Hacker News Reader

Comment by vlad | Hacker News Reader

Brake regeneration is a large part of the braking force for many EVs when the brake pedal is pressed, so the brake pads in some EV cars are actually smaller than their gas siblings.

Brake regeneration also avoids using the brake pedal altogether in many cases because an EV slows down significantly when the gas pedal is released.

With electric power, smaller brake pads, and less need to use them, I'm surprised the article believes there is only a 1% reduction in overall particle pollution for EV's vs. gas cars.

Plus, a typical EV is a small and modern 0-2 year old car compared to the gas vehicles out there, such as a 7-year-old, inefficient, v8 engine SUV.

View on HN

This small reduction of particle pollution was the result of a very old study. At that time, there was no brake regeneration and the car was very heavy. I guess there is no recent study because the result would be obvious.

See my post above for a study from 2016.

Pad size is irrelevant, and smaller pad sizes can actually result in faster release of material.

Regeneration is certainly a benefit, but in my experience with a few different EVs caps out at fairly low levels of braking.

Also, I don't know anyone who's replaced a V8 SUV with an EV. Most of the EV-owning people I know replaced hybrids, generally Priuses.

You may be right, but I'd like to see a source that runs contrary to this instead of pure conjecture:

http://www.sciencedirect.com/science/article/pii/S1352231016...

A big factor is that gasoline engines don't release all that much particulates.

"Electric-powered vehicles, of course, have no exhaust emissions. However, because they’re 24 percent heavier on average, the study found that EVs shed more particulate matter from tires and brakes, and also kick up more particulate matter from road surfaces."

If the brake pads are smaller and aren't required to slow down in many cases, the EV should win, especially when the average EV on the street is likely similar in weight compared to an average non-EV vehicle.

As far as kicking up existing particulate matter, EV's shouldn't be penalized for kicking up dust on the road which came from others cars, which are almost entirely non-EV cars and 18-wheelers.

I bet there are other more significant factors to derive impact on pollution from EVs than brake dust, such as the source of electricity used to charge them.

I'll try to look at the study later to see how the 1% difference between road pollution between gas and EV vehicles was calculated.

> "However, because they’re 24 percent heavier on average, the study found that EVs shed more particulate"

That's a pretty misleading statistic too. EV's are 24% heaver than the average subcompact. But most people are already driving cars significantly heavier than the lightest subcompacts.

According to the EPA, the actual average personal vehicle weight was 3,977 pounds in 2012. That is heavier than most EV's -- it's heavier than any Chevy Bolt, Volt, or Nissan Leaf ever sold.

For example, a 2017 Volt is lighter than a similarly-priced 2017 Avalon, even though the Volt has a 18.4kWH battery in it, does 53 miles zero-emission electric, and gets an extra 15mpg when using gasoline.

The new GDI engines most certainly will...

Reply on news.ycombinator.com