Tímarit Verkfræðingafélags Íslands - 01.05.1947, Page 17

TÍMARIT V.F.Í. 1947
39
REYKJAVIK HOT WATER SUPPLY.
Summary of the article on page 26—38.
Lecture delivered by cliief ensineer Helgi Sigurðsson at a meeting of the Icelandic Engineering Society.
The heating of Reykjavik by means of natural hot
water is one of the largest projects encountered in
industrial and technical developments in Iceland. This
is a description of the project and its approaches.
The first boring for natural hot water in Iceland
was made in 1928, at Thvottalaugarnar near Reykja-
vik, and a district heating system using this source
of heat was completed in 1930.
The result of this small scale district heating system
proved to be advantageous and animated further
executions of this kind.
Heating of the whole town of Reykjavik being
the aim, boring began, in the hot-spring region by
Reykir in Mosfellssveit, in the year 1933.
Estimated quantity of hot water there was 100
1/sec, but the boring increased this to 260 1/sec. Max-
imum output obtained by air lift amounts to 300 1/sec.
Furthermore the mean temperature of the water in-
creased from 82° C to 87° C. The quantity of hot
water required for heating the main part of the town
was thus available.
Building of the hot-water system itself started in
the summer of 1939, at in spite of various difficulties
and delays due to the war, water from Reykjavik Hot
Water Supply was connected to the heating system
of the first house Dec. lst 1943.
By now, 3000 houses get their heat this way in
addition to 70 houses that use water from Thvotta-
laugarnar previously mentioned.
In the hot-spring region at Reykir in Mosfellssveit
43 holes have been bored, 4—8 inch. in diameter and
135—720 m in depth. The additive depth of all the
holes is about 15000 m. Two hot-springs are used
without boring. These holes are scattered over an area
of J/2 km2. The heat varies from 80° C to 90° C, the
mean temperature being 87° C.
Fitting of the holes is achived by fixing a few
meters of steel pipe in the uppermost part of these,
the lower part being a solid rock and therefore not
liable to cave or to fall in.
At ground level there is a side pipe from the cas-
ing pipe leading to the collecting line. On this side
pipe there is a gate valve and an expansion joint
enclosed in a concrete box. The casing pipe is embedd-
ed in the wall of the box and bent to the side above
the wall. When the side pipe is closed the hot water
thus escapes. This bend also serves as an outlet for
gases.
From the holes and the hot springs the water is
piped to a cistern, which is close to the main pumping
station. The total length of these pipelines is about
2800 m. These are steel pipes 4—12 inch in diameter.
A section nearest to the cistern is made of a double
line 13 inch. „Bonna” pipes. Water flows by gravity
from the holes and springs to the cistern and from
there to the pumping station.
The cistern is circular, 11 m in diameter, made
of reinforced concrete. It is divided into two equal
sections by a wall. Each section can be emptied or
filled seperately, this being done in case of inspections
and repairs.
The main function of the cistern is to equalize the
flow and to reduce the velocity, thus preventing sand
from entering the pumps. It has an overflow at 1.4
m from the bottom.
The main pumping station pumps water to the
town. Three pumping units, turbin pumps, each driven
by 300 H.P. electric motor, are in the pumping station.
With maximum water requirement two units are
operated, the third being a reserve unit.
Each pump moves 150 1/sec against a head of 140
m. Pumping hot water makes inlet head necessary,
therefore the pumps are located in the cellar but
the motors on the main floor, this being a safety
arrangement.
From the main pumping station the water runs
through double line 14 inch. steel pipes to tanks built
on the hill Öskjuhlíð close to Reykjavík, the distance
being 15,3 km.
The lines are connected to each other in three
places thus arranged that i/jth of each line can be
closed for inspection and repairs, while 80% of the
quantity of water flows through the rest of the
line without change of head at the pumps.
On the line there are security devices, swing check
valves in four places, air outlet valves and drain
valves where landshape makes these necessary.
Four bridges were built across rivers the line
crossed.
The hot-water tanks on Öskjuhlíð are seven,
four built of reinforced concrete, volume 1100
m! each, and three made of steel, volume 1000 m3
each.
These are built in circle in middle of which a small
operating tower is built. This contains valves for
closing each tank and leveling device recording the
water level in each tank at the main-pumping station.
The function of these tanks is to equalize the flow
through the day, thus equalizing load on the motors
and the main line. The water is used during the