Replacement for SF6:  GE's new 'g3' gas - Page 1
Forum section: electronics / general

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: November 14, 2019, 04:02:36 pm
content: I just stumbled across this which I found interesting. There has been some increasing awareness recently of the environmental impact of SF6leaks from HV switchgear. There was a thread here about it.It looks like GE have developed an alternative gas which is much less damaging and they are rolling it out in to the field.May be of interest to folks here?... It seems encouraging and looks like it passes the 'yeah nice but can I actually go and buy it yet' test.https://www.gegridsolutions.com/press/gepress/Press_Release_g3%20Roadmap_Sept2019.htmProduct Roadmap here...https://www.gegridsolutions.com/products/reference/g3_roadmap_2025-Brochure-EN-2019-10-Grid-GS-1668.pdfThere are some techical details buried away here...https://think-grid.org/search-sf6-replacementQuote

author: dmills
author_rank: Super Contributor
timestamp: November 15, 2019, 12:59:18 pm
content: Am I missing something fundamental here?SF6 has an awesome global warming potential, true, but it is also very, very dense. My recollection of SF6 is that it notoriously pools in the low parts of structures and in such spaces presents a danger of asphyxiation, ~6kg/m^3 at STP, where nitrogen is around 1kg/m^3 under the same conditions.I am having some trouble with the notion of a gas that dense managing to get high enough in the atmosphere to matter. At street level, sure, but 10km up at the top of the troposphere? Got my doubts.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: November 15, 2019, 02:37:02 pm
content: I wouldn't claim to be an expert on the physics but yes, when the gasses mix, they will stay in solution. Otherwise the atmosphere would be stratified with the various gasses in layers according to their density.I'm sure in a still column of gas, there will be some concentration gradient according to density but I suspect it's a very small effect in the atmosphere. Especially when the SF6 has tens of thousands of years of wind, convection, and Brownian motion to get up there.Even if it stayed as a layer on the ground surely it would still contribute to warming? As long as it blocks infra-red from being radiated back in to space...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 15, 2019, 03:01:49 pm
content: Yeah, even under still conditions, diffusion will take it there eventually. And it's not like it's going anywhere down here, it's only broken down in the upper atmosphere as far as I know. Well, maybe a few molecules get chance encounters with lightning bolts. Actually over that time scale, maybe lightning is a notable contributor, no idea.Relevant paper is awfully easy to find:https://www.researchgate.net/publication/326961554_FluoronitrileCO_2_mixture_as_an_eco-friendly_alternative_to_SF_6_for_medium_voltage_switchgearsThe formula is (CF3)2CFCN, which can also be called perfluoroisopropyl cyanide. So it's a pretty heavy molecule, a CFC. Probably the biggest downside is the high boiling point, near that of butane for example. It will liquefy inside equipment, that's been turned off for a while in cold climates (like much of the US right now!).Tim