Captret - Capacitor and Electret

[ibpointless2]

Hi Stefan,

A hair dryer uses about 500+ watts. Do you think painting the caps flat black and using a couple infrared or small 3v laser diodes to heat them will give better efficiency?

The hair dryer is to test the concept, The capacitors will work at room temp. The Laser idea sound cool but its more of a focused energy, but only one way to find out.

[hartiberlin]

I am not sure whether you are referring to negative temperature coefficient of capacitance. There many non-electrolytic materials capable of yielding higher capacitance when subjected to heat.  Barium Titanate is one of those having negative temperature coefficient of capacitance at room temperature.

Yes, my test was with ceramic caps, not electrolytic caps.
These have a strong negative temperature coefficient of capacitance.

Self-compensating is not necessarily self-charging. Take a look on the following equations:

Q = C * V
dQ/dT = V * dC/dT + C * dV/dT

If Q does not change (i.e. dQ/dT=0), decreasing capacitance (i.e. negative dC/dT)  means increasing voltage (i.e. positive dV/dT).

But I believe the Q does change in some situations.

You are right, I forgot, that the C capacitance will decrease and that is
why the voltage rises, but as the voltage goes into the energy formula as square
Energy= 0.5 x C x V^2
I guess this nonlinearity can be used to still generate power this way via
heating such caps.
I will just try it.
Regarding the laser idea, yes any heat can be used and painting
the caps black will also help.
The question is, if there are other cap materials that have even
a stronger negative temperature coefficient than Y5V dielectricum
material.

What about Tantal electrolytic caps ?

Regards, Stefan.

[Ghost_Rider]

Try placing your caps in the sun, like on a roof. Might be better than solar panels.

[ibpointless2]

I had some 104m ceramic capacitors laying around so I tested them to see if they would pick up radiant heat energy.

I was able to get around 100mV from one cap when I touched the cap with my hand. I got around 300mV when I placed it in front of my heater. But the best part was the reading I was getting when I left it sitting in room temperature. Sitting in the room temp I got around 2mV and hooking another one in parallel gave me a little over 3mV. So even ambient heat energy can be collected, and since the ceramic caps are cheap we can make a nice collector. I would like to see how they would do in sun light, maybe I could increase the effect with a magnifying glass. Many possibilities are opening now.

So it looks like the caps are really converting heat into energy.

[ibpointless2]

It also seems that heat is not the only thing that contributes to the power, pressure is a factor too. It seems that the ceramic capacitors can act like piezoelectric too.

Wikipedia: "Capacitors, especially ceramic capacitors, and older designs such as paper capacitors, can absorb sound waves resulting in a microphonic effect. Vibration moves the plates, causing the capacitance to vary, in turn inducing AC current. Some dielectrics also generate piezoelectricity. The resulting interference is especially problematic in audio applications, potentially causing feedback or unintended recording. In the reverse microphonic effect, the varying electric field between the capacitor plates exerts a physical force, moving them as a speaker. This can generate audible sound, but drains energy and stresses the dielectric and the electrolyte, if any.” http://en.wikipedia.org/wiki/Capacitor

I’ve confirmed this with my 104m ceramic capacitor by squeezing my pen against the outer case of the ceramic capacitor on a table. Just like a piezo you must tap pressure against it, just applying a constant pressure does not work.