Full resolution (JPEG) - On this page / på denna sida - VII. Manufacturing Industries. Introd. by [G. Sundbärg] K. Åmark - 11. Other Industries - Electric Power Industry. By A. Enström
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470
vii. manufacturing industries.
100 000—150 000 volts. With this tension, transmission over a distance of some
500 kilometers can be effected, e. g., from Indalsälven to the middle of Sweden.
The cost would not work out particularly high per h. p., provided the energy
consumption called for were sufficiently great. The cost of transmission,
relatively to the power transmitted, appears from the appended diagram (based on
calculations by Centervall and Rossander). The cost is given in kronor per
kilo-watt (1 kilo-watt = 1’36 h. p.) per year. In these figures are included the
transformation cost at both ends of the line. The shape of the curves indicates
how the transmission- (and distribution-) cost rises when less considerable
quantities of power are transmitted.
The effective power-cost is the total of the transmission- and distribution-cost,
on the one hand, and the production-cost, on the other. In the case of
water-power, the production-cost involves interest on the value of the fall, interest on
and amortization of the money invested in the construction of the plant. Under
the conditions prevailing in Sweden, the construction-cost can (according to
engineer Sven Lübeck) be estimated at an average of 250—350 kronor per h. p.,
giving an annual cost of 25 to 35 kr. per h. p. Thus the price of energy will
vary from a minimum of about 25 kr. per h. p., in the case of large supplies
for industrial purposes, to 100 kr. and more, in the case of small quantities of
distributed energy.
As a rule, the demand for energy from the consumers is not a constant one,
but varies from month to month and from hour to hour. A water-driven
generating plant, as a rule, is subject to considerable variation in the water-flow
according to the time of year. In order to secure something like correspondence
between the demand for and the supply of power, it is necessary either to
regulate the water-flow — day-regulation by collecting the water in small
reservoirs, or year-regulation by damming the water up in large lakes — or the
station must be supplied with auxiliary machinery driven by power other than water.
Such auxiliary machinery also renders good service in the case of fault on the
transmission-line, when placed at the receiver end. Indeed, several of the plants
mentioned have erected auxiliary stations, generally steam-driven. Since the
production-cost of steam-power depends almost entirely on the cost of fuel,
while the cost of water-power chiefly depends on the capacity of the station,
a combination of water-power for the normal load with steam-power for
peak-load has been found to be a good economical arrangement. This is particularly
the case with central stations with light-load, such as communal stations. The
light-load generally has a "load-factor" of only about 1 500 hours out of the
8 760 hours of the year, and factories working during the day only require the
supply during 2 600 to 3 000 hours in the year. Certain industries, again, such
as mills, wood-pulp mills, etc. consume energy during nearly 7 000 hours in
the year. These facts, and what has been said above as to the cost of
water-power as compared with steam-power, tend to show the economical advantages
of water-power in industrial development.
It is also clear from what has been said that water-power in use only for a
few hours of the year, as for electric lighting, agriculture, etc., will be rather
expensive. In these cases also the rather complicated and expensive distributing
systems must set limits to the use of water-power. In more populous districts,
however, it has been possible to establish such distribution with economic
success, and in several parts of the country electric energy is used for threshing,
pumping, etc., in a few cases, even for ploughing.
The use of electrical energy for electro-chemical purposes (see Electrochemical
Industry) and for electric smelting-furnaces for iron, steel, zink, etc. is increasing
rapidly. For purely heating purposes, such as in houses, electricity is only suitable
where the energy can be obtained at a particularly low price (surplus energy).
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