The Block Island offshore wind farm, a 30-megawatt facility off the coast of Rhode Island, will be taken offline this spring for expensive repairs. It is the only operating offshore wind farm in the United States. The residents of Block Island will have their electricity produced by diesel generators on floating docks while the wind farm is offline. The Block Island wind farm consists of 6 turbines and has been operating for only about 4 years, since December 12, 2016.
The developers of the Block Island wind farm did not bury the high voltage cables that carry electricity to land deep enough. The cables are being exposed as the seabed is being worn away by tides and storms; the exposed cables are dangerous to swimmers. One part of the repair will cost $30 million and the cost of the other part is currently undisclosed. Ørsted A/S—the Danish power company that now owns Block Island–is bearing the cost of reburying the Block Island cable connecting the turbines to the island grid. The original cable was installed by the previous owner—Deepwater Wind. Ørsted is replacing the cable to a greater depth, which state regulators had originally wanted, but were over-ruled by a state board. National Grid, which owns the cable that connects the island to the mainland, will charge customers of the Narragansett Electric Company to fix the problem. It is unknown what the cost to ratepayers will be.
Over the next few months, the companies will dig up the ocean floor to install new portions of cable at 20 to 50 feet below the seabed, compared to the current 4- to 6-foot depths. In the spring, when the wind farm is offline, they will splice the cables together.
Offshore Wind Energy Transmission an Ongoing Challenge
High-voltage lines that carry power beneath the sea from wind farms to the onshore electrical grid remain a challenge for the offshore wind industry. The current U.S. power and transmission system was not designed for a large offshore wind industry. Offshore wind farms are currently injecting their cables at locations that previously housed retired power plants in order to reach the onshore electrical grid, but that is not a comprehensive solution to avoid overloading and congesting the onshore grid system.
About a decade ago, a “transmission first” planning process for offshore wind was suggested. The Atlantic Wind Connection proposed a transmission backbone to run from Virginia to New Jersey, which was estimated to represent cost savings of $1.1 billion in the PJM Interconnection. The proposal was dropped when it ran into significant regulatory and financial hurdles.
A recent white paper by the Business Network for Offshore Wind pressed for a planned approach to the offshore cable issue, indicating that “comprehensive and coordinated transmission planning will best position the U.S. offshore wind industry to achieve sustained success.”
Like other developments in technology, it will take time and investment to produce coordinated approaches, which will involve several states having different perspectives, power balancing authorities and federal oversight from the Interior Department and the Federal Energy Regulatory Commission (FERC).
State Offshore Wind Plans
Many Northeastern states have made offshore wind procurements including Maine, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Maryland and Virginia, with a total of 6,460 megawatts selected and a future goal of 28,530 megawatts. The Mid-Atlantic States of New York, New Jersey and Virginia are in the process of procuring another 7,540 megawatts.
These states are offering subsidies and contracts for offshore wind power to quickly reach their decarbonization goals. For example, New York has made a pledge to be carbon-free by 2050 beginning with a 100 percent carbon-free power sector by 2040. In 2016, Massachusetts made a commitment to procure 1,600 megawatts of offshore wind by 2027 and an additional 1,600 megawatts by 2035.
The Bureau of Ocean Energy Management estimates about 2,000 turbines could be constructed offshore within a 10-year period. Updating the onshore grid to accommodate the 15,000 to 20,000 megawatts of renewable resources northern states already require through existing policies could cost as much as $10 billion.
The first-hand experience with the Block Island wind farm is indicative of the future pit-falls that the U.S. offshore wind industry can expect as it continues toward replacing existing traditional generating technologies with offshore wind. As with Block Island, transmission poses a continuing challenge for the industry. Currently, the interconnection of cables from offshore wind farms to the onshore electrical grid is happening at points where retired generating units were located. Eventually, all of those sites will be exhausted and the industry will need to look at other areas to tie into the grid. The U.S. electrical grid was designed for traditional generating technologies and it is unclear whether it can smoothly handle power coming from offshore wind sites.