The manmade gas sulfur hexafluoride is a champ at lots of things.
Dense and stable at a broad band of temperatures, it was the original gas pumped into the pockets of Nike Air sneakers to give that cushion and bounce. But it’s particularly good at extinguishing electric current inside a circuit breaker — the majority of all SF6 is used in electrical equipment.
Unfortunately, it’s also the best at trapping heat in the atmosphere.
SF6 is the most potent greenhouse gas on the planet, lingering for thousands of years. One pound of the stuff is the same as releasing 22,800 pounds of carbon dioxide into the air.
The climate impact of the gas has been known for years. It took Nike more than a decade to find a suitable alternative; it eventually replaced SF6 with nitrogen.
But the electrical industry has been slower to transition, in part because SF6 is what Markus Heimbach called a “technically perfect gas.” It is unrivaled in stopping electrical current at very high voltages, which is critical in preventing surges from damaging equipment.
Mr. Heimbach, who manages the high voltage products business at Hitachi Energy, predicts it will be at least a decade before circuit breakers and other electrical equipment with no SF6 will be widely available at all voltage levels.
At the same time, demand for such equipment has never been higher, he said, as the U.S. reconfigures how energy is produced and transported.
Many new gas insulated substations and circuit breakers will continue to be commissioned with SF6 in the coming years. And thousands will be made in the Pittsburgh region, at Hitachi Energy’s plant in Mt. Pleasant and at Mitsubishi Electric Power Products’ campus in Warrendale.
But both companies are also now manufacturing greener alternatives.
At Mitsubishi, engineers are working on rows of circuit breakers that use vacuum-sealed dry air instead of SF6. Such technology is already available for low-voltage applications — like the substations in your neighborhood operated by your local utility. The ones Mitsubishi began shipping to utilities last year are for medium-voltage uses.
This week at its Mt. Pleasant factory, Hitachi Energy will turn over what it believes is the world’s first SF6-free extra high voltage circuit breaker to the New England utility Eversource.
The equipment uses a mix of carbon dioxide, oxygen, and a bit of fluoronitrile instead of SF6. It’s not a zero-emission solution, but it’s dramatically lower-impact than the status quo.
Decades of study
Recognizing SF6’s outsized role in global warming, the Environmental Protection Agency in 1999 invited companies that use electrical equipment — like utilities and transmission firms — to participate in a voluntary SF6 tracking and reduction effort.
The companies shared data on how to spot and fix leaks, how to recycle the gas, and reduce the amount used.
California-based Pacific Gas & Electric, one of the largest utilities in the country, wrote in a case study that it discovered far more leaks than it expected and was losing between 20,000 and 30,000 pounds of SF6 per year in 1999 — equivalent to the emissions from about 57,000 cars. Five years later, the loss rate was down to 11,000 pounds.
California became one of just two states to mandate reduction of SF6 in electrical equipment. The other is Massachusetts.
“The amount of leaks we used to have …” marveled Kevin Goldstein, general manager of the electrical distribution division at Mitsubishi, who has been in the industry for over two decades.
In the past two decades, utilities and equipment manufacturers learned how to better seal SF6 vessels, to continuously monitor for leaks and fix them quickly, he said. According to the EPA, sulfur hexafluoride emissions decreased from 4.3 million metric tons of CO2 equivalent to 2.4 million metric tons between 2011 and 2021, the last year for which data is available.
Having taken mitigation as far as it made sense to go, the industry shifted to finding alternatives for the potent gas.
“Hitachi was a trailblazer” in the space, Mr. Goldstein said. “We can call them a competitor... but they are an educator.”
Even with some products already available, utilities will be slow to change, as they always are, Mr. Heimbach said.
“As it should be,” he added. They are conservative by nature, piloting innovations at a small scale for longer periods before incorporating them into an ever more interconnected grid.
Still, he cautioned, “We need to act fast because the volume of equipment that is put onto the grid is as much as we’ve ever had.”
Even if the installation of SF6 equipment stopped today, there would still be millions of pounds of the gas inside existing equipment that will need to be safely removed.
The volume isn’t trivial: In 2004, Duquesne Light decommissioned a relatively new substation removing approximately 7,300 pounds of SF6, the company wrote in a case study, equating it to the impact of 17,000 cars driving for a year.
Both Hitachi and Mitsubishi offer decommissioning services which include SF6 removal.
But that’s not the most urgent problem, Mr. Heimbach said.
“Before we are replacing all the SF6 infrastructure already out there, we need to make sure we’re not delivering new SF6 infrastructure into the grid.”
Anya Litvak: alitvak@post-gazette.com
First Published: June 19, 2023, 9:30 a.m.
Updated: June 20, 2023, 5:16 p.m.
