Geothermal steam was introduced to the 9 kilometres of pipeline at the Nga Awa Purua Geothermal Power Station near Taupo for the first time earlier this week in a major pipe work clean up job.
Known as a "steam blow‟ its purpose is to clean out construction debris and scale from the pipelines, before the steam is directed into the heart of the power station, the steam turbine.
The $430 million Nga Awa Purua Geothermal Power Station – a joint venture between Mighty River Power and the Tauhara North No. 2 Trust – houses the world's largest single shaft geothermal turbine.
Nga Awa Purua project manager Paul Ware, says the hundreds of turbine blades are machined from individual blocks of special alloy metals. The blades, which range from 100mm to 650mm in length, spin with the turbine at 3000 revolutions per minute and even the slightest bit of debris can cause damage.
“As the turbine cost exceeds $30m, it's critical to ensure there is no potential for debris damage and the steam blow is the all important first stage in the process,” says Mr Ware.
“We don't expect to replace many of these blades during the life of the project, so it's absolutely essential that we ensure the pipes are cleared of debris.”
Steam is currently being diverted into a rock muffler before it reaches the steam turbine. The steam is vented to the atmosphere at this point and the debris left behind. During the blow, up to 2,000 tonnes per hour of geothermal steam will be drawn from wells which are over two kilometres deep.
When commissioned the 132MW station will produce sufficient electricity to power 130,000 homes – the equivalent of every house in Christchurch.
The good progress being made on the project now means synchronisation to the grid – and the first export of power – is now expected in February 2010, well ahead of original plans.
The Nga Awa Purua project is another important contributor to Mighty River Power's growing geothermal programme and the co-ownership model it has developed with the Tauhara North No.2 Trust.
The development of the Nga Awa Purua project is helping the Trust to grow its assets for the benefit of its shareholders and to help achieve its social programme aims, particularly health and education, for the owners and beneficiaries of the Tauhara North No. 2 Trust.
For further information please contact:
Mark Hanson
Acting Communications Manager Mighty River Power
Tel: 09 308 8215