100 000—150 000 volts. With this tension, transmission over a distance of some
500 kilometers can be effected, e. g., from Indalsalven 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 Waterpower,
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 Liibeck) be estimated at an average of 2 5 0 ^ 3 5 0 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 l ||||o r 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 peakload
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 0 0 0 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 waterpower
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, zinh, 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).
T able 100. Consumption of Electric Energy in Towns with more than
15 000 Inhabitants. 1911.
Consumers’ installation in kilo-watts ConsumpOpened
Driving
per 1 000 inhab. tion per
inhab. in
■ in power light power
etc. trams total kilowatthours
1892 steam 67-03 45-36 16-80 1 3 5 1 0 5 9 0 0
1908 f water 1
\ steam j 32-05 37-30 24-80 133-20 122-10
1901 1 water 1
\ steam j 4 8 8 1 120-64 19-40 190-08 208-00
1904 1 water 1
\ Dieselm.j 41:30 41-75 14-76 98-50 54-60
1903 j water 1
\ Dieselm. j
| water 1
27-98 32-41 1 4 1 5 75-90 3 0 46
1891 < steam >
I Dieselm. J
44-39 45-65 1 0 :75 102-00 6 1 0 5
1886 water 45-39 51-92 98-40 85-90
1895 steam 13-68 8-12 21-96 8-38
1907 J water 1
\ Dieselm.j 29-21 19-10 6-36 54-70 15-48
1907 steam 19-41 11-66 ■ 11-90 4 3 2 5 19-88
1906 1 Dieselm. I
\ gas eng. J 43-17 33-93 14-20 92-40 34-85
1894 j steam 1 55-08 58-62 1 \ water J 113-90 96-68
1907 i water \
\ Dieselm.j 28-21 40-62 — 79-90 39-90
1905 ( water (
\ Dieselm./ 38-30 17-30 50-60 23-00
1890 j water 1
\ steam j 42-87 25-45 — 69-06 36-39
1903 i water \
\ Dieselm.j 36-92 52'55 í t— ¡ 90 80 — ■
1906 water 32-77 64-40 98-00 106-80
1891 f water 1
\ steam J 50-34 26;66 23-70 101-06 53-87
19Q8 1 water 1
\ Dieselm.j 2 9-96. 74:90 _ 105-20 121-92
1908 Dieselm. 19,69 13-52 n 34-60 9-11
Stockholm.
Gothenburg
Malmo . .
Norrkoping
Gavle . . .
Halsingborg
Örebro . .
Eskilstuna
Karlskrona
Jonkoping.
Uppsala. .
Bor&s. . .
Lund . . .
Vaster&s .
Ilalmstad .
Linköping .
Karlstad .
Sundsvall .
Landskrona
Kalmar . .
A considerable number of local central stations exist in towns, communes,
and larger populated places. Not less than 90 % of the towns of Sweden are
•equipped with electric central stations, most of them being communal undertakings.
In the older town-plants, steam engines, steam turbines, Diesel motors, gas
engines, ete., were installed, but later on also water-power was used. -In 1909,
75 % of the communal plants depended on water-power; in 64 % heat-engines
were installed; thus 39 % worked with combined systems.
At first, electric energy was distributed within towns by means of continuous
-current, the generating units being paralleled by storage batteries. Nowadays
the direct distribution of alternating current has been more and more adopted.
■Of the above-mentioned townplants, 66 % used continuous current, and 59 %
alternating current; thus 25 % employed both systems.
Electric light has become more and more general, thanks to the appearance
and improvement of the metal filament lamps. Owing to the small consumption
of. current by these lamps, electric light has become as cheap as oil lamps.
The price for electric energy varies between 25 ore and 45 ore per kilo-watt