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

Timing of technology development
The timing of technology development has been found
by the OffshoreGrid consortium to be a large challenge
for an offshore grid. There is a variety of new
technologies needed for safe and secure offshore grid
operation, particularly with respect to power flow control
mechanisms, security issues, increased capacity
and reduction of energy losses.
The key issue to be tackled is multi-terminal operation.
So far, fast DC breakers are not fully developed
and multi-terminal operation is not possible. In case
of an offshore grid failure the complete grid has to be
de-energised, the fault has to be isolated, and only
then can the offshore grid be loaded again. This can
also have serious impact on the onshore grid stability
due to frequency problems. Furthermore it should
be highlighted that TSOs do not have any experience
with multi-terminal operation based on HVDC VSC
technology.
The timing of technology development will depend on
the likely order value, which in turn depends on the
connection method the offshore industry adopts. For
example the adoption of a model whereby offshore
wind farms are clustered around offshore transmission
hubs may drive an increase in the capacity of
individual VSC converter stations, whereas a continuation
of the trend of individual wind farm connection
may not.
OffshoreGrid – Final Report
Commodity prices
The overall cost of the offshore grid is largely influenced
by the cost of the key raw materials, most
notably the raw materials used in HVDC and HVAC
subsea cables, as they form by far the largest component
of the offshore grid. Two metals tend to be used
to form the conductors in power cables, copper and
aluminium. The superior conductivity of copper means
that more electric current (and hence more power) can
be passed down a copper conductor of certain cross
sectional area than down an aluminium conductor of
the same size. This means that copper cables are
smaller than the equivalent aluminium cables which
can make transport and installation easier, both important
and expensive considerations in the offshore
environment. The surge in global demand for copper
however has not only driven the price of copper to
peak levels, but also introduced significant volatility in
the pricing (See Figure 5.1 below). Any manufacturer
using significant amounts of copper as a raw material
would obviously offset this price risk in the equipment
quotes, potentially pushing up the price of many of
the pieces of equipment required for an offshore grid.
Indeed many recent subsea cable orders have been
specified with aluminium, primarily because of the
high copper price.
At the aggregate level, the future development of key
commodity prices is assessed by the OffshoreGrid
consortium as a medium barrier for an offshore grid.
FIGURE 5.1: PRIcE OF cOPPER ON ThE lONdON METAl EXchANGE OvER ThE lAST TWENTY FIvE YEARS (SOURcE: WIkIPEdIA FROM
lME SOURcE dATA)
83