Let’s talk about building offshore wind farms. First of all, this is not ordinary construction work.
The country’s first large-scale project, vineyard wind I, plans to use longer turbines than the John Hancock Building, the tallest skyscraper in Boston, 790 feet high. Wow, boy, these things are heavy. Take the engine room for example. It is a long and narrow part with an engine in it, right behind the blades. It weighs 794 tons. This is almost equivalent to two fully loaded 747 aircraft.
Now, imagine installing these things in the ocean.
Today, we will describe in detail how to actually install offshore wind turbines. Let’s start.
Pick a foundation
The type of foundation used by developers usually reflects the depth of the surrounding water. In the vineyard wind project area 15 miles from Martha’s vineyard, the water depth ranges from 115 feet to nearly 200 feet. For these things, it’s shallow, which means you can use something called monomer as the basis.
A single pile is a steel pipe driven into the seabed. Vineyard wind has a single pile diameter of 34 feet and 312 feet end-to-end. According to the company’s federal environmental license, about half of the structures will be buried on the seabed.
In deep water, developers use something called a jacket. The jacket is a bit like a tripod. They have three or four legs fixed to the seafloor. The vineyard permit stipulates a maximum of 10 jackets.
Pick a turbine
Offshore wind turbines have become larger and larger. Much larger.
Consider this example: each of the five turbines used in the Block Island wind farm on Rhode Island can produce 6 megawatts of electricity. The distance from the waterline to the rotor is about 300 feet, and the turbine blade is 242 feet long.
Now compare it with the turbines used in the vineyard wind power plan. They will be able to generate 13 megawatts of electricity, and the distance from the waterline to the rotor will reach nearly 500 feet. Its blade extends more than 350 feet, almost as long as a football field. Just one turbine can provide enough electricity for 16000 households.
Pick a boat
According to the Government Accountability Office, about 50 ships in the world can only install offshore wind turbines. These ships are sometimes referred to as Jack UPS because their legs are lowered to the seabed and lift the ship off the water when the turbine is installed.
Jack up ships have two challenges. First: they are not Americans. This is problematic because the United States has a law prohibiting ships flying foreign flags from sailing between American ports.
Developers can bypass the law. When deepwater wind built the Block Island wind farm, it used a ship flying the Maltese flag called “brave tern”. The brave tern is moored near Rhode Island and is supplied with parts and equipment by a small team of barges and transport ships.
The vineyard wind plan adopts a similar strategy. Its problem is that few Jack ups are equipped with cranes of sufficient height and strength to install haliade-x. In fact, according to researchers at Tufts University, only three ships can install haliade-x. Vineyard wind signed a contract with deme group in Belgium, which owns a 438 foot long ship called “offshore installer”.
Some assembly required
Paul Murphy is one of the few Americans with experience in offshore wind farm construction. He oversaw the construction of the Block Island wind farm and was one of the heads of ostad A / S’s South Fork, revolutionary wind and sunrise wind development projects in southern New England. We asked him how to actually assemble one of these projects.
His suggestion is: “the best way to build a project in the middle of the ocean is to be in the middle of the ocean as little as possible.”
This means a lot of work on shore. In osterd’s case, its first two projects will be carried out at a staging area in New London, Connecticut. Vineyard wind will use the marine commercial terminal in New Bedford, Massachusetts.
Murphy said that usually, the high part of a turbine called a tower has three 100 foot high parts. These equipment are stacked and welded together on land and equipped with all necessary cables and wires.
They were then floated to the wind development zone and installed using one of the large Jack ups. Once the tower is firmly fixed to the seabed, the nacelle containing the motor is placed on top of it, and each of the three turbine blades is connected.
Of course, this only includes the installation of the actual turbine. The developer also needs to lay transmission cables between turbines and connect them to offshore substations, and then transmit power to the main transmission cable to the mainland.
That sounds simple, doesn’t it?