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Captain Hybrid
Wireless Power Pitched as Replacement for EV Batteries
2/15/2012

Using magnetic resonance coupling, coils in the roadway could wirelessly transmit power   to electric cars cruising down the highway.   (Source: Stanford University)
Using magnetic resonance coupling, coils in the roadway could wirelessly transmit power
to electric cars cruising down the highway.
(Source: Stanford University)

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aftija
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Iron
"The technology is new..."
aftija   2/16/2012 2:28:36 PM
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Nikola Tesla might argue that this is not new technology...but he's long dead.

ttemple
User Rank
Platinum
Re: Far-out there idea, but some questionable responses
ttemple   2/16/2012 2:25:21 PM
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richgtoc, I think your math is wrong. 20kw for 60 minutes is 20kwh.  In those 60 minutes you would travel 60 miles, so the total would be 20kwh for the 1 hour, 60 mile drive, not 1200kwh.

p.s. information on Tesla motors' site makes the 20kw look pretty believable.  They claim to be at about 250 Watt Hours (per mile) at 60 mph, which is a bit lower than 20kw, but their drag coefficient is lower than average.

 

StuDent
User Rank
Gold
Re: Hot swapping
StuDent   2/16/2012 1:40:22 PM
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I saw a TV article recently about an American firm that's having real success hot swapping battery packs with a fleet of Japanese taxis.  That's all I remember about it.

rickgtoc
User Rank
Gold
Far-out there idea, but some questionable responses
rickgtoc   2/16/2012 1:38:56 PM
Personal, powerful, adaptable transportation.  That's the automobile, and it's been the 'American way' for about a century.  The ICE equipped car goes where I want, when I want. Hybrids are the same.  Change to EV and I lose some flexibility about where and when, since I have to adapt schedule to vehicle range and charging requirements - more planning required.  Further restricting me would be a car coupled to a particular kind of roadway, which lets me go when I want, but takes away more flexibility about where, since we will likely not power roadways within 'small battery' distance of every location my ICE powered car can go now.  If I were building massive transportation infrastructure that would provide "almost when I want, but not always everywhere I want" solutions, I'd want my money on mass transit, not resonant coil highways.  Given our current political reluctance to accept even modest tax increases to sustain the existing road infrastructure (Federal gas tax is same 18 cents/gallon as in 1993), I can't say I have much hope for any new transportation systems.

That said, some of the arguments in the comments here both for and against seem built on questionabe values and conversion factors.  For example, 20kW to maintain 60 mph would be 20 kw-H for 60 miles, or a total of 1200 kw-H for a 60 mile trip at 60 mph.  Gross heating val;ue of gasoline is only about 125,000 Btu/gal, or about 36 kwH/US gal.  Using that gross heating value and 100% efficiency (neither of which are reasonable assumptions), it would take 33 gallons of gas to go 60 miles using the stated 20 kW power requirement.  By some miracle, my small pick-up truck only takes about 3 gallons for that distance.  

I had similar questions about the math around the Panama Canal comparison.

Personal transportation is a hot-button issue with lots of folks.  Careless use of figures and conversion factors doesn't help the already charged conversations. Since we tend to think of electrical power in kW and liquid fuel consumption in mpg (in the US), it's worth taking the time to run some reasonableness tests before citing claims about how cheap or costly a particular system might be.

Practical Engineer
User Rank
Iron
These comments sounds so typical...
Practical Engineer   2/16/2012 12:49:36 PM

... of most design reviews and FMEAs I've attended -- where every engineer in the room wants to show how smart he is by DEFEATING an idea rather than selflessly improving the idea.   I concede that this story fits better in Popular Science or Popular Mechanics rather than an engineering periodical.  (I'm suspecting it's a slow news day; engineering periodicals need to fill column-inches, too.)  The challenge is to show how smart you are not by knocking this idea, but rather by taking some small portion of the idea and leapfroging into something better. Then, post your idea here and we'll all show you how smart we are by knocking it endlessly. Cheers!


jhankwitz
User Rank
Platinum
Re: Building out infrastructure a key hurdle
jhankwitz   2/16/2012 11:58:53 AM
I'd sure like to know who funded development of this idea.  I hope it wasn't us tax-payers.  A total waste of resources.  A high-school freshman could tell you this couldn't possible become a reality because of the multitude of negatives. 

I wonder what would happen if I walked across the road with my pace-maker.

Perhaps I could set a big coil in my front yard and power my house.

Mark S
User Rank
Iron
Tesla
Mark S   2/16/2012 11:49:34 AM
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Does anyone remember Tesla's Wardencliff tower? He was going to provide wireless power and built a lot of the project until the banker caught on to what he was up to, and stopped funding him.

kleetus
User Rank
Silver
Re: Building out infrastructure a key hurdle
kleetus   2/16/2012 11:45:15 AM
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Who finds and posts these sophomoric ideas? I'm begining to think that DesignNews is a hack site for the green agenda. If this is truly mainstream engineering thought, this country, and world for that matter, is in more trouble than I thought.

Seriously? designing a roadway like a kids toy slot car track to get power run the electric cars? What happens when I want to pull off the road or go where the power isn't?

In 4 pages of posts there are a litany of reasons which I'm sure were generated in less than 5 minutes of reading this pipe dream article of why this is a poor idea.

I know... maybe we can subsidize electric roads the same way we're subsidizing electric cars. Yeah! Great plan!

bdcst
User Rank
Platinum
Re: Building out infrastructure a key hurdle
bdcst   2/16/2012 11:43:51 AM
Grossly impractical implimentation of power transmission over a distance.  It's a fine technology for cordless charging of cellular handsets, flashlights, wheel chairs, electric scooters, fork lifts, etc.  But for highway use, its DOA.

What happens when a commuter rail line loses its catenary power?   A thousand passengers are stranded, stuck.  Now multiply this by tens of thousands on a major freeway when their vehicles grind to a halt.  Get the picture?

Even electrified railroads have required alternative locomotion sources at times.  I assume those batteryless cars will require some form of serious energy storage and a capacitor bank will be insufficient.

It is very common in electrified rail systems to have gaps between power distribution sources, third rail or catenary gaps to isolate segments.  As long as some of the self propelled cars in a train are not within the gap they will be able to re-start and move along.  Now, picture bumper to bumper traffic.  What if you are stopped between charging coils long enough for the capacitor to run out of charge?  Even if you envision autonomous self driving vehicles controlled by the highway so that traffic jams or accidents will no longer be issues, you still have unforeseen events that could dynamite traffic flow.  For example vehicle breakdown, or a sudden change in the weather, or a wild fire, or vandalism.

DrCMAC
User Rank
Iron
Electric Road Power requirements
DrCMAC   2/16/2012 11:29:14 AM
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A typical mid-sized auto takes around 20KW to cruise at 60 mph. Let's assume that the highway is busy, then cars might be spaced out every 50 yards or so. That would be about 35 cars per mile. The efficiency for transfer of energy done by the original work at MIT was around 40% in a lab environment. Let's take the optimistic assumption that we could achieve that in the real world with a moving vehicle. Each vehicle would require 50KW just to maintain speed, and even more if we were expecting to recharge batteries as well. The total energy requirements per mile would be about 1.75 Megawatts. Every 10 miles of road would require a mid-sized electrical substaion, and of course the additional high voltage 3 phase power lines. The best estimates that I have read to date indicate that the nation would have to quadruple its existing generating capacity to electrify the nations transportation industry. There is simply not enough wind or solar to do this, even if we were to extract 100% of what is available.

All too often such ideas tend to ignore the incredible energy density of gasoline or diesel fuel. Useful alternative transportation means should not not ignore basic physics!

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