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Turn ordinary fan into an induction heater?  RSS feed

 
Bill Bianchi
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I heard about an inventor who converted an ordinary house fan into a heater. Supposedly, the fan did not draw much more electricity than normal when used as a heater.

In trying to figure out how this was done, if indeed it was, I came up with a guess.

I think he attached magnets to the blades so they spin. Then, I think he installed an aluminum ring close to those magnets, close enough that the fields from those magnets reached the aluminum ring.

My theory is that the spinning magnets, which spin when the fan is on, created eddy currents in the aluminum ring, which heated the ring. Air from the fan blades flowed past the hot ring, which heated the air, turning the fan into a bastardized heater.

I can't see how this would not consume more electricity than normal, meaning it seems like it would be less efficient that a standard electric heater. But, it does seem like it would function.

This would make for a fun experiment that I would like to try. Any suggestions as to how to go about it? Doesn't seem too complicated. Would using a metal screen work better than a ring? Is there a better metal to use than aluminum?

Would anyone here (in USA) be able and willing to measure the results? I might be willing to buy 2 identical fans (we'd use them anyway) & convert one to a heater. If someone here had the equipment necessary to measure & compare the electric usage of the converted and unconverted fans, along with the heat output, and they promised to send them back afterward and openly share the results on these forums, I'd be game.

If it worked, I'd also show how it was done,.

Who knows, maybe it would lead to cheap windmills/hydro/stationary bicycle units that heat a working fluid or cook something, rather than generate electricity? Or, a stupid way to use an electric drill or small engine to heat water in a metal container. At the very least, we'd know yet another way not to heat something.

Again, I doubt the efficiency of such a beast. This is more curiosity than an actual attempt to solve all of mankind's energy needs. LOL. But, WTH, it would be interesting and fun to do.

 
Ken Grunke
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I honestly have never heard of the theory of magnets inducing eddy currents in aluminum and heating it up, but I'm not an engineer. You could test it out by getting a small cheap fan and a ring from an aluminum skillet or saucepan that is close to the fan's diameter, with the bottom cut out. Both available at thrift stores. Magnets from some old hard drives - there are two very strong magnets in one unit. Epoxy them to all the fan blades, then somehow cobble up a way to mount the aluminum ring to the fan housing.
Turn the fan on, hoping that the magnets are well glued and balanced on the fan blade.
If you feel any warmth in the ring, then rejoice. Don't expect it to get hot. A basic law of energy and thermodynamics is you cannot get more energy from something than what is put in. If what you say about the magnets affecting the aluminum is true, they will probably introduce some drag and resistance in the process. This will cause the motor to have to work harder, and electric motors generate heat when they do work. I think it's safe to say that the motor will produce more heat than the magnets and aluminum ring.
Don't let anyone's skepticism dampen your enthusiasm. Experimentation is fun!

 
Bill Bianchi
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I saw an experiment on YouTube where a guy boiled water by spinning permanent magnets around a small metal cup. He used an electric motor to spin magnets, but after reading your comment about the motor heating up, I'm more interested in a human powered unit. Also, induction cookers are on the market and they use this heating method, though they use electromagnets rather than spinning permanent magnets---As Seen On TV infomercials. So, I'm confident spinning magnets near metal will heat that metal.

Is there any use for a motion-to-heat device? No idea. First step is to prove it works. If it does and can be human powered, then maybe it can be useful to someone, somewhere, during some situation.o
 
Dave Jackson
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This is very interesting. I am very interested in this as well as I just realized that I have these enormous fans going perpetually to heat and cool my home and office that are essentially going to waste. I figure I should be able to harness some electric back off of them to help improve efficiency of the devices, but also realized that I can circulate air in our attic, thus helping a bit. Seems like this could be something quite useful to add to this, especially in the winter for adding some heat to the mix.
 
Bill Bianchi
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Hi, Dave. Don't get too excited. As mentioned earlier, converting a house fan to an induction heater will require the motor to work harder to overcome the resistance to rotation caused by the eddy currents. This means the fans will draw more electricity to turn than they normally would without the magnets and metal ring. How much more? I don't know. That's why I asked if anyone here had the know-how and equipment to measure both the input electricity and the output BTU's. Figured we could calculate the energy efficiency, or lack there of from that.

I seriously doubt a converted fan will be anywhere near as efficient or energy saving as a portable heater. This is not free energy, or even less costly to run than a regular heater.

This is mostly curiosity on my part. If it works, I'll be looking into using human power and things that can be done using human powered induction heating. Hand-cranked Fuel-less cigarette lighter/fire starter? Maybe. Bicycle powered water cup boiler? Probably.

Nothing earth shattering, here. Just an interesting DIY method I think would be interesting to explore.
 
Troy Rhodes
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Due to the various laws of thermodynamics, we can be sure that if you get 500 watts of heat out of your converted fan, the fan will draw an additional 500++ watts of electricity to produce that heat.

In summary, the paraphrased laws state that:

1. You have to play the game by the rules, no exceptions.

2. The best you can do, energy-wise, is break even. If you put 500 watts of energy into a device, the best case scenario is that you will get 500 watts of useful converted energy/motion/work out of the device.

3. In real life, you can't even break even, ever. There are always losses when you convert energy from one form to another form.


troy
 
wayne fajkus
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Good point troy, but that would be true with any electric heater. Would this be more efficient than a resistance type heater.

It's like a microwave oven to boil water vs a stove top. There should be no argument that the microwave wins.
 
Topher Belknap
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Bill Bianchi wrote:I seriously doubt a converted fan will be anywhere near as efficient or energy saving as a portable heater.


Why? Where is that energy going if not into heat?

A converted fan is almost exactly as efficient as an unconverted one, which is almost exactly as efficient as any other electric heater. Or computer, fax machine,...

A fan increases the speed of air molecules, which if there are confined to the building, just means that the temperature of that air went up. How much? By the watts consumed by the fan (minus the heat that the fan puts into the housing etc., which also eventually probably end up in the air). Thus a fan is an extremely efficient heater.

[note: whether the converted fan draws more power is probably dependent on the particular design of the fan electronics.]

Thank You Kindly,
Topher
 
Troy Rhodes
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Turning electrons into heat turns out to have an efficiency of unity, or 100% if you will. So the induction heater fan will be more or less exactly as efficient as a resistance heater.

Heat pumps are often cited as the exception to the rule, except they are not really turning electrons into heat, they are using electricity to move heat from point A to point B, and can have efficiencies of much higher than unity or 100%.

But that's not really an apples to apples comparison, and no rules of thermodynamics are broken.

In the example of the microwave versus the stove, the heat is created with 100% efficiency in both cases, but the microwave puts virtually all the heat into the water, where you want it. The stove does not.


An air source heat pump might have a COP of 3 or 4, meaning it "produces" 3 or 4 units of heat for every unit of electricity you put in. 3-400% return on investment if you will.

All resistance heating (which includes eddy currents) are 1:1. One unit of electricity in, one unit of heat out.

troy
 
Bill Bianchi
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Wow, that was amazingly confusing. You threw around 100% + efficiency ratings like confetti. I thought there were losses in generating the electricity to power the heaters, transporting that electricity through the power lines, and converting the electricity to heat. Seems like a lot of losses to rate a 100% efficiency. And, a fan is as efficient a room heater as a standard electric heater? Mine just make me feel cool when they blow air on me.

Guess you can tell I'm no physicist.

 
Troy Rhodes
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It all has to do with how you define the system.

If we are trying to decide if the microwave is better than the stove, it's not that helpful to look at what goes on at the power plant and distribution system. In that limited context, both turn electricity into heat with 100% efficiency. The stove manufacturer might use that kind of argument b/c it makes the stove look just as good as the microwave. Of course, in real life, the microwave puts more of the resultant heat into the water, and is more efficient in the real world.

If we are trying to decide if solar panels on my roof are "better" than grid electricity, with regards to the planet, OK, now we have to consider the fact that the distribution system wastes 25% or more of the electricity from the power plant. And if we include externalities like the energy to mine the coal, and scrub the exhaust, and do -something- with all that extra CO2, then the solar panels start to look very good indeed. In this context, we dang well better think about all those other external inefficiencies because it helps us make an informed decision.

But to compare the magic induction fan/heater invention with a plug in resistance heater, it is permissible to ignore all the other inefficiencies of grid electricity, because those outside-of-system inefficiencies don't affect our comparison of the new magic fan to the traditional resistance heater.


hope that illustrates why we can -sometimes- ignore all those other inefficiencies.

troy
 
Topher Belknap
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Bill Bianchi wrote:And, a fan is as efficient a room heater as a standard electric heater? Mine just make me feel cool when they blow air on me.


This is evaporative cooling for you. It cools you at the expense of heating, and increasing the humidity in the room. The sweat on your skin evaporates more readily in a breeze, and takes 970 BTUs of heat (per pound) to make the transition from liquid to gas. That heat comes from you, making you cooler.

Thank You Kindly,
Topher
 
Bill Bianchi
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Okay, once again. I'm going to play with this low-tech induction heating because it's interesting and because it may turn into a way to turn human-powered motion, or natural motion (wind/water) into a novel heating application.

This will not save the world. This is not free energy. It is not a model of efficiency. No laws of physics are being challenged. No magic, good or evil, is involved.

Right now, if you have a stationary bicycle hooked to a generator/alternator and you want a cup of hot coffee from your exertions on the bike, you would charge a battery, then power a heating element from the battery, which would heat your cup of water. That is motion into electricity, electricity into heat, then a cup of Joe.

Using induction, your peddling would spin magnets near a metal cup of water, the metal cup would get hot due to eddy currents, which would heat the water, which would give you a cup of hot Joe. Motion to heat, cutting out electricity generation, electricity storage, and electric conversion to heat via a heating element powered by the battery.

I'm fairly confident the magnets and cup would be less expensive than the battery, generator/alternator, and heating element. Economical efficiency for this limited application? Maybe. An interesting way to heat a cup of water that family and friends probably haven't seen before? Probably.

Then again, only the known is safe. Anything different is bad and must be discredited the moment it rears it's ugly head. Thou must not suffer a witch to live, and as mentioned, this be magic of the darkest kind.
 
Troy Rhodes
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Carry on. Take pictures. post results.

Here's a cool video demonstrating Lenz law, which is all about induced eddy currents. It also gives some insight into how the magnet(s) should ideally interact with the metal.

http://video.mit.edu/watch/physics-demo-lenzs-law-with-copper-pipe-10268/


troy
 
Bill Bianchi
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Thanks for the video, Troy. It demonstrates why this is not free energy.
 
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