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Airbag
for hydropower
Air cushion surge chambers are airbags for hydropower plants. PhD candidate Kaspar Vereide is now designing one
for the large hydropower project Upper Kontum in Vietnam.
When stopping a hydropower plant, a shock absorber is cru-
cial to prevent a massive body of water from crashing into the
plant with great force.
“Many Norwegian hydropower plants have over 10 kilometres
long tunnels, with a cross section that surpasses most road tunnels.
When suddenly stopping all this water, it is like if several semitrail-
ers driving through the tunnel had to stop. This creates large com-
pressive forces in the system,” explains Kaspar Vereide.
Through the HydroPEAK project, he has done a PhD on air
cushion surge chambers, a type of shock absorber that works
like an airbag in the hydropower system.
Large mountain halls as airbags
To create an air
cushion surge chamber, a mountain hall is constructed and
filled with air. When the hydropower plant is switched off,
the water flows into the mountain hall and compresses the air
rather than crashing into the power plant.
«Norway’s largest air cushion surge chamber is 120 000 m
3
.
In comparison, an auditorium at NTNU is between 10 000
and 20 000 m
3
,” says Vereide.
Design of an air cushion surge chamber in
Vietnam
Vereide is now cooperating with Multiconsult to
design an air cushion surge chamber for the 220 MW hydro-
power plant Upper Kontum, which is under construction on
the river Se San in Vietnam.
Air cushion surge chambers are not very common, as they
require certain geological conditions. Owing to the high pres-
sure, the mountain can crack, and the air leak. On the other
side, air cushion chambers do not depend on the surface
topography, in contrary to conventional surge chambers,
which are tunnels or shafts up to the surface.
“To make a conventional surge chamber at Upper Kontum,
they would have had to build a 200 meter tall concrete tower
on the surface, as there is not enough rock above the power
plant,” Vereide explains.
Advantages for pumped-storage facilities
Air
cushion surge chambers also have advantages for pumped-
storage plants, which are used to store energy in periods of
power surplus by pumping water back into a reservoir.
There, the water flow must frequently change direction within
a short amount of time. Because air cushion surge chambers
can be placed close to the turbines, it is possible to make
rapid changes in the power production without damaging
the facility.
Contact:
kaspar.vereide@ntnu.no