The Fusion to Hydrogen Option in a Carbon Free Energy System

To address climate change and keep the global temperature increase within 1.5 degrees C above pre-industrial levels in the long term, ambitious climate policies are required. Decarbonizing all sectors of the economy requires a shift towards electrification. As a consequence, in order to generate a high amount of carbon free electricity, the share of electricity generated by solar and wind power will considerably increase in the years to come. However, the inherent intermittency and variability of both solar and wind power require actions in order to increase the resilience and the flexibility of the power systems and assure the security of supply. To this scope, dispatchable capacity and energy storage systems acting on both short and long terms, will play a pivotal role. The paper discusses various scenarios developed with the COMESE code to investigate the affordability and viability of future possible carbon-free Italian power system configurations, based on both existing and under development energy technologies. The 100% renewable generation option is compared to "nuclear scenarios" where a relevant base-load generation is provided by nuclear fusion power plants. Also, besides the conventional storage systems based on electrochemical devices and pumped hydroelectricity, the deployment of long term storage systems based on hydrogen production, storage and utilization (power-to-hydrogen-to-power, P2H2P) is also investigated. Specifically, excess generation from renewables is used to power electrolysers for hydrogen production. The affordability of this option is evaluated in contrast to the "fusion to hydrogen" strategy, where a continuous hydrogen production for long term storage is provided by fusion electricity. The study proves that the average system cost of electricity for any least-cost 100% renewable power system configuration exceeds that of the corresponding alternative scenario with base-load generation from nuclear power plants. If available, P2H2P works along with batteries as short/medium term storage with benefits on the total system costs, that slightly lowers. Neither converting the whole excess energy into hydrogen in order to avoid curtailment nor operating fusion power plants for a continuous hydrogen production are cost-effective strategies. Indeed, the high costs of the large tank system required for storing hydrogen and the low overall efficiency of the P2H2P process are the primary challenge.