HYDRO-ELECTRIC POWER

New Zealand Times, Volume XLII, Issue 9789, 12 October 1917, Page 2

HYDRO-ELECTRIC POWER

SCHEME FOR NORTH ISLAND REPORT FROM PUBLIC WORKS DEPARTMENT ENGINEER. A. report on the hydro-electric development scheme for tho North island is contained in tho Public Works Statement, presented to tho House of Representatives yesterday. . Mr EParry (electrical engineer) in this report states the present- position, pi the investigation into the scheme i o' developing tho water-power- resources of tho North Island. Before relating the actual position of tho work of in vestigation ho records some underlying principles which governed-hiss-actions in preparing the scheme. ■ ‘‘lt is, 1 think, clear,” states Mr Parry, “that a supply from a’ ‘single source is not tho Pest solution," of: the problem of a general supply tor the North Island; and the question arises as to what is the next largest possible concentration which can bo effected, having regard to all circumstances! it is quite obvious that the unit should uo as largo as possible, not only -on general principles, but also on the special ground that small water-power developments aro unduly costly. Generally speaking, a water-power source of less than about 10,000 horse-powov cannot bo economically developed. . . ■ The scheme which best satisfies ail requirements is one in which, at t e outset, three water-power sources would be developed for supplying respectively the Auckland district, the Hawke’s Bay district, and tho Wellington district. These sources would, in the ordinary course of development, be linked up together,.. and by reinforcing each other provide additional guarantee of continuity of supply. Regarding tho source of , power tor Hawke’s Bay district, undoubtedly the best is Waikaromoana. The amount of power obtainable from this source Is greatly in excess of. the. requirements of this district, and it should bo regarded as a supplementary source tor supplying the Wellington -district. V ery complete surveys have been-carned out during last year and accurate measuremonte made of the flow,’ and all the necessary information obtained to enable the most economical method of development to be prepared and carried out. „ SOURCE FOR THE WELLINGTON DISTRICT. “As regards a source of supply for tho Wellington district, considerable difficulty has been encountered in finding a source which satisfies all the requirements, because, although the rivers are numerous, they' do nbt'lend themselves to economical development, and as a rule the power to be derived from any one source is small compared with the requirements. It has been suggested that tho Hutt river would form a suitable source for supplying the southern end of the Wellington district! The amount of water is barely adequate for the needs of Wellington city if provision is to be made for natural growth and progress, whilst for the amount of’power-available-the - cost of development is excessive. - In any case the amount of power obtainable is not large enough, to supply an extended district, whilst a power station in the Manawatu district is well situated for supplying Wellington, Wairarapa, and parts of the Hawke’s Bay and Taranaki districts, having regard to the distances- and the power to be supplied in, each locality. w • “After considerable investigation the most suitable source for the supply of the southern district is found to be the Mangahao river. This, river,'rises on the slopes of Mount Dundas on ,the Tararua ranges, and flows into. t . the Manawatu near Woodvillo, arid -it is found that by diverting through thehills for a total distance of three miles there is made available the fall of 1040 ft in the sixty-five miles of river between the Mangahao and the loop of the Manawatu near Sbauribti'. 5 ;It : is proposed to develop this source, by tunnelling through the range from the Mangahao into tho Tokomaru Vafley, there diverting a part of the - Tokomar u, and -then from the Tokomaru Valley through into tho valley of the Mangaoro with a power sta-tjori ..situ-, ated within three miles, of tbqj ? ir^l way,, at Shannon. - voc-im I - “Observations of the flow wore-made, during last season, which was..'exceptionally dry, and aro also being made’ during the present season, and based’ upon tho dry-season flow it is possible to obtain 20,000 horse-power on;a’ 50-per-cent load-factor basis by impounding the waters and taking advantage of . the natural features of the country for the purpose. This is sufficient to satisfy the power requirements of the district which it is intended to’serve, for some time to come, but will require to be supplemented in due •course as tho country develops. The. natural extensions of the transmissionlines from three sources will ultimately link them together,so, that by this means security will be- obtained, and also additional supply Obtained for the Wellington district_ from the other sources. It is possible, however, that in course of time the requirements will be so great as to require another development in the Taranaki district, where there is more than one promising source. . “In the design of this scheme I propose to adopt a new principle in regard to the provision for a stand-by. It is necessary to provide an additional power unit over and above tho power obtainable from the source, so as to permit of the overhaul and repair of machinery. ' The Usual method is to install a-n extra unit of Waterplant in the powar-house! In the present instance I propose that the standi hy unit should he a complete steam | set. The advantage of a steam standby set in this scheme is that not only does it serve the purpose of a spare unit, but it also provides means of tiding over short periods of ,exceptional or abnormal low water, thus enabling the available water to be Used to a larger extent. The additional cost of the steam unit over a • water-power unit is not great, and the cost of running on infrequent occasions would be a negligible proportion of the total operating cost, whilst the additional security and value conferred on tho water-power plant is out of all proportion to the added expense. A SUITABLE STEAM PLANT. “I would propose further, instead of installing the steam unit at the power-house, to take advantage of the fact that Wellington city ha s_ already a steam-plant installed which is,of ..the capacity required for the purpose aforesaid, aud as they will deem- it- advisable and prudent to maintain this

in running .. condition to provide against temporary interruptions of the supply, which are inevitable on every transmission system, there should be no difficulty about coming to terms for the use of this plant for relieving the load on the water-power plant in oaso of necessity. Some modification of the existing Wellington plant may bo te cessary to fit in with this scheme, but this is a detail about which t^ re should be no difficulty in a mat-tci which is to tho advantage of both parties. j , “The cost of providing headwords, power station, and plant for 25,000 horso-powor would be at normal prices £420,000, which is under the limit ot £2O per horse-power specified above. This illustrates the advantage ot concentrating the power supply for a considerable district in one source. It, for instance, wo sought to provide for ■the needs of Wellington city and immediate neighbourhood only from this source the cost of hydraulic works for the power required would be excessive, whereas when developed for the full capacity and for the benefit of a larger area and population it becomes a sound commercial proposition. ... i‘.‘As regards tho area to be supplied, there is an economic limit to the area over which a given amount of power can be distributed, and one of the obstacles to a _ satisfactory scheme of power supply in New Zealand at present is the small amount of power required per square mile of area supplied. Having regard to this principle, and stretching it to ’ tho limit, we Should bo working on economical lines in serving the following districts from this source: the whole of the Wellington province as far north as Taihapo and Wanganui, and the southern portion of Hawke’s Bay. I would propose, in ’ th’e first place, to run trunk lines to Wellington, Palmerston North, Wanganui, and Miasterton as chief centres, and from these centres, as well as from intermediate points on the trunk line, to provide tine necessary distribution lines and sub-sta-tiona to serve the 1 surrounding dist riots. - ’ THE COST. “The cost of providing the trunk lines, distribution-lines, sub-stations, and other services to give a supply in bulk to local distributing authorities and to large power-users throughout this area would be £580,000, making a total of £1,000,000, which expenditure is at the rate of £4O per horse-power. The capital charges on this expenditure at per cent., to include intexest, depreciation, and sinking fund, work out at £3 per horse-power per aniiuin; the annual cost of maintenance and operation would amount to £25,000 per annum, or the equivalent ot per horse-power per annum. Both charges require a return of £4 on me average per horse-power per annum in order to provide for all charges with a reasonable provision for depreciation. Wo know by experience in Christchurch that we can secure this revenue without, difficulty, even where economical fuel plants are' already stalled.“The development of the Mangahao would help Wellington out of a difficulty, and from the Government’s point of view Wellington alone would provide wan immediate load on the Station of about one-third of its capacity, and would enable the largo area outlined above to be supplied at the same time 1 both economically and advantageously, and the prospective markets’ In these, -districts, combined . with thqriatriral . increase iri Wellington, should absorb the balance of the power available in.a very short time. “Complete survej’s have been , made o? the Mangahao scheme and plans and estimates _ prepared. A survey of the 'transmission-line between Shannon and Wellington ,is . proceeding and will shortly bq completed, and the position of‘the’’sub-station to serve Wellington and the Hutt Valley has been located. INVESTIGATIONS MADE. “Summarising the foregoing, the scheme of development recommended is that three sources of water-power should be developed in the first place—i.e., Lake Wnikaremo-ana for tho Hawke’s" Bay district; Arapuni Gorge, or some other to be selected, for the Auckland district; and the Mangahao river for the Wellington district. These three sources in a natural course of extension! v will get linked up together, thereby-enhancing the value of each source by adding to the security of supply and enabling a continuous output to be maintained throughout the whole of .the Island. “The position in regard to the investigation. now iis that detailed surveys have, been made of the Mangahao river, of Aratiatia rapids on the Waikato,' of the Arapuni gorge, and the Waikato, Pokaiwtionua, and Waipa rivers near Horahora, and of Lake r Wiiikaremoana. Further investigations and calculations utilising existing surveyl information have been mode of the Hutt river, Huka falls, Kaituna river, and other schemes. Observations of flow made during the recent sequence of dry seasons have necessitated a modification of .previous estimates of tho power obtainable from the various sources. A survey Staff is at present engaged on the transmission-line between , Shannon and Wellington, and will shortly bo transferred to tl|i Auckland district in older to survey a route for the trunk line between the Waikato axid Auckland.

"Considerable difficulty has been found in maintaining the staff for survey purposes, and we have at present only one survey party at work, whereas there should be three or four, with corresponding office staff, in eider to carry out tho work expeditiously; but under present conditions it is Xouna impossible to keep the parties together for long, and! we have to he content with slower progress. “As regards the order of development tho Waikaremoana scheme snouiu bo deferred for the present. The development of this source should, to my mind, bo made dependent upon tho ■construction of the Napier-Gisbornc railway. The railway should open up a better road for tho transmissionlines and -render them more accessible for the construction and maintenance. At present this country is most difficult, especially from a maintenance point ot view. There is every reason also in favour of operating this railway electrically. “The Auckland and Wellington schemes should proceed simultaneously. The work in connection with the latter, however, is more advanced, anti if labour is obtainable, which is very doubtful, the headworks could be put iu band at onoe and prepared iu readiness for machinery and pipe-lines, which, however, could not be obtained during the continuance of the war. A beginn-ng could bo made perhaps by constructing roadways for access to the headworks. “The schemes outlined above provide for tbeuieed of the more settled portions of the country, and inaugurate a general ■'scheme'' of distribution which will ; ip course of time embrace the whole country.”