Home / Uses / Backup and storage power on Stewart Island

Island power at the bottom of the country

Stewart Island, Rakiura, is not connected to the national grid and relies on its own local supply. This page looks at how a hydrogen system could support island homes and businesses.

A small island supply

Island power is expensive to produce and depends on fuel shipped across Foveaux Strait. When the local supply has a fault, there is no mainland grid to fall back on. Accommodation, the store, fishing operators with freezers and community buildings all feel it. A system with instant UPS switch-over and weeks of stored hydrogen gives a business its own buffer.

What it would keep running

Fish and bait freezers
Accommodation hot water and lights
Store refrigeration and EFTPOS
Water pumps
Internet and phone link

Charging on what the island has

Where a property is on the island's supply, the system could charge in quiet periods, depending on how the local tariff works, which is something to check rather than assume. Off that supply, a wind turbine on an exposed site or micro-hydro on a bush stream are the designed sources. Rakiura has plenty of wind and rain.

Hydrogen stored at 30 bar or less keeps for weeks without losing charge, so it suits places where supply interruptions are infrequent but can be long, and where getting a technician or a spare part over the strait can take days of waiting for the weather.

How it works →

The H2OME loop: an electrolyser splits water into hydrogen, the hydrogen is stored in a tank for weeks, a fuel cell turns it into electricity for your home, and the water returns to the loop.

Cost and honesty

Round trip efficiency is 30% or less, so running a business from stored hydrogen costs more energy than using the supply directly. On an island where every unit is dear, that is a real trade-off. It is a resilience tool, not a way to lower bills. The pilot would look at each site's loads and local generation before suggesting it.

Questions

Would it reduce power bills on the island?

No. The round trip is 30% or less, so stored hydrogen power costs more than using the supply directly. Its value is in keeping a business running during outages, not lowering ordinary bills.

Can it run off-grid on Rakiura?

Yes, from a wind turbine or micro-hydro, if the site has enough resource to cover the losses. The pilot would measure that before suggesting any install on the island, since bush-clad sites can be sheltered.

How would it get serviced?

Servicing arrangements for island sites would be planned with each pilot, including what can be done remotely. There is no engine, which removes the routine oil and fuel servicing a generator needs.

Elsewhere

Every use →

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