# Energy From Piezo Crystals

1. Jun 9, 2015

### Hamza Abbasi

Piezo Electric Foot Paths (I am having a problem )?

I am building a Piezo electric footpath which will generate electricity , converting mechanical energy into electrical energy . Before building the actual model I have build a test model. The model is generating fairly high amount of voltages but no current (may be few micro amps ) . What should i do to increase the current? I don't want to use external source of current connecting it with a transistor

2. Jun 9, 2015

### DEvens

Remember conservation of energy. The maximum amount of energy you can possibly get out of the crystal will be no more than the mechanical work done on the crystal. If you put a 50 kg person on the crystal and it is crushed by a distance of say .0001 meter, then the energy is (rounding the acceleration of gravity, and being pretty sloppy with the springy nature of the crystal)

m g h = 50 kg x 10 m/s^2 x .0001 m = 0.05 Joules

which is not very much. And the crystals will not be 100 percent efficient. So you are not going to get very much power out of such crystals from people walking on them, and there simply is not much you can do to get around that.

Usually such crystals are more useful in applications of detecting force rather than converting it to power. And if calibrated accurately they can be used to measure force. So they can get used in such things as measuring weight. But they are not going to be great at converting mechanical work to power.

3. Jun 9, 2015

### Staff: Mentor

So building on what DEvens has pointed out, can you think of other technologies you could use to harvest energy from people walking along a path?

4. Jun 10, 2015

### Jeff Rosenbury

To overcome your problem Hamaza, stack the crystals. Each crystal will only give say 0.001 Joules, but that means stacking them 100 thick will give 1 Joule.

But be aware of the cost. The sidewalk will be a bit springy, and not in a good way. It will be like walking on sand. The energy you are generating will be coming from people's muscles and they will feel it. That's great as some sort of high tech treadmill, but people will tend to avoid your sidewalk and walk on the grass instead.

The military has looked at generating power from a soldier's muscles. They concluded the soldiers were tired enough in combat as it is. So while taking power from those of us who are fat, dumb, and happy might work, active people really don't need to be hamsters in a cage.

5. Jun 10, 2015

### Jeff Rosenbury

Make each sidewalk slab (the part between the cracks) into a small teeter tooter. Place solenoids at each end. Collect electricity. Use it to play children's music?

6. Jun 10, 2015

### dlgoff

So, would a lightning strike causing an extremely large Ground Potential Rise create a large enough Fout, as shown in Figure-7 from this Introduction To Piezo Transducers, to project a pedestrian off the sidewalk? (probably not, just food for thought)

7. Jun 10, 2015

### Staff: Mentor

Boy, talk about having a bad day. One minute you're just walking along, and then BAM! you get hit by lightning and shot 20 feet in the air. Ouch!

8. Jun 10, 2015

### Jeff Rosenbury

Yes. I'm developing this system as transportation. Lightning is much more common than tornadoes, and sidewalks are cheaper than houses. I hope to save on airfares to Australia.

Oz awaits!