Page 38 - DIVA_3_2024_web

international

plant acts as a giant natural battery, storing up
to 34GWh. It is the first variable speed hydro
storage plant connected to the grid.

This variable speed hydro storage technology
enables the plant to monitor the level of excess
electricity in the grid and send the right amount
to wherever its needed, all with an overall
efficiency of more than 80%. This gives the Swiss
network great levels of stability and flexibility.
Only 120 seconds are needed to start up the
plant, and only 270 seconds to switch from
pump to turbine mode. The logic behind it is
simple; when a generator is driven by a turbine
it generates electricity, but when it is supplied
with electricity it works as a motor and
can drive a pump. This principle is used
in pumped storage plants, meaning they
can be used to store electrical energy.
They do this pumping water from a lower
reservoir up to a higher one, meaning it
can be released later to drive turbines.

Pumped storage power plants can
therefore store electricity at times when it
is abundant and supply it using the water
they have pumped during peak periods:
for this reason they are also called peak
energy plants. Of course, even at 80%
efficiency not all of the energy stored is
recovered, so the profitability of a pumped
storage power plant is mostly from power
market price variabilities over time as it can
supply valuable peak energy when needed.

The upper dam, the Muttsee Dam, is 630 metres
above the Limmenrsee Dam, with a volume of
nine million m3. The dam was rebuilt over the
last 10 years and today has a record-breaking
length of 1054 metres. It is also the highest dam
in Europe, at 2500 metres above sea level. Two
hundred and fifty m3 of concrete holds back the
23 million m3 of water on Muttenalp.

So, doors after doors, rooms after rooms, floors
after floors, we followed and examined an
immense construction. Then we learnt that we
had come to the highest point - we were exactly
under the highest dam. It had been my dream to
reach it, but I was not expecting to be underneath
it like this. So, if the dam is at 2500m altitude,
what altitude was the whole construction? I
started my count – if our “inside the mountain”
journey began at 1800m, even with some

w w w. d i va i n t e r n at i o n a l . c h