Tackling SF6 on the electricity networks

SF6 is a highly potent greenhouse gas, widely used by the electricity networks in their equipment. New legislation at EU level makes finding alternatives a priority. However, alternatives that have been piloted typically use “forever chemicals” (PFAS). This raises questions about how networks should balance these concerns given the significant network growth needed to meet net zero. 

This viewpoint draws on a Grid Edge Policy report “Green Grids” written by Sustainability First Associates Maxine Frerk and Judith Ward (together with Janet Wood). 

SF6 is a highly potent, long lived industrial greenhouse gas with a global warming potential (GWP) 25,200 times that of carbon dioxide. Widely deployed over many decades in electrical switchgear, including in electricity networks, it is effective as an electrical insulator and in preventing short-circuits. 

Reflecting growing climate concerns, a wide-scale reappraisal is under way of the use of SF6 in electrical equipment given the equipment can and does leak, adding to greenhouse gas emissions. 

The GB electricity networks have made clear commitments to reduce their levels of SF6 emissions from leakage over the next five years. Most of them also have longer-term commitments to eliminate SF6 by 2050. Thinking is more advanced on the high-voltage transmission networks, which (as a result of their age and scale) account for 93% of SF6 leakage. In particular, National Grid Electricity Transmission and SSEN Transmission have each committed to a one-third reduction in SF6 emissions by 2026 from a 2018/19 baseline.

This commitment sits alongside unprecedented demand for network growth and system reinforcement in the next 5-10 years to enable us to reach the goal of a de-carbonised power system by 2035. 

In this context the GB transmission networks are very focussed on what solutions are open to them over that timeframe to allow them to both deliver the necessary network growth and at the same time to meet their SF6 commitments. As such, including through a variety of innovation projects, the networks have been working with manufacturers to trial different SF6-free solutions that are being developed and coming to market.

EU regulation behind SF6-free alternatives

These changes are being driven at EU level by a new EU F-Gas Regulation which is close to being finalised and which for the first time will introduce an outright ban on new SF6 equipment being installed, with backstop dates depending on voltage, and new rules around spare parts and use of SF6 for top-ups. The Regulation also introduces a ban on certain SF6 alternatives. Despite Brexit, the updated EU F-Gas Regulation remains a key consideration for GB networks as most equipment manufacturers are based in the EU. 

Globally, there are effectively two categories of alternatives to SF6 – those using a synthetic gas and those based on natural origin gases (like oxygen). 

The synthetic gas products are closest in performance to SF6. Hence they offer a readily-used like-for-like alternative (including for retro-fill of existing equipment). However, they still have some global warming potential, albeit far less than SF6.  

In addition, and importantly, the synthetic gases fall into the category of PFAS (“forever chemicals”). This is a broad category of chemicals - everyday uses of PFAS include the manufacture of non-stick cookware, water-repellent clothing, stain resistant fabrics and carpets, some cosmetics and some firefighting foams. However, PFAS chemicals are of growing concern as they are found everywhere, break down slowly in the environment and carry health and environmental risks. 

The near-final version of the EU Regulation published in October 2023 explicitly bans the leading synthetic gas used in switchgear (fluoronitrile) on global warming grounds. Significantly, the Regulation also makes the link between synthetic F-Gases and the PFAS risk. At the same time, there are derogations on the basis of life-time emissions which might provide a way for fluoronitrile alternatives to continue to be used in new switchgear if it can be shown that they are environmentally more efficient overall.

The natural origin gas products are safe for both the environment and health but typically require more space in terms of their physical footprint (in particular at transmission level) and are not suitable in every case. There are also GB specific products (particular voltages or types of equipment) that have not been a priority for manufacturers to develop.

It is expected that the EU Regulation will act as a spur to all major manufacturers to actively look to develop natural origin gas products going forward although there are technical challenges at higher voltages. While there are short-term derogations in the Regulation if suitable alternatives are not available, it is not clear how these derogations will work in practice. .

Following on from the EU F-Gas Regulation, Defra is considering how far to reflect these requirements in GB legislation. 

Separately the EU is looking at introducing a blanket ban on all PFAS products given their potential health and environmental impacts (already proven for some PFAS) and following the precautionary principle. This would preclude the use of synthetic gas-based alternatives to SF6. While policy in this area is at an early stage the uncertainty is already impacting the switchgear supply chain – and again Defra will need to consider how far to mirror any provisions in GB.

Stringent environmental regulation is key to the longer-term aim of driving the market in safe switchgear and supports the networks longer term commitments on eliminating SF6. It would be for regret if over time the UK ends up with lower climate and environmental standards for electrical switchgear than the EU. Nevertheless, faced with long lead-times on equipment procurement plus higher costs, GB networks have understandable concerns about how to square near-term supply chain challenges for F-Gas free equipment with securing delivery of hugely increased network capacity in accelerated timescales. 

Conclusions – navigating a path through 

Given these tensions and trade-offs our view is that there should be two near-term priorities for the networks:

  • placing a laser like focus on reducing leakage rates - and at the same time - 
  • collaborating with manufacturers to support the development of natural origin gas solutions.

Continuing to innovate and share knowledge across networks is key to making progress on SF6 leakage rates. A greater emphasis on monitoring and digitalisation would open opportunities for AI and other tools to predict and better manage leakage – and allow more informed decisions about longer term pathways. 

There is also a need for Ofgem to be more proactive and, for the next price control (RIIO ET3) which is just kicking off, to put in place far more effective incentives on leakage reduction and require greater transparency from the transmission networks. There are also questions about how leakage is measured to ensure no under-reporting, including reviewing how the SF6 is dealt with at the end of its life. Ofgem should scrutinise company performance on SF6 as it would on say reliability – not simply leave it to environmental and other stakeholders to hold companies to account. 

At a policy level, environmental regulations are key in driving the industry and manufacturers to find safer and better solutions. In considering a future UK F-Gas Regulation, front of mind for Defra will be the need to meet successive UK carbon budgets and the UK’s 2050 net-zero target. It is therefore vital for Defra and DESNZ to coordinate and chart a route that balances the need to radically reduce SF6 and F-Gas use in new switchgear, with the need for the GB networks to plan, procure and invest over the next 5-10 years to deliver the network growth required to meet the 2035 target.

The wider health and environmental impacts of PFAS use in electrical switchgear are also important. Early work by Defra / the EU to examine the actual impacts of the particular PFAS compounds used in SF6 alternatives should be a priority, especially in light of the long development and procurement lead-times and the relatively high cost and long life of energy networks. 

Finally, with the EU direction of travel now clear, we need a wider debate involving networks, policy makers, environmental and other stakeholders on how transmission networks in particular should balance the trade-offs in their investment decisions over the next 5-10 years against important near-to-medium-term targets for F-Gas reduction.

This means an open conversation about the pros and cons of installing new switchgear products in GB that contain SF6 or fluoronitriles, including questions on retrofill of existing equipment. We hope that the Grid Edge Policy report provides a stimulus for that debate.