CROWN attempt to make offshore wind foundations cheaper
A group of corrosion,
manufacture, installation and modelling companies have joined forces to
design metallic coatings which have self-healing properties and offer an
alternative to anode cages. Managed by LIC, the CROWN project is aimed
to save large wind farms millions of pounds and lower the Levelised
Cost of Energy (LCoE).
The traditional and most common method of protecting offshore wind turbine
foundations from the harsh marine environment is galvanic sacrificial anodes,
large lumps of aluminium hung from foundations below the water line. When
connected electrically to the foundation they corrode preferentially to
protect the foundation steel from rusting.
Anodes can weigh multiples of tens of tons for large foundations which
can be costly. Large blocks of steel and aluminium also attract additional
wave loads, which in turn forces primary steel sizes upwards. LIC explained
that this drives up the cost of offshore wind energy.
The project is looking at how the use of aluminium and steel, costing several
tens of thousands of pounds per offshore turbine foundation, could be replaced
by the use of self-healing thermally sprayed aluminium (TSA).
In effect, the entire
offshore structure now becomes one giant anode. LIC claim that a further
important environmental advantage is that far less aluminium is corroded
away and released into the oceans.
CROWN is also aiming to establish guidelines for the marketplace to give
developers confidence in switching to TSA coatings on a whole-foundation
scale.
Although TSA and other metallic coating variants have been used in other
industries, and on a relatively small scale within offshore wind, LIS claim
the full potential of the coating system is yet to be fully realised. TSA,
and other similar coatings, could potentially replace sacrificial anodes
altogether, reducing the cost of offshore wind foundations.
TSA also gives the ability to further optimise foundations due to reduced
hydrodynamic loading, not only that but it removes fatigue sensitive details
as often seen with anode cage systems, according to LIC. It also claims
TSA allows for more a robust solution for internal use in monopiles, with
reduced or removed need for forced ventilation/water exchange systems/modelling.
It also has self-healing properties when subjected to small scale damage,
this could reduce operations and maintenance requirements.
TSA has been considered very difficult to apply in the past because the
high temperatures required introduce HSE risks. LIC state that this is
changing, as some large-scale manufacturers have recently developed automated
application systems. The scope of the CROWN project looks to rigorously
investigate many aspects of TSA manufacture and application to prove to
the offshore wind developer community that this is a reliable system which,
with the proper development, can become the new industry standard while
reducing energy costs at the same time.
