375.4 MW. These SOEC systems are optimized to operate at 800 °C with a constant conversion (CC) strategy and a synchronized (SYN) power strategy. Hydrogen products stored as compressed hydrogen instead of ammonia could be more cost-effective. Specifically, under 800 °C with CC-SYN strategy, the LCOH is projected to be $2.59/kg H 2 (compressed hydrogen) and $3.12/kg H 2 (ammonia). In another scenario, hydrogen tanks and batteries are included in the system for temporary energy storage. The economic analysis suggests that integrating energy storage systems is not financially reasonable for the SOEC-based energy island. It will be economically viable if the reduction in battery costs exceeds 75%. To conclude, SOEC-based energy islands have the potential to contribute significantly to green hydrogen production, with applications in the renewable energy sectors and maritime transportation. Realizing this potential, however, requires more research focuses on flexibility and durability, a comprehensive investigation of the synergies of system components, enhanced collaboration between business entities, and increased investments.