Offshore grid debate signals winds of change

For the UK to build up to its target 75GW of offshore wind generation by 2050, new thinking is required on the transmission infrastructure around it. David Blackman looks at the options set to be considered in a government review and how experts see an offshore grid developing.

Duncan Baker, the MP for Norfolk North, can spot the location of the subterranean cables that bring on shore the electricity generated by the windfarms proliferating off the coast of his constituency.

In fields planted with oil seed rape, the bright yellow flowered crop tends to be sparser in the land dug up for the 80 to 100m-wide trenches.

“North Norfolk has prime agricultural land and when they dig it up, you can’t grow crops at the same yield because the nutrients are mixed together.”

Overlooking one of those very fields when speaking to Utility Week last week, the recently elected Conservative MP claims the hit to yields can be “absolutely devastating” to the profits of affected farmers.

Added to that, substations required to help bring the power onto the grid can be as big as a football stadium, he says.

Baker has no doubts that the windfarms themselves, which the new infrastructure that is swamping his area supports, are necessary.

The concentrations of windfarms being developed off the Norfolk coast are not only “great news” for helping the UK to decarbonise but potentially one of the UK’s biggest economic success stories, he says.

The problem is the infrastructure, a particular hot potato in a staycation destination like Norfolk, where the landscape is a big calling card for visitors.

“When you start to blight that, you start to seriously impact one of the most outstanding features of the area,” Baker says.

What makes this disruption particularly difficult to swallow locally is that the transmission lines increasingly criss-crossing the county generate very few jobs for Norfolk workers.

Connecting the dots

Under current transmission arrangements, offshore windfarms are directly hooked up to the National Grid via their own bespoke or point-to-point connections.

This made sense for the first-generation of offshore windfarms, which sprung up in the shallow waters off the East Anglian coast.

The then coalition government liked this system because it injected an element of market forces into offshore transmission, which the grid’s natural monopoly ruled out on shore.

Windfarm developers too were keen to develop their own connections so that they could get their projects up and running without having to wait for a wider network to be developed, says Professor Keith Bell, of the University of Strathclyde. “Any delay to getting connections in place represents major risk to development.”

Offshore windfarm operators prefer to have as much control as possible over their transmission lines, says Munir Hassan, partner and head of clean energy at solicitors CMS Cameron McKenna.

“Offshore windfarms are incredibly sensitive to the way these lines are maintained and operated so that they achieve the absolute maximum availability. Any issue on those lines will have a big revenue impact.”

And as prices for new offshore wind electricity generation plunge, these marginal differences can be important for success in winning auctions through the government’s contracts for difference process.

However, with the waters off East Anglia set to accommodate a large chunk of the 40GW of offshore windarm capacity that the government wants to see by 2030, existing transmission infrastructure is becoming increasingly unpopular locally, says Baker: “We can’t keep doing this, we can’t dig up a community and then three years later dig another corridor a few kilometres away.”

With the UK offshore wind industry on target to generate 75GW by 2050, these issues will soon be a headache in other parts of the UK, such as the communities surrounding the Irish Sea, says Elaine Greig, chief technology officer at the Renewables Consulting Group.

Barnaby Wharton, director of future electricity systems at RenewableUK, says: “If you look at where development is currently happening, the most political salience is in East Anglia but as this industry develops we are going to want to ensure that we reduce landfalls wherever it might need to be.

“It is important that we have a system that minimises this very essential infrastructure and reduces its impact by reducing the number of landfalls.”

Shared systems

Other European countries have set up offshore shared transmission networks, Greig says, partially reflecting their differing geographies.

Germany’s offshore windfarms, for example, were geographically concentrated in parts of the North Sea. The distance between shore and the windfarms meant that it made sense therefore to create shared connections to the mainland.

“The Germans have a different geography and all their windfarms are in the same place and far away so they needed a DC connection and shared systems because it’s too expensive otherwise,” says Greig.

While these offshore grids delivered a financial hit when they were first built, they are now performing “a very effective job” now, she says.

Along with a number of other Conservative MPs from across Norfolk and Suffolk, Baker has been energetically lobbying Department for Business, Energy and Industrial Strategy (BEIS) ministers over recent months for a more planned approach to East Anglia’s offshore transmission infrastructure.

Last month, the department responded by announcing the launch of a review into the UK’s offshore transmission arrangements.

The offshore wind industry recognises that the UK’s existing transmission arrangement are overdue for a revamp, Wharton says: “If you look at the number of windfarms we will want in the future, it’s becoming increasingly clear that the point-to-point connections we currently have aren’t going to be fit for purpose. We want to reduce the costs by having shared connections and reducing the impact on the onshore communities.

“Everyone agrees this is a problem and that everyone one wants to see more shared connections, and that we need to find a solution.”

The problem will become more pressing as more new windfarms are earmarked by the Crown Estate in its upcoming round four allocation, says Greig: “With round four there will be more hotspots, so this is about making sure those hotspots don’t become barriers to offshore wind.”

Another factor pushing the development of a shared network is that high voltage AC cables used for existing point for point connections become less effective than DC the further off shore windfarms are located because they waste more energy.

“As we move further off shore with much longer cables and high voltages, we are moving from the HV AC to DC world,” says Wharton.

Bell, who has recently joined the Committee on Climate Change, says a number of DC transmission lines from different windfarms could feed into a single convertor station.

Onshore meanwhile, delivery of a single and larger corridor is potentially easier because it would involve having to negotiate with fewer landowners in order to secure access to the cables for maintenance and operation, says Greig.

An upside of offshore grid is that it could be used to create new interconnectors, says Bell: “Cables can serve two purposes: bringing offshore wind energy back to shore and if it’s not windy those connections can now serve as interconnectors.”

Hassan says being able to sell power in multiple countries may mitigate the risks for offshore wind developers, faced by days when power prices are very low in the UK because too much renewable electricity is being generated.

Regulatory roadblock

The major obstacle though to the development of an offshore transmission grid has been Ofgem, which has taken a cautious approach to network extensions, like those recently mooted for the Scottish islands, says Bell: “Regulatory arrangements don’t lend themselves to this co-ordination.”

Hassan says: “The idea of having an offshore transmission strategy has fallen at a very simple hurdle. Ofgem’s regulatory framework effectively places the burden of current investment decisions on transmission licensees.

“Point-to-point connections are easier to justify: there will be customer with a particular need for that size of cable coming to shore.

“The question will have to be addressed is who will take the risk on that anticipatory investment: building stuff that may not end up needing to be built.”

Wharton says: “Ofgem is not very keen on very large infrastructure being built before it’s needed but if this is going to work we need to build stuff out in the hope and expectation that maybe five years later, a number of windfarms will connect into it. The debate is how much anticipatory investment Ofgem will allow.”

“Ofgem need to sign off plans to make anticipatory investment to allow this to happen.”

But he is reassured by the “enthusiasm” Ofgem and the grid’s Energy Systems Operator have displayed about tackling the issue, noting that offshore transmission was one of the nine points in the decarbonisation road map published by Jonathan Brearley on his first day as the regulator’s chief executive earlier this year.

Baker agrees. “It feels like a complete change of wind with Ofgem: the new CEO Jonathan Brearley seems to be really engaged with this and supportive.”

And as more windfarms are developed, they will be more likely to be grouped closer together, which will further reduce the financial risks of building shared infrastructure, says Greig.

There are also technical issues involved in building in the hostile offshore environment though.

These have been highlighted by the problems, which have bedevilled the construction of the 320 km so called ‘Bootstrap’ cable between Ayrshire and north Wales, which is designed to provide a fresh way of bringing Scotland’s wind power into the main UK grid.

The highly specialised nature of offshore cables manufacturing supply chain is another potential headache, says Bell: “There are very few companies and they are reluctant to invest in capacity until they have the order books to justify it.”

Even these calculations will though be influenced by how strongly government policy is pushing such solutions, he says: “Everybody is waiting on everybody else: there is a need for clear sign posting.”

Options for offshore transmission

Utility Week understands that as many as eight different offshore transmission options are being looked at. The highest profile of these is the so called Norfolk ringmain, which is being explored by the county’s Tory MPs. Essentially a long cable hugging the East Anglian coast, the idea is that this would come on shore at no more than two points, minimising the amount of land infrastructure that has to be built, says Baker: “As you build more offshore wind, we would keep connecting to this external socket.”

Another option could be to build a convertor sub-station off shore, which could then be hooked up to the individual windfarms by radial lines.

However, there are concerns that reliance on individual points could pose risks to security of supply, says one infrastructure source: “We need to ensure that new offshore wind transmission infrastructure is as secure and robust as the onshore wind. If you have half the offshore wind farms plug into one supply that’s going to be a problem.”

Yet another proposal is to create a “bootstrap” cable, which would bypass Norfolk entirely, enabling the wind farm electricity to be transmitted directly to where demand is greatest in London and the south east. Like the Irish Sea “bootstrap”, this could also reinforce the resilience of the wider grid.

Yet another option could be to use the electricity generated to manufacture hydrogen offshore with sea mounted electrolysers, says Bell: “You could bring it back in the form of hydrogen by putting in a load of electrolysers. You can fit more energy through a metre width of hydrogen pipe than through electricity cables.”

BEIS is due to announce its terms of reference for the review in the autumn. Baker believes it is vital that it is able to come up with a solution, for the sake of both his constituents and the wider carbon reduction agenda.

“We don’t want to get to a situation where don’t have any more windfarms: we still need to hit the 2050 target.”