this post was submitted on 27 Sep 2024
38 points (100.0% liked)
World News
22057 readers
97 users here now
Breaking news from around the world.
News that is American but has an international facet may also be posted here.
Guidelines for submissions:
- Where possible, post the original source of information.
- If there is a paywall, you can use alternative sources or provide an archive.today, 12ft.io, etc. link in the body.
- Do not editorialize titles. Preserve the original title when possible; edits for clarity are fine.
- Do not post ragebait or shock stories. These will be removed.
- Do not post tabloid or blogspam stories. These will be removed.
- Social media should be a source of last resort.
These guidelines will be enforced on a know-it-when-I-see-it basis.
For US News, see the US News community.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
founded 2 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
I... I don't get this. The trains are functioning as batteries? Regenerative braking is nice, but why is only a third going to power the trains themselves? Why not 100%? TFA says they're issuing the "spare electricity" in the grid; "spare?"
These aren't perpetual motion machines; they're not violating the third law, and they consume more energy than they produce. Most off these article is about the (obvious) benefits of adding regenerative braking to subways around the world, regardless of cost; what confuses me is: why are they spending money and effort to route regenerative braking into other uses, which is what the title literally says ("trains", not "train power grid"). It seems like an inefficient and circuitous way to tap other demands into a subway power grid.
Unless what's really happening is that Barcelona is just tapping other demands into the (robust) subway power grid, and coincidentally adding regenerative braking, and someone decided to make the wild conceptual link that the power being fed back into the grid by braking is part of the overall power being used by new sinks. Which is like saying that my piss is being used to provide drinking water, because it goes back into the overall water cycle one way or another.
Could the regeneration be putting out a higher current than what the batteries on the subway train can handle? Not very likely, but I guess that's a possibility.
Or if the trains are running on an electrified rail and don't actually carry much battery capacity themselves so regenerative braking fills that small battery and then dumps the rest back to the grid?
I don't particularly feel that either of those situations are likely to be accurate, but I guess someone could have done something weird in the design.
I would guess it's the latter; the trains draw power from the grid to accelerate, and dump power back into the grid when they decelerate.