Generation of electric power in New Zealand from geothermal steam at the present time amounts to 148 MW at the Electricity Department's station at Wairakei, and < 10 MW at the Tasman Pulp and Paper Company's mill at Kawerau. Exploration commenced in 1950, and in association with geologic, geophysical, and geochemical surveys, wells were drilled at Waiotapu,

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Reporoa, Broadlands, Tauhara, Orakei Korako, and Te Kopia in the central volcanic region of the North Island, and at Ngawha in Northland. At Broadlands the production potential of wells already drilled is about 130 MW, and other wells are being drilled.

Technical studies carried out in New Zealand indicate that capital costs per kW for small geothermal power plants are at least as cheap as those for large plants, making the former attractive for developing countries and isolated districts. Estimates of power-life of geothermal systems are not yet possible, but studies of the effect of draw-off rate show that a maximum power-life is obtained if wellhead pressure is allowed to fall to 75 p.s.i.g. over the life of a field. From a hot-water geothermal reservoir power output can be increased for the same rate of production if the steam-water mixture is conveyed to the powerhouse in a single pipeline and separated in two stages.

More than 500 shallow wells have been drilled in Rotorua and a few in Taupo to tap hot water and steam used in conjunction with heat exchangers to provide space heating and hot-water supplies for domestic and commercial users, for drying of timber lucerne, growing of mushrooms and fruit, and hydrotherapy in the treatment of patients.

Permission has been given to a Japanese group to make a feasibility survey, based on a study of the Broadlands field, of the possibility of using geothermal energy in the production of heavy water.

Hot spring discharges at localities in both islands have been augmented by drilled wells to extend facilities at swimming pools for public use. A recent development in the Bay of Plenty near Tauranga has been the drilling of wells to obtain warm water for public and private swimming pools in areas where the subsurface gradient is 1.5-4 times normal.

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