Electric Transmission of Water Power

by Alton D. Adams

Between these two canals a strip of land about 250 feet wide was left for the location of mills. By this arrangement of canals it is possible to supply wheels located between the high and the low levels with water under a head of about twenty-one feet, and to supply wheels between the lower canal and the river with water under a head of about twenty-nine feet. The entire area of land between the high canal and the river is thus made readily available for factory buildings.

Water for the lower canal is drawn mainly from the high canal through the wheels in buildings that are located between the two canals. It is desirable in a case of this sort to have as much water flow through the wheels between the high and low canal as flows through the wheels between the low canal and the river, but this is not always possible. A gate is therefore provided at the forebay where the two canals start, by which water may pass from the forebay directly into the low canal when necessary, but the head of twenty-one feet between the forebay and the low canal is lost as to this water. Between the high and low canal, and between the low canal and the river twenty-three turbine wheels or pairs of wheels have been connected, and these wheels have a combined rating of 9,500 horse-power.

To carry out this hydraulic development it thus appears that about 1.3 miles of canal have been constructed; one-half this length of river-front has been required, and about one-sixth square mile of territory has been occupied. Contrast with this result what might have been done if electrical transmission of power had been available at the time when this water-power was developed. All but a few rods in length of the existing 1.3 miles of canal might have been omitted, and an electric generating station with wheels to take the entire flow of the river might have been located not far from one end of the dam. Factories utilizing the electric power thus developed might have been located at any convenient points along the river-front or elsewhere, and no space would have been made unavailable because of the necessity of head- and tail-water connections to scattered sets of wheels.

Compare with the foregoing hydraulic development that at Cañon Ferry on the Missouri River, in Montana, where 10,000 horse-power is developed under a water-head of 32 feet. At Cañon Ferry the power-house is 225 feet by 50 feet at the floor level inside, contains turbine wheels direct-connected to ten main generators of 7,500 kilowatts, or 10,000 horse-power combined capacity, and is built on the river bank close to one end of the 500-foot dam. The canal which runs along the land side of the power-house, and takes water at the up-stream side of the abutment, is about twice the length of the power-house itself. The saving in the cost of canal construction alone, to say nothing of the saving as to the required area of land, is evidently a large item in favor of the electrical development and transmission. In its small area and short canal the Cañon Ferry plant is not an exception, but is rather typical of a large class of electric water-power plants that operate under moderate heads.

A like case may be seen in the plant at Red Bridge, on the Chicopee River, in Massachusetts, where a canal 340 feet long, together with penstocks 100 feet long, convey water from one end of the dam and deliver it to wheels in the electric station with a head of 49 feet. This station contains electric generators with a combined capacity of 4,800 kilowatts or 6,400 horse-power, and its floor area is 141 by 57 feet.

Fig. 5.—Canal at Red Bridge on Chicopee River.

So, again, at Great Falls, on the Presumpscot River, in North Gorham, Me. (see [cut]), the electric station sets about 40 feet in front of the forebay wall, which adjoins one abutment of the dam, and there is no canal whatever, as short penstocks bring water to the wheels with a head of 35 feet. In ground area this station is 67.5 by 55 feet, and its capacity in main generators is 2,000 kilowatts or 2,700 horse-power.

A striking illustration of the extent to which electrical transmission reduces the cost of water-power development may be seen at Gregg’s Falls on the Piscataquog River, in New Hampshire, where an electric station of 1,200 kilowatts capacity has been built close to one end of the dam, and receives water for its wheels under a head of 51 feet through a short penstock, 10 feet in diameter, that pierces one of the abutments.