# Conversion of friction energy in to electrical energy is possible?

1. Nov 2, 2015

### Rahulkumar999

It is possible to convert frictional energy in to electrical energy directly?.... please tell me and if possible give me the formulae...

2. Nov 2, 2015

### billy_joule

Some heat engines can convert heat produced by friction directly into electricity:

https://en.wikipedia.org/wiki/Thermoelectric_generator

But in almost all cases it's cheaper and easier to reduce friction in the first place rather than try to capture energy lost due to friction (usually very low quality energy)

Last edited: Nov 2, 2015
3. Nov 2, 2015

### Staff: Mentor

Welcome to the PF.

That's what is used for much of the braking in electric vehicles -- are you familiar with "regenerative braking"?

4. Nov 2, 2015

### rcgldr

That uses some part of the drive train using components similar to a generator, and doesn't rely on friction (other than the friction between tires and road that coexists with the torque to drive the drivetrain when it's acting as a generator).

5. Nov 3, 2015

### CWatters

Friction is a force not energy. As for equations...

If you had a block of mass m being dragged along a surface at constant velocity v and the coefficient of friction was u then the power dissipated as heat would be roughly..

Power = force * velocity = mguv

6. Nov 3, 2015

### Staff: Mentor

Bingo! Without friction, regenerative braking would not be possible.

7. Nov 3, 2015

### Merlin3189

So without friction would any braking be possible?

Perhaps we could use air braking, then use the air pressure to drive a turbine to provide regenerative energy.

8. Nov 3, 2015

### David Lewis

Friction can produce electricity directly via triboelectric effect, as in a Van de Graaff generator.