The cost of burying our grid

Why the debate about undergrounding transmission lines is a distraction

Earlier this month the National Energy System Operator (NESO) published their report into the potential for a net zero grid by 2030. The good news is that they found it is possible, but there’s a lot to do. Meeting the target requires contracting as much offshore wind capacity in the next couple years as the last six combined and delivering new carbon capture and storage technology. It also relies on extending two of Britain’s existing nuclear power plants beyond when they are currently going to be shut in the next few years, an investment programme of up to £40 billion a year, and, of course, it also requires planning reform to make it easier to build new renewable energy sources.

Yet we could do all of that and still miss the target if we fail to deliver upgrades to the transmission grid. This will mean building double the long-distance grid upgrades in the next five years as we have in the previous decade. Failing to upgrade the grid means that constraint payments paid to generators to switch off when the grid can’t handle their power could be up to £9.1bn higher per year in 2030 than if we delivered the grid upgrades needed for clean power. These payments will drive energy bills higher.

Perhaps the biggest question about delivering these much-needed grid upgrades is what they will look like, will they be pylons or buried cables. That was the subject of a Westminster Hall Debate yesterday.

One of the arguments that came up in the debate was:

“We are working to promote the Clean Power 2030 objective, but we want to deliver it more cheaply and quickly, because it is becoming increasingly clear that undergrounding high voltage direct current cables is the way forward for the great national grid upgrade. Undergrounding will carry public consent and will avoid delays, and will therefore be cheaper as well as better for the countryside. Relying on new lines of pylons for the entire upgrade, as proposed, will delay decarbonising the national grid, because they arouse such hostility and will end up costing more because of the delays.”

In making this argument, Sir Bernard Jenkin MP is referencing NESO’s East Anglia Study. Yet this argument relies entirely on the assumption that there will be so much local opposition to pylons (from people like the MPs making the argument), that they’ll be delayed by several years and will therefore cost more than if the underground plan went ahead. And of course the underground cables *definitely* won’t have any of the same planning delays, challenges or local opposition that the pylons may encounter. The very report that he references says that if the pylons are delivered on time to meet the Clean Power 2030 objective, they will be cheaper and quicker than undergrounding the cables.

While some might not like the look of new pylons, if we want to keep the cost down and limit environmental impact of the grid, we need to press on with the existing Government advice to have a strong presumption for overhead lines except when working in national landscapes.

The most in-depth study on transmission grid costs was done by the construction firm, Parsons Brinckerhoff. They found that overhead lines are the cheapest transmission technology with lifetime costs varying between £2.2m and £4.2m per kilometre (in 2012 prices). Burying the cables underground costs between £10.2m and £24.1m per kilometre, five to six times more. Importantly, underground cables were found to always be more expensive when compared to equivalent overhead lines. These are extra costs that billpayers would have to shoulder, when Britain already has some of the most expensive electricity in the world.

Not only are overhead lines six times cheaper than underground cables, they are also better for the local environment. Overhead cables are cooled by the air around them, while underground cables need to be spaced apart to avoid overheating. To match one overhead pylon line, as many as 12 separate cables in four separate trenches may be needed, resulting in a work area up to 65m wide. That means existing hedgerows and trees will need to be cut down to make way for the worksite. Plus all this digging threatens sensitive habitats and could damage archaeological heritage.

Once the construction is complete, access will still be needed for the life of the link, which means restrictions over buildings, trees, and hedgerows over the cables. Even with these restrictions it is much harder to quickly repair underground cables. If a fault occurs on one, it is on average out of service for 25 times longer than an equivalent overhead line.

But this doesn’t mean that we should foist pylons on to communities without sharing the benefits with them. The independent Winser Review highlighted the need to give communities hosting national infrastructure a direct benefit for doing so. The previous government consulted on plans to offer up to £10,000 off electricity bills over a decade for properties close to the transmission network infrastructure, and a wider benefit for the community of £200,000 for every kilometre of overhead lines and another £200,000 per substation. The Labour government should implement the suggestions from the independent review with a community benefit plan to help support people who will live near the new much needed infrastructure.

There’s also been work done on reducing the visual impact of new transmission lines. The Royal Institute of British Architects ran a competition for National Grid and the Department of Energy and Climate Change, as it was then called, for new pylon designs. The designs are quite striking and the winner (see below) has already been installed on the line that will link to Hinkley Point C, the under construction nuclear power station. These are 1/3 shorter than existing pylons and occupy less ground space.

The first update to the design of pylons in nearly a century (source)

If the Government is to meet its 2030 clean energy goal, protect the environment, save billpayers money, and boost energy security, we need to get building new transmission links. The debate on whether to bury underground cables, at great expense, is only a distraction.