by Nicholas Ottersbach
In 2014 the European Union (EU) reinforced a 2006 F-Gas regulation, aiming to strengthen measures to contain the polluting emissions of fluorinated gases (F- gases) (EU Commission, 2015). F-gases are a family of man-made gases with the strongest greenhouse effect. Of all the F-gases, SF6 (the focus of this paper), is the most potent.
This regulation’s aim is to bring down the EU’s F-gas emissions by two-thirds from 2014 levels by 2030 as part of the ultimate objective of cutting overall greenhouse gas (GHG) emissions by at least 80% by 2050 against 1990 levels (Biasse, 2014). However, the new restrictions on the use of SF6 did not affect its largest user, the electrical power equipment industry. The EU regulation mentions phase-out dates for F-gases used in many applications, depending on their global warming potential (GWP) yet it does not mention SF6 in switchgear meaning, in effect, that there are no restrictions (Biasse, 2014). Additionally, Articles 4 and 5 of the 2014 regulation waive leakage tests and detection systems for medium voltage switchgear (MV) (Eur-Lex, 2014), the biggest net-users of SF6 (Burges et al, 2017: 50), meaning that there is now way of knowing if a MV switchgear is emitting SF6 during its lifetime.
Having said this, the regulation does have a provision for reviewing the situation in 2020 which should provide fresh impetus for policy makers, and interested stakeholders, to give this gas the serious attention it deserves. This is especially pertinent as large parts of EU regulations are often followed by developing countries’ laws, to get access to the EU market.
What is SF6? and how is it used?
SF6 is a long-lived, highly potent greenhouse gas. It is manmade and combines excellent electrical properties with chemical stability and low toxicity. Moreover, it’s non-flammable and low in cost. These characteristics have led to its widespread and enthusiastic adoption by the electrical industry, which uses approximately 80% of all SF6 produced (Powell, 2002: 6).
Within the electrical industry SF6 is used as a medium for electrical insulation and circuit breaking in medium (MV) and high (HV) voltage gas insulated electrical switchgear (GIS), but predominantly used for the medium voltage range (Burges et al, 2017: 50). A switchgear is the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate sections of electrical grids. Low- voltage (LV) switchgear are used for controlling electrical circuits within buildings, medium voltage (MV) switchgear for controlling the electrical grids within cities and towns, and high voltage (HV) switchgear for grids that span a greater geographical area such as countries and regions.
How environmentally damaging is it?
With a GWP of around 22,800 over a 100-year time horizon, SF6 is the most potent greenhouse gas regulated under the Kyoto Protocol (Rigby et al, 2010: 10305). Its GWP of 22,800 means that it is 22,800 times more effective at trapping infrared radiation (i.e., creating the greenhouse effect) than an equivalent amount of carbon dioxide over a 100-year period (Blackburn, 2015: 5).
Moreover, SF6 is widely believed to have an atmospheric lifetime of 3,200 years (Diggelmann et al, 2016: 70), although recent research suggests shorter lifetimes. Some say 850 years (with a range of 580 to 1400 years) (Ray et al, 2017: 4626) while other research suggests closer to 1,278 years (with a range from 1,120 to 1,475 years) (Kovács, 2017: 883). In any case, it is clearly an extremely long-lived gas that poses a serious problem through its contribution to the immediate threat of global warming.
As well as having an extremely long lifetime, unlike gases such as CO2, SF6 has no natural sink, origin or effective disposal method, making its accumulation in the atmosphere virtually irreversible (Blackburn, 2015: 5). Without disposal methods that completely destroy SF6, it can be expected that all of the SF6 that has been or will be produced will eventually end up in the atmosphere, remaining there for centuries to come (Dervos and Vassiliou, 2000: 138).
Studies also show that atmospheric concentrations of SF6 have increased by more than a factor of 10 since measurements began in 1973 (Rigby et al, 2010: 10305). They also found that global emissions are higher than ever and have increased by almost 50% between 2000 and 2010 (Rigby et al, 2010: 10305).
Global annual SF6 production is currently around 8,000 t (Damsky, 2016: 1). Furthermore, based on atmospheric data, global SF6 emissions in 2012 were 8,100 t (Dunse et al, 2015: 20) essentially creating a production-emission parity. These emissions are the equivalent of the annual carbon footprint of approximately 40 million American cars (EPA, 2017). Despite these environmental concerns, SF6’s use in the electrical industry is forecast to grow by around 50%, from 2005 levels, by 2030 (Rhiemeier et al, 2010: 29).
Is SF6 a danger to human health?
In its normal and inert form SF6 is relatively harmless to humans. However, when exposed to electrical discharges through everyday usage within SF6-filled equipment, highly toxic by-products are produced that pose a serious threat to those in close proximity to the switchgear (ICF Consulting, 2002: 1).
These byproducts include, among other things, disulphur decafluoride (S2F10) which is a highly toxic gas (Blackburn 2015: 2). It has been referred to by the US Environmental Protection Agency (EPA) as “the byproduct of greatest concern due to its relatively high toxicity,” (ICF Consulting, 2002: 2). Although concentrations of such byproducts are limited, the health concerns are still relevant.
S2F10’s toxicity is on a par with phosgene, the infamous chemical warfare pulmonary agent used during the First World War (Blackburn, 2015: 2). Its weaponization was also considered during the Second World War due to its toxic nature, as it provided little warning of exposure to the victim (Blackburn, 2015: 2).
The presence of such by-products is of real concern due to the documented fact of leakage, as well as uncontrolled releases or discharges that occur during routine development, testing, commissioning, maintenance and repair and decommissioning of SF6 -filled equipment. For companies using SF6, these dangers represent, at best, increased handling costs due to required safety measures, and at worst a real risk to human life. They also lead to legitimate concerns over the health and welfare of utility employees as well as the communities that host switchgear stations.
Has the environmental impact even been underestimated?
SF6’s widely reported GWP of 22,800 firmly establishes it as the most dangerous known greenhouse gas. However, this is only the widely reported value. The IPCC for example, gives SF6 a higher GWP of 23,500 (Myhre & Shindell, et al. 2013: 733). Even these extremely high GWPs are unrepresentative of SF6’s true environmental threat. As previously mentioned, the gas’ widely reported GWP accounts for only 100 years of the its atmospheric lifetime, yet SF6’s atmospheric lifetime probably spans into many hundreds if not thousands of years, making its GWP of 22,800 inadequate when analyzing its true effect on climate change. If one looks to SF6’s GWP for a 500-year time horizon, it grows to 32,600 (IPCC, 2005) and, even then, remains only a fraction of its true impact on global warming. This raises the questions as to whether the gravity of SF6’s impact on global warming has really been understood? And whether we can continue to rationalize its use in the electrical industry?
“Furthermore, research shows that up to 80% of SF6 emissions are not reported at all (Levin et al. 2010: 2655). A reason for this is that Asian countries, such as China, India and South Korea, who are driving the increase in emissions, do not report their SF6 emissions to the United Nations Framework Convention on Climate Change (UNFCCC)(Rigby et al, 2010: 10316). Another reason is that developed countries that do report emissions to the UNFCCC, such as the USA, UK, Germany, are likely to be underestimating their emissions (Rigby et al, 2010 :10318).
Developed countries are likely under reporting their emissions because emissions reduction legislation relies on a ‘bottom-up’ measurement approach, which greatly underestimates SF6 emissions (Weiss and Prinn, 2011: 1934). There are two broad approaches to measuring emissions; bottom-up and top-down. The bottom-up approach measures SF6 emissions at the source of emission, while the top-down approach measures changes in the atmospheric concentration of SF6.
The aforementioned increase in global atmospheric SF6 emissions were measured and modelled extensively and independently by several research studies (Weiss and Prinn, 2011: 1934). They all came to the same general conclusion, namely that global SF6 emissions are greatly underestimated by bottom-up emissions reported to the UNFCCC by developed countries (Weiss and Prinn, 2011: 1934).
Considering that the measurement approaches on which emissions regulation is based is fundamentally erroneous, how can we be certain that the SF6 reduction measures taken so far by the EU, and by extension the electrical industry, have been effective?
Is the mitigation of SF6 emissions difficult? Do better solutions exist?
Due to SF6’s high GWP, its use is regulated by national and international governing bodies (Deux, 2013: 2). This creates further costs and a myriad of bureaucratic compliance legislation for companies, that must be adhered to. For example, when SF6-filled equipment is near the end of its life or has technical problems, special care must be taken in its recycling process and maintenance. Only licensed or authorized hazardous waste managers are permitted to handle, transport and recycle the gas according to national or regional regulations and standards (Deux, 2013: 4). These lifecycle management costs will continue to rise as the global demand for electricity, and, thus, switchgear, increases.
All the externalities of SF6 described in this paper have incentivized big and small manufacturers to find SF6-free solutions to switchgear. Several manufacturers – predominantly in the medium voltage (MV) level – have developed effective solutions based on vacuum switching technology in combination with solid or air insulation as alternatives for SF6 (Porte and Schoonenberg, 2009: 1). Rapid innovations, at least in the medium voltage range, have brought into question the industry claim that SF6 is a necessary evil and that alternatives are too costly (Porte and Schoonenberg, 2009: 1). Unfortunately, similar progress has not yet been made in the high voltage (HV) range.
Nonetheless, from a pricing perspective, research comparing MV SF6 switchgear and SF6-free switchgear found no evidence that the latter was more expensive than the former (Benner et al, 2012: 23). In actual fact, it found that SF6-free switchgear generally can be up to 10% cheaper than the corresponding SF6-containing alternative (Benner et al, 2012: 23).
SF6 is the most potent greenhouse gas in existence and for this reason was included in the Kyoto Protocol’s list of substances of which the use and emission should be minimized. Consequently, SF6 has been banned for all applications in which alternatives exist. However, an exception has been made for HV and MV switchgear in the electrical industry.
The rationale for this was that there was no viable alternative. However, as has been made clear in this paper, this is no longer the case, at least not in the case of MV switchgear. There are alternatives which are technically and commercially viable. With EU regulation No 517/2014 due to be reviewed in 2020, policy makers should campaign for further legislation with the final aim of banning SF6. This will further invigorate the research and development of SF6 -free technologies, not only for MV switchgear, but also for HV applications, finally leading to a full set of alternatives to SF6-based electrical equipment.
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