UNEXPLODED ORDNANCE - Wind Energy Network

SPONSORS OF STEEL FOUNDATIONS
Tata steel
increases efficiency
of offshore wind farm
jacket construction
Offshore wind turbines are
playing an ever-increasing
role in governments’ aims
to continue transitioning to
a low-carbon economy and
meet stated green aims by
2020. Renewable energy is one
of the most cost effective
methods of producing power
in the long run, once the
capital costs of the initial
design, manufacture, assembly
and installation have been
reconciled.
Commitment
The UK is committed to producing 15%
of its energy from renewable sources
by 2020 and to meet this demand,
manufacturers are continuously striving
to produce wind turbines with increasing
power outputs. Wind farms are being
developed in larger numbers, deeper
waters, further offshore and therefore
almost inevitably requiring a move away
from monopile construction to other
alternative foundation structures.
Experience and technical
expertise
With a long-standing presence and
significant technical expertise in the
burgeoning global
renewable energy and
power sector, Tata Steel
has reviewed the factors
affecting the structural
design of offshore wind
turbine platforms, a
significant part of the initial
capital expenditure and has
invested in new routes to
support economical serial
jacket production.
Current factors affecting
the structural design of any
wind turbine include…
• The desire to improve
the power output for each turbine
to enable enhanced return on
investment, leading to increased size
and weight and enhanced structural
stress and fatigue.
• Design guidelines based on offshore
oil and gas installations
• Wind turbines being located further
offshore in deeper waters
• Challenging government targets for the
cost per megawatt-hour (MWh)
• Small wind farm developments are
being replaced with multi stage large
farms
Providing cost effective
solutions
With stretching targets for cost per
kilowatt-hour (KWh) having been set,
Tata Steel has looked at how to minimise
all the incidental costs including that of
manufacturing, installing and maintaining
the structure of an offshore wind turbine
and there are several key factors to
consider, in order to achieve cost effective
solutions.
Design and assembly standardisation
will be important in ensuring economies
of scale within the sub supply chain.
Small deviations from manufacturers
optimised steel tube sizes have been
adding significant additional costs. Close
collaboration between the designer,
fabricator and steel supplier will be
required to ensure design integrity is
optimised while maximising process
efficiency and minimising costs.
Displacing the current supply of the bundle
of individual tubes by steel suppliers with
complete point-to-point assemblies will
enhance fabricator throughput. Painted
assemblies incorporating pre-prepared
machined ends will enable swift assembly
and welding by fabricators.
Tube manufacturing for
offshore structures
There are three primary methods
for manufacturing tubes for offshore
structures; three roll bending, JCO and
UOE, the latter two indicating the shape
during forming. In all cases submerged arc
welding is the preferred option with both
high production single pass welding and
multi pass welding being adopted.
• Three roll bending
Three roll bending has been the traditional
method of producing large diameter three
to four metre cans welded for use in
monopiles. It is a very flexible process
with unconstrained diameters available
and immense quantity flexibility, however
it has a very slow throughput rate. High
production volumes are being considered
for developing wind farms and utilising this
option for legs and braces is unlikely to be
economic.
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