LordOverThis
LordOverThis t1_j5w12bn wrote
Reply to comment by Oodalay in Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology by AutoModerator
Regenerative braking basically is doing that.
The probelm is the laws of thermodynamics. To successfully charge the battery using the kinetic energy of the car would make an EV doing that into a perpetual motion machine of the first kind. You’d be converting KE back to PE, to use to convert back to KE, etc ad infinitum.
In reality, you actually could “trickle charge” the battery using an alternator or something similar to draw a small amount of the energy, but due to the thermal efficiency of such a device not being 100%, as well as inefficiencies (energy losses) in the batteries, controller, motor, and wheel bearings, you end up losing energy compared to just using it to drive the car.
Say you feed 500W into this alternator, which is 99.9% efficient (that in itself would be amazing). Your controller is 99.9% efficient. Your battery’s charge acceptance is 99.9% efficient. The battery discharge is also 99.9% efficient. Of that 500W in, your battery is able to put 498W of it back into the drivetrain again — which would be remarkably efficient — but there’s an obvious problem…you’ve lost 2W to inefficiency. You could’ve just not drawn that 500W, and had 500W going through the drivetrain to start with.
Taking the car out of the picture, it’s trying to charge a battery by having it drive a motor to drive a generator to charge the battery powering the system. The end result is less energy coming back i to the battery than if you’d just used the energy in the battery without running it through anything.
Even more simply it’s like trying to charge a battery with itself.
Regenerative braking works to convert the KE to PE at a time when you’d be wasting that KE anyway — brakes work by converting KE to heat, which is lost forever. Compared to that, all the inefficiency of the system in trying to recover some of that KE is still a massive improvement.
LordOverThis t1_iws29o7 wrote
Reply to comment by fucklawyers in Is there an anatomical reason Chicken Pox scars form where they do? by [deleted]
Same age group here. Not pox partied but instead just childhood incidental exposure, but definitely also just covered in lesions.
I have one scar.
Now we’re at n=2 for data points that not all lesions lead to scars.
LordOverThis t1_ivabb35 wrote
Reply to comment by SayuriShigeko in What is the cause of the steep escarpment at the base of Olympus Mons? by Strong-Ball-1089
It does kinda look like just a big ol’ mass wasting, so that checks out.
LordOverThis t1_iu1mx8m wrote
Reply to comment by phil_style in Ancient City of Magdala Unearthed Near Tiberias, Israel by GullyShotta
Someone will correct me if I’m mistaken, but as I understand it, this kind of dramatic overselling of an archaeological find with significant leaps of logic is extremely common for “finds” in Israel.
Like “we found a pottery shard, therefore Joshua and the Battle of Jericho!” (an example I made up) kind of fluffery goes on a lot.
LordOverThis t1_j5wz0uy wrote
Reply to comment by sinspawn1024 in Why do sample return missions such as OSIRIS-REx use their own reentry vehicles instead of just going to the space station for pickup and return with ISS equipment? by PromptCritical725
It’d be pretty unlikely to collide with the ISS, since it’s already like trying to shoot a bullet with a smaller bullet on a completely different trajectory. Just guesstimating that it’s probably a margin of error of like a milliarcsecond between “intercepted successfully” and “it flew by so far away it couldn’t be seen”, which would put the difference between “intercepted successfully” and “everyone aboard was killed” at even smaller.