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

The higher the price difference between countries, the
more important the trade constraints become.
Trade constraints can be reduced by optimal dimensioning
of each of the different elements. This is
different in each case, and depends on the distances
from shore, the distances between the hubs, the price
difference profiles between the countries, and the capacity
of the wind farm hubs.
4.4 Integrated design –
case-independent model
As was shown in the previous section (4.3), numerous
parameters influence the results. They are very
case-specific, which makes it difficult to draw general
conclusions. On the other hand, general conclusions
are indispensible for offshore grid planning, the supporting
policy making process and also for the project
developers themselves. Such conclusions for caseindependent
concepts have been derived with help of
a dedicated “offshore grid design assessment model”.
With this model, the tee-in solutions and the integrated
hub-to-hub solutions are further assessed and concrete
guidelines are developed in the following paragraphs.
Finally, a practical case study has been elaborated
to check the results against a well advanced real
case. The Cobra cable – a direct interconnector cable
planned between Denmark and the Netherlands – has
been chosen because the consortium considers this
a very important and relevant project in the process
towards an offshore grid (paragraph 4.4.3).
General analysis
The results of the cases presented in section 4.3
are very context-specific and thus not generally applicable.
The present section aims at developing more
general conclusions and understanding about the key
design drivers based on a thorough sensitivity analysis
with a dedicated offshore grid analysis model,
that investigates under which circumstances an integrated
solution is beneficial over a BAU solution. The
approach focuses on two principal design optimisation
problems considered to be the modular building
blocks for any international offshore grid design:
OffshoreGrid – Final Report
• Break-even distance wind farm (WF) to shore beyond
which a tee-in solution is beneficial:
– the larger the distance from the wind farm to
shore, the more cable length can be saved by
going for a tee-in solution,
– the closer to shore, the more the constraints
that it introduces will be important,
– depending on various parameters, there is a
minimum distance (break-even distance) from
the wind farm to shore beyond which a tee-in
solution becomes preferable over a conventional
individual connection and direct interconnector.
• Break-even distance between hubs below which a
hub-to-hub solution is beneficial:
– the shorter the distance between hubs, the
more infrastructure costs can be saved by going
for a hub to hub solution instead of a separate
direct interconnector solution,
– the larger the wind farms (respectively the hubs),
the more the trade constraints that it introduces
will be important,
– depending on various parameters there is a maximum
distance (break-even distance) between
the hubs up to which it is preferable to choose
a hub-to-hub solution over a conventional individual
connection and direct interconnector.
Concrete results that can be used by project developers,
consultants, political decision makers, regulators,
etc. are available on www.offshoregrid.eu.
4.4.1 Minimum distance for
tee-in solution
Introduction
Figure 4.15 and Box 1 explain the optimisation
problem. The objective is to calculate the break-even
distance from the wind farm to shore beyond which a
FIGURE 4.15: EXPlANATION OF ObjEcTIvE: MINIMUM dISTANcE
WINd FARM TO ShORE FOR TEE-IN SOlUTION
Separate better
Tee-in better
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