Grenoble (AFP)
SF6 is not the best known of all and yet it is an ultra-warming greenhouse gas, which electrical equipment manufacturers are now trying to eliminate from electricity stations, where everywhere in the world it was - almost - wonder for 50 years.
At the Schneider Electric R&D center in Grenoble, a smile is in order: engineers have developed a substitute and this spring sees the launch of a range of stations without sulfur hexafluoride (SF6).
"It's ten years of work and a technological breakthrough, believes Christophe Prévé, responsible for this research. So what to replace this gas? By air, compressed to a specific level," replies Schneider.
The objective is not insignificant: SF6, targeted since 1997 by the Kyoto Protocol on the climate, has a warming potential 23,000 times greater than that of CO2 and remains in the atmosphere for up to 3,000 years.
It is the most powerful of greenhouse gases, even if it represents a small part.
For its insulating power, it is used for example in the production of magnesium and was once found in double glazing or the soles of sneakers.
No need for him in personal circuit breakers.
But in medium voltage switchgear, which deliver electricity to buildings, hospitals, industrial sites and other airports, SF6 serves as an essential insulator for safety: when the current must be cut, it prevents electric arcs. .
Its presence makes it possible to reduce the distance between the phases and therefore to miniaturize the stations.
But SF6 can leak, when it is produced in a chemical plant or from an electrical substation when the tank in which it is enclosed with the phases shows a lack of sealing.
Importantly, it can end up in the wild after the post is scrapped, if it is not taken care of and processed.
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“For any electrical technician, SF6 was fantastic in terms of its properties,” notes Philippe Sauer, Power systems France director at Schneider.
"But we have to get rid of it. Today it is our duty to offer the greenest possible equipment".
And the stakes can only increase with the energy transition, which heralds an electricity boom, with increased demand (transport, heating, etc.) and a rise in renewables.
Among all manufacturers, the race for SF6-free has been launched for years.
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In Grenoble, the brand new medium voltage test laboratory, built on the historic site of Merlin Gerin, ancestor of Schneider Electric, has been the scene of countless tests: resistance of materials to corrosion or shocks, lightning impacts ...
And in the end, it was the solution of air, coupled with small ceramic vacuum bulbs where disconnection can be done at high speed, all encapsulated in a tank of a few tens of centimeters whose volume remains similar to the old ones. models.
Because it was necessary that neither the size of the station nor its instructions for use change to make it acceptable, notes the industrialist.
This will be an additional cost for the customer of a few thousand euros (for a post with a lifespan of 30-40 years, the total cost of which is not specified).
So will the SF6-free convince?
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"There are environmental and image arguments" for the buyer, emphasizes Mr. Sauer.
"But also from the moment when technological solutions exist, there will be more regulatory constraints, even one day a ban" of SF6.
GreenAlp, Grenoble's electricity distributor, has been testing the equipment since the end of 2019.
"This is the meaning of history", says Sébastien Julien, of GreenAlp.
"And the presence of SF6 is a technical and financial constraint: there is always a risk of leakage, we must learn to handle, recycle ..."
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California wants to ban SF6 in medium voltage equipment in 2025. The EU could soon strengthen its regulation on fluorinated gases.
To this end, a Commission report published at the end of 2020 notes that alternatives to SF6 are emerging on the industrial side, at an additional cost of 5% to 30%.
Because of the additional cost, he notes, "regulatory measures will undoubtedly be necessary to boost the transition".
© 2021 AFP