DEVELOPING A SMALL WATER POWER

The prime requisite to the creation of a water power is the existence of [falling or flowing water]. The amount of power which may be available varies; first, with the amount of water flowing, and second, with the amount of fall. It requires about one cubic foot of water per second, falling through a height of ten feet, to make available one theoretical horsepower. The fall may be either naturally concentrated at one point in a cascade or it may be artificially concentrated, for the purpose of development, by combining the fall of several cascades or a series of rapids. This may be accomplished by either of two methods; first, by building a dam at the downstream end of the rapids to impound the water so that the entire fall is concentrated at the dam, or second, by building a dam at the upstream end of the rapids and conducting the water through a closed pipe to the lower end of the rapids, where the resulting water pressure will be exactly the same as in the first instance. A variation of the latter method consists of diverting the water from the natural channel at the head of the rapids and carrying it in a canal, on a slight down grade, along the side of a hill to a suitable point at which the water is turned into penstocks which run directly down the slope to the stream, where the power development may be made. The latter method, involving the construction of a canal, is open to the objection that considerable trouble is usually experienced from the accumulation of ice in the winter time. The first two methods described are the most common.

Cascade on Indian Creek, Warren Co., N. Y.

Typical Example of Undeveloped Water Power

The amount of water which flows in a stream, in New York State, whether large or small, is subject to remarkable variation. Only one who has observed very carefully and continuously, by actual measurement, the extremes of fluctuation to which a flowing stream is subject, is in a position fully to appreciate this. Some of the larger rivers of New York State are subject to such fluctuations of flow that the amount of water discharged during flood periods is several hundred times as much as the amount that flows in the extreme dry period. Also in many instances from one-half to three-fourths of the total runoff of the stream during the year occurs during a period of a few weeks in the spring months, when the accumulated snow and ice is melted and runs off in conjunction with the warm spring rains. Unfortunately, reliable data relating to the fluctuations of small streams in this State are very meager. It is, however, a matter of record that the smaller streams for which records are available are subject to greater fluctuations per unit of tributary watershed area than are the larger streams. It seems logical, therefore, to assume that the very small creeks and brooks are subject to fluctuations relatively greater than those recorded for streams of only relatively small size. This fact must be borne in mind by any one who proposes to develop the power on a stream, for if it is overlooked the project is not so assured of success. For most purposes power is required in about the same amount for all seasons of the year, while, as previously stated, the streams run off most of their waters in the spring. Therefore, in developing the power of any particular stream, if the power is required to be fairly constant at all seasons of the year as is usually the case, there are two considerations which must not be overlooked:

First—Will the minimum flow of the stream—that is, the flow which occurs in the driest season of a dry year—be sufficient to furnish the amount of power required?

Second—If the minimum flow is not sufficient, what means are available for storing the surplus water from the wet season until the dry season?

The subject of equalizing stream flow throughout the year by means of storage reservoirs has been so thoroughly discussed in the reports of the Commission that further discussion in this connection does not seem warranted.

Taking a general average throughout the State of New York, large streams may be depended upon to produce from one-twentieth to one-quarter of a cubic foot of water per second per square mile of tributary drainage area, during the driest period. Streams having only one or two square miles of drainage frequently dry up entirely in the dry seasons. If a power development is proposed of such a character that some considerable sacrifice of power might be made in the dry seasons with no serious loss, most small streams may be developed to provide for as much as one-quarter to one-half of a cubic foot per second per square mile. On the other hand it is often found practicable to provide a small auxiliary power plant, such as gasolene or kerosene, to fall back upon in dry weather, or to supply extra power occasionally, in which case the water-power development need not be limited to the minimum flow of the stream.

The power of falling water may be applied to practical purposes in several ways. One of the simplest ways, should it be desired to use the power of the stream to pump water, is by means of what is known as a hydraulic ram. This is a device which operates on the principle of the impact due to the sudden stoppage of flow of a column of water. By means of this device, or engine, water falling through a very small height may be used to raise a portion of the same, or a comparatively small amount of other water, to an elevation considerably higher than the supply. The mechanical efficiency of the hydraulic ram is comparatively high under certain conditions but generally is very low, useful work which manufacturers claim may be realized varying from 38 per cent to 80 per cent. The minimum fall under which a ram will effectively elevate water is about two feet. This fall will elevate about one-thirteenth of the supply to a height of twenty feet. Under the most favorable conditions and a fair amount of fall, a ram may elevate water as high as 120 feet. The proportion of water which may be elevated varies from one-twentieth to two-sevenths of the total supplied; and, accordingly, the proportion of water which must be wasted at the impetus valve of the ram varies from five-sevenths to nineteen-twentieths. These proportions both depend upon the ratio of the amount of supply to the amount to be elevated, that is, a small proportion may be elevated to a considerable height and vice versa. In cases where a small brook of suitable quality is available for domestic water supply, it is often entirely practicable to install a hydraulic ram which will pump a sufficient proportion of the amount of supply to furnish a household with all the water necessary for ordinary domestic purposes, in spite of the fact that the brook may be on a lower level than the house. Owing to the fact that a hydraulic ram may be applied only to the purposes of elevating water, it is not generally considered as a means of developing water power, although in the broadest sense it does constitute such a development.

On the other hand, the purposes for which power is usually required are not only for the elevation of water for a water supply, but for many other and varied requirements. In such cases the power must be developed in such manner that it may be utilized to operate machinery near the site of the development, or transmitted for some distance, and there used to operate machinery or for lighting or heating. To develop water power in this manner requires some kind of a waterwheel.

There are several types of waterwheels, the principal ones being known as “undershot,” “overshot,” “breastwheel,” “[turbine]” and “[impulse].” The overshot wheel is a type very familiar to most readers, being usually of home manufacture. It consists, usually, of a wooden wheel with water compartments arranged at regular intervals around the periphery. The water is fed into the wheel at the top, just off the center. It flows into the compartment at the top and the weight being exerted on one side of the supporting axle causes the wheel to revolve, the water spilling out when the compartment, or water pocket, reaches the bottom. This type of wheel depends entirely for its power upon the weight of the water which causes the wheel to revolve.

The undershot wheel is very similar in construction to the overshot type but depends more for its power on the velocity of the flowing water which strikes the blades, or buckets, on the under side of the wheel.

Turbine Type of Waterwheel

Phantom view of wheel-case

The breastwheel is also similar in construction but is in reality an improvement upon the overshot and undershot types. It depends for its power on a combination of the action of gravity and the impulse of the water striking the blades, or buckets. The water is fed into the wheel a little below the height of the axle and usually enters with considerable velocity, a part of which is transformed into useful work by the wheel.

The turbine is a type of wheel which is very extensively used. It is usually constructed of metal and consists primarily of a series of curved vanes, or runners, whose arrangement is similar to a screw. The action of the water flowing through these curved vanes causes the vanes and shaft to revolve, the vanes being solidly connected to the shaft, which may be either horizontal or vertical.

The fundamental working principle of an impulse waterwheel is the turning into useful work of the impulse due to the velocity of a jet of water issuing from a contracted orifice. This is accomplished usually by conveying the water from the dam or other source of supply to the waterwheel in a pipe of comparatively large size and then gradually reducing the size of the pipe immediately in front of the wheel to a comparatively small size by means of a reducer section, which is fitted with a nozzle the opening of which may or may not be regulated in size. This contraction of the stream of flowing water causes a spouting of the water under pressure and the water issues in a jet with very high velocity. The jet thus issuing from the nozzle strikes the cups of the impulse wheel which are arranged at regular intervals around the circumference of a metallic disc which is centered on an axle. The cups transfer the velocity of the jet to the wheel, and the water drops from them with very little velocity left in it.

Impulse Type of Waterwheel

Showing jet of water striking cups. Wheel illustrated is
very powerful, but principle of small wheels is the same

In general, the turbine type of wheel is best adapted to low heads, or falls, and the use of comparatively large volumes of water, and the impulse wheel is best adapted to the use of a comparatively high head, or fall, and a comparatively small amount of water. There are certain intermediate conditions for which the manufacturers of each type claim their wheel is best suited and in such instance a study of local conditions is always necessary to determine which type of wheel is best adapted.

The development of a water power by means of any kind of a waterwheel results in the conversion of the energy of the falling water into mechanical power which is exerted in a more or less rapidly revolving shaft. In order to apply this power of the revolving shaft to some useful purpose, there are several methods which may be used. The shaft may be directly connected to the shaft of an electric generator, or dynamo, to generate electric current, or it may be directly connected to a machine which it is desired to operate, provided the machine, or dynamo, is required to operate at the same speed as that of the wheel shaft. This is frequently not the case, so that under ordinary conditions the shaft of the wheel is fitted with a pulley, which in turn is connected by belt to another pulley on the machine which is to be driven.

Motor-driven Mangle

By using pulleys of different diameters on the shaft of the waterwheel and the shaft of the machinery to be driven, the speed of the machine may be several times more or less than the speed of the waterwheel. For instance, if the waterwheel revolves 200 revolutions per minute and it is desired to operate a machine, connected by belt, at a speed of 1000 revolutions per minute, a pulley of comparatively small size, say four inches in diameter, is placed on the shaft to be driven, and a pulley of five times the diameter, or twenty inches, is placed on the shaft of the waterwheel. This causes the shaft of the machine to revolve at a speed five times as great as the waterwheel. If the speed of the waterwheel is greater than that required for the machinery to be operated, then the reverse operation is followed out, placing a small pulley on the shaft of the waterwheel and a larger one on the shaft of the machinery to be driven. If the speed of the waterwheel is to be magnified more than about six times, it usually requires the installation of a countershaft and another series of pulleys in order to avoid the use of very large and very small pulleys. A pulley which has a very small diameter does not operate satisfactorily without considerable loss of power, and a very large pulley is objectionable on account of the space which it requires.

When a water power is once developed it may be applied to practical use either near the place of development or at a considerable distance. If it is to be used for power only, and not for lighting, and can be used where it is developed, there is no need of converting it into electricity. But if it is to be used for lighting, or for power to be applied at a considerable distance from the water-power site, then it becomes necessary to convert the power into electricity, in which form it may be most conveniently transmitted from one place to another. This requires an electric generator, or dynamo, to be driven by the waterwheel, and a transmission line, preferably of copper or aluminum wire, to carry the current where it is to be used. In order to reconvert the current into power at the end of the transmission line, where the power is to be used, it is necessary to run the current into an electric motor, the shaft of which is made to revolve by the action of the electric current. This motor may then be connected directly, or by belt, gears or chain drive, to the machine to be driven.

It should be borne in mind that in each of these steps of changing from water power to electric current, in transmitting the current over the wires, in reconverting it into power, and in transferring this power from a motor to a power-operated machine, there are losses of energy. These losses vary considerably in different instances. Assuming, for illustration, that a water power, whose theoretical power is ten horsepower, is required to drive a power machine at a distance, the efficiencies and losses will be somewhat as follows:

Waterwheel, efficiency 80%, Loss 20%, generates 8.0 horsepower.
Connections,“95%,“ 5%,transfers7.6“
Dynamo,“90%,“10%,generates6.8“
Transmission,“90%,“10%,transmits6.2“
Motor,“90%,“10%,develops5.5“
Connections,“95%,“ 5%,delivers 5.0“

Therefore, only five horsepower would be actually delivered to the machine to be driven. This amounts to only half of the theoretical power of the falling water which is actually realized in useful work of the machine being driven. If the power from the waterwheel is to be applied directly without generating electricity a much higher efficiency will be realized.

ACKNOWLEDGMENT

On behalf of the State Water Supply Commission and the writer, grateful acknowledgment is made to the following named persons who have extended courtesies to me by furnishing information or illustrations for use in connection with the preparation of this pamphlet:

D. R. COOPER.

Albany, January 25, 1911.

PUBLICATIONS OF

STATE WATER SUPPLY COMMISSION

STATE OF NEW YORK

REPORTS

First Annual ReportPublished February 1, 1906.

Includes Commission’s annual report on applications for approval of plans for public water supplies; also summarized statistics of public water supplies and sewage disposal in New York State.

Edition exhausted.
Second Annual ReportPublished February 1, 1907.

Includes Commission’s annual report and decisions on applications for approval of plans for public water supplies; also summarized statistics of public water supplies and sewage disposal in New York State, supplementary to statistics published in First Annual Report; also report on River Improvements for the benefit of public health and safety.

Edition exhausted.
Third Annual ReportPublished February 1, 1908.

Includes Commission’s annual report and decisions on applications for approval of plans for public water supplies; also report on River Improvements for the benefit of public health and safety; also contains Commission’s first Progress Report on Water Power and Water Storage Investigations made under chapter 569 of Laws of 1907, including details of Sacandaga and Genesee river studies.

Edition exhausted.
Progress Report on Water Power DevelopmentPublished March 1, 1908.

This is a revised reprint of the part of the Commission’s regular Third Annual Report relating to Water Power and Water Storage Investigations, showing results of engineering studies up to date of publication.

Fourth Annual ReportPublished February 1, 1909.

Includes Commission’s annual report and decisions on applications for approval of plans for public water supplies; also report on River Improvements for the benefit of public health and safety; also contains Commission’s second Progress Report on Water Power and Water Storage Investigations, with special details of Raquette and Delaware river studies and supplementary studies on Upper Hudson and Genesee, also a census of water power developments in the State.

Fifth Annual ReportPublished February 1, 1910.

Includes Commission’s annual report and decisions on applications for approval of plans for public water supplies; also summarized statistics relating to public water supplies approved by the Commission in New York State; also report on River Improvements for the benefit of public health and safety; also contains Commission’s third Progress Report on Water Power and Water Storage Investigations, with details of reconnaissance studies of Ausable, Saranac, Black, Oswegatchie and other rivers, and a draft of a proposed Water Storage Law.

Sixth Annual ReportPublished February 1, 1911.

Includes Commission’s annual report and decisions on applications for approval of plans for public water supplies; also report on River Improvements for the benefit of public health and safety; also contains Commission’s Fourth Progress Report on Water Power and Water Storage Investigations, with details of investigations of Black and Oswego river watersheds, and a revised draft of a proposed Water Storage Law.

MISCELLANEOUS

Pamphlet—“New York State Water Supply Commission” Published September, 1909.
Issued for distribution at State Fair at Syracuse, 1909.
Pamphlet—“New York’s Water Supply and Its Conservation, Distribution and Uses” Published September, 1910.
Issued for distribution at State Fair at Syracuse, 1910.
Pamphlet—“Water Resources of the State of New York” Published September, 1910.

By Henry H. Persons, President of the State Water Supply Commission. Issued for distribution at National Conservation Congress at St. Paul, Minnesota, 1910.

Pamphlet—“Water Power for the Farm and Country Home” Published January, 1911.

By David R. Cooper, Engineer-Secretary to State Water Supply Commission.

Transcriber’s Notes:

The illustrations have been moved so that they do not break up paragraphs and so that they are next to the text they illustrate.

Typographical errors have been silently corrected.