A huge project completed at Ngāwhā

Top Energy chief executive Russell Shaw (left), Renata Tane, Top Energy chairman Richard Krogh, Ngāwhā Marae chairman Richard Woodman, Top Energy Consumer Trust chair Yvonne Sharp and Te Tuhi Robust at Friday's official opening of Top Energy's new geothermal power station. Photo / Peter de Graaf

Top Energy's Ngāwhā geothermal power station (OEC4), one of the biggest projects ever undertaken in Northland, was officially opened on Friday by Te Tai Tokerau MP Kelvin Davis, in collaboration with the Parahirahi Ngāwhā Waiariki Trust and Ngāti Rangi.

Top Energy chief executive Russell Shaw said the 32 megawatt, $189 million station secured an independent, affordable and renewable power supply, ending the region's reliance on the national grid and electricity transported from the south.

He described the three-year construction programme as intense, and reflected on the collective effort of staff and contractors to complete the project six months early, despite Covid-related delays.

"This was a complex project with so many inter-related aspects requiring local and international expertise from Northpower, Network Waitaki, United Civil Construction, Iceland Drilling, Culham Engineering and Israeli firm ORMAT," he said.

He also acknowledged the support of the Top Energy Consumer Trust, without whose backing and major transaction approval the Ngāwhā expansion programme would not have proceeded.

"The trustees have truly represented the interests of all Far North energy consumers connected to our electricity network by supporting the construction of the new geothermal power station," he added.

More than a million cubic metres of earth had been excavated, while three production and three injection wells, from 1350 to 1750 metres deep, were drilled, and extensive pipelines were constructed to take the hot geothermal fluid from the production wells to the power station and to return cooled fluid back to the injection wells.

But most critical was the need to determine the viability of the geothermal resource to ensure it had the capacity and heat to power the station. That was confirmed late in 2018, after drilling, providing the confidence to continue the expansion programme.

"It was an absolute cause for celebration when, after a three-month commissioning period, and an extraordinary year, the station exported its first power to the electricity network on New Year's Eve," Shaw said.

"You can imagine the resolutions that were made that night."

Generation capacity at the Ngāwhā geothermal power station had more than doubled, to 57MW, and would supply all of the Far North's electricity demand for 97 per cent of the year. Excess power was exported to the rest of Northland through the national grid. Prior to new station coming on-stream, electricity from the existing two power stations, with a combined capacity of 25MW, was exported south only about two per cent of the year.

Shaw said the new power station was the culmination of decades of resource planning and consenting, working with the Parahirahi Ngāwhā Waiariki Trust and Ngāti Rangi, community engagement and negotiation with regulators.

"It has utterly transformed the way in which the Far North receives its electricity to become self-reliant," he said.

Now that OEC4 was generating electricity, Top Energy had begun a three-year period of monitoring the geothermal field, to ensure that it performed in a similar way to the model prepared by GNS Science in support of the resource consent application.

The next 32MW station (OEC5) was already consented, subject to confirmation of the performance of the field, but would only proceed if an acceptable business case could be developed.

The company would monitor market conditions over coming years to determine whether OEC5 should proceed. The investment would also be subject to a Major Transaction Approval by the Top Energy Consumer Trust.