Karāpiro hydro station upgrade completed in New Zealand

Mercury has completed testing and commissioning of the third and final new generator unit at the Karāpiro Hydro Station, marking the end of a multi-year refurbishment project.

The $90 million upgrade, which began in 2018 with on-site work starting three years ago, involved the full replacement of the station’s three generators, turbines and water intake gates. The project has added 14MW of generation capacity, bringing the total installed capacity to 112.5MW. Average annual output has risen by 32GWh, enough to supply an additional 4,000 average homes.

The work also included:

• 150 weeks of outage time
• 260,000 on-site hours worked (450,000 including offsite fabrication)
• removal of 1,500 tonnes of scrap metal
• installation of 25km of cable
• the first replacement of a runner chamber in New Zealand
• a switch from oil to water-lubricated turbine bearings

The new units at Karāpiro are about 4% more efficient, generating more power from the same water flow. They are designed to provide at least 50 more years of renewable electricity generation while meeting modern dam safety standards.

In August, Mercury Chief Executive Stew Hamilton hosted the community at a celebration event as the project neared completion. Taupō MP Louise Upston spoke at the event: “Investment in our electricity generation infrastructure is vital to ensure we can improve our capacity and security of supply. Upgrades which increase output without having to build new generation are a huge plus.”

Hamilton said Mercury would now turn its focus to refurbishment projects at Maraetai I, Ōhakuri and Atiamuri on the Waikato River.

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