Captret - Capacitor and Electret

[nul-points]

I can verify that a bit charged capacitor will rise in voltage with temperature.

I had a few years back done an experiment, where I had several 100 nF ceramic caps in parallel charged up to 2 Volts or so and when I used a hairblower to blow hot air at them and heated them up this way, the voltage rose to over 10 Volts when I remember correctly.

I just wonder, if this effect could be used for an efficient  thermo to electric generator ?

[..SNIP..]

The question is, if it is enough to discharge the caps, so they will fall in voltage again and if the voltage will rise then again due to them being still hot, or if one has to cool them down again, before a new heating cycle can begin ?

hi Stefan

someone once said "there's nothing new under the sun"

and we seem to prove that statement quite often on this forum - there's so much information - it's easy to miss something relevant and a lot of duplication of effort occurs!


i also did an extensive study of capacitor self-charging a couple of years back and reported my results (from a full months datalogged data) which clearly showed capacitors could self-charge even whilst shunted with a light load resistance:

  http://http://www.overunity.com/index.php?topic=9393.0

the anomalous voltage increase was not due to previous charge because in one case the capacitor had been constantly shunted with a load resistor for 6 months before recording a linear increase in self-charge voltage - temperature being one of the main correlations with the capacitor voltage

all the data was obtained at room temperature


my latest experiment builds on this effect using DIY Zn-Cu cells in conjunction with a ballast capacitor

the results for the first 1000 hours (from early december '10) show that it's possible to sustain/charge the cell using ambient room heat at the *same time* as the cell is permanently connected to an LED flasher circuit as a load - ie. this arrangement is OU, like a solar cell, drawing its sustaining input power from ambient heat

  http://www.overunity.com/index.php?topic=10174.0

so i'd say it's not necessary to cool before recharging - i believe the heat input can be converted to electricity and stored at the same time as the load is taking what it needs

cheers
sandy

[hartiberlin]

I can verify that a bit charged capacitor will rise in voltage
with temperature.

I had a few years back done an experiment,
where I had several 100 nF ceramic caps in parallel
charged up to 2 Volts or so and when I used
a hairblower to blow hot air at them and heated them
up this way, the voltage rose to
over 10 Volts when I remember correctly.


I just wonder, if this effect could be used for an efficient
thermo to electric generator ?

Maybe one can just use Fresnell lenses or silvered satellite dishes
to heat a capacitor bank and then discharge it into a load and recharge
it again via the heat ?

This would need probably need very heat dependend dielectricums.

The question is, if it is enough to discharge the caps,
so they will fall in voltage again and if the voltage
will rise then again due to them being still hot,
or if one has to cool them down again, before a new
heating cycle can begin ?

I guess this should be a neat test to see, how much
difference energy a heated ceramic cap from 20 degrees Celsius
to 100 degrees Celsius can deliver ?

Hi All,
I just redid this experiment again, cause i just found this 10x 100 nF cap bank.

Well, putting it onto a digital voltmeter and charging it up to around 5 Volts did
discharge it too fast.

Then I pulled out my trusty old Hameg HM312 scope with its 100x scope head
which has a 100 MegaOhm input impedance.
Scope ground was tesafilm taped, so the earth ground
had no connection to the scope ground and capbank could
not charge up this way...

Then I gave this capbank a charge from an old 9 Volt battery, which
has still around 5 Volts.

The voltage at the capbank of 1 uF stays at 100 Megaohm fairly long charged
up this way.
Then I used again a hairblower to heat up the caps.
The voltage rises to about 10 Volts this way after a few seconds and
the caps are pretty hot then.

So this principle works quite nicely and I will try to buy now
many more 100 nF caps and research, which caps
have the best heat dependence.

I also tried it with my 2700 uF 35 Volts
electrolytic cap, but it did not rise up the voltage,
maybe in the millivolts range, but definately not in the Volts range...

So I guess ceramic caps are the best for this and with this
effect it could be build probably a great thermo to electric energy
converter..
As these 100 nF blocking caps are also dirt cheap, you can buy
very many at very cheap prices...

So this upcoming summer I will have a good use for
my fresnell lenses I recently bought...

I think it is best to use already about 5 to 10 Volts as the starting
voltage and then heat it up,
as I saw, that starting with just 2 Volts it did take much longer to
get the voltage to 4 Volts , so doubleing the voltage is easier,
if the cold start voltage is already higher.

Then it is best to use a few white LEDs in series
as the load, so they have a higher threshold voltage.

So if one starts with 10 Volts and heats this capbank up,
at least 4 x 2.5 Volts threshold white LEDs should be put in series,
so that the capbank voltage will never go lower as 10 Volts
and all over 10 Volts will light up the LEDs permanently,
but under 10 Volts they will just switch off...

So a few LEDs in series are the perfect load for such
a thermo to electric generator.

Regards, Stefan.

[hartiberlin]

Here is a quick picture from the experiment,
so you see, what I mean.

Regards, Stefan.

[hartiberlin]

Okay, in this experiment I won 37.5 mikroJoules when going from 5 to 10 Volts on
a 1 uF capbank.

When using 100 uF as the capbank ( many more 100 nF caps in parallel)
and starting at 10 Volts and heating it up to 20 Volts you
already win 15 milliJoules !

Now when using just 1 Farad as the capbank and
then going from 10 Volts to 20 Volts you already win
150 Joules ! That are 150 Wattseconds, that means
more than 2 Minutes you can draw already 1 Watt !

So then it really gets interesting !

Now what is the easiest method to get a large capbank and
what is the best and cheapest cap material for this ?

[ibpointless2]

Okay, in this experiment I won 37.5 mikroJoules when going from 5 to 10 Volts on
a 1 uF capbank.

When using 100 uF as the capbank ( many more 100 nF caps in parallel)
and starting at 10 Volts and heating it up to 20 Volts you
already win 15 milliJoules !

Now when using just 1 Farad as the capbank and
then going from 10 Volts to 20 Volts you already win
150 Joules ! That are 150 Wattseconds, that means
more than 2 Minutes you can draw already 1 Watt !

So then it really gets interesting !

Now what is the easiest method to get a large capbank and
what is the best and cheapest cap material for this ?

Wow i like where this is going!

150 Joules is a good bit of power, but you'll need a good bit of those capacitors too. This could get very expensive if we don't use the right capacitors. Maybe we could make our own, have them custom built into a parabolic shape to help in gather the most energy from the sun? I even had the idea to make a chairs seat out of capacitors so that when you sit your body heat made power to run a LED.

The big question is if this is better than a solar panel? These caps only need heat so no need for the sun, but the sun does give off a lot of heat. I wonder if you could paint the capacitors black to help them absorb more heat energy? You could make a custom one to put on a car and have it generate power, or even put it on your house? Hook it up to a 12 volt battery and have it charge that battery and use your LED diode idea to keep the battery charging.

Now the big question is if we can build our own custom Ceramic capacitors?