Mercury’s Ngā Tamariki geothermal station nears completion

NZX-listed Mercury says the new fifth unit at its Ngā Tamariki Geothermal Station, near Taupō, has begun delivering power to the national grid.

Mercury said the $220 million project is on track to be fully commissioned by March, adding another 46 megawatts (MW) of renewable energy baseload capacity to the station and taking its installed capacity from 86MW to 132MW.

Chief executive Stew Hamilton said bringing the fifth unit online was a significant milestone.

When generating fully, the station’s annual average generation output will increase by 390 gigawatt hours (GWh), providing the equivalent of enough power for about 55,000 homes, Hamilton said.

The total annual average generation output for the station will be about 1120GWh – enough to power the equivalent of 158,000 average homes – greater than all of residential homes in Christchurch.

The Ngā Tamariki expansion is one of three major renewable generation developments, totalling $1 billion, that Mercury has underway.

These include the Ngā Tamariki expansion, stage 2 of the Kaiwera Downs Wind Farm in Southland and the Kaiwaikawe Wind Farm in Northland.

Mercury is reinjecting up to around 80% of non-condensable gases (NCGs) – mostly from carbon dioxide – back into geothermal reservoirs at the first four Ngā Tamariki units.

The company intends to introduce reinjection to the fifth generation unit, completing the $3.3m reinjection programme.

The Ngā Tamariki expansion project was developed with support from Mercury’s commercial partner Tauhara North #2 Trust and with mana whenua Ngāti Tahu Ngāti Whaoa to ensure the sustainability of the geothermal reservoir.

As part of the expansion project, two new geothermal wells have been added.

Ngā Tamariki’s nine wells extend to depths of more than 3000m, reaching temperatures of up to 290C.

Jamie Gray is an Auckland-based journalist, covering the financial markets, the primary sector and energy. He joined the Herald in 2011.

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