MightyRiverPower is shutting down its largest geothermal power station, the 140 Megawatt Nga Awa Purua installation, to perform temporary repairs after finding geothermal fluids have damaged the three-year-old unit.
Commissioned in 2010, Nga Awa Purua is the largest of MRP's five geothermal power stations, representing close to 30 percent of its 469MW of rated output from steamfields in the central North Island.
The one to two week outage follows modifications to allow ongoing operation, which has reduced output at the plant to around 95 percent of normal capacity.
Geothermal fluids contain a mixture of caustic chemicals, which can corrode or cause build-up on turbine blades which are directly exposed to them.
"This shut means we can open up the turbine so that we can properly assess the issue to increase reliability of the plant through until permanent repairs can be made in about 15-18 months," said William Meek, chair of the 65/35 joint venture with Maori investor, the Tauhara North No2 Trust.
"The outage will not have a material financial impact, with revenue losses mitigated by current wholesale market conditions," said Meek in a statement, referring to weak demand for electricity and current low wholesale prices. "The current estimated repair and turbine blade replacement cost to the joint venture is expected to be about $15 million in the 2015 financial year."
MRP shares rose 1 percent to $2.12 in trading today, and have dropped 15 percent from their $2.50 sale price in May.