HYDRO-ELECTRIC POWER

Evening Post, Volume XCVI, Issue 15, 17 July 1918, Page 11

HYDRO-ELECTRIC POWER

THE MODERN STEAM PLANT

CAN WATER-DRIVEN PLANT PRODUCE ELECTRICITY CHEAPER? 10 IB* EDITOR. Sir, —From the numerous letters and reports of speeches on the-subject of hydro-electric development which have been appearing in your paper lately it would appear that the majority of the gentlemen who are strongly urging the Government to immediately undertake the construction of one or more schemes in the North Island take it for granted that generation by steam is antiquated, and that if a hydro supply of electricity becomes available the local householders will obtain it at a fraction of the present cost. The idea of harnessing the power flowing to waste iirour rivers appeals to the average layman, and he naturally jumps to the conclusion that power can be produced and delivered at a very low cost compared with power from a steam plant. This letter is writtesoyith a view to showing that this generally accepted opinion is not necessarily a correct one, and to urge the need for a caroful investigation of the claims of-both systems, particularly at the present time, when it is imperative that- no large sums of public money should be spent unless there is a certainty of an immediate return on the investment. Whilst the . necessity for conserving our coal fields for the use of future generations is recognised, as is also the advantage of a supply of electricity from a source which will practically be independent of interruptions due to labour troubles, these reasons in themselves are insufficient to warrant the undertaking at the present time of large development schemes with a capital outlay far in excess of that of steam plants of similar capacity. In advocating the necessity for giving the whole position careful consideration, the writer desires .to direct attention to several extracts from a statement of great importance which appeared recently in the Proceedings of the American Society of Givil Engineers. This statement, which was submitted'to a special committee of the U.S.A. Chamber of Commerce on 14th January, 1918, on behalf of the Engineering Council.of America, by Mr. Calvert Townley, bears a preface reading as follows: " Being empowered, as it is, to speak for the American Society of Civil Engineers, the American Institute of Mining Engineers, the American Society of Mechanical Engineers, and the American Institute of Electrical Engineers on matters of common concern to all these bodies, the council's official utterances concern only such underlying principles and economic facts as are endorsed by all engineers and beyond the field of controversy.".. The portiop of this statement deserving special attention reads as follows :— "It has beeri frequently pointed out that as the nation's coal supply is der pleted, the cost of coal must rise, thus increasing the cost of steam electric power as fi competitor and raising the market value of hydro-electric power accordingly. The rising price of coal is a matter of record, but it is not so generally known that the improved efficiency of steam producing machinery (boilers, engines, generators, and auxiliaries) has more than, kept pace, so that the net cost of producing electric power from coal has steadily declined. As applied to the prewar period, it may bo stated that over a period of 10 years the cost of -coal has risen on an average of 1 per cent, per year, while the cost of electric power produced from" coal has fallen on an ;j.vorage '2-^ per cent, per year. In addition to these facts—stjll referring to prewar conditions—the cost of steam electric generating equipment has bepn greatly reduced. This fact is due partly to ,Mie introduction and subsequent ■ improvement of the steam turbine, and in part to the great increase in the size of the units now available. There- is nothing to indicate that the limit of improvement in the design of steam prime movers has been reached or is even in sight. It is, therefore, a reasonable assumption that further advances in the art will.continue to occur and to cut down both the fixed charges and the operating cost of steam power as a competitor of water. "The largest modern steam turbine has now'some twelve times the capacity which the largest reciprocating engine had fifteen years ago. Stated another way, the cosb of the steam electric plant per unit of capacity just before the war v/as about one-third of what it was fifteen years previously, while the energy it produced per pound of coal has increased 50 per cent. The cost of producing power from either' water or steam is a function of load. Fixed charges remain practically unchanged in bpth instances, whether the output in energy be large or small, but with a steam plant, increased output means increased fuel consumption, while a water plant operates either with or without a load, with but a little variation in expense/ Taking the case of a steam plant where the cost of fuel per unit of installed capacity per year would be 11£ dollars (48s), and assuming the other operating and maintenance charges to fairly offset those of a water installation of equivalent size, 11^ dollars represents the additional fixed charges which the hydro-electric plant could carry and produce power at equal cost. If the fixed charges total H£ per cent., therefore the hydro-electric investment per kilowatt capacity could exceed that pf steam by 100 dollars. "This is not an abnormal excess, and many hydro-electric developments exceed the cost of equivalent steam-driven plant by much greater amounts, and in these cases they become commercial projects only if either coal be more expensive iper unit of output, or the plant factor be higher or some other operating or maintenance conditions bs more favourable.

Hydro-electric power is inferior to steam electric power in every particular except cost, and therefore water-driven service must be cheaper than steamdriven in order to.justify its existence. A steam plant costs" usually only from pne-fifth to one-half as mudh per unit of capacity ag a hydro-electric' plant, so that the latter must carry very much heavier fixed charges. "The disability of water service is usually even greater than the ratio of the costs cf two equivalent complete developments. Steam flow is subject to seasonal variation .and therefore to complete or partial interruption by drought in summer and floods are a. menace.

"Long transmission lines may break, or the service be disarranged by lightning. The losses on such Jines vary with load and are frequently responsible for annoying pressure variations. On account of these and other reasons hydroelectric power cjinnpt prevail against steam competitions at the §a.me or a. slightly lower price. It jnust be mate^ dally lower.

"We do not mean to amply that water power may not be a- commercially practicable conipet-itor of steam. Many successful hydro-electric' installations give substantial proof of the contrary. We do wish most emphatically to combat, however, the widely held but mistaken view tljai any water driven plant will prpd'uee power at lower costs than steam and that the margin a's so la.rge that investors generally are eagerly 'seeking a. chance to put money intoiiydrpjelectrifl projects.

"The most careful investigation, frequently demanding. substantial expsndiivpie and the keenest eerjitiny by experts;

is needed to discriminate between worthy and commercially impracticable projects and the difference is often so small that the imposition of even what seems to be> minor burdens is sufficient to turn the scale in favour of steam and entirely prevent what might otherwise be a desirable hydro-electric development," Seeing that the above statement is the result cf mature consideration by representatives of all the great engineering institutions of America., it behoves our authorities to make comprehensive investigations before committing the country to a number of large and costly developments, especially in view .of the financial *■ position which would have to be faced during the next ten or fifteen years. —I am-, etc., CAUTION. 16th July.