24. HARNESSING UNDERGROUND HEAT

Nearly thirty years ago when Bernard Shaw' visited New Zealand he suggested that the geothermal capacity of North Island, so abundantly evident from its geysers and hot springs, could be harnessed for industrial power. Now a geothermal power station at Wairakei has been delivering 6,500 kW of electricity to the national grid for some months. It is the first natural-steam-driven generating plant in the southern hemisphere and its development has proved so satisfactory that up to twenty-seven bores to tap steam down to 3,000 ft. and to deliver 70,000 kW of electricity are scheduled.

A second phase of development at the site will increase the power output to 150,000 kW and it is estimated that the natural steam potential in the area can support development of up to 260,000 kW. Once testing and installation are complete - and this is the tricky part of the operation - natural steam is the cheapest power source in the world. The cost of all three stages of New Zealand's Wairakei project is estimated at $21 million.

Wairakei is in fact only one small outcrop of the vast thermal region of New Zealand's North Island. The whole region extends across the centre of the island in a huge triangle, whose points are marked by the active volcano Ruapehu to the south, the spa town of Te Aroha in the west and an island offshore that rises blazing out of the Bay of Plenty on the eastern seaboard. The United Kingdom consultants who have been advising the New Zealand government on the development estimate that there are 7,390 million British Thermal Units locked up in this triangle waiting to be used.

It is possible that, when this new source of natural power is exploited, the steam may give out when released. Virtually nothing is known of the source of the underground heat, nor of its geophysical cause. At the present state of knowledge the chances are even for steam production from underground to continue unimpaired.

(from Discovery, August 1961)