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How much re-gen could tires generate?

Discussion in 'Technical' started by swengl, Mar 7, 2015.

  1. swengl

    swengl Member

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  2. evp

    evp Nerd

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    Yeah, not so much. They might be able to generate 10 or 20 Watts as you're driving down the road using 20 kW. This is the same answer I give to people who say "why don't they coat the car with solar cells so it can drive all day without recharging?". But in the case of the solar cells, you might at least be able to pull 1 kW on a perfect day.
     
  3. swengl

    swengl Member

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    I also saw an article a while back that mentioned the development of regenerative shock absorbers. The concept alone is pretty awesome. As long as it doesn't negatively impact the range, every little bit would help, no?
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    There's a big "it depends" on these kinds of things:

    Does the additional weight, especially unsprung weight, negate any savings?

    Is it robust, or does it require maintenance, periodic replacement (meaning more than once every 100,000 miles)?

    Does it actually just take power from the battery and put it back in (less any energy conversion or heat production losses)?

    Does the amount of energy it captures degrade over time or with conditions (dirty car, snow, rain, etc.)?
     
  5. AB4EJ

    AB4EJ Member

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    Over the years, I have seen many, many technologies that harvest energy from processes (getting energy from sounds in the air, clothing that generates power when you walk, etc.). These are all clever but generally generate only tiny amounts of power, i.e., enough to power a watch or pocket calculator. The energy contribution from these concepts to powering something large like a vehicle, would be so small as to be "lost in the noise," in anything other than laboratory conditions. (Probably even then.)
     
  6. AWDtsla

    AWDtsla Active Member

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    The laws of thermodynamics say this is stupid. Replace the tired with hard plastic discs, your tire losses will be minimal - and you don't need to piezo electrically stiffen the tire. Of course it's the flex that gives you traction and ride quality anyway. Regardless, tire losses are minimal compared to drag.

    See how much Can EVs handle the distances we drive? A Study
     
  7. bxr140

    bxr140 Member

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    Yes. Every little bit helps. The answer is always that every little bit helps. There's still plenty of wasted energy in an EV, and any research into recovery of that energy is a step in the right direction. Certainly there are some practical matters/hurdles to address, but as long as those issues approached as a problem to solve, progress will be made.
     
  8. ggr

    ggr Roadster R80 537, SigS P85 29

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    Well, sort of, some times. Maybe the recovery of energy from the tires causes slightly higher rolling resistance? I don't know, I'm just speculating. But about 10 years ago the US Army was experimenting with generating energy from soldiers' backpacks moving up and down, using it to recharge radios and so on. It looked like free energy. But the reality was that it altered the dynamics of the backpack enough to make the soldiers uncomfortable and tire quicker. It was better to give them a hand-crank charger.
     
  9. RDoc

    RDoc S85D

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    I've never noticed passenger car tires getting hot from driving so am very doubtful there's much energy there to be harvested. Starting with a small potential energy source, harvesting it with a pretty inefficient system, then putting it through the power conditioners...
     
  10. bxr140

    bxr140 Member

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    Could be, but if its a net gain on energy (see swengl's comment on not negatively impacting the range), its still a Good Thing. Will this tire ever come to be? Who knows, but hopefully they don't get discouraged by people that are just poking holes.

    If everyone spent their time drilling into the top items on the 'wasted energy' pareto, we'd miss out on a whole lot of what Progress has to offer.
     
  11. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    I'm trying to figure out how you can get a net gain of energy while still retaining ride comfort.

    1. All the energy used in a Tesla comes from the battery. (Remember, regen just puts back some kinetic energy already spent by the battery.)

    2. Due to flexing a certain amount of heat is generated (which causes the tires to increase in pressure).

    If you're taking energy out of the tire, then either the heat generation is reduced or the battery has to supply the additional energy. Understand it would be great if it works, but my thought is that it will be similar to runflat tires--you can do it, but there are penalties that make them less than ideal.
     
  12. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Perhaps it isn't intended to harvest while driving / flexing, but rather when the vehicle is stopped. The article makes mention of hot parking lots on a sunny day. It may be that the energy is recovered once the car is stopped, rather than a convection transmission into the air.
     
  13. bxr140

    bxr140 Member

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    I'd like to think that for the development phase the goodyear team has decoupled those criteria. Trying to solve many variables at once isn't the most efficient path to a solution.

    Yes, but the tire has already "taken" energy from the battery and is, mostly through convection, dissipating that energy as heat into the surrounding air. They're just trying to recapture some of that otherwise lost energy, just like the motor is recapturing energy that would otherwise be dissipated as heat through the [conventional] brake system. I don't think Goodyear's solution will have anything to do with tire pressure.
     
  14. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    I don't think it will either. Tire flexing is another matter. The point about pressure was that it increases when the tire flexes and heats up. Assuming that the energy is captured while the tire is rotating (which we don't know yet), the energy has to come from somewhere. My thought is that to create the energy and not increase the drain from the battery, something has to give. The obvious thing to give is the flexing. In regenerative braking, the motors just replace the pads and rotors so it's easy to see how the energy gets transferred. It's less obvious in a tire. However, if you can transform the heat into electricity so that the tire runs cooler, that's a real win. I just have difficulty seeing how that will work.
     
  15. bxr140

    bxr140 Member

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    It sounds like they're going from the thermoelectric effect, which doesn't care if the tire is in motion or not...other than the fact that vehicle motion is a method to create heat in the tire. That heat is generated whether or not it is subsequently captured, so there's no 'energy has to come from somewhere' aspect.
     
  16. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Of course it has to be electricity generation from (otherwise dissipated/wasted) heat. Anything else would be "free energy"/perpetual motion.

    Now the question of course is does capturing this heat negativity impact the driving dynamics of the tire? And due to the unsprung weight increase from the thermo-electric generator in the tire do we really end up with a net gain at the end of the day? And is it worth is cost-benefit wise (the obvious parallel is PV panels on the roof of the car).
     
  17. bxr140

    bxr140 Member

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    Absolutely. Those are problems to solve, and it may turn out that current/near term technology won't allow the practicality trade to close.

    It's not a huge deal if they can't make it work now, because it will be feasible at some point. When it comes to energy, you can start with more, use less, or recover more. These tires attach the first and last.

    I Look as this concept like the 'cover your car in PVs' idea. At some point that will make total sense...it just doesn't today (mostly because of mass/cost).
     
  18. Johan

    Johan Took a TSLA bear test. Came back negative.

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    May well be that before these issues are worked out we live with ubiquitous virtually unlimited energy supply (solar, fusion?) and energy storage that's cheap and for practical purposes without limits (400 kWh battery weighing 400 pounds for $10k). If so these tires become moot.
     
  19. bxr140

    bxr140 Member

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    Could be. Even so, if the electric tire of the future behaves and costs exactly like the non e-tire of the future, there's zero downside. Why wouldn't everyone want another couple miles range for free?
     
  20. liuping

    liuping Active Member

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    But cost, comfort, handling and noise have to be taken into account. If it's noisier, the ride is less comfortable, or it handles worse, it's not "a good thing".

    The same money (or less) could be spend on a single extra solar panel on you roof, and it would generate far more electricity, everyday, even when you are not even driving.

    - - - Updated - - -

    It likely would not even add that much. A mile driving uses roughly 300wh. If these produce 50Watts (doubtful), you'd have to drive for 6 hours to gain 1 mile of range. After 6 hours, I'm pretty sure you'd already have to be stopped to charge, so the extra mile won't really make much difference.

    Also, the chances of it costing "exactly" as much as a normal tire are pretty small. Even just the extra electronics on the car to use the electricity generated are going to cost something.
     

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