Cable feasible but expensive: report

Supplying Stewart Island electricity consumers via a cable from the mainland is feasible, a new report says, but would be expensive.

The report, still in its draft form, has identified four possible routes for laying the cable beneath the Foveaux Strait seabed, ranging in price from $15.7 million to $34 million.

The island has a permanent population of about 400. Households and businesses are supplied from five diesel-fuelled generators, at an annual cost of about $500,000.

The Stewart Island Electricity Supply Authority, owned by the Southland District Council, has commissioned Venture Southland to investigate alternative supply options including hydro, wind, solar and a cable from the mainland.

Venture Southland enterprise projects manager Robin McNeill said the cable report indicated the ''shortest, fastest route'' might be the most expensive in the long run, as it would take a cable through the middle of the Bluff oyster beds and could place it at risk of being dredged up.

The report also said laying two cables might be be more cost-effective in the long term than laying one.

The often rough conditions in Foveaux Strait would make it difficult to lay a cable or cables, Mr McNeill said.

''This is not a minor undertaking ... You need calm conditions. A cable-laying boat could be waiting for days, at a cost of perhaps $50,000 a day.''

The draft report into the electricity cables had been seen by the the Stewart Island Electricity Supply Authority board and had gone back to him ''for a few tweaks'', he said.

Trial wind, solar and hydro sites had been in place since about March and were producing data being collated into a major report, due out in about six months. The report into the cables would also be released then, Mr McNeill said.

''The cables are just another option for us to explore ... until we get the final analysis of all the options. Then we can have some informed discussion.''

The $20,000 solar power monitoring station on the island destroyed by wind gusts in July would be rebuilt, Mr McNeill said.

The winds flipped the steel frame, which held seven large solar panels, and damaged the inverter, which converts the solar energy into electricity and records solar information.

The inverter had been repaired and he was ''relieved'' all the data recorded before the wind gusts had been retrieved.

Most of the frame was able to be reused, but new solar panels would have to be installed, he said.

He hoped the station would be operating again within a month.

allison.beckham@odt.co.nz

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