Offshore Electricity Infrastructure in Europe - European Wind Energy ...

esults
• A three-leg interconnector where the teed-in wind
farm (hub) is also connected to Germany. This
design thus links the Netherlands, Denmark and
Germany allowing multilateral electricity trade.
Investigated cases
Seven different cases are investigated (Table 4.5 and
Figure 4.19). The objective is to evaluate:
• Whether the inclusion of a wind farm on the cable
is beneficial. For this assessment the teeing-in
of two different wind farm/hubs is analysed separately:
Butendiek (400 MW) and HDE002 Cluster
(1,300 MW). (Case 2 and Case 7),
• Whether developing a link between the Cobra cable
and a large shore-connected German wind farm
cluster (HDE002) is beneficial – the so called threeleg
configuration (Case 3 and Case 4),
• Whether the connection capacity of the German
wind farm cluster HDE002 to shore can be reduced
in capacity (different sizes investigated) by introducing
a link to the Cobra cable (Case 5 and Case 6).
Costs and benefits are compared against the Hub
Base Case 2030 (Case 1).
Costs and benefits
Figure 4.20 shows the results of the cost-benefit
analysis for the Cobra cable case study. It is possible
to conclude that the inclusion of a wind farm on
the Cobra cable is beneficial for all cases (see next
section).
• Three-leg interconnector is beneficial.
The results show that for higher connection capacities
from the wind farm to the Cobra cable (i.e. the
more German wind that can be sent to either the
Netherlands or Denmark), the benefits are higher.
• Connecting the wind farms only to the Cobra cable
and not to Germany creates the most beneficial
cases - even if the capacity of the wind farm is higher
than the capacity of the Cobra cable.
• Teeing-in the large wind farm cluster (almost double
the capacity of the Cobra Cable) yields the biggest
net benefit. This proves the conclusion on splitting
the wind farm to-shore connection and connecting
it to two separate countries, as discussed in
Section 4.4.1.
Discussion
It may seem surprising at first sight that the tee-in
design is beneficial for all cases. However, considering
the overall power system configuration, the explanation
is rather simple. At times of high wind generation
in Northern Europe, German electricity prices are lower
than Danish and Dutch electricity prices. This is due to
the simple market logic that wind energy is generated
at almost zero marginal costs and therefore lowers
spot market prices in Germany significantly 24 .
Due to these price gradients it is beneficial to export
electricity from Northern Germany. This of course also
holds for offshore wind energy that can be transmitted
to neighbouring countries instead of being fed
into the mainland grid where low electricity prices give
low returns. This is in particular the case for northern
Germany: with massive onshore and offshore wind
power capacity, there will often be excess wind power
generation during periods of high wind which lowers
the spot market prices. The wind power is therefore
transmitted to the Netherlands or to Denmark where
higher prices promise higher returns. According to the
model, this is more beneficial than an interconnection
between the latter countries 25 .
This conclusion is supported by the case-independent
model where it was shown that increasing the connection
capacity to the country which usually has the
highest prices is the most beneficial option (section
4.4.1). Following this reasoning and taking into account
the results from the case-independent model,
the most promising grid design solution is to connect
some of the German wind farms to two or three neighbouring
countries. With a relatively modest extra cost
24 The model of course allows trade exchange across national borders similar to today’s coupled electricity market. However interconnection
capacity is limited and therefore high wind power generation in Germany first of all lowers the electricity prices within the
German boundaries.
25 In Germany there is a strong need for onshore reinforcement between Northern Germany and the Southern part. In the model,
planned onshore reinforcement is already taken into account and the offshore wind farms are connected deep inland. However,
the massive wind energy deployment in the North still leads to excess energy and low prices. In case the onshore bottlenecks are
solved, this might have an impact on the benefits of the tee-in solution.
56 OffshoreGrid – Final Report