Jökull - 01.12.1979, Blaðsíða 57

approximately 80 kg/s, and the steam flow from a
single well ranges up to 25 kg/s at atmospheric
pressure.
Geysers are active in two high temperature areas
in the country at present. Gunnuhver in the
Reykjanes field, SW-Iceland, was reactivated in an
earthquake in 1967 and erupts at a few minutes
intervals to about five meters. The most famous
geyser in Iceland is of course the great Geysir in
Haukadalur, S-Iceland, which has given name to
all erupting springs in the international geological
terminology. Geysir has been mostly dormant for
the last decades but erupts at least once during
most years. Its highest eruptions were up to about
70 m and lasted for about 10 minutes. It has a 20 m
deep vertical surface pipe. Measurements show the
eruption to originate at about 10 m depth in the
pipe. The boiling temperature at that depth is
about 120°C, but the water is sometimes super-
heated by 5—6°C before it is instantly flashed to
steam. The volume of steam at this pressure (depth)
and temperature is about seventeen times that of
the water and it is the steam explosion that throws
the water column above into the air. A small geyser
in the Geysir field, Strokkur, was reactivated by
drilling in 1963. It erupts every few minutes up to
10—15 m. The first written record of geyser activity
in the Geysir field is from annals in 1294 describing
earthquakes in the area.
GEOTHERMAL UTILIZATION
Geothermal energy is very important for the
national economy of Iceland as nearly one third of
the net energy consumption of the country is from
geothermal resources, the other two thirds being
nearly equally divided between hydropower and
fossil fuel, the latter of which has to be imported.
Although hot springs were widely used for
washing and bathing through the 1100 years of
settlement of the country it was not until in the last
five decades that the distribution of hot springs
started markedly affecting the distribution of
population centres in the country with the growth
of villages and school centres built at hot spring
localities in the farming communities. Large scale
utilization of geothermal for space heating started
in the nineteen-forties. At present nearly 70% of
houses in the country are geothermally heated.
There are about twenty main district heating ser-
vices operating with a total installed capacity of
about 600 MW, (thermal), the largest of which is
the Municipal Heating Service of Reykjavík with
about 450 MWt installed. The geothermal water
used for space heating is mostly from low tempera-
ture areas; the mineral content is low (200—400
ppm) and the water can be used directly. A plant has
recently started operating in the Svartsengi steam
field where a 240°C brine (% seawater) is used for
district heating with the use of heat exchangers. Some
of the steam is used for generating electricity for
in-plant needs. The present installed capacity is 50
MWt, but will later expand to 100 MWt. A
remarkable experiment has been in operation for
three years in the Westman Islands where heat is
extracted from a thick partly molten lava flow for
space heating of a town of 5000 people. About 15%
of the houses are now heated in this way, and the
system is being extended over the whole town. The
heat source (the lava erupted in 1973) is estimated
to last at least 15 years.
There are nearly 140.000 m2 of geothermal
greenhouses used for growing vegetables and
flowers; artificial lighting is used on a small scale to
lengthen the growing season. Geothermal water
and steam is used for various purposes such as fish
hatching, fish drying, wool washing, hay drying,
and candy making. Industrial utilization on larger
scale includes a factory for drying and cleaning of
diatomaceous slurry and a factory for drying
seaweed for alginate production. A pilot plant has
recently been built for extracting salt out of a
geothermal brine in the Reykjanes field. Due to the
ample hydropower resources of the country
electricity has only been produced from geothermal
on a small scale as yet. A 60 MWt (electric) power
station is at present under construction in the
Krafla field in N-Iceland. The project has been
seriously affected and delayed by volcanic activity
in the area, and the power station is only producing
about 6 MWe at present. A 3 MWC power plant
operating since 1968 in the Námafjall field had to
be closed in 1978 due to volcanic activity.
SELECTED REFERENCES
Árnason, B., 1976: Groundwater systems in Iceland
traced bydeuterium. Soc. Sci. Islandica, 42: 236
pp.
Arnórsson, S., 1975: Application of the silica
geothermometer in low-temperature areas in
Iceland. Am. J. Sci., 275: 763—784.
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