HARNESSING THE WATER-FALL
Electric Energy--High Pressure--Transformers--Development of
Water-power.
The electrical transmission of power is exemplified in everything which
is based on the generation of electricity. The ordinary electric light
is power coming from a generator in the building or a public
street-dynamo.
However, when we talk in general terms of electric transmission we
mean the transmission of energy on a large scale by means of overhead
or underground conductors to a considerable distance and the
transformation of this energy into light and heat and chemical or
mechanical power to carry on the processes of work and industry. When
the power or energy is conveyed a long distance from the generator,
say over 30 miles or more, we usually speak of the system of supply
as long distance transmission of electric energy. In many cases power
is conveyed over distances of 200 miles and more. When water power is
available as at Niagara, the distance to which electric energy can be
transmitted is considerably increased.
The distance to a great extent depends on the cost of coal required
for generation at the distributing point and on the amount of energy
demanded at the receiving point. Of course the farther the distance
the higher must be the voltage pressure.
Electrical engineers say that under proper conditions electric energy
may be transmitted in large quantity to a distance of 500 miles and
more at a pressure of about 170,000 volts. If such right conditions
be established then New York, Chicago and several other of our large
cities can get their power from Niagara.
In our cities and towns where the current has only to go a short
distance from the power house, the conductors are generally placed in
cables underground and the maximum electro-motive force scarcely ever
exceeds 11,000 volts. This pressure is generated by a steam-driven
alternating-current generator and is transmitted over the conductors
to sub-stations, where by means of step-down transformers, the pressure
is dropped to, say, 600 volts alternating current which by rotary
converters is turned into direct current for the street mains, for
feeders of railways and for charging storage batteries which in turn
give out direct current at times of heavy demand.
That electric transmission of energy to long distances may be
successfully carried out transformers are necessary for raising the
pressure on the transmission line and for reducing it at the points
of distribution. The transformer consists of a magnetic circuit of
laminated iron or mild steel interlinked with two electric circuits,
one, the primary, receiving electrical energy and the other the
secondary, delivering it to the consumer. The effect of the iron is
to make as many as possible of the lines of force set up by the primary
current, cut the secondary winding and there set up an electromotive
force of the same frequency but different voltage.
The transformer has made long distance the actual achievement that it
is. It is this apparatus that brought the mountain to Mohammed. Without
it high pressure would be impossible and it is on high pressure that
success of long distance transmission depends.
To convey electricity to distant centres at a low pressure would require
thousands of dollars in copper cables alone as conductors. To illustrate
the service of the transformer in electricity it is only necessary to
consider water power at a low pressure. In such a case the water can
only be transmitted at slow speed and through great openings, like
dams or large canals, and withal the force is weak and of little
practical efficiency, whereas under high pressure a small quantity can
be forced through a small pipe and create an energy beyond comparison
to that developed when under low pressure.
The transformer raises the voltage and sends the electrical current
under high pressure over a small wire and so great is this pressure
that thousands of horse-power can be sent to great distances over small
wires with very little loss.
Water power is now changed to electrical power and transmitted over
slender copper wires to the great manufacturing centres of our country
to turn the wheels of industry and give employment to thousands.
Nearly one hundred cities in the United States alone are today using
electricity supplied by transmitted water-power. Ten years ago Niagara
Falls were regarded only as a great natural curiosity of interest only
to the sightseer, today those Falls distribute over 100,000 horse-power
to Buffalo, Syracuse, Rochester, Toronto and several smaller cities
and towns. Wild Niagara has at last indeed been harnessed to the
servitude of man. Spier Falls north of Saratoga, practically unheard
of before, is now supplying electricity to the industrial communities
of Schenectady, Troy, Amsterdam, Albany and half a dozen or so smaller
towns.
Rivers and dams, lakes and falls in all parts of the country are being
utilized to supply energy, though at the present time only about
one-fortieth of the horse-power available through this agent is being
made productive. The water conditions of the United States are so
favorable that 200,000,000 horse-power could be easily developed, but
as it is we have barely enough harnessed to supply 5 million
horse-power.
Eighty per cent. of the power used at the present time is produced
from fuel. This percentage is sure to decrease in the future for fuel
will become scarcer and the high cost will drive fuel power altogether
out of the market.
New York State has the largest water power development in the Union,
the total being 885,862 horsepower; this fact is chiefly owing to
the energy developed by Niagara.
The second State in water-power development is California, the total
development being 466,774 horsepower over 1,070 wheels or a unit
installation of about 436 H.P.
The third State is Maine with 343,096 horse-power, over 2,707 wheels
or an average of about 123 horse-power per wheel.
Lack of space makes it impossible to enter upon a detailed description
of the structural and mechanical features of the various plants and
how they were operated for the purpose of turning water into an electric
current. The best that can be done is to outline the most noteworthy
features which typify the various situations under which power plants
are developed and operated.
The water power available under any condition depends principally upon
two factors: First, the amount of fall or hydrostatic head on the
wheels; second, the amount of water that can be turned over the wheels.
The conditions vary according to place, there are all kinds of fall
and flow. To develop a high power it is necessary to discharge a large
volume of water upon properly designed wheels. In many of the western
plants where only a small amount of water is available there is a great
fall to make up for the larger volume in force coming down upon the
wheels. So far as actual energy is concerned it makes no difference
whether we develop a certain amount of power by allowing twenty cubic
feet of water per second to fall a distance of one foot or allow one
cubic foot of water per second to fall a distance of twenty feet.
In one place we may have a plant developing say 10,000 horse-power
with a fall of anywhere from twenty to forty feet and in another place
a plant of the same capacity with a fall of 1,000, 1,500 or 2,000 feet.
In the former case the short fall is compensated by a great volume of
water to produce such a horse-power, while in the latter converse
conditions prevail. In many cases the power house is located some
distance from the source of supply and from the point where the water
is diverted from its course by artificial means.
The Shawinigan Falls of St. Maurice river in Canada occur at two points
a short distance apart, the fall at one point being about 50 and at
the other 100 feet high. A canal 1,000 feet long takes water from the
river above the upper of these falls and delivers it near to the
electric power house on the river bank below the lower falls. In this
way a hydrostatic head of 125 feet is obtained at the power house. The
canal in this case ends on high ground 130 feet from the power house
and the water passes down to the wheels through steel penstocks 9 feet
in diameter.
In a great many cases in level country the water power can only be
developed by means of such canals or pipe lines and the generating
stations must be situated away from the points where the water is
diverted from its course.
In mountainous country where rivers are comparatively small and their
courses are marked by numerous falls and rapids, it is generally
necessary to utilize the fall of a stream through some miles of its
length in order to get a satisfactory development of power. To reach
this result rather long canals, flumes, or pipe lines must be laid to
convey the water to the power stations and deliver it at high pressure.
California offers numerous examples of electric power development with
the water that has been carried several miles through artificial
channels. An illustration of this class of work exists at the electric
power house on the bank of the Mokelumne river in the Sierra Nevada
mountains. Water is supplied to the wheels in this station under a
head of 1,450 feet through pipes 3,600 feet long leading to the top
of a near-by hill. To reach this hill the water after its diversion
from the Mokelumne river at the dam, flows twenty miles through a canal
or ditch and then through 3,000 feet of wooden stave pipe. Although
California ranks second in water-power development it is easily the
first in the number of its stations, and also be it said, California
was the first to realize the possibilities of long distance electrical
energy. The line from the 15,000 horsepower plant at Colgate in this
State to San Francisco by way of Mission San Jose, where it is supplied
with additional power, has a length of 232 miles and is the longest
transmission of electrical energy in the world. The power house at
Colgate has a capacity of 11,250 kilowatts in generators, but it is
uncertain what part of the output is transmitted to San Francisco, as
there are more than 100 substations on the 1,375 miles of circuit in
this system.
Another system, even greater than the foregoing which has just been
completed is that of the Stanislaus plant in Tuolumme County,
California, from which a transmission line on steel towers has been
run in Tuolumme, Calaveras, San Joaquin, Alameda and Contra Costa
Counties for the delivery of power to mines and to the towns lying
about San Francisco Bay. The rushing riotous waters of the Stanislaus
wasted for so many centuries have been saved by the steel paddles of
gigantic turbine water wheels and converted into electricity which
carries with the swiftness of thought thousands of horse power energy
to the far away cities and towns to be transformed into light and heat
and power to run street cars and trains and set in motion the mechanism
of mills and factories and make the looms of industry hum with the
bustle and activity of life.
It is said that the greatest long distance transmission yet attempted
will shortly be undertaken in South Africa where it is proposed to
draw power from the famous Victoria Falls. The line from the Falls
will run to Johannesburg and through the Rand, a length of 700 miles.
It is claimed the Falls are capable of developing 300,000 electric
horse power at all times.
Should this undertaking be accomplished it will be a crowning
achievement in electrical science.