4 ms·

If I'm not mistaken the biggest disadvantage of supercapacitors is the energy density by mass[1], which means that while they hold a good power density by mass

If I'm not mistaken the biggest disadvantage of supercapacitors is the energy density by mass[1], which means that while they hold a good power density by mass it's only temporary. Good at sprinting not so good at marathons. It's great that there are advances in the field for many reasons, but I don't think they could replace batteries in the short-middle term, which seems to be the point of the "scientific click-bait" article. [1] http://berc.berkeley.edu/storage-wars-batteries-vs-supercapacitors/ http://berc.berkeley.edu/storage-wars-batteries-vs-supercapa...

Retric 10y ago
Regenerative breaking systems is one of the obvious places for supercapacitors. They are not quite at the energy density or cost level where every car uses them, but with some minor improvements they will become standard. The advantage is of course better mileage and increased battery lifespan. PS: There are even advantages with IC engines: http://articles.sae.org/11845/ http://articles.sae.org/11845/
- franciscop 10y ago
  I didn't think about regenerative breaking and of course it looks like a good place. But in the end of the cannot this be absorbed by the batteries with a good configuration? I mean, adding N supercapacitors that can absorb X power each would be proportional as configuring it as M batteries (where M >> N) charging that can absorb Y power each where Y = X * N / M => Y << X, which seems doable. So you'd either need enough capacitors to use them effectively (adding cost/complexity) or enough batteries, right? Is that the reason why Tesla can do regenerative braking except for strong stops? Because the batteries can absorb part but not all of the sudden energy?
  - jon_richards 10y ago
    I imagine the strong stop problem is more about actually stopping the car fast enough. Easier to do with friction than induction.
    - marcosdumay 10y ago
      That will depend on your speed. High speeds favor inductive braking. Anyway, if I were to guess, I'd say it's because ABS tech is very mature, and inductive breaking is not, thus safety favoring friction.
  - Retric 10y ago
    Battery's don't really like very short partial charge cycles, and the electronics to track these energy spikes get's difficult. Storing ~e6 J in ~5 seconds takes a lot of battery's. Also of note, because battery systems can only take X energy the rest of the system is only disguised to supply X energy. Most hybrids use battery's and simply kick in normal breaks if you do more than a slow stop. But, with super cap's a lot of this goes away. They can store more energy so you can add larger alternators and recover more energy. Further, they have a higher % efficiency for charge / discharge cycles.
    - Roboprog 10y ago
      So, you have 3 tiers of rate vs capacity? * Capacitor - high charge / discharge rate (power), low capacity (total energy). (and high risk of electrocution and spot welding) * Battery - medium power, medium capacity. * Small ICE - low power, high capacity.
- lucaspiller 10y ago
  The density/weight needs to be improved a lot for it to be effective compared to existing battery technologies though: Mazda supercapacitor: 0.007kWh @ 6kg - 857kg/kWh Prius with nickel-metal hydride batteries: 1.3kWh @ 42kg - 32kg/kWh Tesla with lithium-ion batteries: 85kWh @ 544 kg - 6.4kg/kWh
  - Retric 10y ago
    Breaking systems only really need to contain enough energy to stop a car. So, up to 1/2 * 2,000kg * (40m/s)^2 = 1.6e6 J which is a lot of energy, though less than 3.6e+6 J. Going down a mountain is an important edge case, but frankly not something that you really need to use super caps for as these systems still have mechanical breaks for backup, and the lower peaks is more acceptable for battery's. In an electric car you would then use that energy to speed up again, thus allowing for 10s if not hundreds of charge cycles on a single trip. Note: 2000kg ~= 4,400lb, 40m/s ~= 90mph.
    - deleted 10y ago
      [deleted]
    - sjfiekzjndn 10y ago
      You forgot to divide by two. It's actually 1.6 MJ, not 3.2 MJ.
      - Retric 10y ago
        Just edited before seeing your note. But, thanks I always forget about that 1/2.
        abakker 10y ago
        Just to be pedantic, it is "brakes" for slowing things down, and "breaks" for ruining or damaging something.
  - candiodari 10y ago
    Are these figures right ? Gasoline lists on wikipedia [1] as 46.4 MJ/kg which Google gets as 77g/kWh. [1] https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density

Retric 10y ago

Regenerative breaking systems is one of the obvious places for supercapacitors. They are not quite at the energy density or cost level where every car uses them, but with some minor improvements they will become standard. The advantage is of course better mileage and increased battery lifespan. PS: There are even advantages with IC engines: http://articles.sae.org/11845/ http://articles.sae.org/11845/

franciscop 10y ago
I didn't think about regenerative breaking and of course it looks like a good place. But in the end of the cannot this be absorbed by the batteries with a good configuration? I mean, adding N supercapacitors that can absorb X power each would be proportional as configuring it as M batteries (where M >> N) charging that can absorb Y power each where Y = X * N / M => Y << X, which seems doable. So you'd either need enough capacitors to use them effectively (adding cost/complexity) or enough batteries, right? Is that the reason why Tesla can do regenerative braking except for strong stops? Because the batteries can absorb part but not all of the sudden energy?
- jon_richards 10y ago
  I imagine the strong stop problem is more about actually stopping the car fast enough. Easier to do with friction than induction.
  - marcosdumay 10y ago
    That will depend on your speed. High speeds favor inductive braking. Anyway, if I were to guess, I'd say it's because ABS tech is very mature, and inductive breaking is not, thus safety favoring friction.
- Retric 10y ago
  Battery's don't really like very short partial charge cycles, and the electronics to track these energy spikes get's difficult. Storing ~e6 J in ~5 seconds takes a lot of battery's. Also of note, because battery systems can only take X energy the rest of the system is only disguised to supply X energy. Most hybrids use battery's and simply kick in normal breaks if you do more than a slow stop. But, with super cap's a lot of this goes away. They can store more energy so you can add larger alternators and recover more energy. Further, they have a higher % efficiency for charge / discharge cycles.
  - Roboprog 10y ago
    So, you have 3 tiers of rate vs capacity? * Capacitor - high charge / discharge rate (power), low capacity (total energy). (and high risk of electrocution and spot welding) * Battery - medium power, medium capacity. * Small ICE - low power, high capacity.
lucaspiller 10y ago
The density/weight needs to be improved a lot for it to be effective compared to existing battery technologies though: Mazda supercapacitor: 0.007kWh @ 6kg - 857kg/kWh Prius with nickel-metal hydride batteries: 1.3kWh @ 42kg - 32kg/kWh Tesla with lithium-ion batteries: 85kWh @ 544 kg - 6.4kg/kWh
- Retric 10y ago
  Breaking systems only really need to contain enough energy to stop a car. So, up to 1/2 * 2,000kg * (40m/s)^2 = 1.6e6 J which is a lot of energy, though less than 3.6e+6 J. Going down a mountain is an important edge case, but frankly not something that you really need to use super caps for as these systems still have mechanical breaks for backup, and the lower peaks is more acceptable for battery's. In an electric car you would then use that energy to speed up again, thus allowing for 10s if not hundreds of charge cycles on a single trip. Note: 2000kg ~= 4,400lb, 40m/s ~= 90mph.
  - deleted 10y ago
    [deleted]
  - sjfiekzjndn 10y ago
    You forgot to divide by two. It's actually 1.6 MJ, not 3.2 MJ.
    - Retric 10y ago
      Just edited before seeing your note. But, thanks I always forget about that 1/2.
      - abakker 10y ago
        Just to be pedantic, it is "brakes" for slowing things down, and "breaks" for ruining or damaging something.
- candiodari 10y ago
  Are these figures right ? Gasoline lists on wikipedia [1] as 46.4 MJ/kg which Google gets as 77g/kWh. [1] https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density