Climate change: Electrical industry's 'dirty secret' boosts warming

by Matt McGrath, Environment Correspondent, BBC, September 13, 2019

 … It's the most powerful greenhouse gas known to humanity, and emissions have risen rapidly in recent years, the BBC has learned.

Sulphur hexafluoride, or SF6, is widely used in the electrical industry to prevent short circuits and accidents.

But leaks of the little-known gas in the UK and the rest of the EU in 2017 were the equivalent of putting an extra 1.3 million cars on the road.

Levels are rising as an unintended consequence of the green energy boom.

Cheap and non-flammable, SF6 is a colourless, odourless, synthetic gas. It makes a hugely effective insulating material for medium and high-voltage electrical installations.

It is widely used across the industry, from large power stations to wind turbines to electrical sub-stations in towns and cities. It prevents electrical accidents and fires.

However, the significant downside to using the gas is that it has the highest global warming potential of any known substance. 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.

It also persists in the atmosphere for a long time, warming the Earth for at least 1,000 years.

So why are we using more of this powerful warming gas?

The way we make electricity around the world is changing rapidly.

Where once large coal-fired power stations brought energy to millions, the drive to combat climate change means they are now being replaced by mixed sources of power including wind, solar and gas.

This has resulted in many more connections to the electricity grid, and a rise in the number of electrical switches and circuit breakers that are needed to prevent serious accidents.

Collectively, these safety devices are called switchgear. The vast majority use SF6 gas to quench arcs and stop short circuits.

"As renewable projects are getting bigger and bigger, we have had to use it within wind turbines specifically," said Costa Pirgousis, an engineer with Scottish Power Renewables on its new East Anglia wind farm, which doesn't use SF6 in turbines.

"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."

How do we know that SF6 is increasing?

Across the entire UK network of power lines and substations, there are around one million kilograms of SF6 installed.

A study from the University of Cardiff found that across all transmission and distribution networks, the amount used was increasing by 30-40 tonnes per year.

This rise was also reflected across Europe with total emissions from the 28 member states in 2017 equivalent to 6.73 million tonnes of CO2. That's the same as the emissions from 1.3 million extra cars on the road for a year.….

Electrical company Eaton, which manufactures switchgear without SF6, says its research indicates that for the full life-cycle of the product, leaks could be as high as 15% - much higher than many other estimates.

Louis Shaffer, electrical business manager at Eaton, said: "The newer gear has very low leak rates but the key question is do you have newer gear?

"We looked at all equipment and looked at the average of all those leak rates, and we didn't see people taking into account the filling of the gas. Plus, we looked at how you recycle it and return it and also included the catastrophic leaks."….

read … The BBC

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One example of how SF6 is being used in Hawaii to protect circuit breakers from the erratic electricity produced by wind and solar: 

“Maui Electric has already added dual differential protection to a majority of the 69kV lines and replaced a majority of the 69kV breakers with 3 cycle SF6 breakers in an effort to reduce fault clearing times. The final two 69kV transmission lines are due to have the protection upgraded in 2017 and the final 69kV circuit breakers will be replaced in 2018. Maui Electric also has plans for upgrades to all of the 23kV line protection, 69kV bus protection, and transformer protection over the next decade.” 

“In 2014, the average cost for breaker replacements was almost $135,000. [] The failure data assembled during the evaluation indicates that the SF6 breakers are failing in a manner and timeframe that is different than would be expected for oil breakers. This SF6 failure data was not available when the strategy was initially developed in 2014. The strategy scenario analysis was performed with consortium failure data which is based primarily on oil breakers. Since the failure data is different and because all the oil breakers are being replaced with SF6 breakers, the strategy should be revised based on the failure modes and failure probabilities for SF6 breakers as well as the oil breakers.” (pg 48-49)

UHERO: “The 2007 Intergovernmental Panel on Climate Change Assessment Report indicates that: the methane (CH4) Global Warming Potential (GWP) is 25, the nitrous oxide (N2O) GWP is 298, the HFC-23 (hydro-fluorocarbon) GWP is 14,800, the HFC-134a GWP is 1,430, and the sulfur hexafluoride (SF6) GWP is 22,800.”  (GWP of CO2 is ‘1’)

How much SF6 has been put in place by HECO to satisfy the needs of windfarms and solar in Hawaii?  Google: SF6 HECO Hawaii