Georgia Tech Unveils Groundbreaking Supercritical CO2 Circuit Breaker

ATLANTA, Ga. — Researchers at the Georgia Institute of Technology are set to begin testing a revolutionary high-voltage circuit breaker that utilizes supercritical carbon dioxide (CO2) to quench electrical arcs. This innovative device could potentially replace conventional high-voltage circuit breakers that commonly use sulfur hexafluoride (SF6), a greenhouse gas noted for its environmental harm.

SF6, while an effective insulator, is recognized as one of the most potent greenhouse gases, having a global warming potential nearly 25,000 times greater than carbon dioxide, according to David Enslin, program director at the U.S. Advanced Research Projects Agency–Energy (ARPA-E), which funded the research. “SF6 is fantastic for performance, but terrible for the environment,” Enslin stated.

The new circuit breaker is being developed in response to increasing regulatory pressures to reduce SF6 usage in electrical equipment. These devices are critical components across power grids, providing crucial safety measures by interrupting electrical current during faults caused by events such as lightning strikes.

Georgia Tech’s design employs supercritical CO2, a state of carbon dioxide achieved at high pressures and temperatures, making it dense enough to effectively quench electrical arcs and reduce the likelihood of reignitions. The prototype, which operates at 72-kV, is slated for tests at the University of Wisconsin-Milwaukee starting in late April.

“Using supercritical CO2 for circuit-breaking is a novel approach, but constructing the breaker to withstand the extreme pressures required poses significant engineering challenges,” said Andrew Graber, a lead researcher on the project. The team faced difficulties sourcing a bushing capable of withstanding 120 atmospheres of pressure, ultimately leading them to create their own using a combination of materials such as mineral-filled resins and steel pipes.

The upcoming synthetic tests are crucial. If successful, the Georgia Tech team plans to test the breaker under real-world conditions at a location in Chalfont, Pennsylvania. “Our goal is to see how this technology can fit into current systems that use traditional high-voltage circuit breakers,” Graber explained.

If the circuit breaker reaches the market, it will compete against established players like GE Vernova, which has been developing SF6-free circuit breakers for over two decades. In 2018, GE introduced a gas-insulated substation in Europe utilizing a gas mixture with less than 5 percent fluorinated gas, significantly lowering its greenhouse warming potential.

“Our system was designed to be a drop-in replacement for existing SF6 breakers, maintaining compatibility while being more environmentally responsible,” said Paul Irwin, a senior product specialist at GE Vernova. However, challenges remain for maintenance workers, who will still need to wear protective gear when working on these systems.

Additionally, advancements in solid-state technology are emerging as potential alternatives to mechanical circuit breakers. Enslin noted that solid-state devices offer the capability to interrupt electrical flows in milliseconds, significantly faster than traditional mechanical systems, although these technologies are still in the early stages of commercial development.

The implications of transitioning away from SF6 are considerable. In 2018, global emissions of SF6 from electrical equipment were estimated to be 8,200 tonnes, accounting for about 1 percent of total emissions for that year, highlighting the urgent need for alternatives in the industry.