The Press.

Press, Volume LXIII, Issue 12934, 14 October 1907, Page 6

The Press.

MONJXAY, QOT9BBB 14. 1907.

AN LJSSON FROM GENEVA. Our readers will remember that when, the harnessing of the Wtims,k,»riri w«a first mooted, the hydro-electrio initallation at Chevres, near Geneva, was referred to v » highly- suoceseful example of such works, and it wax suggested th«t the services of Monsieqr Turrettini, the engineer who designed the undertaking, should bo obtained to adviae the Christchurch City Cquncii in regard to tho harnessing of the, Wa> makaiiri. It may also bo remembered that some three or four months ago it ««» mentioned in "Tho Press" that owing to the Chevres installation not fyilfityin* an eipert Commission had. 'been appointed to report on the work, and that the members or that Commission had pointed out serious defects in its construction, and recommended extensive alterations and improvements. Furthermore, in consequence of tho hydraulic installation, evert with these improvements, being incapable of furnishing the required amount of power during certain months of *he year, tho Commission reported that, in their opinion, it was necessary t'i supplement it by a steam lotion, estimated to cost £100,000. In view of tho importance of the subject, -no communicated wjth the municipal authorities of Geneva for the purpose of ascertaining whether the recommendations of the Commission had been carried into effect, and if so, with what result. With great courtesy the. Director of tho Electric Service at Geneva has furnished us with full information not only as to the engineering details required, tut also as to the financial working of the service. The particulars supplied eeem to us of great importance, and YQ have little doubt our readers will be interested in a brief summary of the facts disclosed. At first eight it would seem as if

Geneva were exceptionally well placd for the development and nee of electric power—much more favourably situated than Christchurch in this respect. The works in questions-known a* "I'Usine de Chevres"—are situated about four miles from Genera, at a point below the junction of the Arre with the Rhone, co that there is a large body; of water to be utilised. A substantial concrete dam or "barrage" with sluice gates to allow tho water to escape in time of flood is thrown across the river, •nd an intake canal 40 metres wide leads the water to the turbines. On escaping from the latter, it is led ieto 4 tail-race, separated by an embankment from the main channel along which the river makes its way from the sluice gates above mentioned. The chief drawback of the river from the engineer's point of view is that, as in the caw of mountain, rivers in New Zealand, there is » considerable difference between the cummer level and the winter level. In the case of the Rhone, the power available is less in the cummer when the river is in flood from the melting snows, than it is in winter when the river is low, because, in the former case, it is necessary to open the sluice gates to keep the -waterin Lake Geneva from rising to flood-level, the consequence of coqrse being to reduce the difference in level between the water above the "barrage" and that below. In other words, the head of water available for the turbines is lessened. Speaking generally, it is found that while in winter there is a fall of about 26 feet available, in summer the head of water is reduced to about 14 feet, and sometimes even less. It was in consequence of this great reduction of power in summer—the extent of which had not bean fully foreseen—that it hae been found necessary to provide a stea,m plant to supplement the hydraulio installation in, the, eqramer months. To meet tH» variation, in the level of the water, the I turbines are installed in pairs, one above the other on the aaine shaft. Tfwturbines in the lower rank are worked in the winter and those in the upper ranls in the cummer. There are fifteen of such groups of turbines of 1000 h.p., and three small turbines of~lso h.p.

It is not necessary to go into all the criticisms passed by the expert Commission on, the construction of these worl|». They found fault with the alnice gates, -with the int*ke canal, ■with the position of the turbinee-r----which they said ought not to hare been placed at the end of th.c. cuWe-eao formed by the intake c*n«l—with the "digue eeperative" marking off the tail-raoe, and with various other featuree. It will be sufficient to, mention briefly the improvements whiohi they, held to b» absolutely neotseary, and whfoh Ijare fine* b««n carried out. Opening* h>v«vbeen mad© In the "dign* •4f»T»M«i , ' >t h*ving bam found that the channel left for tht «*9*p* of tk,e «am body of -wat«i in good. tira«i was too amalj. An immenae gating ooathig upwards of £5»,000, ha* baen conatructed above the intake can*} to keep out drift|wood, leave*, grajpj, etc., which formerly clogged up the grating \n front of the turbines at th* end of the oul-d**a<p, and thus led to frequent •toppffee of the machinery. IV tu,rbjn«! thjieiselTee have undergone mmc euoMMful raodificatione, and a boating w#te? «»te now enab)f%th«fn to be got at «a|jly f»T Purpose* of repair. llieee improvemente, ti*# Pireotor o| the Electric Service injformt v*, eiw* g<IQd # Tei«Ul an 4 much more v<mes » f»W»WIW now than formerlyr But, of course, they d$ nob *mt the great difficulty experienced ftotia the d*aci*ncy of power in fummer. At that timt of VIW 5»»T» M Moire «iph»^t«4 t the 4i#ouHy is due to there, oeiqg. too much wi|tW; b«t ♦▼♦? win**' - . »1thoqfh «r« mud» faore favourable, it sometimes happens that the worke suffer from there not being i wfte? epqugh, #yen when the sluice gatee are dosed. The result of the variations in the low of the Hhone lif that out of a possible 10,000 h.p. I at tb* work* Mi 40QO \a 6000 β-ju oan bo counted upon several i-moßthe jti the year, and the record has soßMttaex f*Uen. to a« low a» 2000 h.p. 1b meet this- deficiency the reserve steam plant has been provided. The complete project is for the est%bjiahjpent of five, turbo gen--1 eratom of 860 kiilowatts furnishing a cpntmuom ?H rif * n ,' t °f &® vo ' ts or * ne , an.d five turbo-alternato|f of 1000 h.p. or more to supplement the water turbines. At present only threes turbo-geaeraters and one turboalternator have been installed. Up to the end , of 180Q the on the steam reserve amounted to upvranLa of £80,000. The entire capital cost of the Chevree lyorke at that date amounted to 13,560,150 francs, or, say, over half a million sterling. The financial aspect of the undertaking is. so interesting, however, that it must be reserred for another article. We fancy many of our readers Trill be surprised at the facts to be disclosed.