Kettles, washing machines, ovens, heating, plug-in electric vehicles — these are some of the appliances that will be powered by offshore wind someday, Prime Minister Boris Johnson promised U.K. citizens in an October speech. But to make that promise a reality, the country may need to re-envision how to plan, and pay for, the transmission networks that will carry that multi-gigawatt resource to its shores.
The government has big ambitions for offshore wind and has raised the country’s target from 30 gigawatts to 40 GW by 2030, in line with recommendations from its official climate advisers, the Committee on Climate Change. This is a significant change from the 10.4 GW currently installed in U.K. waters.
But the government has realized that the current approach to designing and building offshore transmission — developed when the sector was nascent and expectations were for 10 GW to be built by 2030 — is outdated.
In the U.K., project developers are required to finance and build transmission assets to bring the energy onshore, which at the time was a way of de-risking offshore wind projects. However, as the number of offshore wind farms rises, constructing individual point-to-point connections for each one is inefficient and increases impacts on both the environment and local communities.
The government is therefore working on a strategy to coordinate offshore networks and their connections. The timing, siting, design and delivery of offshore wind will all be considered, as will the design and delivery of transmission infrastructure.
Connecting the dots
The government has commissioned technical consultancy DNV GL as a lead partner in the project. Initial analysis by the firm has found that an integrated approach to the offshore grid could save £6 billion ($7.8 billion) in capital and operating expenditure through 2050, the equivalent of 18 percent of costs. It could also reduce the number of onshore and offshore assets, cables and landing points by around 50 percent.
Maksym Semenyuk, a consultant on energy markets and technology at DNV GL, says that the biggest considerations from a technological point of view are the size of the wind farm and its distance from the shore. As the U.K. builds out its ambition, wind farms will be located farther from the shore. High-voltage direct current (HVDC) connections are more suitable than the high-voltage alternating current connections typically used today, since HVDC loses less energy as it travels across distances.
HVDC also allows more flexibility on the location of grid connections, which can be moved farther onshore where there are fewer local impacts and preexisting network capacity already exists, rather than having to connect at the closest point on the shore, as is the case with HVAC, he added.
“You’re addressing...the goal to evacuate the energy [and] creating benefits for the system operator by connecting more strategically,” he says. The industry has already used HVDC technology, which has been installed in wind farms in Germany and will soon be used for the first time in the U.K., Semenyuk said.
The chief regulatory aspect that needs to be considered by the review is the grid code — the rules on how wind farms can be connected to the transmission network. For example, the rules may limit the size of the cables that can be connected, he said.
There are also questions to be resolved over how the assets are governed, considering that the wind farm operator and the system operators are both using them, he says. “Who has the responsibility to build them, the responsibility for signing the contract for operating them, and how the government’s contracts-for-difference [rules] will apply — there are a number of dimensions that need to be thought of before implementation,” he said.
The firm hopes its work will help develop a standard approach that will benefit the industry not just in the U.K., but in other countries.
Brexit won't prevent the strengthening of European ties
Separately, but linked to the same issues, U.K. transmission network owner National Grid in September announced a project with Dutch counterpart TenneT to develop a plan to link wind farms to the energy systems of both countries via multipurpose interconnectors.
The Netherlands is targeting 11.5 GW of offshore wind capacity in the North Sea by 2030, and the system operators are exploring the connection of up to 4 GW of offshore wind between the two countries. The connection will enable spare transmission capacity to be used to trade electricity between the countries, maximizing the use of offshore infrastructure. They hope to have an asset in operation by 2029.
“This project is really interesting because it combines the connections between wind farms with the interconnectors between countries,” explained Barnaby Wharton,RenewableUK's director of future electricity systems. “A wind farm could send electricity to the U.K. or the Netherlands depending on who needs the power.”
Integrating different sources of power across an interconnector is exceedingly important, because as the U.K. builds out, the grid will need extra flexibility, and this is a sophisticated way to enable that, he said.
Jonathan Marshall, head of analysis at the Energy and Climate Intelligence Unit, said that both projects are about planning more strategically for an electricity system that is heavily reliant on renewable energy. “It’s going from thinking you’ll have a few wind farms in the future to realizing that renewable energy will be the backbone of the grid and that you need to follow that through with everything you’re building,” he says.
The U.K.’s transition period in leaving the EU is due to end on December 31, 2020. Brexit has meant that the U.K. has had to leave the North Seas Energy Cooperation initiative, a collaboration between eight Northern European countries to support offshore grid development and renewable energy potential in the region. This may impact how the U.K. government can engage in international projects most effectively, Wharton said.
“But as we have seen from recent activity, the U.K.’s plans for interconnection with other markets are still going ahead,” he added.