The story of Block Island caught my eye. Block Island off Rhode Island is a permanent home to 1000 residents. In the summer times, daily visitors number between 10 to 20,000. Electricity supply has been problematic with some using generators and their own wind turbines. An application by the community for a grant for an undersea cable to connect to the mainland grid was rejected. The proposed wind turbines, 5 Haliade 6MW turbines, seemed a no-brainer for most though there were those who objected to it. But this small, private wind farm went ahead and began commercial operation in 2016. But there have been problems. Within a couple of years, the undersea cable connecting to the mainland (as part of the wind farm project) became uncovered at the island end for it had only been buried in places at four-foot depth to save money. Warning flags appeared on some beaches for a while and the cable had to be reburied at the cost of $31million. This reburial also has also problems with blockages and sediment.
There is some controversy over who paid for this reburial with claims that the National Grid profited by $46million from customer surcharges for maintaining the cable. The National Grid denies this.
This June, 2021 it was noticed 4 out of 5 of the turbines had ceased operation. The community on the island struggled to get any information from the operators, the Danish-based Orsted, who claimed that the turbines were down for regular maintenance which was best performed in summer. Ignoring the fact that it is the summer when the island needs the power most, this caused a lot of frustration and the turbines were down for the best part of two months. It emerged then that stress fatigue was noted on the support structures of the “helihoist” platforms on some of GE Haliade turbines in the Merkur project in the German North Sea. Stress lines were subsequently found in Block Island’s turbines but a risk assessment has deemed them safe and repairs were also undertaken.
The Haliade turbines are the same turbines being considered for some of the Copper Coast windfarms – though likely they will be of more recent versions and of higher wattage – which will have well over 100 turbines if projected output is anything to go by.
In the end, the shutting down of the turbines caused no power interruption for the island as the cable, though still being reburied, continued to connect them to the national grid. As far as I know, the turbines are operational once again.
Below I have picked out four wind farms and listed their specifications. I have also added my own notes as to why they are of interest in the case of the wind farms planned for the Copper Coast, three of which I have listed below for comparison
Energia’s North Celtic Sea Project (5-10km offshore) proposes a 600-800MW(approx.600,000 homes) wind farm and suggests that between 40-60 turbines are the usual amount (many factors will determine that, geography, turbine type and height, distance from shore. For example the London Array at 600MW has 175 turbines).
ESB/Equinors’ Celtic Offshore Windproposal (10km offshore) is also for 600MW (approx. 600,000 homes) and has no mention of the amount of turbines.
SSE Renewables floating wind farm The Celtic Sea Array(25km offshore) proposes an 800MW wind farm with no turbine estimate.
Beatrice Up to 2007, wind farms were only built in depths of 20 metres and less. Then came the experimental two turbine Beatrice wind farm off the east coast of Scotland (25km from shore and at a 40 metre depth). Beatrice has since been expanded closer to shore. What’s interesting to note is that Beatrice powers homes in southern Scotland via a 160km long subsea cable and underground cables to Blackhillock Substation in Northern Aberdeenshire via underground cables. This required the construction of two new converter stations, one at Blackhillock, which, at the size of 24 football pitches, is now the largest substation in the UK.
Of added interest re:the length of this cable to us on the Copper Coast is that the governments of the UK, Northern Ireland and Ireland commissioned a study about a decade ago which concluded that the development of an offshore interconnected grid would provide the UK with an increase of imports in the form of renewable generation from the Irish market and improve the interconnector capacity between both markets (Aoife Foley, Paraic Higgins, The evolution of offshore wind power in the United Kingdom, 2013). Could the power generated on the Copper Coast be used in the UK?
Distance from Shore: 13km
Area:131 square km
Water Depth: 56 metres.
Number of Turbines: 84
Turbine Height:188 metres (maximum pile depth to the highest point of the blade sweep up to 288)
Turbine Type: Siemens Gamesa 7MW
Foundation: Jacket (with the jacket substructures up to 81m tall).
Operator: SSE on behalf of a joint venture partnership.
Electricity Generation: 400, 000 homes.
The London Array
Once the biggest offshore wind farm in the world, the London Array is 20km off the Kent coast. Maintained and operated from the port of Ramsgate. Turbines are between 650 and 1200 metres apart. The blades have a swept area of one and a half times the size of Wembley Stadium’s football pitch. The turbines are designed to run for more than 20 years. That means basically that after two decades or so many wind farms will be decommissioned. Like our Metal Man and his pillars. Only eleven times taller. And more numerous.
Distance from Shore: 20km
Number of Turbines: 175
Turbine Height to tip of blade:147 metre
Turbine Type: Siemens 3.6MW
Water Depth: 25 metres
Foundation: Monopile (i.e. basically an extension of the turbine underwater)
Area: 100 square km
Operator: RWE, Orsted, Masdar & La Caisse de dépôt et placement du Québec (CDPQ)
Electricity Generation: 500, 000 homes.
Located off the Yorkshire coast, Hornsea One spans a huge area over five times the size of the city of Hull. The offshore wind farm uses 7 MW wind turbines, with each one 190 metres tall – larger than the Humber Bridge concrete towers.
Distance from Shore: 120km
Number of Turbines: 174
Turbine Height to tip of blade:190 metre
Turbine Type: Siemens Gamesea 7MW
Water Depth: 25 – 30 metres
Area: 407 square km
Electricity Generation: 1 million homes.
Dogger Bank Wind Farm is an offshore wind farm that will be the largest in the world when it’s finished, knocking Hornsea 1 off the top spot. It’s worth noting as it is located between 130km and 190km from the North East coast of England. Turbines are GE’s Haliade X 13 and 14 MW, over two and a half times taller than the Statue of Liberty and are likely to be considered by some developers for the Waterford coast. Dogger Bank will be capable of powering up to 6 million homes on completion in 2026. The subsea export cables will make landfall in Yorkshire, where around 30km of underground cables will take the electricity to converter stations near Cottingham before passing through the adjacent Creyke Beck substation onto the National Grid.
Distance from Shore: 130-190km
Number of Turbines: 600 (up to 200 for each phase).
Turbine Height: 260 metres
Turbine Type: General Electric’s Haliade X 13/14MW
Water Depth: 18-63metre.
Area: 8660 square km
Electricity Generation: 6 million homes
BONUS Farm: Block Island off Rhode Island. America’s first offshore wind farm was operational in 2016 and its operation has since been taken over by the Danish company Orsted. Though it is a pilot windfarm – 5 Haliade 6MW turbines less than 5km offshore – this ‘little’ windfarm deserves its own post because for most of this summer the turbines were shut down and the island’s residents did not know why. I’ll post about it on Saturday and move the planned post for creating an artist’s impression of turbines further along.