PO104

Upscaling TLPWIND® floating technology for 10MW Offshore Wind Turbines

Juan Amate1, Gustavo D. Sánchez 2, Gonzalo González1, Pablo Ceña2, Álvaro Luna1, Francisco Ginés1
1Iberdrola Ingeniería y Construcción, Madrid, Spain, 2Iberdrola Engineering & Construction, Glasgow, UK

Abstract

The latest developments in Offshore Wind have presented an increase in the rated power of the Offshore Wind Turbines Generators (OWTGs). 7/8 MW OWTGs are currently starting to be installed and are mainly considered by several developers for future projects.


The use of larger OWTGs has clear benefits regarding the energy harnessing since fewer units are needed for the same Offshore Wind Farm (OWF) scheme, but on the other hand it introduces a higher loading into the substructure which results in a challenging design. In this sense, Floating Wind technologies have shown to be less sensitive to an increase in the OWTG power as most concepts are predominantly Wind Turbine agnostic.


Iberdrola Ingeniería y Construcción (IIC) has studied the impact of implementing larger WTGs in its floating tension leg technology, so called TLPWIND®.


The upscaling process has proved a notable reduction in the Levelized Cost of Energy (LCoE) when going from 5 MW to 10 MW OWTGs, being this reduction even more remarkable when designing for locations with mild meteorological conditions. Although the complexity of the design and the logistics are slightly increased as a result of having heavier and larger structures, when assuming a fixed installed power for an OWF the overall cost per MW is significantly reduced as a consequence of the platform scale optimization and by having much less units to manufacture and install. As a consequence, CAPEX reduction of up to 20-25% and a direct LCoE reduction of 15-20% can be achieved.

Method

IIC has performed TLPWIND® concept designs for 2MW and 5MW OWTGs achieving a TRL5 at this scale for different representative sites. Three scaled model tests campaigns have been carried out to achieve the TRL5 condition, which have concluded with a thorough correlation of the numerical models. Thanks to the outstanding results obtained from the correlation exercise, IIC has developed the capacity to accurately extrapolate and optimize the design of TLPWIND® floating substructures to fit larger OWTGs at diverse sites with a range of different environmental severity. This methodology has been applied within H2020 LIFES50+ project to obtain concept designs for three different representative sites (mild/moderate/severe environmental severity) for a 10 MW OWTG. Also, within TLPWIND UK project an LCoE calculation tool was developed and applied.

Results

The use of larger OWTGs for TLPWIND® technology has a direct impact on the platform dimensions and the conception of the logistics. When considering an increase of the OWTG rated power from 5MW to 10MW, the following results are obtained:


• The increase in weight of the platform could be as low as 30%.
• Platform's span and draft increment is in the range of 15%-30%.
• 25-30% investment cost reduction for the manufacturing of the platforms.
• 15% cost reduction for the mooring system components supply.
• 20-25% cost reduction for the load-out operations, OWTG pre-assembly in port and offshore installation of the TLPWIND® unit.
• The use of 66kV interarray cables can provide up to 30% less investment cost due to the need for lower cable lengths.

Conclusions

One of the key advantages of Floating Wind technologies is the potential to fit larger OWTGs being able to significantly reduce the LCoE. The studies conducted by IIC have confirmed the benefits of the application of larger OWTGs for TLPWIND® technology resulting in a promising LCoE reduction, besides of proving its technical feasibility at 10MW from a design, fabrication and installation perspective.


In this regard, TLPWIND® 10MW designs can maintain the outstanding dynamic behaviour presented for previous developments in 2MW and 5MW at the same time that the installation philosophy using an ad-hoc semisubmersible barge can be equally carried out. As a result, a typical 500MW OWF could be installed in much less time which entails less offshore installation risks and overall weather dependence.

Objectives

• Overview of TLPWIND® floating technology development
• Technical evaluation of a TLP floating substructure at different OWTG scale (2MW, 5MW, 10MW)
• Cost reduction potential of Floating Wind technologies
• Economic assessment of Floating Wind
• Floating Offshore Wind Farm development modelling
• Floating Wind development future outlook