Testing starts at Northland's newest power station

The most visible feature of the new power station is the array of fans used to cool the pentane after it has been through the turbines. Photo / Peter de Graaf

Huge plumes of steam rising over the countryside east of Kaikohe are a sign the country's newest power station is nearing completion.

The first tests of Top Energy's new Ngāwhā geothermal power station has started with valves at the top of the production wells opened, allowing steam to blow down the pipelines, through the power station and out the mufflers — two steel towers for venting surplus steam when the station is started up or shut down.

Chief executive Russell Shaw said following the success of the initial tests the next step, in about two weeks' time, would be to fill the system with pentane gas.

Once the plant is running the pentane will be heated by geothermal fluid in a heat exchanger before driving the turbines to generate electricity.

Engineers from Israeli firm Ormat, which supplied the power station, were conducting the tests.

Shaw said they been allowed into New Zealand as essential workers after completing the required two weeks' isolation.

Current testing at the new power station entails opening the valves at the top of the well in the foreground and allowing steam to blow down the pipelines, through the plant and out the mufflers in the distance. Photo / Peter de Graaf

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The new plant is expected to generate 32MW of power, more than the 25MW of the two existing plants combined. The total output will be close to the Far North's peak consumption of 70MW.

If another 32MW expansion goes head in 2023 as planned the Far North will become a power exporter.

Shaw said the Covid-19 pandemic, in particular the construction shutdown in level 4, had hit the project's timing and budget.

However, it was still due to be completed before Christmas — six months ahead of the original schedule which anticipated power coming on stream from June 2021.

During the lockdown Top Energy had to keep paying its contractors but didn't receive relief from the Government.

The full financial effect would not be known until the project was complete but Shaw expected Covid would add about 10 per cent to the overall cost.

The looming closure of Tiwai Pt aluminium smelter, New Zealand's biggest power consumer, would not alter the power station's viability.

''We are the most insulated generator in New Zealand from that problem because we're the furthest away. It will have an impact on the overall market but it's likely to have the least impact on us.''

New pylons transport the power to Kaikohe substation. Photo / Peter de Graaf

About 250 people are still working at the site.

New 100kV transmission lines from Ngāwhā to Kaikohe substation were completed at the end of August.

The last major pieces of the power plant to be installed were the mufflers, which weigh 30 tonnes each.

More than 75km of electrical and control cables is currently being laid across the site.

Earlier this year the total cost of both stages of the expansion, if they go ahead as planned, was put at $320 million.