Plan to ditch diesel power
A research fellow says $8 million in capital expenditure can get Stewart Island off diesel power.
Dr Soheil Mohseni has designed an energy network for the island as part of his PhD studies at Victoria University of Wellington, looking at off-grid networks.
The storage and generation components of Mohseni’s model would cost about $8m, fuel the ferry and save islanders 54% on their power bills, he said.
Even with a roughly $3.2m instillation, plus replacement, operation and maintenance, Mohseni said the system would be a money-maker in about eight years, with a projected 14% per annum return on investment.
The lion-share of electricity on Stewart Island comes from Southland District Council-owned diesel generators, and customers pay an average of 52 cents per kilowatthour, about 1.6 times the average national price.
Each litre of diesel used by Stewart Island’s generators produces 2.7kg of CO2, Mohseni says in the research.
Mohseni used artificial intelligence to model a self-sustaining renewable energy system of 12 components including wind
turbines, solar panels, batteries and a hydrogen refuelling station.
‘‘The technology can last 20 to 25 years. That means a decade of pure profit at least.’’
Building an expensive distribution network would be unnecessary because the island already had that, he said.
‘‘The only barrier here would be to make it socially acceptable as well,’’ Mohseni said.
The council would not comment on the report or anything related to it as it was not councilcommissioned and ‘‘we haven’t seen it’’, a spokesperson said.
Reports and plans for renewable energy on Stewart Island have repeatedly come and gone. The latest wind turbine project was canned in February 2021, despite a $3.16m backing from the Government’s Provincial Growth Fund. In a council-written report, the private consultants developing that project noted ‘‘staunch’’ opposition from landowners and repeated land access issues.
Submarine power cables have been suggested, in 2015 and 2020.
Hesitation towards renewable energy was not a New Zealandwide issue, Mohseni said.
‘‘Change is scary, it’s always scary,’’ Mohseni said.
‘‘If we can come to a point that we can assure people the energy bills will come down, and will be reduced, that will make it much easier and desirable for them.’’
‘‘Advantageously, local residents believe that reducing the consumption of diesel and developing a renewables-based energy generation system is one of the island’s highest priorities.’’
The research, Off-Grid MultiCarrier Microgrid Design Optimisation: The Case of Rakiura–Stewart Island, Aotearoa–New Zealand, was published in academic journal Energies in October 2021.
Mohseni is now working on a more robust and advanced version of the model.
Council infrastructure and environmental services group manager Matt Russell said council had been involved in numerous alternative energy assessments for the island in recent years.
Unfortunately none had proven viable, he said.
The council was confident that as technology improved and capital costs decreased, alternative supply options would become a reality for the island, Russell said.
In the meantime, the council would monitor the situation, focus on the efficiency of the existing network and explore funding opportunities, he said.