August 17, 2022
Letters, New Jersey

Why wind turbines can’t go farther out

Why Wind Turbines Can’t Go Farther Out | Feedback | The SandPaper | August 17, 2022 | www.thesandpaper.net

Carl Menk asked why the federal Bureau of Ocean Energy Management (BOEM) cannot move the wind farms 40 to 50 miles offshore, and he cites the Hornsea Wind Farm as an example (“Plea to Legislators,” 8/10). Yes, the Hornsea Farm is about 55 miles off the east coast of England. That is about one-third of the distance from England to the Netherlands. So, why can’t Ocean Wind and Atlantic Shores move their projects off the New Jersey coast farther out? This requires a technical explanation.

The explanation revolves around the sea floor topography/depth and the structure of wind turbines. The seafloor at the Hornsea site is shallow, between 90 and 120 feet deep. This relatively shallow water allows for a relatively simple foundation, that structure between the ocean floor and the ocean surface. Above the foundation, all of the turbines are the same, but each foundation is uniquely designed for the specific depth and seafloor conditions at the individual turbine location.

The foundation must support the turbine structure, resist the wind that drives the turbine and contend with sea currents and hurricanes. The shallow-water foundation design is usually a monopole; think of the vertical part of a traffic light pole on steroids. This is a relatively simple design and relatively inexpensive.

The Ocean Wind and Atlantic Shores sites, the ones closest to LBI, are also shallow-water sites. But just beyond the eastern limits of the lease sites, the seafloor starts to drop away. The sea topography quickly changes from shallow to 150 to 190 feet deep. Wind farms in this deeper water require a more complicated, massive and expensive foundation.

The six wind farm sites in the New York Bite are typically in water that is 180 feet deep and require more complicated foundation designs. Think of an Eiffel Tower about 200 feet tall dropped on the seafloor. The cost of each one of the wind turbine foundations increases as the water gets deeper, and does so very rapidly.

So the British, Dutch and other western European nations are lucky to have a shallow sea in which to locate their offshore wind farms. They can build wind farms much farther out using relatively simple and inexpensive foundations. They have built a lot of farms in the shallow sea between England and northern Europe. This is why they are a decade ahead of the U.S. in developing the technology. We will have to import their turbines for a long time before we can become wind energy independent.

Beyond 200 feet deep, the rigid structures (monopole and Eiffel Towers) become impractical. For deep-water sites, the wind farm industry will be using floating foundations, much the same as some oil rigs. In these designs the wind turbine floats on the surface and is tethered to the ocean floor. These are much more complicated designs. For instance, the turbine blades must be turned into the wind, but the foundation is not rigidly attached to anything to hold it still. The technology is being tested in limited situations such as the proposed sites off Maine, and will someday be ready for general deployment.

Also in The SandPaper, there appears to be some misunderstanding about the relationship between the BOEM and the wind farm developers. I see talk about BOEM moving the wind turbines farther out to sea, or legislators enacting laws to move the wind turbines. To be clear, the relationship between the BOEM and the wind developers is that of landlord and tenant, as defined by a legal contract. The developers are paying the federal government for the right to build and operate wind farms at specific locations in the ocean. These locations are defined in the BOEM’s environmental assessment document. When the contract is executed and the bid price (up to $7 million) is paid, the developers will be required to build the wind farm in conformance with the terms of the lease. Barring some failure on the part of the developer to comply with the terms of the lease, neither the BOEM nor the federal government has any power to arbitrarily change the lease terms, such as the location of the wind turbines.

The execution of the leases is the culmination of many years of preparation and planning. The process is designed to assure the technical and financial competence of the prospective bidders and to avoid any favoritism in the selection process. The lease is needed to assure the financial reliability of the project and facilitate the securing of capital (at least $4-plus billion per farm) for the project. Capricious changes to the lease contract by BOEM could be seen as a failure to adhere to the basic principles of commercial law. The draft lease documents are available online.

Wind turbines work most efficiently when they are farther out to sea. If you want to move the turbines out of sight from LBI, we need to develop made-in-America floating wind farms. It is my hope that some of the money appropriated in the just-passed Inflation Reduction Act will be directed to a national effort to become the world leader in the design, production and export of floating wind turbines suitable for deep-sea operations.

The writer is a registered professional engineer in several states, now retired after 50 years of experience including utility power generation and transmission and transportation consulting.