Jökull - 01.12.1961, Blaðsíða 60

water at an intake temperature of 180° C and
an effective heat transport of 500 Tcal/year.
The heat is to be utilized for space and in-
dustrial heating in the city of Reykjavík. The
computed cost of transportation is approximate-
ly one $/Gcal.
The reasons for selecting high-temperature
water as the heat carrying medium are the fol-
lowing. First, the thermal area in Krysuvik pro-
duces wet steam with a high water/steam ratio.
Second, space heating is a suitable market for
water at temperatures below 100° C. Third,
high-temperature water is more suitable for long-
clistance piping than steam. The use of steam
as the heat carrying mediurn would require a
much larger cross sectiott of the pipe and lead
to a double line. The cost of transportation
would be considerably higher.
It should at this juncture be realized that
there is still little experience in the long-dis-
tance piping of high-temperature water. The
questions of safety and possible serious damage
are to be studied thoroughly. It is not known
what will happen in the case of a rupture of a
pipe. High-temperature water is to be regarded
as an explosive ancl it is not quite inconceivable
that the rupture of a single pipe will result in
a very serious damage to the entire pipeline.
The sudden release of pressure at the place of
rupture will cause critical velocity and great
thrust which may cause the rupture to pro-
pagate.
In conclusion, it may be statecl that similar
projects involving pipelines of a length of 50
to 100 km would not appear altogether unrea-
listic at conditions in Iceland, provided that
space lieating constitutes the main market for
the heat. But this distance is no doubt the upper
limit to the transportability of high-temperature
water. For comparison, it can be stated that the
maximum transportability of natural-steam for
power generation is of the order of 10 km.
(4) SPACE HEATING.
(a) Domestic and district heating.
Iceland is, as already stated, the only location
where geothermal space heating is of economic
importance. As of now about 45,000 pepole live
in houses heated by geothermal energy. It is
expected that this number will be doubled in
the coming decade.
There are in Iceland 5 district heating systems.
The most important one, the Reykjavik Muni-
cipal District Heating Service, serves about
40.000 inhabitants of the city. The other systems
are located in 4 small communities.
(i) The Reykjavik Municipal District Heating
Service. Design details of the R. M. D. H.S. are
given by Sigurdsson (G/45) ancl a few economic
data are given by Bodvarsson and Zoéga (G/37).
The effective amount of heat delivered by the
R. M. D. H. S. is produced in the two thermal
areas already mentioned, the Reykir ancl the
Reykjavik areas. (See TABLE 1). The Reykir
area is connected to the city by the mentioned
pipeline.
About 4.400 houses are connected to the R.
M. D. H. S. through a system of street lines of
a total length of approximately 55 km. House
connections are not included in tliis figure. The
thermal water is in niost cases applied directly
to the radiators in the houses.
A special feature is the combination of single-
pipe and double-pipe district systems in conn-
ection with an oilfired booster plant which
raises the temperature of the thermal water clur-
ing colcl spells. The climatic conclitions in
Reykjavik are such that it is not economical
to let the thermal water carry the total heat
loacl during the cold spells. The most econo-
mical load on the thermal water is, in fact,
attained at an outside temperature of around
zero degrees C. The booster plant supplies the
additional heat-load which is required during
colder days. The outside daily average temp-
erature in Reykjavik rarely drops below —10° C,
and it appears sufficient to design the heating
system for a maximum load at a stationary daily
average of —6° C.
The temperature of the thermal water in the
main supply line is now arouncl 94° C. The
booster plant is clesigned to raise this tempera-
ture considerably above 100° C, which, as a
matter of course, is above the temperature that
can be tolerated in directly connectecl house
systems. The most suitable methocl of solving
the problems of temperature and heating effici-
ency involvecl is the use of a combinecl single-
pipe and double-pipe return-system in a part
of the city.
About 85% of the district system of the R.
M. D. H. S. is a single-pipe system supplving
thermal water directly to the heating systems of
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