NATURAL HEAT

New Zealand Herald, Volume LXX, Issue 21562, 5 August 1933, Page 17

NATURAL HEAT

POSSIBLE UTILISATION POST-VOLCANIC AREAS HARNESSING LATENT ENERGY The possibility of utilising the great beat energy of the interior of the earth, especially in thermal regions, for the agricultural, industrial and domestic needs of mankind is discussed in an informative article in the Journal of Agriculture by Messrs. J. A. Bruce and F. B. Shorland, of the chemistry section of the department. Technical considerations, they say, hinder any immediate commercial development in normal regions, but in post-volcanic areas the internal heat of the earth is close to the surface and can be satisfactorily harnessed and applied to the needs of agriculture and industry. Increasing attention is being directed toward the development of heat resources in a number of the world's thermal regions, as a result, mainly, of Prince Conii's achievements in establishing steam-power units and boric acid recovery plants at Larderello, in Italy. Japanese scientists and engineers have of recent years been among the most closely interested visitors to Prince Conti's geothermal plant, and it is thought that these people may be already making a beginning in the exploiting of their own extensive thermal areas. Messrs. Bruce and Shorland are preparing a report on the whole subject of the utilisation of natural heat resources, and intend carrying out experiments wLen opportunity permits. Developments Is America The most important developments in the investigation of post-volcanic phenomena in America, they remark, are to be found in California. The Sonoma natural power plant now delivers 11,000 kilowatts to the neighbouring district. The problem of harnessing the steam in this district is relatively simple, as the unwanted gases are easily eliminated from the water vapour. An interesting agricultural utilisation is reported from a locality in the State of Nevada, where hot water from a quiescent geyser crater is piped to largo dipping-baths employed for ridding the cattle of external parasites. In the case of Chilean thermal areas, which are under investigation by a syndicate of Chileans and Italians, preliminary experiments indicate that at 270 ft. depth a considerable volume of steam particularly suitable for industrial application is available. The natural steam power plant at Larderello owes its origin to Prince Ginori Conti. The satisfactory results of his preliminary experiments on a small scale since 1904 led to the establishment of the large turbine power plant at Larderello, which has been in continuous use since 1916, distributing power for use at Leghorn, Siena, and Piombino, as well as supplying various local works. Technique in Italy "The steam supply for the Larderello station is obtained from some 12 wells, which, together gire 120,000 kg. of steam per hour at two atmospheres pressure," the writers say. "At first the steam was not led directly to the turbines, because the quantities of noncondensable gases in the steam would have proved a hindrance to the condensing apparatus. It was therefore decided to heat with the natural steam appropriate evaporators for feeding the turbines, the water for these evaporators being obtained by condensing the natural steam. "Tho modern tendency has been to abolish all intermediate apparatus, especially the condenser plant. At Serrazzario, near Larderello, for example, entirely satisfactory results have been obtained with a 600 kilowatt turbine directly coupled to the natural steam. According to Conti, such power, from the point of view of generating expenses, can be compared to hydro-elec-tric power, with the advantage, however, that the plant is considerably cheaper, while it has all the advantages of ordinary steam minus the expense of fuel. "Boring for natural steam is not a simple process. The technique at Larderello consists in boring with the slow percussion drill, or, as is now jnore generally the case, large rotary drilling machines. Iron tubes are set down to line the walls of the well as drilling progresses. At a depth of about 100 ft. steam is usually found. The steam is diverted through a special head-piece attached to the well and bearing a horizontal tube, whila tho rods of tno drill-ing-machine pass through an opening on the top of the head-piece. Possibilities in New Zealand "When tho requisite depth has been reached the drilling-rods are withdrawn, and the steam either comes up spontaneously, or, as is more isually the case, the weight of water in the tube holds the steam. A rough piston is inserted in the tube and rapidly extracted. If the operation has been successful, a miniature explosion takes place, and after several days tho well settles down to its normal output and is ready for use." From observations made by, one of the writers during a recent visit to Rotorua, it is thought that tho thermal area there, while far more extensive and perhaps more powerful, is not intrinsically different from the Larderello area. If small-scale experiments were organised on a rational basis and a survey made of our thermal regions, it is thought that large-scale power plants would ultimately be practicable, as at Larderello. • Abundance of Hot Water

The abundance of hot and boiling pools in and around the town of Motorua lead the writers to the supposition that the hot water will one day bo satisfactorily tapped and utilised by means of a suitable system of pipes for the forcing of glasshouse crops, in addition to heating homes, offices and business premises. Chemical tests of typical warm soil collected from near some of the innumerable warm pools at Rotorua indicate that the acidity of the earth in certain cases is much too great for the production of crops, and before satisfactory agricultural utilisation was possible it would be necessary to convey the warm water underground to loss acid areas with the aid of series of noncorrodable pipes. In this connection it is pointed out that in the case of a large pipe-line leading from a large area of boiling water near the Spout Baths for a distance of nearly two miles to the Ward Baths, the temperature drop is 50deg. C.