Brooks McKinney

Sep 16th 2020

Connecting Offshore Wind Energy to Onshore Users


To help reduce greenhouse gas emissions and U.S. reliance on fossil fuels, more and more communities on the Eastern Seaboard are turning to offshore wind energy. As of early 2019, nearly 26 gigawatts of offshore energy were operational, in development or planned according to the 2018 Offshore Wind Technologies Market Report developed by the National Renewable Energy Laboratory and the U.S. Department of Energy.

How best to connect that power to onshore users — the top two contenders are dedicated transmission lines from each wind farm to shore, often called generator lead lines, and shared ocean transmission grids — has inspired earnest debate among wind farm developers, independent transmission developers, government agencies and environmentalists.

To be clear, there is currently only one operational offshore wind farm in the U.S — the five-turbine, 30-megawatt (MW) Block Island Wind Farm off the coast of Rhode Island — and no ocean transmission grids. Developed by Deepwater Wind (which was acquired by Danish power company Ørsted in 2018), Block Island became operational in 2016.

Reckoning With Risk

“In the near term, the transmission grid debate is complicated,” explained Kirsty Townsend, director of North American special projects for Ørsted, the world’s largest wind farm developer. “Many of the risks associated with such grids, such as the costs of onshore transmission upgrades or the costs of downtime or delays in development, have yet to be fully vetted and allocated appropriately, which poses a potential cost risk to consumers.”

Ørsted doesn’t view shared offshore grids as the wrong choice in the long term, Townsend continued, but would like to see the concept matured in a way that recognizes and mitigates those risks.

Harnessing the Wind

Offshore wind farms consist of multiple wind turbines, each on its own stationary or floating platform. Each turbine includes a two- or three-blade rotor that converts wind energy into electricity as it turns. The power from each turbine is delivered by underwater cables to a stationary collector station within the wind farm.

From there, the power is delivered to a “point of interconnection” on shore using either high voltage alternating current (HVAC) cables (for wind farms located within 30 miles of shore) or converted to direct current (HVDC) and exported to shore (for wind farms located more than 30 miles offshore). These power export cables are typically buried in trenches in the sea floor.

Under the current rules of engagement, generator lead lines are designed and constructed by the wind farm developers. A shared ocean transmission grid, by contrast, would collect power from multiple wind farms and deliver it to shore in one or more higher capacity lines. Ocean transmission grids would also be developed, funded and constructed independently of the power generation process.

Connecting With Consumer Wallets

Independent transmission companies such as Wakefield, Massachusetts-based Anbaric Development Partners believe that ocean transmission grids offer the most favorable long-term benefits for consumers.

“Offshore wind developers typically connect their wind farms to landfall locations with the closest access to the onshore grid,” explained Peter Shattuck, president of Anbaric’s proposed Connecticut OceanGrid. In the long term, he added, that approach is problematic.

“The current approach gives ‘early bird’ offshore wind developers the most favorable cable landfall locations and potentially puts future developers at a cost disadvantage, which ultimately hurts consumers.” he said. A more critical issue, he continued, is that a given landfall location may not have sufficient local power demand or the transmission infrastructure to receive and connect large amounts of wind power to the grid. Such a bottleneck could lead to significant and costly upgrades to the onshore transmission infrastructure.

A more cost-effective approach, he proposed, would be to build an offshore transmission grid and connect it to the onshore grid at population centers where demand for electricity is much higher, where the existing infrastructure would need fewer upgrades to accommodate the infusion of wind energy. Such an approach would also require fewer cables running to shore from the offshore grid, which could decrease the potential impact of cable installations on sensitive marine habitats.

Keeping Fishermen on the Water

Lane Johnston, programs manager for the Responsible Offshore Development Alliance (RODA), a coalition of fishing industry associations and fishing companies that works to ensure the compatibility of offshore development with commercial fishing interests, concurs with Shattuck’s “less is more” outlook.

“If [an offshore transmission network] means there’s going to be fewer structures in the water and fewer opportunities for conflicts with fishing, that would be better,” she said.

The most important consideration for fishermen, Johnston offered, is that they have the opportunity to participate in the debate about how transmission lines can or should be run and how that might affect their livelihood.

“We need good science and credible information to help fishermen keep fishing,” she said. “With better information, we can provide more educated recommendations about how to minimize the impact of the offshore wind industry on the fishing industry.”

Clearing Regulatory Hurdles

Any transmission grid or generator lead line installed offshore must be vetted and permitted by the Bureau of Ocean Energy Management (BOEM), the U.S. Department of the Interior agency responsible for managing development of the nation’s offshore resources. The agency reviews and provides environmental and technical guidance on offshore wind projects within the nation’s so-called “exclusive economic zone,” which extends from approximately three to 200 miles offshore.

“Before BOEM can grant a ‘right of way’ for a new transmission line, we have to analyze and assess each project for potential competitive interest,” explained Josh Gange, an energy program specialist in BOEM’s Office of Renewable Energy Programs. “We’re required to publish the details of each project, what it is, where it’s located, and provide a comment period for other potential developers, the general public and other stakeholders.”

If BOEM determines that a competitive interest exists, he added, the agency will conduct an auction among bidders for the desired right of way. Once that right-of-way grant is issued, the winning bidder completes a detailed survey of the proposed route, and maps out details of the project in a General Activities Plan. BOEM also oversees the preparation of an environmental impact statement, conducts a technical review of the project, and conducts project reviews with other government organizations potentially affected by the project.

“We consult with organizations such as NOAA (National Oceanic and Atmospheric Agency) regarding fisheries issues or endangered species protections, and the Department of Defense, who might advise us to avoid an area for national security reasons,” said Gange.

Coordination Challenges

Ultimately, any decision to develop ocean transmission grids lies in the hands of state energy agencies such as the Massachusetts Department of Energy Resources (DOER). Like other New England states, Massachusetts views offshore wind energy as a way to help meet its green energy goals and grow energy-related jobs.

To date, the state’s electric distribution companies have procured approximately 1,600 MW of the 3,200 MW offshore wind energy they plan to acquire by 2035, all of it from wind farm projects that use generator lead lines. According to Joanna Troy, DOER’s director of policy and planning, one option for delivering the remaining 1,600 MW to shore could be to solicit proposals for independent transmission of that power.

“In our 2018 Offshore Wind Study,” she said, “we noted that there are benefits to coordinated [i.e., shared] offshore wind transmission, but there are also costs and risks associated with it.”

Troy recognizes, however, that any regional offshore transmission grid — think of it as an “interstate highway for power” — would require coordination with other states and the Independent Service Operator New England to get developed and start producing the large-scale cost and reliability benefits touted by some transmission developers.

Leaning Forward

Anbaric is already laying the groundwork for such interstate coordination to play out. In November 2019, the company filed an application with BOEM for non-exclusive rights of way to develop a Southern New England OceanGrid, an offshore transmission network that would connect up to 16,000 MW of offshore wind energy to Massachusetts, Rhode Island and Connecticut.

Among its benefits, offers Shattuck, would be increased competition among offshore wind developers vying for power purchase agreements (PPAs) with onshore utility companies.

“Connecting (transmission lines) to the onshore grid can be one of the most challenging aspects of developing offshore wind farms,” he said. “By separating transmission from offshore wind energy generation, companies can focus on optimizing the costs of the power produced by their wind farms and not have to include transmission costs in their PPA bids to utilities.”

Protecting the Present

Ørsted’s Townsend concurs with Shattuck that developing offshore transmission lines and connecting them to the onshore grid pose risks for offshore wind developers. But she also believes her industry is better positioned to manage and mitigate those risks.

“There is a lot of risk associated with constructing offshore transmission lines, which is why we inherently prefer to control those assets,” she said. “We have the experience to build them to a quality standard, maintain them, mitigate risks and keep the overall cost of green energy down.”

The related concern, expressed by advocates of both generator lead lines and offshore transmission grids, is described as “project-on-project” risk: Offshore wind developers fear that shared ocean transmission grids won’t be ready in time to bring offshore wind energy ashore, while independent transmission developers suggest that under the current approach, onshore transmission upgrades may not be ready in time to connect generator lead lines.

Committing to the Journey

Shared ocean transmission grids, Townsend believes, represent the future for the offshore wind industry, particularly for the U.S., with its onshore grid constraints. In the near term, however, she believes the quest should be a journey, not a quick fix.

“The current problem is that no single entity — federal or state — has sufficient information or political will to bring together the right people to design both the technical and regulatory system that will provide a permanent, ‘no regrets’ solution,” she said.

The goal, she continued, should be to “stay on the path in a disciplined, streamlined way; try to avoid any wrong turns we might regret later, and work together to reach a destination that represents a profitable and productive future for all parties concerned.”

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