Author Topic: Eddy current water heater (Read 14269 times)

fungus · « **on:** November 07, 2006, 09:25:52 PM »

I was thinking that with water heating wind generators, they would be quite ineffecient. Would this work? The orange is copper pipes and the red is coils to power a small water pump, pumping water to a heat exchanger. I guess this would most likely be used with a VAWT or else a 'water slipring' would have to be constructed. Would this design work or would there be too much ineffiency in the piping?
This is a quick mockup of what the stator would look like:

Titantornado · « **Reply #1 on:** November 07, 2006, 02:47:37 PM »

Hmmmmm, if it would work, I'd think this would cause more heating. (though I could easily be wrong)

windstuffnow · « **Reply #2 on:** November 07, 2006, 04:17:23 PM »

Rods diagram would work better but if you soldered the tube to a copper plate you'd get much more heat from it.

I've built one that way and it will heat 5 gallons of water from 70* to 140* in under 10 minutes at approximately 200 rpm. The test disc was 8" in diameter and had 12 magnets on it and was driven by my lathe. I had a small circulation pump on it as well. They work pretty good. I've only played with it on a small scale so far but I'd bet a large unit driven by a VAWT would produce some decient hot water. Just another one of my circular projects ( 'round to it )

.

RP · « **Reply #3 on:** November 07, 2006, 05:33:21 PM »

Here's how I'd do it. Make a shell from soldered copper sheet with an impeller inside it. The flux from the rotating magnets turns the impeller thus increasing the pump speed as the rpm and (heat power) increases. Dual rotor would work well with this too.

The big problem with any of this will be heat losses in the the supply and return lines though...

gizmo · « **Reply #4 on:** November 07, 2006, 05:33:50 PM »

This thread may interrest you. Its directly heating the water in the tank using a VAWT.

http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=230

Glenn

vawtman · « **Reply #5 on:** November 07, 2006, 05:39:06 PM »

Hello fungus

Why do you think this idea would be more efficient than simply running a heating element?

Seems to me by the time you got the heat to where you needed it everything would be lost has i am.

Nice thoughts though.

electrondady1 · « **Reply #6 on:** November 07, 2006, 06:21:21 PM »

ed's results sound incurageing ,

realy like the looks of titans diagram

if the geni was close to the radiator it would be simple to insualate

electrondady1 · « **Reply #7 on:** November 07, 2006, 07:36:08 PM »

the more i think about his he better it sounds.

since stator heat can be a problem

it has been reported that temperatures of 400 degrees can be produced.

if it's possible to capture the normaly damaging stator heat we might be able to increse the efficiency

if a single sheet of copper or aluminum were introduced between the mag rotors the gap between rotors could be reduced conciderably increaseing flux density.

i'm thinking the coolant tube could be bonded to the metal sheet at its outside edge . out past the magnets.

rp i think your idea for a pump built right in is slick.

oh no!

more experiments!

Titantornado · « **Reply #8 on:** November 08, 2006, 05:10:01 AM »

The more I thought about my design, the more ideas come to mind. Like, instead of 1/2" tubing, why not bundle two lines of ice maker tubing (1/4") together instead, then just manifold them together where they exit. It would allow the magnets to come closer together, increasing the flux, and increase the surface area to the fluid.

Hmmmm, I might have to build an experiment around my unfinished turbine. I got some ice maker line sitting right there by the rotors . . . . . . . .

kitno455 · « **Reply #9 on:** November 08, 2006, 05:42:09 AM »

would you need to be able to adjust the airgap to prevent stalling at low wind speeds?

allan

Titantornado · « **Reply #10 on:** November 08, 2006, 08:02:37 AM »

I'd imagine so. Or, bigger blades. The tank style RP suggested would have a massive amount eddy current drag, though, I love the built in pump idea. I guess if it's diameter was kept small enough, it wouldn't be too bad, but then, would that give the fluid enough time to pick up the heat?

vawtman · « **Reply #11 on:** November 08, 2006, 05:32:44 PM »

Oh goodness Ed would this design for heating water be better than the axial and elements?

Now you got me thinkin through the roof with the turbine.

Thats all i want is water heating capabilities with the turbine.

Any chance for a drawing? Sorry to be a bother.

This whole thing is getting cool i mean hot.

How do the eddies effect turbine startup?

Thanks

windstuffnow · « **Reply #12 on:** November 08, 2006, 08:38:03 PM »

Hi Vawtman,

I really don't know but it seems to me the eddy current heater, being a direct source, would be more efficient than an alternator heating an element. Any power you put into it give a direct response where an alternator has losses from the start... I don't know for sure but it seems logical in my mind.

Running the magnets in close proximity to copper, aluminum or brass will act as a brake or constant load on the turbine. Kind of like shorting the leads on an alternator, very difficult to turn. You'll have to play with the air gap to get it to run within the turbines speed range. You could have an adjustment system that could be governed by the rpm - the faster it runs reduces the gap. Just speculating.

I would think a drag machine would be well suited for a heavy load like that without having to "dial it in". It doesn't need high rpms to create heat it needs torque. You could actually use a reduction drive on it for your lift machine allowing the turbine to run faster while increasing the torque on the heater.

It would be an interesting test... I've never taken it any farther than my lathe and 5 gallon bucket then stuffed the data in my journal for future reference.

I also experimented with the frenette friction heater, basically a drum in a drum with oil in it. That would also reach 140 degrees but it took much longer to achieve it. It was claimed he heated his house with the unit powering it with a 1 hp motor... I find it difficult to believe but I suppose its possible if he had a small house. 1hp = 2500 BTU so running it continuous might come close to doing a few rooms in my house.

More food for thought.... so many ideas... so little time...

.

ghurd · « **Reply #13 on:** November 09, 2006, 05:52:55 AM »

Decent 'indoor bike trainers' operate with drag from eddy currents.

They seem to have very little drag at low speed, but I do not know how they manage it.

I saw a couple better ones ($500?) with the 'heating unit' cast in Al, with fins, looked like a B&S mower head.

Might be worth a look at how they do it? At high end bike shops like Cannondale.

G-

electrondady1 · « **Reply #14 on:** November 09, 2006, 07:16:20 AM »

i think i might give this a shot.

like vawtman i am only interested in producing heat with my windmills.

it's often discused on the forum how a given geni is producing say 5oo watts electricity while disipating an equil or greater amout of power in the stator.

like ed has said it might be more efficient to produce /harvest the heat directly .

as well, in order to produce a usefull (for heating) current the voltage should be high, like near 200 volts. this is very difficult for a drag type devise turning at less than 200 rpm.

vawtman · « **Reply #15 on:** November 09, 2006, 04:00:53 PM »

Ed thanks for the reply.

Have you in all your endeavers thought about running the alt or direct heater(has this would be)through to the basement with isolation devices for the towers to protect the structure?

Just think all of the losses would be used except for the bearings.

Whats the hp of your lathe?Almost seems what a 120v element would do in that time.10mins 70degrees 5 gals

One could probably get 30ft of 3/8s copper tubing in the stator area of 12in diameter.

Would you need to ground or bond this device from static?

Definitly worth playin with i think.

Thanks

windstuffnow · « **Reply #16 on:** November 09, 2006, 06:29:49 PM »

For the most part, I don't like attatching turbines to my house. I did put the small Lenz2 on my roof but on really windy days it has a distinctive alternator growl that comes through. Not real bad or it would have been off the roof by now. Anyway, I did think of putting up a large VAWT with it's own basement section for the heating unit, next to the house. The extra costs didn't spark an interest in the project.

Your right though, there would be very little losses running a drive shaft down to the heater. I believe my lathe is 3/4 hp motor or 550 watts so yea, bypassing the motor and plugging in a 550 watt element would most likely do the same job. The idea isn't to plug it in though, it's to get it free. The eddy current heater is simply one way of doing it with a wind turbine. It might be interesting to do a breakdown of costs between the alternator driving the element and lines compaired to the eddy heater and plumbing to the hot water storage... Sometimes the losses are more easily absorbed when the price is right !

.

electrondady1 · « **Reply #17 on:** November 12, 2006, 08:47:07 AM »

i might be talking to myself at this stage but i keep thinking about the possibilities of an eddy currant heater .

rp's pump design is too hard to resist.

i've been sketching a vawt with a single mag rotor setup to eliminate a shaft or bolts passing through center.

a flat metal plate suspended on bolts like a stator

this would be the source of heat .

i think i could use a hard drive motor as the bearing for the impeller. this could be attached to the metal plate and be contained in a properly formed shroud .

it has occured to me that it might be possible to use air rather than a fluid to transfer the heat.

its difficult to know what sort of temperatures might be induced in the metal plate or the air volume/transfer rate possiple untill i do a series of experiments.

the varyables would be the mag rotoreddy currant plate clearance , and the depth of the fan /shroud controling the volume.

any thoughts guys?

RP · « **Reply #18 on:** November 12, 2006, 04:05:00 PM »

Well I'm glad you like the self pumping idea. A few more thoughts for what it's worth:

For the impeller bearing I think you'll want a stainless steel bearing or it'll rust up pretty quick if you use water as a heat transfer medium.

The impeller will be trying to attach itself to the magnet rotor unless designed carefully. For instance consider using only small metal bits as the magnetic driver to keep the attractive forces down. I'd be afraid of an imbalance in the attraction trying to drag one arm of the impeller into the casing otherwise.

Actually the impeller could also be a slotted disc of thick aluminum or copper. The same eddy currents that make heat would drag it around in a circle and there would be zero static force trying to attract it to the rotor. The slots would add impetus to the water to make it move. Of course you could add fins or bars to it as well.

Using air as a heat transfer medium will require a large "tank" and large ductwork to carry it around. Water would be really easy in small tubes, etc. Also, a relatively small volume of water can heat a lot of air on the other end.

If you can lay your hands on a stainless steel "ring bearing" you could make a torus (doughnut) shaped tank and use dual rotors.

For the tank construction I'd make a male mold out of oak on a wood lathe, attach a sheet of copper to it and spin-form it on the lathe to stretch it to form around the wood form (like how they make bowls). You could even be fancy and have some shallow grooves shaved into the wood and use these to form stiffening ribs in the copper.

After you have the main tank piece formed you simply make the opeings for the tube nipples and solder on a flat sheet for the other face.

electrondady1 · « **Reply #19 on:** November 12, 2006, 08:05:01 PM »

rp that would be a thing of beauty.

if as windstuff ed has said rpm wont matter then a lot of the design criteria we use for producing an electrical current come into question for this new purpose . the design of the rotors is a the result of the requirements of an electrical coil .

well since we are no longer using electrical coils things will change quite a bit.

right away it would seem you would want as much flux as possible in as small a space as posssible to avoid any disipation of the heat.

i'm wondering for instance if a space is required between poles.

Tony Zara · « **Reply #20 on:** April 13, 2008, 09:20:33 PM »

Would a regular car radiator work well for this? Aluminum fins, copper pipe. Am I missing something?

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Author Topic: Eddy current water heater (Read 14269 times)