High Power Potential For Geothermal Steam

Press, Volume XCII, Issue 27735, 12 August 1955, Page 13

High Power Potential For Geothermal Steam

“The Press” Special Service

WELLINGTON, August 11. At least 200,000 kilowatts of electric power could be obtained by drilling for geothermal steam in the thermal zone of the North Island, according to an estimate given in a bulletin. “Geothermal Steam for Power in New Zealand,” published by the Department of Scientific and Industrial Research apd compiled by Dr. L. I. Grange, director of the Geological Survey. The thermal region covers many hundreds of square miles from Ruapehu to the Bay of Plenty. The department’s assessment of the power potential of this area has come from shallow drilling of the Wairakei and other areas on the basis of the present heat-flow. The natural heat-flow from 14 centres, of which Wairakei, Waiotapu and Orakei-Korako have the highest flows, totals 7,390,000,000 British thermal units an hour. This total, says the bulletin, can be roughly converted into terms of electricity to give a total power potential for these areas of about 250,000 kilowatts. As it is unlikely that areas capable of yielding under 10.000 kilowatts will be brought into production, the total can be reduced to about 200.000 kilowatts. This figure is based on heat-flow at the surface, and it is apparent that at least this amount will be obtained on

drilling. How much m’ore can be tapped is not known. In addition, there is a great store of heat in the high-temperature underground water in the thermal region. This is a great bank of energy, but for how long and at what rate it could safely be drawn upon is not known. Dr. Grange notes that proposals were made for the use of geo,thermal steam in industrv 20 years ago. It was in 1949 that the Government, heeding a warning of the State Hydro-Electric Department that hydro power would not meet the North Island’s needs for much longer, directed a geothermal investigation. Although drilling has been concentrated at Wairakei, geological, geophysical and other scientific surveys have been made over many parts of the thermal region. At wairakei 30 holes have been sunk to depths of from 574 feet to 3200 feet. Half of these are regarded as development wells and the remainder as exploratory. Two of the deeper eight-inch bores have a combined output of more than 17,100 kilowatts. A contract is to be let shortly for the construction of a power station of 40,000 kilowatts at Waikari to operate in conjunction with a plant extracting heavy water. It is planned to double this output '