# Piezoelectric tires



## iti_uk (Oct 24, 2011)

I like the concept, but it seems like a lot of cost, unsprung weight and complication to provide enough power to almost run a cigarette lighter. (4.6W with a double layer, so 18.4W on a 4-wheeled vehicle).

Add to that the danger of damaging the system when you hit a pot-hole or a large stone on the road, and the greater vulnerability to changes in tyre pressure (lower volume of compressed gas changes pressure more quickly than a larger volume of compressed gas, given the same leakage rate) and I think we're heading into a cul-de-sac.

Chris


----------



## sajas (Nov 23, 2011)

iti_uk said:


> I like the concept, but it seems like a lot of cost, unsprung weight and complication to provide enough power to almost run a cigarette lighter. (4.6W with a double layer, so 18.4W on a 4-wheeled vehicle).
> 
> Chris


18.4W per minute.... 

Now, they established with double layer you still get 100% power from friction, with PVDF film instead of PZT as they used, I believe you might get even up to 4 layers with full use of friction.

Also, they used PZT while PVDF has much greater power production, especially in cases where large force is exerted on them, so In case it would be feasible to create some 2-3 KW of power while going 60 kmph I think it would be very well worth, ESPECIALLY since piezoelectric elements are pretty much cheap.


----------



## iti_uk (Oct 24, 2011)

sajas said:


> 18.4W per minute....


?? Joules per second per minute? Energy acceleration? 18.4W is the rate at which four of the double-layered wheels would produce energy, not the the volume of energy.



sajas said:


> Now, they established with double layer you still get 100% power from friction, with PVDF film instead of PZT as they used, I believe you might get even up to 4 layers with full use of friction.


Unless we're talking on the molecular level, it's mechanical strain, not friction which produces the electronic potential across the piezoelectric cells.



sajas said:


> Also, they used PZT while PVDF has much greater power production, especially in cases where large force is exerted on them, so In case it would be feasible to create some 2-3 KW of power while going 60 kmph I think it would be very well worth, ESPECIALLY since piezoelectric elements are pretty much cheap.


2-3kW is a factor of 100 greater than the results they got with 2-layer PZT. Assuming they use 4 layers with all layers working equally well, in order to reach your 2-3kW, PVDF must produce 50 times the elecronic energy per unit force than PZT. I don't think that this is the case.

And you're still left with the danger of damage, the difficulty of maintaining pressure in the reduced volume of the tyre, and the added unsprung mass.

Chris


----------



## Ziggythewiz (May 16, 2010)

Anything that produces a current does so by resisting something, in this case the tire's rotational deformation. If you could make these things produce a significant amount of energy, it would require an additional significant amount of energy to keep your tires rolling.

The concept is no different than hooking an alternator to each wheel. Energy isn't free; if it were we would all just spontaneously combust from all the energy we're failing to capture all around us.


----------



## Jan (Oct 5, 2009)

Ziggythewiz said:


> Anything that produces a current does so by resisting something, in this case the tire's rotational deformation. If you could make these things produce a significant amount of energy, it would require an additional significant amount of energy to keep your tires rolling.
> 
> The concept is no different than hooking an alternator to each wheel. Energy isn't free; if it were we would all just spontaneously combust from all the energy we're failing to capture all around us.


In practice you're probably right. But in theory is this, just like electromagnetic suspension, getting a little useful energy back, what otherwise is lost as heat. 

It's all part of the rolling resistance. In practice it's better to minimize the losses in the first place. Low resistance tires are practically speaking better. OK, less interesting, that's true.


----------



## iti_uk (Oct 24, 2011)

Jan said:


> It's all part of the rolling resistance. In practice it's better to minimize the losses in the first place. Low resistance tires are practically speaking better. OK, less interesting, that's true.


^^^^^ This. It is more efficient to minimize the losses from a single system than to introduce many systems to try and re-capture lost energy, each with its own efficiency losses. (Says the man designing a motor-per-wheel car. Yeah, I know...).

Chris


----------



## dtbaker (Jan 5, 2008)

sajas said:


> So my question is, according to their numbers, it seems to me, 1 wheel with double layer of piezo benders in entire interior might supply lots of power for EV.
> What does everyone think about this?


there's no free energy....

but I think there might be some useful capture using a simple magnet/coil to assist typical shock absorbers. by using vertical travel from bumps and vibration the energy that would normally be 'lost' to the springs/shocks might be captured. 

you know, like those shake-up flashlights.... using the work to assist vibration dampening.


----------



## iti_uk (Oct 24, 2011)

dtbaker said:


> there's no free energy....
> 
> but I think there might be some useful capture using a simple magnet/coil to assist typical shock absorbers. by using vertical travel from bumps and vibration the energy that would normally be 'lost' to the springs/shocks might be captured.
> 
> you know, like those shake-up flashlights.... using the work to assist vibration dampening.


This is much more feasible, given that we would be replacing a system designed to lose energy with one which is designed to collect that energy. The same goes with regenerative braking, where a loss of energy from a system is desired. With wheels, with regards to their rolling resistance, every attempt to conserve energy is made by those designing the system, so this theory would not work well for the piezo-tyres.

Chris


----------

