One of the most obvious ways to mitigate the effect of the high cost of REEs is to eliminate rare earth magnets and return to conventional materials. With conventional radial designs, however, that means going back to the bad old days of large, heavy motors. This is because conventional materials simply cannot produce the same field strength as rare earth alloys.
Neodymium iron boron (NdFeB), for example, features an energy product -- essentially, a measure of field strength -- of around 55 MGOe, compared to roughly 4.5 MGOe for ferrite. That bump in energy product is what makes it possible for radial rare earth motors to deliver lots of muscle in a tiny package compared to their ferrite counterparts. The solution required taking a different approach to the problem.
Figure 2: The stator assembly consists of six of these laminated-steel field poles, each surrounded by a bobbin-wound coil. (Source: NovaTorque)
The design starts with a stator assembly formed of six laminated field poles of oriented steel, each threaded through a bobbin-wound coil (see figure 2). The rotor consists of two separate conical ferromagnet assemblies designed to match the cavities on the ends of the stator, leaving a conical air gap. Now, instead of the interaction taking place in two dimensions, it takes place in three dimensions.
If we compare the cross-sectional area of the stator at the coils with the surface area of the laminated pole structure, the ratio is roughly 2:1. This leads to a correspondingly large increase in flux density for the same motor diameter. What that means is that even with ferrite magnet material, the axial design can deliver similar torque density compared to a radial designs based on REE magnets.
“By concentrating flux in three dimensions, we can use quite a bit of low-cost ferrite material and concentrate flux to get a flux density in the stator that is comparable to what you would have in a rare earth magnet motor," says Alan Crapo, vice president of engineering at NovaTorque Inc. Essentially, the approach flips the conventional model of moderate Φs and very high ΦR to moderate ΦR and very high Φs. The result is better performance from conventional materials. “We can get the same kind of efficiency as rare earth magnet motors and we can operate the steel at similar flux density levels that rare earth magnets will operate at," says Crapo.
There are tradeoffs, of course. Even with the flux focusing, the axial designs need more of the conventional magnet material to get the desired performance. The NovaTorque team added more magnet material without significantly increasing frame size by narrowing the air gap between rotor and stator. In addition, the team potted the stator to enhance heat transfer. The result is a motor that may maintain a competitive frame size but more of the overall volume is filled with motor materials, giving it more mass and inertia than its rare earth counterparts.
The problem is human beings. If you were to be objective, you'd see that as humans are social animals, government is inevitable as some sort of hierachy is always developed. Any argument that government is the source of all our problems is therefore simply invalid.
Also, what "over-regulation"? That argument can be ignored as it's a canard. The claim is a) not supported with any examples and (b) generally created from a very narrow economic definition, generally from a specific ideological perspective, that conveniently ignores externalities not considered improtant by the claimer.
So, the fact remains that REE are rare, China happens to be the major source, and trade agreements and policies have made it more difficult for the US to apply any leverage to coerce China to export them more freely. Therefore, the only valid alternative is to develop more efficient means for using electricity that reduces the need for these rare elements.
There is and will continue to be a high cost for neodymium and dysprosium materials because of the negative environmental impact of mining, with the escalating use of electric vehicles and wind turbines, and yes, with speculation. Mines are reopening because of the RE high cost but will they stay open if the high costs diminish? Some countries are already making their move: http://www.raremetalblog.com/2012/02/cerium-neodymium-and-dysprosium-prices-keep-tumbling-report.htm. And yes, there are certain kinds of electric machines without permanent magnets that have higher efficiency, torque density and power density with lower cost than permanent magnet electric machines.
Sorry to be so smart alec. It just comes so naturally.
I know we are social animals, but it is about liberty. Liberty is everything, and it is the nature of government to try and capture all the power it can and limit the liberty of the people, ergo the "Patriot Act." That is why the Constitution is so important. It puts limits on government and leaves the power to the states. The Fed is where the problems are.
But enough of that. About the Rare Earths. I spoke from an article I read recently, so I was referring to that. I cannot remember the source, but I accepted it. I'm easy that way. I know China is an awesome source for these, but not the only source. Right now it is the main supplier, and thus they control the market. They control the market on a lot of things, politicians included. Oops, back to politics.
What do you mean by "liberty"? It's essentially a meaningless word as it means whatever anyone wants it to mean, ranging from implying that one can do whatever one wants without any consideration as to the consequences of those behaviors to behaviors constrained by ethics and morals. So, what do you mean? The constitution is interpretable, so while the constitution puts limits on government, it provides wide latitude for action in the general welfare and the constitution itself denies unconstrained libtery because it replaced the Articles of Confederation.
Also, it's not that China is an awesome source, but that it may have a greater concentration of REEs. So, their resources are their resources and while we have trade agreements, we must still deal with the fact that what is in their control is in their control and while the US has made the conscious decision to give away our technological knowledge and allow foreign mining interests access to our resources for essentially nothing, China may not do so.
As for that article you linked to, it provides absolutely no details about its claims, such as what do they mean by "not rare", and any support as to whether they are more common than Cu. Start here: "Rare Earth Elements—Critical Resources for High Technology".
@Rob- This reminds me of silver mines in the Cerro Gordo area of California, near Death Valley. The silver boom was the catalyst for LA's growth in the late 1800's. For awhile the ore was shipped to LA and then processed. Of course they soon realized almost all the weight they were hauling was slag, so mills were built next to the mines.
So asteroids will be mined but the valuable materials will be extracted on site, enroute to Earth, or perhaps on the moon. Maybe the output is ingots which are shaped and coated to reenter the atmostphere. True there's a risk from stray ingots landing in the wrong place, but then again 400 ton aircraft loaded with billions of BTUs of fuel fly overhead every day!
Sounds like a Burt Rutan problem-solving exercise!
Thanks for your comments--sorry for the delayed reply. The remarks about "rare earth elements" being something of a misnomer are correct. You can find more detail in a U.S. government report at http://tinyurl.com/bqjudr8. "The more abundant REE are each similar in crustal concentration to commonplace industrial metals such as chromium, nickel, copper, zinc, molybdenum, tin, tungsten, or lead (fig. 4). Even the two least abundant REE (Tm, Lu) are nearly 200 times more common than gold..."
The issue is that the elements are typically found bound with other materials, so they require effort to extract. The dynamic going on with China is that they mine REE ores as a byproduct of another mining operation -- they're basically turning scrap into revenue. This is partly why they were able to drop prices.
As far as alternative sources go, the Mountain Pass mine actually features REEs In much higher concentrations and Chinese sources, at least for some of the main REEs. This may help the mine to be more cost competitive as they get things up and running. The bottom line is that the cost is coming down but will probably never get anywhere near as low as they were in the heyday. That said, the ability of engineers to design around the problem is part of what the and driving down demand and causing the speculators to release their inventory, hence driving down the overall cost. There are enough design options around that I think we'll be okay.
That makes sense, Kenish. Make the output from the mine pure and dense so you're not transporting any waste. I understand that's how port developed. If you added alcohol to wine, you could ship a richer product at the same weight.
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