Author Topic: a magnetic idea (Read 4851 times)

hvirtane · « **on:** October 10, 2006, 04:37:00 PM »

Some time ago I found in an old book an idea to convert heat energy into mechanical energy using permanent magnets. This idea probably works, but has anybody got any idea about the efficiency? Please see the picture.

- Hannu

inode buddha · « **Reply #1 on:** October 10, 2006, 01:17:09 PM »

I have never heard of this, but it is interesting. I did know that iron loses its magnetic attraction a high temperatures. I'm willing to wager that any useful mechanical output is no greater than the heat value of the input. But it may be a very fascinating machine, and it looks like something I could afford to build and test over the next few months.

wooferhound · « **Reply #2 on:** October 10, 2006, 02:49:45 PM »

It would be slow . . .

dinges · « **Reply #3 on:** October 10, 2006, 03:45:29 PM »

I think they're making use of the Curie-effect. Above a certain temperature, steel loses its magnet properties. For steel, it is about 700 deg C (from memory; don't shoot me if I'm wrong).

http://en.wikipedia.org/wiki/Curie_point

The heating and cooling is a relatively slow method. I doubt it would make a useful, practical generator, but it should work, in theory.

Ungrounded Lightning Rod · « **Reply #4 on:** October 10, 2006, 04:53:09 PM »

Right.

Also: Just below curie temp it becomes very susceptable to magnetization.

I doubt it would make a useful, practical generator, ...

It's a heat engine. Even if it was VERY good it wouldn't be any better than carnot cycle. And it is working on the very narrow temperature range between above- and below- curie point, so it would be very inefficient.

Better to use a more optimized heat engine with a decent working fluid and a large temperature difference between hot and cold sides, and hook it to a genny.

hvirtane · « **Reply #5 on:** October 10, 2006, 05:10:00 PM »

I don't think it to be very efficient. Just trying to investigate ideas to use solar heat energy simple ways.

What about changing the device so that there would be a shielding tube to reduce the magnetic force instead of heating the ring? Would it work? What kind of material could be used for the tube? Would for example heated steel work?

Please see the picture.

- Hannu

Ungrounded Lightning Rod · « **Reply #6 on:** October 10, 2006, 06:00:08 PM »

Nope.

It's a perpetual motion machine of the first type: Energy from nothing. Doesn't work.

This particular version fails because it takes as much force to insert a segment of the disk into the "shield" as you lose in attraction from being "shielded". No net torque.

WXYZCIENCE · « **Reply #7 on:** October 10, 2006, 08:13:50 PM »

Hvirtane, I have a soldering iron by Weller that uses the effect you describe to control the temperature of the tip 600 to 800 degrees. I think it your design would be very slow turning.

Joseph.

hvirtane · « **Reply #8 on:** October 11, 2006, 01:07:52 AM »

"the effect you describe to control the temperature of the tip 600 to 800 degrees."

How does the switch (to cut the electricity) work? Maybe the same way we could control the temperature of some other things, too.

- Hannu

hvirtane · « **Reply #9 on:** October 11, 2006, 01:16:52 AM »

'it takes as much force to insert a segment of the disk into the "shield" as you lose in attraction from being "shielded".'

Might be. I think that with this 'shielded' version the magnetic flux might concentrate to the ring on the front of the 'shield'. But if we would use heat energy as the method to achieve the 'shield', the energy is not created from 'nothing'.

- Hannu

Ruud · « **Reply #10 on:** October 11, 2006, 03:29:22 AM »

coincidentally I made my fist Curie engine a few weeks ago. Click here to see a video of it. (1,2MB) See also picture below this comment.

As for the design of your Curie engine, I wouldn't use one solid ring or disk if I were you, but divide it into isolated segments as the heat will otherwise spread out rapidly over the entire disk, minimizing the differences in magnetic strength. Also, use nickel instead of iron, as it requires far less heat.

Try to find something as close to pure nickel as possible. I used an old nickel Coin (French Franc) which worked pretty good, but coins with lower percentages of nickel, such as the Euro coin were much harder to 'demagnetize'.

(The curie point of nickel is around 350 degrees celcius, iron needs to be about twice as hot)

hvirtane · « **Reply #11 on:** October 11, 2006, 03:59:14 AM »

Click here to see a video of it."

Your engine looks interesting. Could you, please reformat your video in another format so that it would be usable outside microsoft systems?

- Hannu

Ruud · « **Reply #12 on:** October 11, 2006, 05:03:00 AM »

I'm sorry Hannu, I've tried but WMV is the only format I can save them in from M$ moviemaker.

hvirtane · « **Reply #13 on:** October 11, 2006, 05:42:06 AM »

"WMV is the only format

I can save them in

from M$ moviemaker."

Not even 'mpeg3' or 'quicktime'?

- Hannu

Slingshot · « **Reply #14 on:** October 11, 2006, 09:43:35 AM »

Moviemaker can only save files in two formats, .avi and .wmv. Of the two, only .wmv is sufficiently compact for internet transmission.

If you have any version of Nero, it will transcode .wmv to MPEG-1. Just use the "Video CD" option from the menu.

ghurd · « **Reply #15 on:** October 11, 2006, 10:23:00 AM »

That is the first time I saw one actually work.

It is faster than I expected.

G-

Ungrounded Lightning Rod · « **Reply #16 on:** October 11, 2006, 02:58:03 PM »

Heat doesn't create a "shield".

Heat causes the electrons in the metal to flip spin states sufficiently that they stop being attracted to the magnet.

See the above about "heat engines": It works, but very poorly.

stephent · « **Reply #17 on:** October 11, 2006, 06:37:44 PM »

Not sure about using a Mac---but Linux can play those files using Kaffeine.

RP · « **Reply #18 on:** October 11, 2006, 08:07:54 PM »

Plays fine on my Mac OSX.3 but I use Flip4Mac so Quicktime can play them.

Ungrounded Lightning Rod · « **Reply #19 on:** October 12, 2006, 09:41:26 AM »

The curie-point transition is very abrupt. The metal has its greatest magnetic susceptability just below it (because the heat is jogging the electron spins and they flip easily), none at all just above it. So only a very small temperature change is necessary to make the switch, letting it cycle quickly.

The problem for efficiency is precicely the small difference in temperature between the two operating points. Virtually all of the heat's energy is wasted, only the amount from its passage through that narrow temperature band participates in the carnot cycle.

hvirtane · « **Reply #20 on:** October 13, 2006, 07:01:35 AM »

"Virtually all of the heat's energy is wasted, only the amount

from its passage through that narrow temperature band

participates in the carnot cycle."

But that narrow temperature band also allows it

not to waste the energy?

We can keep for example the ring (in my picture)

very near the transition point all the time by using for example

a solar mirror and some good insulation...

If the ring would be made of isolated pieces

of nickel iron and ...

- Hannu

Ruud · « **Reply #21 on:** October 13, 2006, 08:03:23 AM »

I agree with Hannu. It takes a while before the metal gets hot enough, but after that, the metal will remain hot and it only takes a small amount of energy to get it over the curie point.

Actually, if you want high RPM, it might be more of a problem to cool the metal fast enough for the next rotation, than it is to heat it.

dinges · « **Reply #22 on:** October 13, 2006, 08:15:08 AM »

Do as someone else suggested: calculate the Carnot-efficiency of the contraption, and weep.

Carnot eff. = (Thigh-Tlow)/Thigh

(all temperatures in Kelvin)

note that a small temp difference (a few degrees) lowers Carnot efficiency to nearly zero. Let's assume a temp difference (Thigh-Tlow) of 10 deg. K (=10 deg.C); Thigh, assuming to be the Curie temp, of steel, is 1043K.

Carnot eff = 10/1043 = .01 = 1%.

Now, even for a heat engine, that is lousy.

And yes, I know that with a parabole you could get 'free' energy, so some may say efficiency doesn't matter. It does to me though.

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Author Topic: a magnetic idea (Read 4851 times)