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DNV GL supports rapid development of offshore wind industry in the US

by Ahmed Phuly and Andreas G. Jensen

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Andreas G. Jensen Andreas G. Jensen
Project Manager, Principal Engineer

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Horns offshore wind farm
The environmental conditions along the northeast coast of the US are similar to those in the North Sea, and substantial knowledge transfer is possible.
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  • Keywords: Energy, Renewables Certification

The combination of offshore wind’s enormous energy potential and the requirements for new energy sources due to aging energy generation facilities sets the scene for a rapid development of the industry in the United States (US). The constant flow of successful lease auctions conducted by the Bureau of Ocean Energy Management (BOEM) for the US East Coast and even unsolicited lease applications for offshore areas is the litmus test of industry interest. This is despite the well-known need for long-term support mechanisms and installation vessel complications related to the Jones Act, the solution of which one can only speculate about. It basically shows the industry’s trust that these challenges will be overcome.

To get approval for an offshore Wind farm, US regulations require that an independent third party is appointed to certify the design, fabrication and installation to BOEM. DNV GL’s Renewables Certification has been active as a Certified Verification Agent (CVA) from the very beginning of the US offshore wind journey. The CVA is nominated by the offshore wind facility’s developer for approval by BOEM, on behalf of which the CVA preforms its activities. The CVA duties* outlined in the US code of Federal Regulations (CFR) match very well the systems and schemes applied for the approval of offshore wind farms in Europe. This is not a coincidence as the CFR and European regulations on offshore wind both evolved from the offshore oil and gas industry.

DNV GL acts as CVA for Cape Wind and VOWTAP offshore wind farms
Currently DNV GL is nominated as CVA by BOEM for the Cape Wind and VOWTAP offshore wind farms on the Outer Continental Shelf and performing CVA activities for offshore wind farms in State waters applying the CVA set-up.

The Cape Wind project was the first to receive BOEM approval for its Facility Design Report and Fabrication and Installation Report with DNV GL as CVA. The assets considered by DNV GL as CVA were the wind turbines and their support structures, the offshore transformer station, and the sea cables.

Development of well proven CVA concept from oil & gas industry to fit offshore wind
The CVA process is well known for US offshore oil and gas structures, where vast experience is available. The novelty is the adoption of the wind turbines’ specific considerations into the well proven oil and gas CVA process. Here, a notable difference is the design implications stemming from the highly dynamic loads from the wind turbine making fatigue a design driver for major parts of the structures. Further, the capital flow from a single oil and gas structure is much higher than for a single wind turbine support structure; this drives the requirement for a high degree of optimization, stripping the structure for conservatism while maintaining a reliable structure with low and predictable operating costs. This development is made possible by sophisticated design tools now available for wind turbine structural design in combination with trial and error learning from thousands of offshore foundations already installed, mainly in the Northern Europe.

The offshore wind industry is under constant innovation and optimization pressure from the rapid and continuing increase in turbine and support structure size. For the CVA this requires the ability to adapt to novel concepts and approaches if these can be demonstrated to deliver the intended safety level. DNV GL has been part of this evolution over the last three decades and demonstrated the ability to adapt along with the industry and authorities. Notable examples are the development of recommended practices, standards, and joint industry projects, in close cooperation with industry and authorities and the widespread use of these by the industry.

Benefitting from lessons learned in Europe
DNV GL has a strong presence across the US with offices on the east and west coasts and the Houston office with US-based offshore experience and trained offshore surveyors. These US personnel are strongly supported by DNV GL’s Renewables Certification team in Europe, which provides experience from CVA-like activities performed for most offshore wind farms under operation and at various stages of completion.

Specific US conditions such as hurricanes have turned out to be manageable and for the northeast coast with attractive wind resources the turbines developed for North Sea conditions have been shown to be suitable for this area.

The environmental conditions along the northeast coast of the US are similar to those in the North Sea, and substantial knowledge transfer is possible. Together with the added innovation power from US developments it will further drive down the levelized cost of offshore wind energy, allowing a truly global market to emerge.

*The CVA’s primary duties for the Facility Design review are per the US Code of Federal Regulations (CFR) 30 §585.706: “The CVA must use good engineering judgement and practices in conducting an independent assessment of the design of the facility. The CVA must certify in the Facility Design report to BOEM that the facility is designed to withstand the environmental and functional load conditions appropriate to the intended service life at the proposed location”.