In the new year, the first offshore wind farm in the United States will shut off its turbines, and its customers on nearby Block Island in Rhode Island will revert to diesel generation.
The sun rising at Block Island Wind Farm off the coast of Rhode Island. Deepwater Wind.
The rocky seabed around Block Island has been worn away by tides and storms, sometimes exposing high-voltage cables in a popular swimming location that developers failed to bury deep enough when the facility was brought online in 2016. To splice in newly buried cables, the wind farm will go offline for a brief period this spring.
At $30 million for one leg of the fix and an undisclosed amount for the other, it’s a costly problem to crop up for the nation’s first offshore wind farm, and it’s not totally isolated.
High-voltage lines that will be buried at sea to carry power from the burgeoning offshore wind sector and inject it into the onshore grid represent the most complicated, and as yet uncertain, aspect of an industry poised to boom, experts say. From grid congestion to technical troubles, the offshore wind’s transmission challenge is the focus of growing attention as the industry advances.
“We cannot afford to develop the offshore grid in piecemeal,” Judy Chang, the undersecretary of energy for the Massachusetts Executive Office of Energy and Environmental Affairs, said at a Federal Energy Regulatory Commission conference held on offshore’s transmission challenges Tuesday.
Block Island represents just 30 megawatts of power, a pilot project that preceded what could be a wind boom driven by state commitments to buy offshore wind and decarbonize power systems.
Block Island is leftover rock and gravel from a glacier’s ancient retreat. The seafloor surrounding it proved too rocky for the cost-saving technique that developer Deepwater Wind and utility National Grid PLC used to lay the Block Island cables.
State regulators had flagged that problem, but a state board ruled in favour of the developer’s proposal.
John Dalton, president of the consultancy firm Power Advisory LLC, said the technical issue is not one likely to be repeated in the region and called the point where subsea cables have to climb ashore as a common pinch point for environmental issues, if only because it’s “where offshore wind becomes most apparent to stakeholders.”
The geography of the seafloor is a critical aspect of wind siting that happens at the federal and company level and can make whole regions unfeasible until technology advances — such as in the Gulf of Maine, where researchers are testing floating technology in hopes of bringing offshore wind power to the deep gulf.
Ørsted A/S — the Danish power company that acquired Block Island when it bought Deepwater Wind in 2018 — is bearing the cost of reburying the Block Island cable connecting its turbines to the island grid.
Ørsted is focused on replacing the original cable to achieve a greater burial depth.
Over the next few months, new portions of cable will be thread at 20 to 50 feet below the seabed, compared to the current 4- to 6-foot depths.