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Challenges with Wireless power to EV
mathias.h@kytron.no   10/16/2013 10:14:37 AM
I have been working with high efficiency transfer of magnetic energy over large air gaps for some time, and see two reasons why this might not be a wide range success for EV. This comes despite some successful demo projects.
The magnetic transfer can be considered as a transformer with very large spread inductance. The spread inductance limits the possible transfer of energy. By use of resonance the spread inductance can be reduced,- but LARGE CURRENTS are circulating in the copper coils. This means high copper loss must be accepted or very big amounts of expensive copper must be used compared to a standard transformer of the same size.
The transfer of power also increases proportional to drive frequency, but eddy current and proximity effect losses (and currently also slow IGBTs) are limiting how high it is possible to go in frequency. Very expensive copper wires of litz type can be use but the copper budget for a road will then be even much higher. Next comes the personnel danger. Under the car there must be mounted an efficient screen for the B-field, a ferromagnetic plate returning the field back down , and the field must only be left on for a short moment as long as the drive coil is safely under the car. This reduces the duty cycle for the energy transfer and further increases the transfer losses.
Designs like this look very nice in a limited experiment, and scientists involved have a lot of fun playing with this without coming up with a viable solution for the public in my opinion. 

I myself believe much more in an advanced very low weight carbon fiber based overhead dual-brush solution based on damm fast optimally controlled servos tracking overheead power lines at millisecond level,- thus a two wire electrical connection. The power line can be made as an "open" two-wire cable protected from rain/snow on the active underside.
The bruch device is intelligent and pops up from the car and connects as soon as it observes such lines. Preferably operates at aronund 2-3kV so that it  can drive a simple converter. The cars /trucks/busses must have some battery. The power lines are only needed on long straight parts of the roads. Thus this system will be much less expensive to build/maintain than the systems for traditional streetcars/trolleys. 

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Re: Building out infrastructure a key hurdle
wbswenberg   2/23/2012 5:05:48 PM
Down town would be good.  What if you only need a few coils in strech?  The power line are there already.  What if it is just a power line in the road bed?  Lot of solutions.

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Wireless Power Pitched as Replacement for EV Batteries
vimalkumarp   2/22/2012 6:02:49 AM
I may be wrong, but i feel this is an invention for the sake of invention. Implementing this will be a herculean task. There is no mention about the health hazards which i presume will be low in this case. But to be positive this is a brave attempt

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Danger Will Robinson
etmax   2/20/2012 8:45:47 AM
Has anyone stopped to consider the risk to health of 10-20kW of radiated energy magnetic or otherwise? I get a mild headache rather quickly using a mobile, and that's only ~5W. Crazy stuff. It's true Uni's aren't turning out much these days in terms of a braod understanding of the real world.

William K.
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Wireless power pitch, Efficiency????
William K.   2/18/2012 8:27:15 PM
Once again there seems to be less attention to the efficiency of the transfer. Really good transformers carefully built on a low loss core achieve up to 98%, if the coupling is good, and if everything is operated within the design specifications. BUT these really good transformers are not cheap.

Now what would the cost be to put a decent transformer into a mile of roadway? If it needs to transfer 10KW toa vehicle for that distance it is going to need to be "fairly big and heavy", and it will cost a fair amount. To avoid it being horribly inefficient it will need to switch on as the car enters each section and switch off as the car leaves. I designed a system like that for a maglev train quite a few years back, and while it was quite reliable and relatively simple, it would not be cheap. So now we would have a mile of quite expensive roadway, which may not last one winter with Michigan's road-salt application policy, And you have a very expensive mile of roadway. Of course to be of any real value there would need to be lots of miles of roadway. So that would be quite expensive already, with no power connections and no cars.

Next, where is all of the power for the roadway going to come from, and how will the data about who used how much at what time be recorded. This is important because it is only fair to charge those who use the energy for using it, similar to the way today we each pay for the gas that we put in our tanks. So now we add a fairly complex billing system to the price of the road. All this and still no discussion about the car and what it costs, nor any mention about the effect of all of these magnetic coupling fields on people in the area.

My point here is that just because it can be done does not mean that we can afford it. I yhave not mentioned the environmental concerns that others brought up, but they are valid also.

andy t
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don't know how far or how many coils???
andy t   2/18/2012 4:46:05 PM
A vehicle at highway speed easily needs 10kW, more likely 15-20kW of motor power. If we assume 10kW, that means this feigned mystery of how many coils is easy...it's CONTINUOUS for the full travel distance of a car. If it's 20kW, one coil the full length of a car won't cut it, so now you need to pull a trailer. So, rather than all the heat, EM radiation produced by inefficient induction coupling (resonant or otherwise), we actually use a TON (literally more than that) less copper by using overhead trolley wires (or embedded slot car style power rails). How did I figure all this out? I didn't go to, or get a cushy academic job professing impracticality at, Stanford, I guess.

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Leading edge vs bleeding edge
GlennA   2/17/2012 5:28:25 PM
Isn't the U.S. Navy developing a magnetic induction launch system for aircraft carriers to replace the 'old-tech' steam system ?

Years ago I saw AGV's in an auto plant.  At each 'wait' point there was a charging station.  Disney World has a monorail - not the fancy Mag-Lev, but at the time it was a showpiece.  This concept may not be ready for the 'big-time', but just as certain cities have light rail and subways, the first step may be a public transit application.  I don't know if it can be cost-effective vs. the catenary electic.

The internal combustion engine was at one time referred to as the infernal combustion engine.  It helped solve the pollution problem of the emissions of the horse-drawn carriage.  The future is hard to predict.

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Re: The big picture.
kleetus   2/17/2012 12:44:21 AM
Wow... There's an old adage, "I can explain it to you, but I can't understand it for you." I think that's very apropos now.

Touting the talking points from your favorite greenie website isn't going to help you amongst the thinking crowd. You conveniently neglected to cover real costs to implement, and real environmental damage from all the components made from 'unobtanium' that will be/are necessary to make these systems work to the levels you expect.

No I don't want to see 6k dead soldiers, a few of which were friends of mine, and I lost 343 brothers and sisters on 9/11 so put that card back in the deck. We didn't ask for 9/11 and I don't agree with our response. We shouldn't be playing nice war like we did in Viet Nam, we should go scorched earth so the people that respect only force recognize, we have it, and will use it again. These methods don't work well for training pets, children or dictators, and the state of the world today proves this.

But veering off the path to reason, I somewhat agree, we shouldn't be getting our oil from the middle eastern nut jobs... so, why then can't we develop our own? That's right... we're going to FORCE everyone into impractical EVs by making the cost of fuel whether it's subsidized or not (um... just like the Volt) so expensive they'll HAVE to go to the new alternate technology.

So Chevron isn't allowed to engage in energy storage or management of any kind other than fossil fuels? Is that what you're driving at? (I know full well you're insinuating that they are evil and are trying to drive up the costs to further their pig-ish capitalistic goals). Well, by that logic, who should be allowed to have those patents? GE? Wait... they don't pay taxes, that won't work... How about Solyndra? Oh... they went out of business... dang it...

Fact is Chevron, which is one of many companies in the energy business, is looking at ALL FORMS of energy. Be it fossil fuel, bio, electricity, whatever if they plan to be around the next 50 years, they better have a handle on what's up and coming.

Besides that, NiMH is dead... Li+ is the way to go... unfortunately neither of which are good for the environment to produce or dispose of. A bit of an inconvenience there for saving mother earth, which after all, is the big picture here, don't kid yourself or anyone else here. 

If EV is so fantastic, why are developing nations still working from ICE? They may be including some EV, and for commuter routes that's probably a good idea, but for any non-programed independent route that needs to be taken, you just can't extend the extension cord long enough and put in enough plugs. If EV is the way to go, all the new roads, and infrastructure should be being built from the ground up, when it's most cost effective, not 50-75 years after the road has been in service. Unless of course, it's not really all that feasible in the end.

EV racing... yeah, I think I saw that on Speed. Oh.. never mind that was a top fuel dragster. For the amount of subsidization your EV has received, and continues to receive, You're investing (well, not you, the tax payers) a lot more money behind the scenes from the final sale price, to all the components tied into the design from start to finish. 

So, I'll keep supporting the gas companies, and I'll push for utilization of our own resources here in the states and tell the dictators to go pound sand wherever they please to put it. You hug your pillow tight tonight and stick with the 99% crowd, they can use another good spokesperson.


Jerry dycus
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Re: The big picture.
Jerry dycus   2/16/2012 10:00:26 PM
Okay, maybe I'm a bit short in my critique because I'm generally annoyed with the initial premise here, that's hiding in the background that no one is talking about which is:

Why are we thinking of this in the first place?

------------ Because we keep spending trillions to overseas oil dictators and terrorists in military/yr, Persian Gulf/OIl wars  and balance of payments costs. Now we know the cost of oil, other FF will rise so the smart thing is get off the train before it wrecks.                           My EV takes so little energy it isn't noticable on my $24-45 Electric bill.  So I do EV's for cost, sercurity of my fuel source I can make myself cheaply and to be patriotic and keeps us out of future oil wars. Or do you like the 6k US soldiers dead, etc for international oil companies?  But other than that, no reason.

Why are we talking about the idea of electric vehicles to begin with? The ICE has been a steady workhorse for man for about a century in various forms. It does the job, cheapy effectively, and by most people's account, efficiently.

-----------  Depends on what you call cheaply. 20% of your tax bill directly subsidies oil companies. Real cost of oil is another $2-3/gal.  And sorry but eff is not one of oil. EV's are 3-6x's as eff. But even strait up, KIS well designed EV's can be far cheaper using lead batteries and forklift tech and still get 100 mile range as the EV-1 did on lead.

So what's all this about? Getting away from fossil fuel? Why? Well, someone thinks that the ICE is bad for the environment and causes global warming/cooling/change/weather... whatever the name of the day is.

------------  Go down and read the numbers on the gas pumps.  Add up all you spent on gas last yr. Now double that in 2-3 yrs.

The whole premise of this exercise is to do something that when looked at through the lenses of overall efficiency, cost effectiveness, reliability, and total environmental damage makes absolutely no sense what.so.ever.

-----------  As done it doesn't and not likely ever to be used by cars but third rails for semi's, buses could be good.  Since a fueled gen only takes 30-60lbs to give an EV unlimited range at about 100mpg, YMMV, it makes little sense using more than 100 mile batt range in most cases.  Remember the EV-1 charged like this and when it caught fire a couple times because it's not a good system, they used that as an excuse to crush them.  None of this is new and used over 100 yrs and very limited.

------------  Best way to do it is have some PMagnets on a trolly under the EV or even ICE car, semi and coils in the road pull it along making a linear motor. Keep the gap under 1" and it's eff.

It is never a bad thing to consider alternatives, or revisit ideas as new technology becomes available. But there does come a point where pouring good money after bad, to sway public opinion, support faltering businesses that can't compete with the legacy technology, is just a really dumb idea.

------------  You mean after lies and bad, costly, overweight EV designs on purpose
Chevron buying the NiMH battery patents, PR campaigns and huge corporate welfare to big oil?

And to those who are complaining about those of us who are 'quick to tear apart' ideas vs. build them up, I'd submit to you that we just come to the conclusion above faster than you did, and are ashamed that more professionals aren't as astute.  (Truth be told however, it would appear that reality is winning out over fantasy in the end.)

-------------- We have been driving EV's for decades quite well thank you. google EV Clubs or EV racing and you might find out what the world is missing.

----------So think about the next time you fill up that instead of $40 in a similar EV you'd spend only $4 plus save the time, hassle of gas station stops.  That's it, $4, now $10, now $50 1-5x's/week and soon it adds up to real money.  Mine stays in the bank for other better things.  So keep up the good work supporting oil companies, dictators and terrorists.

William K.
User Rank
Re: Seen it all before...
William K.   2/16/2012 8:01:20 PM
Yes, I agree that even the best resonant coupling will not be so very efficient. I have observed the other writeups and they either ignor efficiency completely, or they express power transfer in terms that I find non-informative. It becomes clear that there is something to hide. At least I see it that way. Your assertion tends to verify what I have been observing. Thanks for the input.

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