[NewCandle] Energy Harvesting

[Horace Heffner]

On Oct 22, 2008, at 4:26 PM, Keith Nagel wrote:
>
> So what else can we use? Yea olde magnetic pickup. I'm imagining
> something like a speaker cone arrangement.

How about a plain old variable gap capacitor?

If you use mechanical energy to pull apart two plates having a charge  
then work is done and the voltage necessarily rises. You can now  
discharge the plates through a circuit to obtain the electrical  
energy. All you need in addition is a trickle charge to maintain the  
average charge on the plates and full wave rectification.

      D1                   V1
P---|>|---R1--o-------C2--o---B1--------Load
|             |               |           |
G     Mech.==>C1              G           G
               |
               G

   Fig 1 - Diagram of mechanically driven capacitor gap power supply

In Fig. 1 a HV DC power supply P and D1 maintains a high voltage by  
trickle charge through on the plates of a variable gap capacitor C1,  
the gap of which is varied by mechanical power.  The AC power from  
generated by the mechanically driven gap oscillations of C1 are  
transmitted through the DC current blocking capacitor C2 and a  
rectifying bridge B1 to the load.

One advantage to this design is the RMS voltage V1 is only limited by  
the gap breakdown voltage, thus the advantage is avoiding in many  
cases problems obtaining sufficient voltage to effectively drive a  
bridge rectifier B1.  If a sufficient voltage V1 is difficult to  
obtain, it is still possible to drive a FET bridge B1 (and diode D1  
if necessary) using plate position sensing or potential sensing  
circuitry to drive the gates provided the energy required is not  
excessive.

An alternative to power supply P plus D1 is to eliminate them and  
make at least one plate of the capacitor C1 a charged electret.

Best regards,

Horace Heffner
http://www.mtaonline.net/~hheffner/




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