Inquiry for piezoelectric energy harvesting

[bundit]

Hi all,

I' m new in this forum. Greeting to all
I'm doing a project of energy harvesting from piezoelectric bulk type by force impact input. The output of the device when no load is a pulse like with amplitude 60-70 V.peak and pulse width about 500 us.
The standard technique of full bridge rectifier with parallel storage capacitor, the voltage across the cap. gets 20-30 mV(storage cap: 220-470 uF) at the first impact and rate decreases thereafter.

I would like to ask for any idea to get the storage energy more efficiently.

PS. The purpose is to store the harvested energy into a capacitor and give to a DC-DC converter for charging a battery. The energy sources brought from piezoelectric together with electromagnetic induction which now gets quite satisfactory energy output.

Can anyone help me on the piezoelectric energy harvesting issue? I also attach the photo and primary experiment.

Thank you
Bundit

[MonsieurM]

check this out .... it might help

Bismuth-Ferrite Piezoelectric Material Opens New Roads for Energy Generation - The Green Optimistic

[bundit]

Thanks for the post.

[Ernst]

Perhaps, it could help if you would use Ge-diodes, as those have a lower voltage drop.
But you would probably need 2 in series to handle this voltage with a safety margin.
Also I would use an oversized ceramic capacitor (for a much higher voltage).
It seems that you need at least about 135 nF to store the energy of one pulse. I don't know how many pulses you want to collect in the capacitor before you will 'process' this energy.
I would also double this size as well, just to be safe.
So for example:
To collect 10 pulses you will need 1.35 uF, so I would take 2.7 uF/600V, that should give you about 35 Volt.

20 mV x 470 uF = 9.4 uC per pulse
9.4 uC / 70 V = 134.3 nF
10 pulses = 94 uC
94 uC / 2.7 uF = 34.8 V

Well, to be honest, I do not have much experience with piezoelectric devices but this is how I would start out.

Ernst.

[Dave45]

Can we use the Z pinch to hammer a piezoelectric crystal?

Can we make our own crystal using ice formed in a magnetic field?

Some questions I intend to follow up on soon.

The Z-Pinch Effect - Chuck Missler - YouTube

[bundit]

Thanks for your calculation but a few confuse with its for back-forth in the equation C=Q/V.


By the standard charge storage by a capacitor, the voltage increase

Perhaps, it could help if you would use Ge-diodes, as those have a lower voltage drop.
But you would probably need 2 in series to handle this voltage with a safety margin.
Also I would use an oversized ceramic capacitor (for a much higher voltage).
It seems that you need at least about 135 nF to store the energy of one pulse. I don't know how many pulses you want to collect in the capacitor before you will 'process' this energy.
I would also double this size as well, just to be safe.
So for example:
To collect 10 pulses you will need 1.35 uF, so I would take 2.7 uF/600V, that should give you about 35 Volt.

20 mV x 470 uF = 9.4 uC per pulse
9.4 uC / 70 V = 134.3 nF
10 pulses = 94 uC
94 uC / 2.7 uF = 34.8 V

Well, to be honest, I do not have much experience with piezoelectric devices but this is how I would start out.

Ernst.

[Ernst]

Confused?

Ok, let me try to explain what I was thinking (I can be wrong, as I have said I have little experience with piezo electricity).

Assuming that 1 pulse in a 470 uF capacitor resulted in 20 mV, that would mean that 1 pulse releases a charge of 9.4 uC. You said that this pulse has a maximum of 70 Volts. So I should choose a capacitor in which this charge (9.4 uC) stays below 70 Volts, otherwise the capacitor will not accept the full charge. This means the capacitor has to be bigger than 135 nF for every pulse you wish to collect.
Say you want to collect 10 pulses before you drain the capacitor again, then you would need a capacitor bigger than 1.35 uF. So I would start with a 2.7 uF capacitor.....

You were using a 470 uF cap. Of course, that is a valid option, but the resulting voltage is so low that it is difficult to use.

Well, those were my thoughts....

Ernst.