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primary power, steam and electric, used by industries in the City of Philadelphia, and more than twice that utilized in Cleveland.

In addition to the hydro-electric plants these companies operate approximately 400,000 horse power in steam-electric plants. These are essential auxiliaries in the economical utilization of hydroelectric plants in a region such as this. A system of transmission lines for the distribution of current has been provided, which reaches nearly every important industrial center in the region. The transmission systems of the different companies are interconnected in such a way that it is possible to transmit power from the great steam-electric plant at Muscle Shoals at the western end of the system, to Raleigh and Goldsboro in central North Carolina. The distance is about six hundred miles. During the summer of 1921, when the flow of the streams of the Atlantic watershed was unusually low, the combined output of the steam and hydro-electric plants in the Carolinas and Georgia was insufficient to meet the industrial demands of the region. Power to the extent of 35,000 horse power daily was transmitted from the Alabama steam-electric plants make up the deficit, and it made possible the continued operation of the eastern mills. The combination of hydro-electric and steamelectric plants, with interconnection over a wide area, is of the greatest importance in the economical operation of the individual, plants. The system is highly developed in this region.

Perhaps the greatest problem involved in the operation of hydroelectric plants is brought about by the fact that the amount of power available fluctuates greatly from time to time. This is due to the irregularity of flow of streams. Industries are seldom able to adapt themselves to fluctuating power supply, but must have a steady supply throughout the year. Hence it is generally economical to develop only the primary or low water power in the case of an isolated or single plant which is to be utilized alone. This is an unfortunate situation, in that the cost of installing generators to develop the secondary power is comparatively small. involves no addition to the dam or general equipment, but merely the addition of the extra turbines, generators and their equipment. In some cases steam-electric plants have been built in order to provide power during periods of low water. Thus, under the plan partly completed at Muscle Shoals the primary power of 100,000 horse power is enlarged to 190,000 by the building of a great steam-electric plant of 90,000 horsepower. A continuous supply of 190,000 horsepower is thus assured at all times.

Since the flow of streams throughout the region fluctuates considerably from time to time it has been necessary to provide auxiliary steam-electric plants in many cases.

Several factors are significant in the location of such plants. Cheap coal is a primary factor, but an adequate supply of water for condensing purposes is equally essential. An almost unbelievable quantity of water is necessary in the modern steam-electric plant. For each ton of coal burned eight hundred tons of water is necessary. For a 30,000 kilowatt plant, such as the original one of the Alabama Power Company at Gorgas, a stream of 160 second feet flow is required. To find sufficient condensing water at the mouth of the mine would be quite rare. In the Boston to Washington survey condensing water was not found in the bituminous fields in sufficient quantity to warrant building a superpower steam plant, and practically all the proposed superpower stations are on tide water. Only a complete report on stream flow, based on years of observation, would determine at what points near the sources of fuel supply sufficient condensing water was available. The location of the steam plant in relation to tying in with the hydro-electric plants is also an important consideration.

Auxiliary steam plants of small size are fairly well distributed throughout the system. The most advantageously located plant is at Gorgas, in the Warrior coal field in Alabama. This plant was built by the Alabama Power Company and began operation in 1917 with 30,000 horse power, as an auxiliary to the electric power system of that company. During the war the plant was enlarged to 70,000 horse power by the War Department, in connection with the Muscle Shoals project. The mines which furnish coal to the plant are located directly at the power site, and condensing water is procured from the Warrior River. During the same period the Government constructed the reserve system plant at Muscle Shoals with a capacity of 90,000 horse power. In the latter case the coal must be brought from the Warrior field, but the necessary water is secured from the Tennessee River. Doubtless many more auxiliary steamelectric plants will be constructed as the water power of the region is developed. These will be either in Alabama or East Tennessee

'Proceedings of the First Annual Meeting of the Southern Appalachian Water Power Conference, Ashville, N. C., June, 1922, pp. 53-55.

as near the coal fields as the necessary water can be found. It is more economical in general to produce the power near the coal fields and transmit the electric energy than to haul the coal long distances.

Significant, too, in the economical operation of hydro-electric plants is the interconnection of powers. Fortunately, the rivers of any large section do not vary in flow in an exactly parallel manner. The period of lowest water is almost never the same over the whole region of the Southern Appalachians. At a time when one plant is able to develop only its primary power another plant, some distance away, may be able to develop a considerable amount of secondary power. This latter may be delivered over transmission lines to industries which during most of the year are dependent upon the secondary power of the first plant. Interconnection of powers, therefore, particularly if involving a large region which has several independent drainage systems, greatly enlarges the volume of secondary power which may be installed and utilized. In the possession of widely distributed hydro-electric powers, interconnecting transmission lines, and cheaply produced steam-electric auxiliary power, the region of the Southern Appalachians is particularly fortunate. The connection of powers is also important in guarding against accidents to individual plants which might seriously hamper the supply of power. For example, in the summer of 1919 an accident at the Great Falls plant on Caney Fork temporarily cut off the power supply of Nashville. The difficulty was overcome shortly by the diversion of power from the Hales Bar plant on the Tennessee River. In case of emergency Nashville might draw power from either of these plants, from those on the Ocoee, on the Coosa in Alabama, from Tallulah Falls or other points in Georgia, or from the reserve steam plants in Alabama. The same situation holds for any part of the system.

The problem which exists at Muscle Shoals is of special interest in relation to the factors just discussed. Muscle Shoals has a primary power of about a hundred thousand horse power, but a secondary power four or five times as great. This is due to the great fluctuation of flow in the Tennessee River which varies from 7,000 to 499,000 feet per second. The steam-electric plants at Muscle Shoals and the additions to the Gorgas plant were built with the idea of utilizing a part of this secondary power, but even with these auxiliaries more than half of the generating capacity

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which it is planned to install must still be secondary in character. The total installation planned at Muscle Shoals is greater by about a third than the power now developed on the American side at Niagara Falls. However, the power at Niagara is all primary, available the year round, so that there is no real comparison between the two cases.

The insistance by the representatives of Henry Ford that both the steam plants at Muscle Shoals and at Gorgas be included with the water power indicates the importance which is attached to this method of making useful the otherwise wasted secondary power. The utilization of the remaining 300,000 horse power of secondary power, if Muscle Shoals is to be a self-contained unit, must depend either upon the establishment of seasonal industries, which can operate during times of high water, half the year or less, or upon further expansion of the auxiliary steam power.

On the other hand, were the Muscle Shoals connected with the system extending to Tennessee and eastward to North Carolina, forming an integral part of that system, the problem would be somewhat different. Much of the secondary power might be used, as is that of other plants now operating, by exchange of power from time to time. The steam auxiliary plants, too, instead of furnishing power to Muscle Shoals industries alone, might be utilized, as they have been during the past three years, as auxiliaries to the entire system, and thus be kept in operation a larger part of the time.

Most of the development of this great system of electric powers has taken place during the past ten years. By no means has it come to an end. The Alabama Power Company now is developing a project of 60,000 kilowatts at Mitchell Dam on the Coosa. Under the recent Water Power Act it has acquired rights at Cherokee Bluffs on the Talapoosa, where a large power will be developed. Additional powers are projected on the Ocoee in East Tennessee, and the Aluminum Company of America plans to develop some 500,000 horse power on the Little Tennessee ultimately. The Tennessee Power Company expects to enlarge the installation at Great Falls by 10,000 kilowatts within a short time. Work probably will be resumed on the Tugaloo project of 48,000 kilowatts in Georgia within a brief time. These are but a few of the projected powers of the region. It is interesting to note that in many cases installations much greater than the primary power have been erected, though many large powers still are unused. According to the recent survey completed by the U. S. Geological Survey at present there are developed 1,647,000 horse power from the rivers of the region. The minimum power available, figured on the basis of low water, is estimated at 2,384,000 horse power. The maximum, available fifty percent of the time, but without storage, is estimated at 3,883,000 horse power.

These are doubtless very conservative estimates. There are large possibilities of expansion by building reservoirs for the storage of flood waters, in fact, this has been done already in the case of the Tallulah Falls plant in Georgia. Probably the maximum figure will mount to at least 5,000,000 horse power ultimately available.

If the development of the past ten years is any measure of future trends there undoubtedly will be necessary a large expansion in the electric power equipment of the region. The fact that nearly all power expansion in recent years has been electric seems to indicate the same sort of power demand for the future. Indeed, electric power in many cases is superceding steam power. In a power survey undertaken by the War Department in 1918 it was found that the power companies in the five states whose lines are interconnected, generated 1,840,000,000 kilowatt hours during the year.' It was estimated that, exclusive of the demand of the Aluminum Company of America and the possible Government demands for power for the manufacture of nitrate at Muscle Shoals, 1,000,000,000 additional kilowatt hours per year would be needed in the region by the end of 1923. This would necessitate a 55 percent increase in power during the period of five years, a rate of growth not as rapid as that which actually took place between 1913 and 1918. In 1921 the Alabama Power Company estimated it would require 500,000 additional horse power by the end of 1926, and is building toward that end. The transmission systems of the region are being extended rapidly, while interconnections and standardization are being perfected. It is possible that in the near future these lines may be extended to the Gulf, at Mobile, New Orleans and other points, and north to the Ohio at Louisville and Cincinnati. All of these points are within economical transmission distance. The system as it exists at present, though of vital importance to the region, doubtless is but the beginning of a much greater future dependence upon electric power.

*Col. Charles Keller; The Power Situation During the War, published by the authority of the Secretary of War, Washington, Government Printing Office, 1921.

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