The green energy revolution is being throttled by a major constraint in our electricity network, specifically the B6 Boundary, a 400kV roadblock.
The Scottish Boundary separates the Scottish electricity transmission network, headed up by Scottish Power Energy Networks, from the National Grid’s Electricity Transmission network covering England and Wales. While often referred to as the B6 Boundary, it’s part of a wider set of constraints limiting how much clean energy can move south, and it’s becoming an increasingly urgent problem as renewable generation grows.
Why B6 is a bottleneck
The B6 Boundary separates the Scottish electricity transmission network, headed up by Scottish Power Energy Networks, from the National Grid’s Electricity Transmission network covering England and Wales.
The two existing overhead lines and HVDC cable which straddle the B6 boundary are vital pieces of the UK’s power infrastructure, but their lack of capacity is throttling the abundance of Scottish renewable power from reaching the homes and businesses that need it.
It’s especially difficult to transmit this power when generation is high – as more and more renewable energy is generated, the more gets stuck north of the border, putting additional strain on our infrastructure.
Fixing the pinch point — but not fast enough
It’s simple, the UK’s nationwide grid needs more capacity at the B6 pinch-point. There are efforts underway – projects such as Eastern Green Link 1 (Torness to Hawthorn Pit), which is specifically designed to increase capacity across the B6 Boundary, and Eastern Green Link 2 (Peterhead to Drax), which tackles constraints further north but also helps reduce pressure on B6 by taking power earlier, both play a crucial role in relieving this key bottleneck.
However, building entirely new power lines is an expensive activity, with long lead times to build. With the clock ticking to act on climate change and decarbonise the UK’s energy supply, we don’t have that kind of time to spare.
A faster solution: battery storage
There is a quicker solution. While we wait for the necessary infrastructure reinforcements we need across this boundary, we should continue to invest in energy storage.
Battery electric storage systems (BESS) allow grid operators to store the clean energy generated by Scotland’s many on- and offshore wind farms at times of high renewables output, storing to then be injected back into the system when there is spare capacity to flow the power across to high demand areas in England and Wales.
How BESS can relieve the B6 Boundary
Battery storage sites in Scotland have an essential role to play in solving the B6 Boundary bottleneck problem, as they can store energy while the three existing connections transmit at full capacity.
Once space becomes available, this stored energy can travel south as part of a steady, consistent flow of green power across England.
BESS will also put an end to expensive, taxpayer funded curtailment costs – when renewable energy generation has to be switched off because our grid is unable to handle the volume of clean power being generated.
Data centres can help balance the grid too
There’s another way to make better use of Scotland’s abundant renewable energy, by keeping more of it in Scotland. Locating energy-intensive infrastructure like data centres north of the B6 Boundary would reduce the need to transmit as much power south in the first place. With the right design, these facilities can be paired with local renewable generation and battery storage, creating a more balanced, efficient system. This approach not only eases pressure on the grid, but also supports economic growth by bringing high-value digital infrastructure and jobs to Scotland.
The true cost of inaction
As a consequence of the B6 Boundary and other pinch points, the UK’s grid currently lacks the capacity to readily transmit clean energy from where it’s generated to the areas that need it most.
It’s estimated that more than £1bn was wasted in curtailment payments during 2024, and the B6 Boundary is a major part of the problem. And latest estimates from NESO suggest that if unchecked, curtailment costs on the Scottish boundary alone could reach £3bn by the end of this decade.
Our role in solving the problem
Battery storage is the answer. At Apatura, we’re working hard to put in place the assets that will solve the UK’s energy grid woes. Our portfolio consists of approved BESS projects with a combined capacity of more than 1.5GW, which we expect to be up and running by the end of the decade. Most importantly, they’re all strategically located north of the B6 Boundary, where they can make the most difference.
Investing in BESS is the easiest way to fast track our path to net zero – it’s the key to unlocking Scotland’s full renewable energy potential, solving the B6 Boundary problem, and providing the UK with reliable and readily available clean electricity.
