# Piezoelectric Generator Project

Discussion in 'The Projects Forum' started by Aero, Mar 8, 2016.

1. ### Aero Thread Starter New Member

Jan 18, 2012
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This is what i have: (10) 27mm piezoelectric transducers (actual PZT crystal size is 18mm in diameter x .01mm? very thin), vibrated once per second. With each having varying output ranges of voltages from, 0.7 volts to 2.3 volts, after 2200 seconds. And utilizing a good harvesting module, storing the output to rechargeable batteries, Will i be able to use this voltage to charge a cell phone battery?

2. ### RichardO Well-Known Member

May 4, 2013
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The short answer is: "No". Here are some quick numbers:

The energy (in watts) in a capacitor is (voltage squared times frequency times capacitance)/2. Your transducers probably only have a few nF of capacitance. If we assume something like 0.05 uF each then you would have about 0.5 uF total. Lets also assume that voltage is 1.5 for all of the transducers. 1.5v squared times 1 second times 0.5 uF is about 1 micro Watt. 2200 seconds is about 1/2 hour. So, accumulating this energy for 2200 seconds, that is only 0.125 watt hours of energy. I am guessing that the battery in your phone is more like 10 watt hours. You will only be able to get a fraction of the power from the transducers into the battery.

3. ### Aero Thread Starter New Member

Jan 18, 2012
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Thanks for the reply, I'm sorry i posted a cell phone battery, when i meant a 1.2 volt 2500mAh rechargeable battery. So 10 piezoelectric transducers outputting 0.5 volts each, connected to a 470uF capacitor. After 57 steps you should have about this much energy in a capacitor:
(E=1/2*C*V^2), E= 1/2*470uF*267.9V =16.86605 Joules divided, by 57 steps equals 0.2958956 joules per step. Using the 1.2 volt battery as a target, it should take about 3,041.61 steps or 1.383 miles, to charge the battery. My goal is to create a system for charging small batteries through human motion in order to light up a few bright LED's for at least 4-5 hours a night. Giving people an alternative to burning kerosene, wood, dung, etc., which contributes to Hut Lung Disease. The key was finding a reliable delivery system. Couple that with a harvesting module and battery, i believe a viable product may arise after with real world testing. Again Thanks for replying and any help on this project is absolutely appreciated.

4. ### Alec_t AAC Fanatic!

Sep 17, 2013
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Afraid not. Since the capacitances of all the transducers and the 470uF reservoir cap are in series, the total capacitance is about one tenth of the capacitance of an individual transducer, so very small (certainly not 470uF!). I prefer Richard's figures in post #2.