251–260 of 919 posts
I just realized how much energy efficiency is being squeezed out of a Tesla. It's incredible. A normal diesel fueled sedan such as the Chevy Cruze diesel runs at about 31mpg, which is 13.2 km/l or 15.3 km/kg. Diesel has a mind-boggling 12700 Wh/kg energy density[1], which translates to an efficiency of ~827 Wh/km for the Chevy. By contrast, the Tesla Model S, has a ~540 kg battery[2]. At 272 Wh/kg (from the posted ar…
For reference hobby lipo batteries used in small quadcopters are around 155-160 Wh/kg.
Lithium ion battery packs built from the very best Sony and Panasonic high-C rate cells for UAV applications are right around 250Wh/kg.
Earlier quoted context omitted.
I doubt it would be classical music and whale song playing over a beautifully calm scene.. More like kids watching movies without headphones, over loud conversations and screaming babies if other public transport is anything to go by. But we can dream!
Experiences vary. I was on a Tokyo subway train (Chūō-Sōbu Line(Local)). For a couple of minutes after boarding it was so quiet that it was eerie. When I started hearing quiet noises I relaxed. Anyway, mass transit does not have to be noisy. It varies by custom and culture.
"CATL has announced a new “condensed” battery with 500 Wh/kg which it says will go into mass production this year" This is a lot more credible than most of the battery stories, because CATL is already producing a ton of batteries, lending them some credibility. This is a little under 2x the density of current batteries.
Current mass produced batteries, which tend to hover around 260-300 Wh/kg. Higher density (but still under 500) are available, but in far smaller quantities for a very high cost. The exciting part of this announcement is that if anyone can scale manufacturing, it is them.
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Why is it so important to plant goal posts where parent doesn't? Some people like to have the freedom to choose between things, it isn't about trying to be some kind of villain.
Then explain how polluting and making lots of noise is freedom? Is speed limits imposing on your freedom to drive as fast as you want? Seat belt laws imposing on your freedom to have your kids unsecured in the car? I seriously don't understand this mindset.
What some people don't want to hear is that their freedom must be limited where it impacts other people. Nobody is alone in the world.
Someone should do a followup on all the batteries break-troughs on the front page of HN over the last 5 years and count how many got into production. Still, an announcement from a big company like this is a lot more credible than from research labs or small start-ups, IMO.
It’s interesting that battery stories generate so much opprobrium when battery performance has increased so dramatically over the last couple of decades.
I just realized how much energy efficiency is being squeezed out of a Tesla. It's incredible. A normal diesel fueled sedan such as the Chevy Cruze diesel runs at about 31mpg, which is 13.2 km/l or 15.3 km/kg. Diesel has a mind-boggling 12700 Wh/kg energy density[1], which translates to an efficiency of ~827 Wh/km for the Chevy. By contrast, the Tesla Model S, has a ~540 kg battery[2]. At 272 Wh/kg (from the posted ar…
The big reason for this is thermodynamics. A conventional internal combustion engine car has to convert chemical energy to kinetic energy - the absolute best theoretical efficiency of this might be 70%, but in practice it's more like 30%. Electric cars have to pay the same thermodynamic penalty, but they pay it at the power station (In practice, thanks to renewables, not all the electricity used to charge a car will…
While ICE are heat engines with a theoretical limit of 70%, they’re more specialised subsets described by the Otto (gas) and Diesel (… diesel) cycles, which have a much lower theoretical maximum.
Just plugging the temperature ranges into Carnot will give you a Carnot limit of 50%, and using Otto will yield 46% (https://physics.stackexchange.com/a/98992).
Add in that gas engines are not spherical and into a vacuum (losses and delays) and you’re in the 30s.
I just realized how much energy efficiency is being squeezed out of a Tesla. It's incredible. A normal diesel fueled sedan such as the Chevy Cruze diesel runs at about 31mpg, which is 13.2 km/l or 15.3 km/kg. Diesel has a mind-boggling 12700 Wh/kg energy density[1], which translates to an efficiency of ~827 Wh/km for the Chevy. By contrast, the Tesla Model S, has a ~540 kg battery[2]. At 272 Wh/kg (from the posted ar…
The big reason for this is thermodynamics. A conventional internal combustion engine car has to convert chemical energy to kinetic energy - the absolute best theoretical efficiency of this might be 70%, but in practice it's more like 30%. Electric cars have to pay the same thermodynamic penalty, but they pay it at the power station (In practice, thanks to renewables, not all the electricity used to charge a car will…
Earlier quoted context omitted.
BMW claim that a diesel 3 series will get 61mpg. Volkswagen reckon a Golf 2.0 TDI will do 68mpg. Electric is still significantly better, but you didn't need pick a terrible diesel car as an example.
The Cruze is way better than that anyway, you'd need to be in an excruciating traffic jam to get that low mileage. Well, my 12 years old (gas) Honda Fit does +40MPG being very "pedal happy" and near 50 driving normally, and my dad's 20 years old (diesel) Citroen Xsara Picasso does around 60MPG
3.9l/100km in a Xsara, really?
I just realized how much energy efficiency is being squeezed out of a Tesla. It's incredible. A normal diesel fueled sedan such as the Chevy Cruze diesel runs at about 31mpg, which is 13.2 km/l or 15.3 km/kg. Diesel has a mind-boggling 12700 Wh/kg energy density[1], which translates to an efficiency of ~827 Wh/km for the Chevy. By contrast, the Tesla Model S, has a ~540 kg battery[2]. At 272 Wh/kg (from the posted ar…
What about charging efficiency?
This of course doesn't include losses in transmission from the power station and in electricity production.