Engineer Advises Exploitation Of Lower Hinemaiaia Site

Taupo Times, Volume IV, Issue 191, 23 September 1955, Page 4

Engineer Advises Exploitation Of Lower Hinemaiaia Site

Following a recent request from the Borough Couneil j for a report on the development of the demand on the Council's Hinemaiaia River hydro-electric power scheme, and on the 1 best ways of meeting this growing demand, the^ Council's j consulting engineer, Mr. Lloyd Mandeno, has submitted such 1 a report under date September 12, 1955. After reviewing the increase in both demand and re- 1 venue, and discussing further power requirements, the report J recommends development of the site originally located twoJ miles up the Hinemaiaia River from the Lake, and states that J it can be developed more rapidly than any other site on the 1 river.

Mr Mandeno's report was before a special meeting of the Couneil on Monday evening last, when Mr Mandeno was present and dealt with a number of questions- arising from the report. Following discussion the Couneil decided, on the motion of Cr K. O. Lewis, seconded by Cr K. ' E. Young, that at an ordinary meeting to be held on October 5 it would consider a motion to borrow the sum of £105,000 for the construction of a power station- on the site recommended and the necessary transmission line requirements. Growth of Demand The report commences by saying that it would be conceded that no single person in the country, even as recently as three or four years ago, had foreseen the growth of permanent population and of building construction which had since taken place In Taupo and environs. No doubt the establishment of the power supply system had encouraged this growth, and had thus itself helped to create the problem of keeping abreast of the demand. The rnanner in which the demand for power had increased is tnen indicated for the years 1953, 1954 and 1955 up to August, by the following figures giving in kilowatt hours the power generated at the power station in each month, in each of the three years mentioned : January: 16,900; 93,500;- 232,764. February : 12,500; 79,200; 177,378. March : 16,400; 93,500 ; 207,060. April: 20,800; 113,700; 217,800. May : 28,600; 150,300; 259,380. June: 31,900; 159,660; 282,900. July : 39,800; 177,540; 302,760. Amgust : 38,400; 189,936; 284,640. For the remainder of the years 1953 and 1954 the figures are as follows. September: 40,600; 171,548. October : 43,400 ; 166,504. November : 49,320; 153,048. December : 64,430; 179,868. The report then continues : ''When these figures are plotted as a graph it will be apparent that there is no evidence of the rate of growjth of the demand slackening off, and it seems that, if the Couneil is able to cater for the demand, the increase will continue at the rate of about 1£ million kilowatt hours per annum. "Nor can this demand be said to have been created by uneconomic enticements in the form of low tariffs. The cost of power to the Council's consumers is in fact at present higher than in most towns. The average overall charge per unit sold being at present slightly over 2d. "As the amount of power generated has increased so has the revenue risen. iSales of power for the six months ending with the August meterreading were as follows : 1954, £8938 ; 1955, £13,857. It thus appears that the Department's revenue for the current year should reach about £27,000, and the surplus of profit for the current year should be in excess of £6000. Capacity of Plant "A careful review of the flow records kept at the Hinemaiaia headworks shows that the present generating plant, had it used all the availnble flow up to the capacity of the

past two years have generated about! 8$ million units per annum, whilst if;/ a second machine of about 750 had been also available the outpu| would on average have been aboul 11£ million units per annum. 'These figures compare ' with ap| proximately 2,100,000 units generate&j in the year ending 31st March' lastri and an estimated output of 31 mjjl lion units in the current year. These; figures " would apparently indicatej that there is fair reserve capacity, still available in the present tJppegj Hinemaiaia site, but the diflSculty j that the full available output of m power station cannot be usefully aih aorbed until connection is made witfi the State G-rid, when it will be possible to dispose of all surplus poweh| "In the meantime, from the reco«M or flow which have been recorded; twice weekly at the power house, it; Is apparent, that in spite of the fa& ly consistent flow of the river, ther| are periods when, as we reported las| October, the available output falls & 20,000 units per day, and in the lal| autumn of this year the flow fell St® further. "Approached from another MtfSw the present installed capacity of ths: plant is 1140 k.w. and on several oj| casions in recent months the demail| on the plant has exceeded - 750 k.f| Having in mind the rate of growth demonstrated in the figures QU0te| above, it is apparent that the plagl capacity must be augmented at early date." Further Power Requirements Ij Dealing with further power requ§8 ments, Mr Mandeno continues: UM the past five months new consumaffl have been steadily added to the'Sjfl tem, at the rate of 25 per moafl practically all of theni within M Borough, ,and the total is now ara| 1200. Amongst earlier consuiaKK connected, it is now apparent their previous reluctance to rely lifl the service, for such domestic requjS ments as cooking and water heah® has disappeared, and so the domeffl demand is growing." Referring to sawmilling, the states that at present one mill onijr" relies entirely on the power sup^ra but another has just been connexji® which will depend entirely on fl municipal supply. Two other are increasing their connections; H several hundred horse-power, and'n| application has been received frffl another mill in which motors will ta?| tal 300 h.p. It is apparent that further deni| opment will occur in the sawmillSH| industry, and we have been approa|i ed on the possibility of giving sup™ to an undertaking utilising 600 in the v-icinity of Taupo. The report continues by polhjtffl out that the Wairakei geotheriffl| power station and heavy water ii^| try is already increasing deman^M the Council's system. The ment Land Development branch e^| pects to have approximately farms esta'blished near Taupo ly, and their Superintendent made evident the importance he.'lH taches to availability of power, ially for pumping water. Further Development Advisera Pointing out that the economic being of Taupo is largely wrappSI|H

tries referred to, tlie report continues : "Having in mind the dependence of these industries upon power supply, and also the certainty of shortages and increasing costs of power from the National system, it is apparent, that the Council should take early steps to ^augment its generating' capacity. "We have no reason to recommend other than that the power available from the Hinemaiaia River should be further exploited. Below the present power station the river drops over 350 feet to the Lake, and the greater part of this fall can be economically developed for power generation. "Our recommendation is that tlfs site originally located two miles up from the Lake should now be developed. This site is very accessible. It can be developed more rapidly than any other site 5n the river. Its development ties in with the general plan of* development of the river and, as will be seen, the estimated cost of developing it makes it a very economic one. For various reasons the plan of development now proposed is some-' what different from that originally recommended, and the power house should now be placed further down stream, so as to utilise a greater fall. Proposal Described "It will be remembered that the Council expended a considerable sum on geological investigations on this site in 1948 and 1949, and that following these the considered opinion of the officers of the D.S.I.R. was favourable. We enclose drawing No. 207/64 showing the proposed method of development. "The working head will be devel-' oped by the construction, in the narrow 50ft deep canyon, of a small arch dam having a total height of about 70ft, compared with 55ft in the present development. Flood w-aters will pass over the crest of the dam and over spillways on either side of it. Other features of the scheme will be very similar to the upper development. "The principal difference in this lower development is the inclusion of a fairly lengthy conduit, consisting of *reinforced concrete factory made pipes, six feet internal diameter, which will . . . connect the intake with the surge chamber, some 1850 feet downstream, and from this point the steel penstock, approximately 350 feet in length, will convey the water to the power house. Type of Generator "The power house, we propose, will house one machine capable of developing 1250 k.w. It is proposed that this unit will be of the simplest description using ^an induction generator instead of the usual synchronous .type. The use of such a machine is possible only as an auxiliary on an existing generating system. We are not aware that there are any existing instances of the use of such a machine in New Zealand. "Its advantages are that it greatly simplifies the control and other electrical equipment of the station, and is thus specially adapted for use in imattended stations. We propose that the present station should be unattended and so make no provision for permanent housing. "We recommend that the power be generated at 3300 volts, and stepped. up to a transmission pressure of 33,000 volts. It will involve running a ILmile spur line to connect with the existing transmission line, which ♦we propose shall be converted from 11,000 to 33,000 volts operating pressure as far as the southern boundary of the Borough, and ultimately on to Wairakei. "New transformers will be required for stepping up the pressure at the upper station, and for stepping down at the Borough boundary." Estimated Cost of Works The report then details the estimated costs of the works mentioned, total ling £92,975 for the construction of the proposed new power station, plus £9570 for the transmission re-

quirements referred to in the report, making a grand total of £102,545. The report states that "it should be possible to complete these works soon after arrival of Government pcwer at Wairakei, and thus to dispose of the whole of the Council's surplus as soon as this lower Hinemaiaia .Station can be completed. There should be no question, therefcre, that the venture will be selfsupporting from the start. "It is estimated that it will be capable of generating 9,000,000 units per annum at an annual cost of about £7000. The Council will be assuring itself of an economic source of supply and will be providing for the growing requirements of the Councirs area of supply. It will at the same time assist in some measure to relieve the impending shortage of power in the North Island. "We see no reason why the proposed lower plant should not be operating in less time than it took to instal the upper scheme, which was operating with the small generating unit in less than two years from the receipt of authority to proceed. From eorrespondence we have had with manufacturers we believe that better deliveries of generating plant will now be possible. "Whilst seeking authority for this additional generating plant your Council might. seek authority for the additional capital which is bound to be required for extension of the reticulation system, but in view of the urgency of increasing generating capacity both for local use and for sale to the State, we propose to omit discussion of this aspect in the present report. "We recommend that application be made for authority to raise a loan of approximately £105,000 for the purpose above set out."