Energiforsyning i Arktis – hvilken vej vælger Grønland? - Artek ...

models taking surface roughness, orography
and obstacles into account and works quite
well in reasonably flat terrain. It contains
correction models in complex terrain, but
with some uncertainties. Figure 5 from [5]
shows an example of WAsP results in
Sarfannguaq based on the measurements
from one 10 m high meteorological mast.
The uncertainties from the highly complex
terrain in the peninsula around Sarfannguaq
are considered high. Further, the variation
of the wind speed with height may be very
different from the WAsP result again due to
the complex terrain. It is considered
important to apply a CFD calculation of the
flow over the peninsula for various wind
directions to supplement the WAsP analysis.
Figure 5: Estimated mean wind speed in
Sarfannguaq using WAsP on the
measurements from one meteorological
mast. Red color indicates 6.09 m/s and
purple 5 m/s. The Figure is taken from
reference [5]
Once the annual production is known one
has to look at the annual consumption to
choose a reasonable size of a wind turbine.
According to [5] the mean consumption in
Sarfannguaq is 61 kW, the minimum and
maximum consumption is 24 kW and 134
kW, respectively. A wind turbine will always
need to be combined with another system
eg diesel driven generator or a large energy
storage to cover periods of no or low wind
speeds. At higher wind speeds the wind
turbine can relive the diesel engine driving
the generator and thus reduce the diesel
consumption and save oil. One has,
however, to keep in mind that when
10
reducing the torque one also changes the
efficiency of the diesel engine that then runs
less optimal. The proper size of a wind
turbine for e.g. Sarfannguaq is thus an
economical study taking into effect the price
of the wind turbine, the wind resources
available, the cost of diesel, the
consumption, the variation of the
consumption (day versus night, winter
versus summer), the operational data
(efficiency) of the diesel engine etc. The 6
kW wind turbine from the Scottish company
Proven is small compared to the mean
consumption of 61 kW and also a relatively
expensive wind turbine. However, it was
chosen because it is considered a very
robust design requiring a minimum of
service and is able to survive very high wind
speeds as presented in previously [7]. It is
thus expected that it will run even at the
rough environmental conditions on
Greenland with low temperatures, snow and
ice and occasional severe storms. The idea
is thus to gain experience with running a
wind turbine under arctic weather conditions
and the interaction with the existing diesel
production plant. If this experiment is
successful one can start looking for slightly
larger and preferable also cheaper wind
turbines that are expected to be more
economically attractive for a typical small
village in Greenland.
Most commercial wind turbines are not
designed for arctic climate, but can be
modified. This includes special oil that keeps
its viscosity at extreme temperatures, anti
or deicing devices, protection of electronic
circuits etc. Many of the problems and some
of the modifications made in practice are
described in a Diploma final thesis from DTU
Mechanics [6]. There is so far no operational
experience from the turbine in Sarfannguaq,
but hopefully this turbine will run without to
many problems since a it was chosen based
on its simplicity and robustness.
3. Storage
One of the main barriers of using wind
energy is that one does not control the wind
speed, i.e. sometimes there is a need for
electrical power but there is no wind and
sometimes there is a lot of wind but no need