Large-scale offshore wind build-out may shift U.S. power flow

New offshore wind energy (OWE) research showing that East Coast offshore resources could fuel one-third of U.S. energy needs leads some industry participants to wonder whether a shift in U.S. power flows could be coming.

Exactly what the transmission system changes are that might be necessary to handle integration of OWE is under study at this time. Near-term changes from first-to-market participants, such as Cape Wind and Atlantic Wind Connection (AWC), have been either modeled or proposed. Long-term grid changes from the kind of OWE build-out suggested recently by researchers at Stanford University, while largely theoretical and not well-studied, may include development of lines that can deliver the large OWE load to the U.S. interior.

NSTAR Electric, the Boston-based utility subsidiary of Northeastern Utilities (NYSE:NU), began work on Cape Cod for the Lower SEMA transmission line that a company spokesperson says is neutral in terms of Cape Wind, but could carry energy from the proposed 130 wind turbines of the wind farm in the future.

Cape Wind’s developers worked closely with NSTAR to secure approval for interconnection of the offshore wind farm to Cape Cod. The Massachusetts Energy Facilities Siting Board signed off on the interconnection of Cape Wind’s buried electric cables in 2005.

The New England ISO (ISO-NE) also approved the interconnection after ensuring it would not interfere with regional transmission or reliability.

The primary route for the Cape Wind interconnection would extend from the electrical service platform through Nantucket Sound, traveling underground from Yarmouth, Mass., on existing NSTAR rights-of-way to an interconnection with the grid at NSTAR’s Barnstable switching station.

The main upgrade on NSTAR’s Lower SEMA project begins in Carver, Mass., and terminates in West Barnstable, Mass.

Linking for efficiency

Large-scale OWE development off the East Coast in the future likely would not rely on a single wind farm interconnection, such as the Cape Wind model.

Scientists for the Stanford University’s Department of Civil and Environmental Engineering Atmosphere/Energy Program performed a quantitative analysis of East Coast OWE potential, drawing conclusions for the most suitable locations for large-scale development of OWE based on wind resource, shallow bathymetry, hurricane risk, and peak-power generation potential. The study was released Sept. 14.

The authors of the analysis said that the ideal transmission infrastructure to support these locations would feature a bulk offshore interconnection to which multiple wind farms would link. This configuration would ensure certain operational efficiencies for the wind farm and its associated infrastructure.

The AWC design offers an example of the Stanford model with an offshore line that would allow OWE developers to tap into resources off the East Coast in the region covered by the PJM Interconnection.

AWC is an East Coast offshore backbone electric transmission system proposed by Trans-Elect to integrate up to 7,000 MW of offshore wind turbine capacity into the regional power grid for PJM. The proposal does not make specific recommendations for where the line would connect to the terrestrial grid, but a spokesperson for AWC told TransmissionHub Sept. 20 that the company has studied the interconnection options.

In order to understand where an offshore backbone would connect along the coastline, projects need to be included in regional transmission plans, the spokesperson added.

PJM, however, has no specific proposal in place to warrant that step.

“Our existing process for interconnection of generation is that transmission needs are built to connect generation when there is a proposed generator,” a spokesperson for PJM told TransmissionHub Sept 20. “PJM wouldn’t plan or build for something that hasn’t yet been specifically proposed.”

New East-to-West export 

One of the major changes that could come out of a high level of offshore generation development is the need for additional onshore development to move the OWE into the interior.

Development of new offshore resources could “create the need to beef up the existing transmission in order to export power from the East to the West,” the PJM spokesperson said.

The Delmarva Peninsula provides an example of a potential point where OWE would be transmitted to mainland demand centers.

“If that were the case, a project similar to [the Mid-Atlantic Power Pathway (MAPP)] is potentially a way that you could move power from there into the interior,” the spokesperson said.

The MAPP bulk transmission project – now removed from PJM’s transmission plans – was originally designed to relieve the current East-West grid by enabling transfer of power sources west of the Chesapeake Bay from the Delmarva Peninsula to the Mid-Atlantic region.

MAPP was removed from the plan, according PJM, because the issues it was designed to resolve are no longer on the planning horizon.

“One of the benefits of having the Atlantic Wind Connection, even in the absence of wind power, is that you still have a grid unto itself that can move power from East to West,” AWC’s spokesperson said.

Like Cape Wind, the AWC offshore transmission project, which received a finding of “no competitive interest” in May from the Department of the Interior, continues to progress through the permitting process.