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.
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.
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.
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www.windenergynetwork.co.uk
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