From the proposed backbone Atlantic Wind Connection project in the mid-Atlantic to individual efforts by offshore wind developers, offshore transmission efforts continue to move forward.
The Atlantic Wind Connection project is a proposed offshore backbone electrical transmission system that will be able to connect up to 7,000 MW of offshore when complete. It is led by Trans-Elect Development Company and involves Google, Good Energies and Marubeni Corporation.
Atlantic Wind Connection (AWC) CEO Robert Mitchell told TransmissionHub that combining several wind farms onto a backbone transmission line smooths out wind’s variability.
“When you have a single radial line, the wind farm developer is captive to delivering the wind to one point on land whether that area is in need of electricity or not,” he said. “With a backbone, with multiple on and off ramps like the interstate highway, the power can flow to where it is most needed and…most expensive, so if you can deliver extra power to where it is most expensive, you do the consumer a huge favor because that’s going to lower the cost of energy in that area.”
Mitchell noted that, because there is “one land holder” involved with offshore wind – the federal government – as opposed to many with on-land wind projects, the challenges are “going to be easier” to address.
Furthermore, people in the mid-Atlantic states understand this is a huge opportunity for the region to experience additional economic development benefits, jobs, new tax base and new opportunities for existing businesses, he said.
The biggest challenge, Mitchell said, is there is not a mechanism within PJM Interconnection (PJM) to put a transmission line designed to serve primarily renewable energy. However, AWC, the states, and PJM are working on establishing a method for how to consider public policy transmission to get into the transmission expansion plan. “That process is underway and I’m optimistic that a reasonable plan will be put together and that the [AWC] will qualify,” he said.
Cape Wind Associates, owned by Energy Management, continues its efforts on building the nation’s first offshore wind farm in Massachusetts.
“In our case, when we started out, it was obvious that we didn’t have built that kind of [transmission] system in place here,” Mark Rodgers, Cape Wind communications director, told TransmissionHub. “So it would be, just as it is typically for a land-based wind developer, our responsibility to provide transmission” to interconnect to the grid.
According to Cape Wind’s final environmental impact report, an electrical service platform (ESP) will have to be installed and maintained within the approximate center of the wind turbine generator (WTG) array. The ESP will serve as the common interconnection point for all of the WTGs within the array and each WTG will interconnect with the ESP through a 33-kV submarine cable system, the report added.
From the centrally located ESP within the wind park, the wind-generated energy from each of the WTGs will be transformed to 115-kV. Two 115-kV AC submarine transmission circuits will bring the electric energy from the ESP to the mainland, a distance of about 12.5 miles. Those submarine transmission lines will make landfall at the proposed location at the end of New Hampshire Avenue in the town of Yarmouth, Mass. From this landfall, the report added, an upland 115-kV transmission line will be installed in an underground conduit system within existing roadways for about four miles until it intersects the existing NSTAR’s (NYSE:NST) NSTAR Electric transmission line right-of-way (ROW) at Willow Street in Yarmouth. From that point, the upland transmission line will go west and then south in an underground conduit system about 1.9 miles along the existing NSTAR Electric ROW to the Barnstable switching station.
The report also said the interconnection with the existing NSTAR Electric transmission system will allow renewable energy from the WTGs to be distributed to consumers connected to the New England transmission grid.
The proposed electrical interconnect facility on the proposed route will be two 115-kV solid dielectric submarine transmission lines and two 115-kV solid dielectric upland transmission lines. The submarine transmission lines, the report added, will be jet plowed below the seabed and the upland transmission lines will be encased in an underground concrete transmission ductbank system.
Costs associated with the project’s transmission aspect are all Cape Wind’s, Rodgers said.
“As the country’s first utility-scale offshore wind project, that’s how it’s going to work,” he said. “Future projects may work differently. The Atlantic states, for example, if [the AWC backbone transmission] proposal goes forward…that might provide a lower cost option for those projects.”
Rodgers said the benefits for a wind developer to develop its project’s own transmission line “would be in terms of project management so it’s a unified project management over the entire project. It can be built in a way that is most logical and straightforward, which may mean that a lot of the electric infrastructure is built first.”
What Cape Wind anticipates doing, he said, is coming online “row by row, so we don’t have to wait for the entire project to be built before we can start generating electricity. That will require the electric transmission system to be in place, so that’s what we’re planning on doing on our project.”
Rodgers said Cape Wind hopes to begin project construction sometime in 2013.
Under an agreement, NSTAR and Northeast Utilities (NYSE:NU) have pledged to buy power from Cape Wind, which also has a 15-year power purchase agreement with National Grid plc subsidiary National Grid USA for 50% of the facility’s output.
Wind Energy Systems Technology
Efforts are also underway in Texas to build what could be the nation’s first offshore wind farm.
The Wind Energy Systems Technology, or W.E.S.T. Company was the founding group regarding offshore wind power in the northern Gulf of Mexico, W.E.S.T. Chairman/CEO Herman Schellstede told TransmissionHub.
W.E.S.T. leased five sites in Texas-controlled waters, including in Galveston and Corpus Christi, for a total acreage of 85,000 acres. Coastal Point Energy joined W.E.S.T. in 2008 to assist in the development of the Texas leases, he added. “In 2011, we elected to release four of the Texas leases and focus all efforts on the Galveston, Texas lease,” he said, noting that the design calls for a 150-MW wind farm. “However, at this time, we will be installing one 3-MW advance wind turbine for testing. This installation should be complete by October.”
He said: “We then must test the system for several months. We have the basic layout of the Galveston wind farm completed. We have permits to place several test turbines, however, we must verify our test turbine to ‘fix’ the design.”
Schellstede said, “We plan to employ 3-MW generators in the 150-MW wind farm, hence 50 platforms will be required.”
The offshore wind farm will employ two different cables, he said, adding that the 50 platforms (3-MW) each will be interconnected with a gathering sub-bottom cable of 34 kilovolt capacity, he said. The power will be directed toward a gathering station and located on the gathering platform will be transformers that will increase the power to the shoreline at a 123-kW level.
Schellstede also said that the gathering lines from the wind tower to the gathering platform are about 15 miles in length. The trunkline cable from the gathering platform is 9.2 miles. He also said the power will be transmitted to an onshore location at Galveston.
On benefits of a developer building its project’s own transmission line, he said: “Here in the U.S., it is the only method to sell the power. The utilities must accept the power at the shoreline.”
The second part of this feature, which will look at the future of offshore wind in the U.S., will be published Monday, March 19.