The reason for this was simple. Although there were many days when the North Sea wind was blowing steadily, the limited capacity of the power transmission lines across the Scottish border meant Seagreen’s energy could not be supplied to the place where it was needed: England.

Another official dataset shows that Seagreen sold 1.2 million gigawatt hours (GWh) of electricity to the grid. But had it not been asked to disconnect its turbines because of the network’s inadequacies, that figure would have been more than three times higher — 3.7 million GWh. And because Seagreen’s customers still needed their electricity, that in turn meant that energy consumers also had to pay for alternative, fossil-fuel power stations to be switched on in England.

This problem with the high-voltage wires, known as “constraint”, is rapidly getting worse. Scotland’s weather makes it an excellent location to build both onshore and offshore wind farms, but by the end of 2022, the country had already installed renewables with an output capacity of 13.9GW — far more than it will ever need. To apply the same arithmetic as the Seagreen website, 13.9GW would be enough to power more than 20 million homes, about eight times as many as the current Scottish total.

Meanwhile, the National Grid openly admits that the power lines across the border have a maximum capacity of just 6.3GW. In fairness to them and Miliband, they plan to spend £4 billion on building two new ones, Eastern Greenlink 1 and Eastern Greenlink 2, involving hundreds of miles of undersea cables linking the Scottish coast with northern England. If built on time, they should be open by 2030, with a further two which are not yet costed projected for the 2030s.

Unfortunately, Miliband’s planned vast expansion of onshore and offshore wind suggests these power lines will be nowhere near sufficient. Each of the four proposed new links will have a capacity of just 2GW but according to the “TEC register”, an official database that records planned energy projects which will need to be linked to the grid, by 2030 Scottish renewable capacity will have grown by another 19GW. That would make it more than twice as big as it is now.

By 2035, a further 33GW of Scottish wind and solar power should have come onstream. By then, new technologies such as using electricity to separate hydrogen from water and storing huge quantities to burn in adapted power stations may have reduced the need to transmit electricity from Scotland to England. But this is unproven, and according to the renewable energy advocate Michael Liebriech its prospects are “overblown”.

Currently, the costs of fixing constraint — known as constraint payments — are adding around £1.5 billion to consumers’ bills each year, and a report published by the National Grid in May claimed they are set to rise steadily until 2030. Meanwhile, the cost of building new Scottish wind farms whose energy may not be used will run to many billions.

Andrew Montford, director of the campaign group Net Zero Watch, is withering about the plans to expand Scottish renewables without considering the cross-border problem. “Construction of these new and planned wind farms should never have been allowed,” he told me. “Questions need to be asked about who authorised such foolishness.”

Miliband, however, remains undaunted. Citing another recent Government report, a department spokesperson insisted: “We can achieve clean power by 2030 with cheaper electricity, even factoring in constraint payments, and a more secure energy system for Britain.” Since the election, there has been a “record-setting round of renewables projects, with enough power for the equivalent of 11 million homes […] We will work with industry to rewire Britain, upgrade our outdated infrastructure to get renewable electricity on the grid, and minimise constraint payments.”

British businesses already face electricity costs more than twice as high as the rest of Europe, and almost five times those in America. If Miliband’s department turns out to be wrong, the political and the economic cost will be immense.

---

David Rose is UnHerd‘s Investigations Editor.

DavidRoseUK

---