Use Of Natural Thermal Steam May Be Answer To N.Z. Power Problems

Bay of Plenty Times, Volume LXXVI, Issue 14638, 6 April 1948, Page 4

Use Of Natural Thermal Steam May Be Answer To N.Z. Power Problems

THOROUGH SCIENTIFIC INVESTIGATIONS IN ROTORUA AREA

The utilisation of natural steam from tijo thermal districts is claimed by two New Zealand sciem be the solution to power problems Department Mr J. Healey, of the Geological Survey oh W of Scientific and Industrial Research, and Mi R ; of the Auckland Industrial Development Laboiaioius, been deeply into the matter. • -Rn+nrm are eonThe fruits of their .investigations.at Roto ua aie tained in a report which has arrived in Wellington.

The report by the scientists indicates that investigation of the matter has gone far since Mr J. A. Bruce first suggested the establishment'of a small geothermal power generating plant in New Zealand many years ago. After pointing out that drilled wells in thermal regions may be regarded as steam pipes coming away from an underground boiler, and that some of the 100 wells bored in Rotorua in the last few years have yielded v/orking pressures of 601 b to the square inch from relatively shallow depths, the new report says that the use of steam from such wells for generating electricity is the most obvious and rational use that may be made of an important national asset. "There is no argument as to the possibility of such a scheme, since electricity is at present generated in Italy on a large scale in steam plants using steam from drilled wells, notably at Lerderello and Castelnuovo."

The combined output of the No. 2 plants in each of these places is equivalent to that of Arapuni. There are a number of smaller plants in addition, but the size of a plant is not limited as in the case of hydroelectric generation where there is a limit to the amount of water available.

"Provided a suitable thermal area is selected, a plant of any size may be constructed and the power generated simply by drilling sufficient wells to fulfil the requirements. In the North Island, where water power is definitely limited, and there seems little chance of ever coping with ultimate demand with hydroelectric generation, the use of volcanic heat is a logical development. "Capital costs in the case of generation of electricity from geothermal heat are less, as there are no dams to be built, nor diversion tunnels. The cost, of drilling a number of wells must be considered against these. The time factor would appear to be an important one, since the investigational work necessary on a dam site frequently takes several years, whereas that on a natural steam plant site mighi take as many months." While the New Zealand armed forces were in Italy Mr F. E. N. Tuck, a mechanical engineer of the Public Works Department, wasgiven the opportunity to visit the Italian natural steam generating plants. He wrote a report on what he was able to observe during the period of his visit, took a large

number of Photographs and collected what he could m the way oi plans of the various plants. On the chemical side he was assisted by Mr D. E. Jobley, who inspected and reported on the chemical works attached to each generating plant, where various chemicals are extracted from the steam. These give valuable byPl °At°the present time the need for electric power is great and any means that offers the possibility oi large generating capacity with extensive development should odviously be investigated," the new report continues. "To put tne scheme finally into operation it would be necessary to build a drilling machine capable of dnJling wells to the diameter and depth mat might be required. As a preliminary, provision should be made in the near future to sink a test well to a depth of 1000 ft, or even 3000 ft, in which temperature and flow ot steam may be measured. "A small experimental plant might be constructed, but in view of Italian developments it would probably be more profitable to send New Zealand engineers to. Italy, or to import, temporarily, Italian engineers." . There are numerous areas m the Rotorua-Taupo region suitable for investigation for development purposes. It is interesting to note thai the New Zealand conditions most closely resembling those in the areas developed in Italy are to be fcund in North Auckland at Ngawha Springs, five miles from Kaikohe. • . "Geologically," says the report, "the Ngawha area is very similar to that at Larderello, and considering the distance of North Auckland from the present and likely future generating stations, this would be a most.suitable location for a natural steam-generating plant. In a recent survey of the area it was discovered that boric acid is extremely high in the waters from Ngawha Springs, and the recovery of boric acid would be a valuable by-product.

"In the case of a new venture such as this, considerable preliminary work is required, but once this was completed and the first station in operation, it would be likely that investigational work preceding later development would be comparatively little and much less than that required for hydroelectric development.. We have the resources, and they appear to be practically unlimited."