Balancing hydrogen and nuclear: How nuclear expansion reshapes power-to-gas and hydrogen storage in a carbon neutral energy system

Achieving carbon neutrality requires flexible power systems to integrate variable renewable energy. Power-to-gas enables hydrogen storage from excess electricity, while rising demand from AI and data centers renews interest in nuclear power. This study examines the interaction between power-to-gas deployment and nuclear expansion in the context of South Korea's 2050 carbon neutrality using the EnergyPLAN model. The results show that 6,489 GWh of hydrogen storage is sufficient in the baseline scenario, and 32.4 GW of nuclear capacity eliminates the need for natural gas generation. However, excessive nuclear expansion reduces the role of power-to-gas and increases electricity curtailment. Increasing wind power to 140 percent of baseline minimizes excess electricity more effectively than solar alone. Policy implications include aligning hydrogen storage with seasonal demand peaks, coordinating nuclear growth with demand-side flexibility, and optimizing the mix of wind and solar to improve overall energy system efficiency.