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INTEGRATED TELESCOPIC TOWER AND EVOLVED SPAR FLOATING SUBSTRUCTURE FOR LOW-COST DEEP OFFSHORE WIND AND NEXT GENERATION OF 10MW+ TURBINES

Periodic Reporting for period 3 - TELWIND (INTEGRATED TELESCOPIC TOWER AND EVOLVED SPAR FLOATING SUBSTRUCTURE FOR LOW-COST DEEP OFFSHORE WIND AND NEXT GENERATION OF 10MW+ TURBINES)

Reporting period: 2017-11-01 to 2018-11-30

Main objective of the project is to design a disruptive technology to reduce cost of floating offshore wind energy,contributing to the socalled green development,reducing CO2 emissions and providing sustainable energy outputs that can be massively implemented and also profiting local development in European regions.This overriding objective was achieved through the development of the TELWIND technology,which in order to reduce the levelized cost of energy (LCOE) has set himself several smaller and easier to verify objectives.Most significant objectives are:
• Reduce and optimize the number of materials required for the manufacturing of the floating platform.
• Achieve a simple and industrialize manufacturing and installation processes.
• Ensure full independence of scarce and costly heavy-lift or special purpose vessels during the complete offshore installation process.
• Increase competitiveness by reducing dependency from deep draught ports and scarce installation means.
These objectives were achieved by completing the overall design of the floating platform from a life cycle holistic perspective,where most relevant components and systems were designed,Researching and further detailed design on the two ground-breaking technologies and the opportunities that revolve around them were key to success.One of these technologies is the evolved spar configuration and the ballast tank, which allows taking advantage of inherent benefits of spar platforms without jeopardizing manufacturing and installation process.The second technology is the telescopic tower,which allows for a simpler manufacturing with more conventional means and an optimized transport,also allowing for an easy and streamlined scalability of the system for larger more powerful wind turbines.Finally,when combined,all of these advantages allow for a higher regional impact,which is an important consideration for the regions where offshore wind farms are being implemented,allowing for local communities to retain as much of benefits and the economic push that the floating wind farm can provide. It was found out that about 50% of infrastructure can be procured and built locally,and the remaining 50% can be procured on other European countries.
Technical scopes & activities are:
• Research on the overall hydrodynamic behaviour and detailed structural design of the floating platform
• Cutting edge simulations by building Fully coupled aero-hydro-servo-elastic numerical models
• Design of suspension tendon system plus laboratory testing
• Construction & installation assessment supported by numerical models & tank testing & real-time simulations
• Extensive tank testing campaign in operating & installation conditions
• Detail design of critical & expensive components like moorings & power cables.
• CapEx & OpEx estimate & financial feasibility study for a stand-alone installation and array integration in a multi-megawatt floating offshore wind farm
• Project certification by a internationally well-known reputed certifying institution as TUV SUD.
• Demonstration of scalability by designing a floating substructure for 12MW wind turbine.
In this periodic and final report,the design of the 5MW floating substructurewas finalized based on a detailed structural design and a fully coupled model with a 5 MW reference wind turbine.The upgraded platform enhanced the performance of previous designs avoiding singular events like cable slacking,thus improving the performance of the wind turbine.Mitigation of motions was also profited from the bespoke controller designed for this specific floater.The geometry of the tower was adapted to new envelope of loads.Additionally,the 12MW basic design was successfully finalized,demonstrating the expected easiness for scalability and subsequent cost reduction.Results obtained were contrasted with the 2nd large scale tank testing campaign to fully characterize and validate the dynamic response of the wind turbine.Significant advances have been performed on the design of tendon,upgrading the fatigue life of the tendon system and finalizing the laboratory tests of the suspension cables.Design of mooring system,anchoring and power cables are also an important milestone to complete the overall design from a lifecycle perspective.Once all the analysis and simulations were carried out,the construction,transport and installation procedures were written down and integrated in a global strategy analyzing the impact of weather downtime on the overall deployment at sea.The engineering scope was accompanied by the cost and financial assessment along the project, thus the design was always governed by the financial key parameter indicators.Finally the environmental impact on the offshore site (Great Canary island) was positively addressed,together with estimations on carbon footprint and local content impact. Due to the positive outcomes of these assessments, the social perception to floating wind farm is foreseen favorable.
The TELWIND evolved Spar concept aims to reproduce the advantages of the different state-of-the-art concepts while avoiding their major disadvantages. It will profit from the inherent advantages of spar buoys in terms of stability, low wave sensitivity and independence from soil conditions, while economically overcoming their main acknowledged disadvantages, thus enabling a radical step forward for competitive deep offshore wind.On one side, the evolved spar configuration with suspended ballast tank will make it possible to achieve the same or even improved stability and motion control with significantly reduced material usage and with no need for very large drafts. But probably even more important will be the capacity to have a construction and installation process in which the complete system can be preassembled on the harbor and simply towed out to the site, therefore reproducing the most distinctive and relevant advantage of semisubmersible platforms.What is more, thanks to the telescopic tower and self-buoyant upper platform, such a complete harbor preassembly will have limited height (<60m), width (<40m) and draft (<9m) even for 10MW+ turbines, which improves the capacity for work industrialization and ensures its scalability for the next generation of extremely large wind turbines based on largely available onshore means and infrastructure.TELWIND also profits from the proven structural efficiency and economy of precast concrete, a material particularly well suited for low-cost industrial production of repetitive units, which further enhances its unique capacity for an industrialized and scalable onshore preassembly, which is a key attribute for risk and cost reduction that no state-of-the-art solution could match.The project l provide highly-developed solution with the potential to qualitatively reduce the costs of deep offshore wind while simplifying the installation process, avoiding the dependence on any large auxiliary offshore crane or vessel, and allowing for industrialised on-shore focused construction and better risk control and mitigation.The TELWIND technology can significantly contribute to the industrialization capacity and cost competitiveness of an industry which is key to provide EU with the capacity to generate large enough amounts of locally sourced renewable energy, thus improving EU energy security and contributing to the gradual solving of global climate and energy challenges.
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