The stators are burt because they are overdriven. It's as simple as that. There's no mysterious or magic material that will save it from this.

All that needs to be done is take great care and be sure the furling system is working/designed properly.

Yes, the machine will have less output when furled, but if you already are having high enough winds to make it furl your battery bank is probably full by now and you're just dumping the excess power, so why have it make more power if it's going to dump?

Also, I've seen "professional" made turbines like Proven for example burn out, and these have laminated stators which can take serious abuse.

As I said in the begining, it's more a matter of protecting the machine in high winds rather than finding some magical material that will remove heat from the stator fast enough to keep it from toasting .

If you can tame its physical properties you still have the almost impossible problem that it is a metal and a good electrical conductor. You will build yourself a nice eddy current brake and possibly an effective liquid metal magnetically operated pump. I can't see how it could be any better than any other metal, all of them would need to be finely laminated and sodium would be more of a problem in this respect than any of the common metals.

Use in engines is a totally different issue.

I never worked in a shop where one of the valves was cut open. I understand it was a bit more excitement to cut one open than one wanted. Some claimed it was more excitement than was survivable.

I also found a heat conductive potting there as well:

 http://www.mgchemicals.com/products/832tc.html

Maybe a combination of the two epoxies would work well. If the coil wires were coated with the high epoxy during the winding process and then cased in the heat conductive epoxy, or the other way around, it could be a wonderful thing! Maybe even use carbon fiber instead of fiberglass? It would be worth doing a few test coils to found out!

1. ) Sodium reacts with water as stated and is not good.  (Kinda fun though)
2. ) Salts dissolve in Water and would need a protective coating.  If it is epoxy or resin it would reduce the desired heat dissipation.  Probably not feasible.

Epoxy isn't horrible, as some heat transfer does take place, but a greatly increased heat transfer to the atmosphere will reduce the internal temperature of the coils and prevent the wire from failing on those occasions when the stator is overdriven.  Mortar mixed with fine sand would do exactly this.  Metal sleeves could be inserted during molding for the mounting holes, with hard rubber bushings applied to reduce vibrations.  The stator could transfer 5 times more heat through a given thickness, and would not fall apart if overheating did occur like the fiberglass stator that we viewed.  It is interesting that the fiberglass stator photos did show that most of the heat buildup was directly around the coils.  The black charred fiberglass was directly above the coils thus most heat transfer is around this general region.  If mortar were used weight saving could be had by reducing the size of the stator to the area needed for mechanical strength of the unit, as weight may be the primary disadvantage of using mortar.  (Hole in center and mortar or epoxy tabs for mounting.)  

I'm driving to Florida from Ohio tonight for vacation and wont return for two weeks. Taking the kids to Disney World. (Do they pay for promotions on Otherpower?) Wish I could contribute more to the tread, as I value the opinions many of you have on this subject.

Kevin L

My gut tells me that we need to just focus on achieving earlier, more reliable furling to reduce power output in high winds.  Our systems are for battery charging so the extra energy that comes in storms is of little value to us.  Keeping our systems low-maintenance and operational in remote locations is of value to us.

Hugh, can you elaborate on your new steeper angle for the tail vane, or point me to somewhere where you've discussed this.

I disagree, while talc powder does have good thermal conductivity, when mixed with epoxy the increase in overall thermal conductivity will be minimal.  The best method to reduce overheating of the stator is to find a better heat conductor to tranfer the heat to the air.  Of course furling would provide some protection, but as we have seen many times on this board, overheating of the coils is still occuring during storm conditions during full furl.  Using a meduim with a low thermal transfer rate such as Epoxy (0.35 W/m K) or Fiberglass Board (0.04 W/m K) is inviting the prospect of overheated coils.  Motar cement(1.73 W/m K) is a significantly better conductor of heat, and since heat is the primary cause of coil failure, it does makes sense to look at the possibility to use mortar as an epoxy replacement.

Kevin L