A multi-user, ‘planned’ transmission system for offshore wind off the New England coast of the US could generate grid savings of up to $1bn, according to a new report by consultancy The Brattle Group.
The report – ‘Offshore Transmission in New England: The Benefits of a Better-Planned Grid’ – was prepared for transmission developer Anbaric and highlighted the limitations of connecting each wind farm to shore individually compared with a planned approach.
A planned solution would involve a high-capacity offshore transmission system serving multiple wind farms, reducing marine cabling and optimising onshore landing points, the report said.
Taking a multi-user approach is “likely to result in lower costs in both the near- and longer-term, by lowering risks and costs of onshore upgrades and increasing competition for both offshore transmission and generation”, it said.
The current approach of relying on individual generator lead lines would require extensive onshore grid upgrades at an estimated cost that is triple expected upgrades in a planned approach, The Brattle Group added.
The consultancy said the current plans would cost ratepayers an estimated additional $1.1bn overall.
“By relying on landing points closer to population centres and at robust onshore grid locations, a planned system reduces grid congestion and the need for expensive, disruptive onshore transmission projects that could hinder the growth of offshore wind,” the company said.
Planned offshore transmission would reduce the need for seabed marine cabling by about 50% or 572km for the next 3.6GW of planned offshore wind, reducing impact on fisheries and marine ecosystems, it said.
The report also said that planning and procuring transmission separately from generation increases competition and can reduce costs 20%-30%, based on studies of UK offshore and US onshore transmission trends.
Taking a multi-user approach would also utilise offshore wind lease areas more fully, the authors argued.
“In an unplanned system, after each developer interconnects the bulk of their lease site, it may be cost-prohibitive to interconnect the residual areas in the lease, forfeiting potential wind power,” they said.
A planned transmission approach utilising more efficient direct current technology would reduce losses and deliver more power to shore than alternating current technology used to date, they added.
Study co-author Walter Graf said: “Substantial additional offshore wind development will be necessary to achieve the New England states’ clean energy goals.
“At the necessary scale, a planned approach to offshore transmission will significantly reduce the environmental footprint and the overall costs of offshore wind generation.”
Anbaric chief executive Edward Krapels said: “Developing a shared ocean grid is the most effective way to scale offshore wind.
“The next phase in achieving states’ goals depends on building transmission infrastructure in a way that reduces overall costs, protects fisheries and the environment, and enables continuing growth of New England’s best energy resource.”
Massachusetts House of Representatives speaker pro tempore Patricia Haddad said: “Transmission is vital for achieving Massachusetts’ offshore wind goals.
“We can green the grid, create jobs, and efficiently reuse coastal power plant sites by developing transmission first, and this study shows why that’s a good approach for Massachusetts and New England.”