Renewable energy generation from wind and solar resources carries inherent variability. The variability can be classified in different time scales – second, day, seasonal, etc. The second-to-day variability can be managed by short-term storage systems(e.g. lithium-ion battery, Pumped Hydro Storage, Concentrated Solar Power). This variability can also be reduced by aggregating wind and solar generation over large geographic regions. However, to balance the long-term seasonal variations of winds and solar would require access to an even larger geographic span, sometimes can be intercontinental. Long-term seasonal storage, such as hydrogen, would also be another solution.

The cost for large-scale hydrogen production is still unclear. The transmission lines required to cover long distances are costly. Nevertheless, our recent study has shown the potential economic viability of having such an international High Voltage DC (HVDC) interconnector connecting the Australian National Electricity Market (NEM) grid to Indonesian Java-Bali grid through the Northern Territory to help both nations achieve carbon-neutral electric power system by 2050. Understanding the trade-off between the capacity of the international HVDC interconnection and the capacity of storage needed for this Australasian power system (with different cost projections) is an important question. understanding the economic viability of using hydrogen storage to balance seasonal variations of winds and solar for both countries is equally important.

Results will show tradeoffs between transmission and storage using our model that compares costs of electrical systems over Australia and Indonesia with large-scale high capacity transmission linking major consumption centres in both countries against systems with dispatchable renewables and storage. The model conducts the capacity expansion study for this Australasian power system considering a 23-node transmission network comprising the NEM, Northern Territory and Java-Bali. The model is driven with hourly wind and solar fields from ACCESS-A and technology costs from the new CSIRO Technology Projection report.