The role of storage in the emerging Power-to-X Economy: The case of Hawai'i

Highly renewable energy systems for island regions provide opportunities to investigate fully self-sufficient energy-industry systems. New perspectives into the nature of 100% renewable energy systems suggest that a Power-to-X Economy may emerge, as renewable electricity will become the fundamental energy carrier. In systems with high renewable shares, the availability of low-cost storage options is essential to balance high shares of variable renewable electricity, especially of solar PV and wind power. While direct electrification is the most cost-effective and efficient solution, indirect electrification through power-to-X processes is required for those demands that cannot be directly electrified. Using the LUT Energy System Transition Model, energyindustry system transition pathways to 100% renewable energy and the role of storage technologies were investigated for the case of Hawai'i comparing cost-optimal routes reaching net-zero emissions by 2040 and 2050 to current government projections. Additionally, e-fuel import scenarios are investigated and compared to selfsupply scenarios. By installing 39 GW of solar PV, responsible for 96% of total electricity generation of 32 TWh, the levelised cost of electricity in Hawai'i can be reduced to 27.5 <euro>/MWh. Total electricity storage capacities, including stationary batteries, pumped hydro energy storage, and vehicle-to-grid batteries, reach 46 GWhcap in 2050, with total throughput at 7.7% of total electricity demand. Due to the low projected costs of these storage options, they only cost 38% of the LCOE in 2050. These results highlight the importance of storage for the Powerto-X economies of island regions such as Hawai'i to achieve high levels of energy independence.