Sulphur Hexafluoride (SF6) is widely used in the electrical industry in order to prevent short circuits and accidents, and is widely reported as the most powerful greenhouse gas known to humanity. However, in the last few years the emissions have risen rapidly. Leaks of the lesser known greenhouse gas in the UK, and the rest of the EU in 2017 alone was the equivalent of putting out an extra 1.3 million cars onto the road.
Thanks to the green energy boom, in an unintended consequence, the levels are rising.
It is a cheap, non-flammable, colourless, odourless and synthetic gas, that makes it a hugely effective insulating material for medium and high-voltage electrical installations. It is used all across the industry, from large power stations to wind turbines to electrical sub-stations in towns and cities, mainly because it prevents electrical accidents and fires. The downside, however, is that it has the highest global warming potential of any known substance, in fact, it is 23,500 times more warming than carbon dioxide (CO2); just one kilogram of SF6 warms the Earth to the same extent as 24 people flying London to New York return. In addition, it persists in the atmosphere, consistently warming the Earth for 1,000 years.
We continue to use the gas, because of the way that electricity is generated in the modern age. The drive to combat climate change means that people look to different sources of power, namely wind, solar and gas. These all require connections to the electrical grid, and a rise in the number of electrical switches and circuit breakers (known as switchgear), which are needed to prevent serious accidents, and the vast majority of which use SF6 gas to quench arcs and also stop short circuits.
Costa Pirgousis, an engineer with Scottish Power Renewables has said, "As renewable projects are getting bigger and bigger, we have had to use it within wind turbines specifically, as we are putting in more and more turbines, we need more and more switchgear and, as a result, more SF6 is being introduced into big turbines off shore. It's been proven for years and we know how it works, and as a result it is very reliable and very low maintenance for us offshore."
It is known to be increasing, as across the entire UK network of power lines and substations, there are around one million kilograms of SF6 installed. A study has found that across all of the transmission and distribution networks, the amount that was used was increasing by around 30-40 tonnes per year. The rise was reflected further across all of Europe, seeing total emissions from the 28 Member States in 2017 to be equivalent to 6.73 million tonnes of CO2. Researchers at the University of Bristol who monitor concentrations of warming gases in the atmosphere have said to have seen significant rises in the last 20 years.
Predominantly, it enters the atmosphere from leaks in the electricity industry. The electrical company Eaton specialise in manufacturing switchgear without SF6, and they have said their research suggests for the full life-cycle of the product there can be leaks as high as 15% - despite the older gear having higher rates, most people haven't upgraded to the new, and so the leaks are still high. It is important to factor in the filling of the gas, and how it is recycled and returned. If the leaks carry on contributing to the atmosphere, the results will be catastrophic; the global installed base of SF6 is due to grow by 75% by 2030, and since it is a synthetic gas it cannot be destroyed or absorbed naturally - it will have displaced or forcibly removed to stop impact on the climate.
Currently developing countries face no restrictions on use, whereas those already developed have to report to the UN every year on how much they use. This appears not to be working however, as it is detected that there is nearly 10 times the amount of SF6 concentrations in the atmosphere over what countries have said in their reports - the methods used to calculate emissions in richer countries had led to the results being "severely under-reported" in the past two decades.
Falling under the category of an F-Gas, there has been significant attempts by the European Commission to prohibit the use of these gases, back in 2014. Strong opposition from industries across Europe arose, stating that "if you want an energy transition, and you have to shift more to electricity, you will need more electrical devices, and then more SF6" - meaning that if it is not used then energy transition would be slowed.
That isn't to say an effort isn't being made. Energy regulator Ofgem is looking to work with utilities to try and limit leaks of the gas, a spokesperson stating: "We are using a range of tools to make sure that companies limit their use of SF6, a potent greenhouse gas, where this is in the interest of energy consumers."
The idea of an alternative has been batted around in the recent years, and at least for high-voltage applications, experts say that very few solutions have been rigorously tested, that there is no real alternative that has been proven, and that the ones that are being considered take too long to prove that they are safe. For medium-voltage applications there are many options that have been tried and tested. It is believed that the electrical industry is refraining from the change due to their conservative nature.
