The US stands ready to take advantage of the development of new, large turbines for offshore wind and cost reduction achieved in the European market, but when it comes to foundations the picture is more complex
There is currently one, small offshore windfarm off the coast of the US, with five turbines and a total capacity of 30 MW. Several large-scale projects are about to take off, including one of 800 MW, but although the US has long built structures for the offshore oil and gas industry, there is a dearth of experience in engineering, manufacturing and installing foundations for offshore wind energy.
Seabed conditions off the east coast of the US differ from many of the sites exploited for offshore wind in Europe. Unlike Europe, the US does not, at least yet, have a large number of companies able to manufacture foundations and the picture of what kind of foundations will be used for offshore windfarms off the US east coast is complicated by states’ desires to provide jobs and undertake manufacturing.
In the US, it is states that determine energy policy. Politicians in states such as Massachusetts, New York, Rhode Island, Maine and others want to invest in clean energy and build offshore windfarms and they want their region to get a share of the work.
The first – and to date only – offshore windfarm in the US – Block Island, made use of jacket foundations, but it is unclear what the best foundations might be for upcoming projects. Monopiles have been the preferred choice for many, if not all, projects in Europe, and in particular for projects by leading developer Ørsted.
Another question that needs to be addressed is how best to industrialise the production of foundations in the US: producing foundations for offshore wind requires series production of multiple units, sometimes on a very large scale, quite unlike the oil and gas business. Without a way to successfully industrialise and mass produce foundations, the opportunities for cost reduction will be limited.
To get a clearer idea of what the best kind of foundations might be for offshore windfarms off the east coast of the US, OWJ spoke to Cameron Dunn, who leads Arup's offshore wind efforts across the US.
Mr Dunn has indepth technical expertise focused primarily on offshore engineering and is a professional engineer with offshore and onshore consulting engineering experience. He told OWJ that any developer planning to build a windfarm off the US east coast would first need to undertake very detailed site inspections to determine the nature of the seabed.
“In the northern east coast area, the seabed is predominantly glacial till,” Mr Dunn explained. Glacial till has formed the basis of the seabed in some offshore windfarms in Europe, but not all glacial till is alike, Mr Dunn said. In the northern east coast region of the US it consists of a lot of loose sand, but with boulders in that sand that could make piling tricky. As he pointed out, this is complicated by the fact that as turbines have grown in size and capacity, so monopile foundations have grown – and are growing – in size and as they grow so ‘errata’ – such as boulders – could be more of a problem.
Developers such as Ørsted – which have developed a business model based around using monopiles – should take note, he said. Jackets could be an alternative, having three to four smaller piles. While not eliminating the potential to have installation issues, the jacket would be stable even if the piles encountered boulders or installation problems.
Other types of foundation could also be used in the US market. They include gravity-base foundations and suction buckets, which have been proposed for Lake Erie Development Corporation’s Icebreaker project in the Great Lakes. All are ‘possible’ Mr Dunn agreed, but each has its advantages and disadvantages, and each represents a different kind of engineering and manufacturing challenge for the supply chain in the US.
Steps have already been taken by at least one leading European manufacturer of foundations, EEW SPC, to bring its expertise to the US market. In April 2018, Bay State Wind, the 50/50 partnership between Ørsted and Eversource, the New England transmission builder, entered into an agreement with EEW, the steel pipe manufacturer, to open a facility in Massachusetts to manufacture offshore wind components.
Bay State Wind and EEW will collaborate with Gulf Island Fabrication, which specialises in building for the offshore oil and gas industry. Together, the companies plan to use specialised steel manufacturing technology not currently utilised in the US. The companies plan to build a new manufacturing and load-out facility they anticipate will generate approximately 500 annual construction jobs with up to 1,200 additional annual indirect jobs in the local community. They will work together to produce monopile foundations and transition pieces, including secondary steel components, painting and pre-fabricated components for foundations.
Other similar agreements between European companies with expertise in foundations and US entities keen to get involved in the market must be under discussion. There are companies in the Gulf states that have long built jacket-type foundations for structures for offshore oil and gas, which would like to become involved. Gulf Island is one of the biggest, then there are companies such as Kiewit with a fabrication facility in Texas and five or six others that could play a role in fabricating structures.
“Engineering jackets is not going to be a problem for the supply chain in the US,” Mr Dunn said, but building large numbers of them and transporting jackets built in the southern US for installation in the northeast could be costly. Further, building jackets in the southern US would not provide the employment opportunities that politicians in offshore wind states crave.
“Jackets are essentially made of tubulars and require specialist welding skills. For large and extra-large monopiles for new-generation turbines you are going to need a fairly sophisticated facility that can roll steel, and for gravity-base structures the requirements are different again,” Mr Dunn told OWJ. “Another issue is portside infrastructure. Where would the load-out ports and storage facilities for east coast offshore wind energy be?”
All in all, said Mr Dunn, there are serious questions that need to be answered in the coming months about what kind of foundations to use, who might manufacture them, where they would be manufactured and how and from where offshore wind projects in the northeast will be staged.
That is before issues such as the dearth of installation vessels in the US market begin to be addressed, not to mention potential environmental concerns that would need to be looked at, such as the potential effect of noise created by piling on marine mammals, such as the northern right whale.
Gravity-base foundations do not require piling and installing suction bucket foundations does not create the same kind of noise as driving a monopile into the seabed, so might be an option, but they are less well-suited to use in gravelly soils. The latter might be better suited to use further south on the eastern seaboard, Mr Dunn suggested, where the seabed is of a silty/sandy type.
“One of the keys to this whole process is going to be making use of the expertise in the Gulf of Mexico and generating sufficient interest in investment on the east coast,” Mr Dunn concluded.