Private geothermal power station to crank up power

By CHRIS DANIELS energy writer

One of the energy sector's lesser-known achievers, the privately owned Mokai geothermal power station, is about to increase capacity by a third.

Investment of more than $40 million in the station, 30km from Taupo, will boost output by 39 megawatts.

Mokai is owned by the Tuaropaki Trust, which owns 2700ha of land around Taupo and has 1700 Maori beneficiaries.

Though financing for the expansion is still being finalised, the contract to build the new plant has been awarded to Israeli company Ormat, which hopes to have it finished by the end of 2004.

Pat Brown, one of the partners at Taupo accountancy firm Stretton & Co, which provides support for Tuaropaki, said the trust did its work quietly and without fanfare.

Brown said he understood that when the station was completed in 1999, the trust was the first indigenous group in the world to raise finance for such a project.

Mokai was running extremely well, performing ahead of expectations and earning a profit, much of which went to paying off debt or was put aside for expansion, he said.

State-owned enterprise Mighty River Power runs the station and also has a commitment to buy some of the electricity it produces.

The geothermal plant was being expanded slowly as the nature and capacity of the field became apparent, said Brown. This was known in the sector as "suck and see".

In the past, geothermal fields were depleted quickly.

"We are just plodding along at the start. We'll observe it for a few more years before we take the next step."

The trust, said Brown, took a long-term view of the field and its use, wanting it to be available forever and a day, hence the caution at the beginning of the project.

Chris Bromley, a geothermal scientist at the Institute of Geothermal and Nuclear Sciences, said the Mokai field had been developed slowly with the idea of finding out how fast hot water could be taken from it.

While the new expansion would take the station's output up to 100MW, there was probably potential to double this capacity.

Bromley also thought the total amount of energy provided by geothermal fields could be doubled, by expanding existing fields and developing new ones.

For comparison, the gas-fired Otahuhu B power station generates 380MW; the Huntly station, the country's largest thermal station, generates 1000MW; and the Clyde Dam 432MW.