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the water before it goes back into the ground is
straightforward. For example, you can let the
sun heat it up in a pond or send it through solar
boilers on the roof. The groundwater available
in the winter will be warmer, and the savings
on energy consumption and heating costs will
be even higher. When the weather is cold, we
can cool off the water even more before it goes
back into the cold store, making cooling in the
summer even cheaper.
Clean up the soil immediately
Old industrial soil contamination is still found
in the subsurface in many urban locations.
Clearing up all that contamination is often too
expensive, but we do need to stop it spreading
further. An ATES system can actually spread
the contamination as it pumps groundwater
up and down, and so the authorities may
refuse permission. However, an ATES system
also creates opportunities to clear up old
contamination. The higher temperature of the
groundwater around the warm store may, in
specific conditions, accelerate bacteriological
breakdown. The bacteria can be given an
extra boost, for example by adding nutrients.
Another option is to clean the water pumped
up by the system before it goes back into the
ground.
Keeping up with the neighbours
More and more ATES systems are being
installed and this makes it more likely that
different warm and cold circuits will interfere
with one another. Warm water from a warm
store may flow in the direction of a cold store. In
your own system, this problem can be tackled
quite easily, for example by storing warm and
cold water in different sand layers. Things get
more complicated if other systems nearby
also affect the temperature of the groundwater
beneath your building. In that case, the trick
is to design the new system so that the return
is not impaired, but actually enhanced, by
the extra heat or cold from the neighbours.
This requires detailed information about the
structure of the subsurface and the impact of
the different ATES systems on groundwater
flows and groundwater temperature.
HOWDOES AQUIFER THERMAL
ENERGY STORAGE WORK?
ATES systems pump up warm groundwater in the winter. The heat is
transferred to the heating system in the building through a heat exchanger.
The cooled groundwater then goes back through another well to the cold
store. In the summer, that cold water is actually pumped back up to cool the
building. The number of ATES systems is on the rise throughout the world. The
Netherlands currently has approximately 2,000 operational ATES systems,
and this number is expected to increase to about 20,000 by 2020. Deltares
experts are working on the optimisation of ATES systems, bringing together
expertise about groundwater, subsurface structure, hydraulics, water quality
and sustainable energy. For more information:
wijb.sommer@deltares.nl
DELTARES, JANUARY 2014