Toyota developing wireless charging

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Toyota developing wireless charging

brucedp4

Resonance charging more efficient than electromagnetic-induction

http://www.automotiveit.com/toyota-to-develop-wireless-charging-with-witricity/news/id-002572
[image] Toyota to develop wireless charging with WiTricity
May 1, 2011

Toyota said it has entered a technical cooperation with WiTricity to
develop wireless charging systems for electric-vehicle batteries.

The Japanese carmaker said it wants to accelerate the development and
eventual implementation of wireless charging for cars. “The charging
of a plug-in hybrid or electric vehicle could be as simple and
convenient as parking near an embedded charger at a home or in a
parking facility,” Toyota said in a press release.

Toyota will also participate in a WiTricity capital increase.
The Massachusetts-based company uses a resonance charging technology,
which allows charging without direct contact. WiTricity believes its
technology is more efficient than electromagnetic-induction, another
wireless technology that is gaining traction in mobile phone charging
systems.

WiTricity was founded in 2007 to commercialize a new technology for
wireless electricity invented two years earlier at the Massachusetts
Institute of Technology (MIT).

A team of physicists developed the theoretical basis for this novel
method for wireless electric power transfer in 2005, and validated
their theories experimentally in 2007.  The magnetic fields of two
properly designed devices with closely matched resonant frequencies
can couple into a single continuous magnetic field. The team showed
how to use this phenomenon to enable the transfer of power from one
device to the other at high efficiency and over a distance range that
is useful for real-world applications.
[© 2011 automotiveIT International]


http://news.cnet.com/8301-11128_3-20058305-54.html
Toyota invests in wireless car charging
by Candace Lombardi  Apr 28 2011

[image
http://i.i.com.com/cnwk.1d/i/tim/2011/04/28/2.6_img_witricity_obstacle.jpg
Diagram of how a device with WiTricity couples with its source to draw
power from the source's magnetic near field.
(Credit: WiTricity)]

Charging your hybrid or electric car may someday become as simple as
pulling into the driveway.

Toyota Motor has invested in and has signed an agreement with
WiTricity to collaborate on a wireless automotive charger that doesn't
need any point of contact to charge a car's battery, Toyota said
yesterday.

WiTricity has developed technology that could eventually enable a
plug-in electric or plug-in hybrid vehicle to be charged by simply
parking the vehicle in the vicinity of a car charger embedded with a
special device.

The Mass.-based company has already been developing the technology for
 consumer electronics like cell phones, laptops, game controllers, and
 TVs. Now with the help of Toyota, WiTricity hopes to bring its
technology to cars like the Prius.

Toyota "believes that resonance wireless charging is suitable for
automobiles and aims for its early practical use," the carmaker said
in a statement.

Unlike electromagnetic-induction wireless chargers that require a
special mat or cases for things like cell phones to make contact with
the electricity source, WiTricity's resonance wireless charging system
does not require contact.

WiTricity uses something called highly coupled magnetic resonance. The
charger, directly connected to AC power, has a magnetic resonator that
generates a magnetic near field. An embedded "capture device" in the
item to be charged (in this case a car) then receives a transfer of
electric power from that magnetic near field to which it's
specifically attuned. The power via that magnetic near field can be
delivered over distance, through obstacles like walls, and even to
multiple devices simultaneously.

The company says its akin to the resonance that takes place when an
opera singer shatters a glass. A glass can absorb sound waves

"WiTricity power sources and capture devices are specially designed
magnetic resonators that efficiently transfer power over large
distances via the magnetic near-field. These proprietary source and
device designs and the electronic systems that control them support
efficient energy transfer over distances that are many times the size
of the sources/devices themselves," the company said in a statement.

This method of wireless charging is also more efficient than
electromagnetic-induction, according to WiTricity.

Toyota is not the first high-profile automaker to express an interest
in wireless charging. In January 2010, General Motors announced at
from CES that it was partnering with Powermat to offer wireless
charging for the Chevy Volt interior that would allow consumers to
charge items like cell phones by simply placing them on the dashboard.
However, that technology is for charging electronic devices, and not
the car itself.
[© 2011 CBS Interactive. All rights reserved.]


http://www.ecoseed.org/green-transportation/other-green-transportation-technologies/article/73-other-green-transportation-technologies/9627-toyota-and-witricity-plans-to-charge-electric-cars-without-cords
Toyota and WiTricity plans to charge electric cars without cords
By Oliver M. Bayani  Apr 28 2011

Green News, Witricity Toyota, magnetic induction wireless charger,
magnetic resonance wireless charger, Toyota wireless charger, Witricty
wireless charger, wireless charger electric car, wireless charger
benefit, E.V. chargers

[image
http://www.ecoseed.org/articleImages/Toyota-and-WiTricity-plans-to-charge-electric-cars-without-cords_295x220.jpg
Electric cars and plug-in hybrids can recharge simply by parking at a

designed charging space that can transfer electricity wirelessly
through a receiver installed in the car’s chassis.]

Japan’s Toyota Motors, the world’s biggest car maker, has teamed up
with Massachusetts-based start-up WiTricity Corporation to raise
capital and develop special chargers for electric vehicles without the
need for plugs.

The two firms will develop chargers where electric cars and plug-in
hybrids can recharge simply by parking at a designed charging space
that can transfer electricity wirelessly through a receiver installed
in the car’s chassis.

WiTricity uses magnetic resonance for its chargers instead of
electromagnetic-induction, another wireless charging technology
primarily used for consumer electronics. In its press release, Toyota
said that resonance is “more efficient than electromagnetic-induction”,
since the latter can only work over short distances.

Both technologies use a magnetic field to transfer electricity
wirelessly. However, magnetic resonance makes electricity transfer
more efficient by ensuring that the power source’s and the receiver’s
magnetic field frequencies match, making it easier for electricity to
run through the air.

Aside from efficiency, power can also travel longer distances and be
transmitted to multiple devices at once, compared to magnetic
induction chargers that need cars to be precisely aligned before it
can charge.

The Wireless Power Consortium, an industry group formed to create
standards around wireless power, said careful design can achieve at
least 70 percent transfer efficiency. But WiTricity said its
resonance-based chargers can reach efficiencies of more than 90
percent. That means it only loses 10 percent of the electricity it
transmits to the car battery pack.

Toyota isn’t the only automotive partner for WiTricity. The company
concluded an agreement with Delphi Automotive, which already makes
wired electric car chargers, in September last year.

Randy Sumner, director of global hybrid vehicle development at Delphi,
said Witricity’s chargers can deliver up to 3.3 kilowatts of power,
the same rate as most residential plug-in chargers.

Toyota said that resonance wireless charging is suitable for
automobiles and is planning for its "early practical use”, the company
said in a press release .The automaker hopes that charging without
the use of cumbersome wires will spur wider use of electric vehicles
and plug-in hybrids.

Witricity has raised $15.5 million in total since its 2007 founding,
according to boston.com. According to the company’s website, it
received its initial venture capital funding in November of that year
from Stata Ventures and Argonaut Private Equity.

A team of physicists, led by Professor Marin Soljacic, from the
Massachusetts Institute of Technology developed magnetic resonance for
wireless electric power transfer in 2005, and validated their findings
experimentally in 2007.

Up for completion
Witricity is not alone in the dream of cordless car charging,
Virginia-based startup Evatran L.L.C. promises a wireless charging
system with 80 percent efficiency. It had its first public trial last
March, installing the device in Google Inc’s headquarters in
California.

Evatran’s wireless electric vehicle charger, dubbed Plugless Power,
uses magnetic induction , a competing technology Toyota snubbed in a
press release. However, pictures of its charging systems on their
websites look strikingly similar with Witricity’s.
[]






{brucedp.150m.com}
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Re: Toyota developing wireless charging

gtyler54
Sounds like they starting to catch up to Tesla, who did it a century ago.

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of brucedp4
Sent: Saturday, 7 May 2011 10:39 p.m.
To: [hidden email]
Subject: [EVDL] Toyota developing wireless charging


Resonance charging more efficient than electromagnetic-induction

http://www.automotiveit.com/toyota-to-develop-wireless-charging-with-witrici
ty/news/id-002572
[image] Toyota to develop wireless charging with WiTricity
May 1, 2011

Toyota said it has entered a technical cooperation with WiTricity to
develop wireless charging systems for electric-vehicle batteries.


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Re: Toyota developing wireless charging

Peri Hartman
Sounds very cool.  Especially if you could get by with a 10mile battery
range - really tiny package.   My hunch, though, is it will be cheaper and
eventually more beneficial to simply improve battery technology so that it's
possible to 300 miles per charge and have 3 minute quick charging.  Yes,
that's a big deal, but so is installing how many 10000s of miles of highway
wiring.  And what about all the rural roads?  Either way, an upgraded power
grid would be needed.

Peri

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of George Tyler
Sent: 07 May, 2011 1:45 PM
To: 'Electric Vehicle Discussion List'
Subject: Re: [EVDL] Toyota developing wireless charging

Sounds like they starting to catch up to Tesla, who did it a century ago.

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of brucedp4
Sent: Saturday, 7 May 2011 10:39 p.m.
To: [hidden email]
Subject: [EVDL] Toyota developing wireless charging


Resonance charging more efficient than electromagnetic-induction

http://www.automotiveit.com/toyota-to-develop-wireless-charging-with-witrici
ty/news/id-002572
[image] Toyota to develop wireless charging with WiTricity May 1, 2011

Toyota said it has entered a technical cooperation with WiTricity to develop
wireless charging systems for electric-vehicle batteries.


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"WiTricity" (was: Toyota developing wireless charging)

Bill Dube
In reply to this post by gtyler54
The "wall to load" efficiency of the overall circuit was only 15%. :-(

The theory looks very interesting, especially the low measured RF
power between the transmitter and the receiver coils, which is
roughly just 10% of the actual power transmitted to the load. They
have not as yet demonstrated a device that would be practical for
_efficiently_ transferring power, yet. They might, but there is a lot
of power lost in the resonant circuit itself, at least in specific
oscillator circuit they used in their experiment.
http://engsci.unavoidable.ca/esc201/esc201-praxis-researchreviewpaper-wirelesspower.pdf
and
http://www.google.com/#sclient=psy&hl=en&source=hp&q=Wireless+Power+Transfer+via+Strongly+Coupled+Magnetic+Resonances+&aq=f&aqi=g1g-v4&aql=f&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=c47720ba43ce4197

When they manage to demonstrate good efficiency "from the wall to the
load" then we should open the champaign. Until then, there is nothing
wrong with a $20 plug and receptacle.

Bill Dube'

At 02:44 PM 5/7/2011, you wrote:

>Sounds like they starting to catch up to Tesla, who did it a century ago.
>
>-----Original Message-----
>From: [hidden email] [mailto:[hidden email]] On Behalf
>Of brucedp4
>Sent: Saturday, 7 May 2011 10:39 p.m.
>To: [hidden email]
>Subject: [EVDL] Toyota developing wireless charging
>
>
>Resonance charging more efficient than electromagnetic-induction
>
>http://www.automotiveit.com/toyota-to-develop-wireless-charging-with-witrici
>ty/news/id-002572
>[image] Toyota to develop wireless charging with WiTricity
>May 1, 2011
>
>Toyota said it has entered a technical cooperation with WiTricity to
>develop wireless charging systems for electric-vehicle batteries.
>
>
>_______________________________________________
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Re: "WiTricity" (was: Toyota developing wireless charging)

Jeffrey Jenkins
Bill Dube wrote
The "wall to load" efficiency of the overall circuit was only 15%. :-(
Resonant coupling is supposed to be very efficient (~80-85%) if the two coils are less than 1/6th of a wavelength apart (within the so-called "near field"). The poor overall efficiency reported by the MIT researchers was almost certainly the result of some bad engineering decisions (too high an operating frequency resulting in high skin and proximity effect losses, the Colpitts oscillator requires the "switch" operate in linear mode; I'd use a Class-E design instead, etc...)

Anyway, I think that resonant coupling will eventually be the number one way of charging EVs at home. I wouldn't want to transmit more than a couple of kW with it because of the RFI/EMI issues but you can't argue with the convenience - just park the car as usual and charging begins automatically.

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Re: "WiTricity" (was: Toyota developing wireless charging)

Bill Dube
Read the papers they have published, and the reviews of those papers
(all on line) and then comment.

There are many things we _wish_ were true, but non-contact charging
is not a reality.

After reading the publications (I admit that I did not slog through
the pages of field equations) it looks like they have essentially
"moved" the inefficiency. (A phrase Eva came up with while we were
discussing this.) It is quite possible (not a certainty, but
possible) that the actual RF field between the coils is transferring
energy at some efficiency nearing 50%, the resonant circuit needed to
make that happen has _terrible_ efficiency.

Resonant circuits slosh the energy back and forth, by their very
nature. If you think about it for a few minutes, it becomes apparent
that any time you move large quantities of energy back and forth, you
just can't avoid losses with every cycle. It is like pouring water
from one glass to another. You splash or spill just a tiny bit each
time, unavoidably.

If you isolate your efficiency measurement to just one portion of a
system, and ignore the rest of the system, you can often find some
part that is very efficient. This is what these folks have done. The
standing wave between the two coils might be showing very high
efficiency, but once you include the rest of the components needed to
sustain that standing wave, the efficiency drops to 15%.

What they have done reminds me a bit of a laser beam. The photons in
the beam travel with remarkable efficiency over spectacular
distances. The device that generates those remarkable photons is
always inefficient, however. Some laser are more efficient than
others, but it is never very efficient way to move large amounts of
energy from one place to another.

Even the "best" part of this device has awful efficiency compared to
the entire journey along the power grid that delivers electrical
energy to your house. Think of having to generate more than _twice_
the amount of electricity than you do now to run your electric car
one mile. (Actually, it would be six times the amount for this
system, but...) This would make an EV a poor choice economically, and
ecologically.

Plugging in is easier than rolling up the window when you park. It is
only the fear of change that is difficult.

Bill D

Bill D.


At 04:26 PM 5/8/2011, you wrote:

>Bill Dube wrote:
> >
> > The "wall to load" efficiency of the overall circuit was only 15%. :-(
> >
>
>Resonant coupling is supposed to be very efficient (~80-85%) if the two
>coils are less than 1/6th of a wavelength apart (within the so-called "near
>field"). The poor overall efficiency reported by the MIT researchers was
>almost certainly the result of some bad engineering decisions (too high an
>operating frequency resulting in high skin and proximity effect losses, the
>Colpitts oscillator requires the "switch" operate in linear mode; I'd use a
>Class-E design instead, etc...)
>
>Anyway, I think that resonant coupling will eventually be the number one way
>of charging EVs at home. I wouldn't want to transmit more than a couple of
>kW with it because of the RFI/EMI issues but you can't argue with the
>convenience - just park the car as usual and charging begins automatically.
>
>
>
>--
>View this message in context:
>http://electric-vehicle-discussion-list.413529.n4.nabble.com/Toyota-developing-wireless-charging-tp3505313p3507962.html
>Sent from the Electric Vehicle Discussion List mailing list archive
>at Nabble.com.
>
>_______________________________________________
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Re: "WiTricity" (was: Toyota developing wireless charging)

Al-57
In reply to this post by Bill Dube
Efficient wireless energy transfer is another pipe dream. Even if they could
achieve 85% that is not good enough.
Here we are trying to improve efficiency with electric vehicles and now they
want to throw that efficiency out the window because they are to lazy to
plug in a cord?
Give me a break.

Al

----- Original Message -----
From: "Bill Dube" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Sunday, May 08, 2011 12:58 AM
Subject: [EVDL] "WiTricity" (was: Toyota developing wireless charging)


> The "wall to load" efficiency of the overall circuit was only 15%. :-(
>
> The theory looks very interesting, especially the low measured RF
> power between the transmitter and the receiver coils, which is
> roughly just 10% of the actual power transmitted to the load. They
> have not as yet demonstrated a device that would be practical for
> _efficiently_ transferring power, yet. They might, but there is a lot
> of power lost in the resonant circuit itself, at least in specific
> oscillator circuit they used in their experiment.
> http://engsci.unavoidable.ca/esc201/esc201-praxis-researchreviewpaper-wirelesspower.pdf
> and
> http://www.google.com/#sclient=psy&hl=en&source=hp&q=Wireless+Power+Transfer+via+Strongly+Coupled+Magnetic+Resonances+&aq=f&aqi=g1g-v4&aql=f&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=c47720ba43ce4197
>
> When they manage to demonstrate good efficiency "from the wall to the
> load" then we should open the champaign. Until then, there is nothing
> wrong with a $20 plug and receptacle.
>
> Bill Dube'
>
> At 02:44 PM 5/7/2011, you wrote:
>>Sounds like they starting to catch up to Tesla, who did it a century ago.
>>
>>-----Original Message-----
>>From: [hidden email] [mailto:[hidden email]] On
>>Behalf
>>Of brucedp4
>>Sent: Saturday, 7 May 2011 10:39 p.m.
>>To: [hidden email]
>>Subject: [EVDL] Toyota developing wireless charging
>>
>>
>>Resonance charging more efficient than electromagnetic-induction
>>
>>http://www.automotiveit.com/toyota-to-develop-wireless-charging-with-witrici
>>ty/news/id-002572
>>[image] Toyota to develop wireless charging with WiTricity
>>May 1, 2011
>>
>>Toyota said it has entered a technical cooperation with WiTricity to
>>develop wireless charging systems for electric-vehicle batteries.
>>
>>
>>_______________________________________________
>>| REPLYING: address your message to [hidden email] only.
>>| Multiple-address or CCed messages may be rejected.
>>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>>| OTHER HELP: http://evdl.org/help/
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>
> _______________________________________________
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Re: "WiTricity" (was: Toyota developing wireless charging)

Bill Dube
My sentiments exactly.

At 08:17 PM 5/8/2011, you wrote:

>Efficient wireless energy transfer is another pipe dream. Even if they could
>achieve 85% that is not good enough.
>Here we are trying to improve efficiency with electric vehicles and now they
>want to throw that efficiency out the window because they are to lazy to
>plug in a cord?
>Give me a break.
>
>Al
>
>----- Original Message -----
>From: "Bill Dube" <[hidden email]>
>To: "Electric Vehicle Discussion List" <[hidden email]>
>Sent: Sunday, May 08, 2011 12:58 AM
>Subject: [EVDL] "WiTricity" (was: Toyota developing wireless charging)
>
>
> > The "wall to load" efficiency of the overall circuit was only 15%. :-(
> >
> > The theory looks very interesting, especially the low measured RF
> > power between the transmitter and the receiver coils, which is
> > roughly just 10% of the actual power transmitted to the load. They
> > have not as yet demonstrated a device that would be practical for
> > _efficiently_ transferring power, yet. They might, but there is a lot
> > of power lost in the resonant circuit itself, at least in specific
> > oscillator circuit they used in their experiment.
> >
> http://engsci.unavoidable.ca/esc201/esc201-praxis-researchreviewpaper-wirelesspower.pdf
> > and
> >
> http://www.google.com/#sclient=psy&hl=en&source=hp&q=Wireless+Power+Transfer+via+Strongly+Coupled+Magnetic+Resonances+&aq=f&aqi=g1g-v4&aql=f&oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=c47720ba43ce4197
> >
> > When they manage to demonstrate good efficiency "from the wall to the
> > load" then we should open the champaign. Until then, there is nothing
> > wrong with a $20 plug and receptacle.
> >
> > Bill Dube'
> >
> > At 02:44 PM 5/7/2011, you wrote:
> >>Sounds like they starting to catch up to Tesla, who did it a century ago.
> >>
> >>-----Original Message-----
> >>From: [hidden email] [mailto:[hidden email]] On
> >>Behalf
> >>Of brucedp4
> >>Sent: Saturday, 7 May 2011 10:39 p.m.
> >>To: [hidden email]
> >>Subject: [EVDL] Toyota developing wireless charging
> >>
> >>
> >>Resonance charging more efficient than electromagnetic-induction
> >>
> >>http://www.automotiveit.com/toyota-to-develop-wireless-charging-wi 
> th-witrici
> >>ty/news/id-002572
> >>[image] Toyota to develop wireless charging with WiTricity
> >>May 1, 2011
> >>
> >>Toyota said it has entered a technical cooperation with WiTricity to
> >>develop wireless charging systems for electric-vehicle batteries.
> >>
> >>
> >>_______________________________________________
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> >
> > _______________________________________________
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>
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Re: "WiTricity" (was: Toyota developing wireless charging)

Cor van de Water
So what would you say if a device was designed
that can be installed in the garage or carport
of an EV owner and when you drive the EV roughly
over it, this would feed the car with, say 98%
efficiency while having the added advantages
that it does not require to plug or (forgetting
to) unplug the vehicle, is inherently safe
because of the isolation it provides, will
automatically start charging when an EV is
detected and preset parameters are met (such
as time of day for charging at night during
low tariff) or even identify the
vehicle for billing per car.

I understand that for the majority of the
population there is no issue with plugging
in a device like a cellphone or a vacuum,
but there is a reason that many people pay
premium prices for wireless/cordless equipment
and this usually has to do with convenience.
If an EV can offer this without hurting the
efficiency too much, would you still feel
the same sentiment?

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     IM: [hidden email]
Tel: +1 408 383 7626        VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of Bill Dube
Sent: Sunday, May 08, 2011 9:48 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] "WiTricity" (was: Toyota developing wireless
charging)

My sentiments exactly.

At 08:17 PM 5/8/2011, you wrote:
>Efficient wireless energy transfer is another pipe dream. Even if they
>could achieve 85% that is not good enough.
>Here we are trying to improve efficiency with electric vehicles and now

>they want to throw that efficiency out the window because they are to
>lazy to plug in a cord?
>Give me a break.
>
>Al
>
>----- Original Message -----
>From: "Bill Dube" <[hidden email]>
>To: "Electric Vehicle Discussion List" <[hidden email]>
>Sent: Sunday, May 08, 2011 12:58 AM
>Subject: [EVDL] "WiTricity" (was: Toyota developing wireless charging)
>
>
> > The "wall to load" efficiency of the overall circuit was only 15%.
> > :-(
> >
> > The theory looks very interesting, especially the low measured RF
> > power between the transmitter and the receiver coils, which is
> > roughly just 10% of the actual power transmitted to the load. They
> > have not as yet demonstrated a device that would be practical for
> > _efficiently_ transferring power, yet. They might, but there is a
> > lot of power lost in the resonant circuit itself, at least in
> > specific oscillator circuit they used in their experiment.
> >
> http://engsci.unavoidable.ca/esc201/esc201-praxis-researchreviewpaper-
> wirelesspower.pdf
> > and
> >
> http://www.google.com/#sclient=psy&hl=en&source=hp&q=Wireless+Power+Tr
> ansfer+via+Strongly+Coupled+Magnetic+Resonances+&aq=f&aqi=g1g-v4&aql=f
> &oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=c47720ba43ce4197
> >
> > When they manage to demonstrate good efficiency "from the wall to
> > the load" then we should open the champaign. Until then, there is
> > nothing wrong with a $20 plug and receptacle.
> >
> > Bill Dube'
> >
> > At 02:44 PM 5/7/2011, you wrote:
> >>Sounds like they starting to catch up to Tesla, who did it a century
ago.

> >>
> >>-----Original Message-----
> >>From: [hidden email] [mailto:[hidden email]]
> >>On Behalf Of brucedp4
> >>Sent: Saturday, 7 May 2011 10:39 p.m.
> >>To: [hidden email]
> >>Subject: [EVDL] Toyota developing wireless charging
> >>
> >>
> >>Resonance charging more efficient than electromagnetic-induction
> >>
> >>http://www.automotiveit.com/toyota-to-develop-wireless-charging-wi
> th-witrici
> >>ty/news/id-002572
> >>[image] Toyota to develop wireless charging with WiTricity May 1,
> >>2011
> >>
> >>Toyota said it has entered a technical cooperation with WiTricity to

> >>develop wireless charging systems for electric-vehicle batteries.
> >>
> >>
> >>_______________________________________________
> >>| REPLYING: address your message to [hidden email] only.
> >>| Multiple-address or CCed messages may be rejected.
> >>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> >
> > _______________________________________________
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> > | Multiple-address or CCed messages may be rejected.
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>
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Re: "WiTricity" (was: Toyota developing wireless charging)

martinwinlow
In reply to this post by Bill Dube
Im with you, Bill, but...

For those of us beyond using a plug (*so* passe) I had wondered about  
a direct connection using an extendable boom which mates with a  
receptacle - the only analogy I can think of is the mid-air refueling  
system used by military aircraft.  As you drive into your garage or a  
parking bay, you deploy your articulated/compressible boom and it  
finds its way into the cone-shaped receiver.  Once properly engaged it  
signals you to stop and the two systems talk to each other and off you  
go.  Wouldn't work on the street tho.

Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk

On 9 May 2011, at 05:47, Bill Dube wrote:

> My sentiments exactly.
>
> At 08:17 PM 5/8/2011, you wrote:
>> Efficient wireless energy transfer is another pipe dream. Even if  
>> they could
>> achieve 85% that is not good enough.
>> Here we are trying to improve efficiency with electric vehicles and  
>> now they
>> want to throw that efficiency out the window because they are to  
>> lazy to
>> plug in a cord?
>> Give me a break.
>>
>> Al
>>

_______________________________________________
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Re: "WiTricity" (was: Toyota developing wireless charging)

Jeffrey Jenkins
In reply to this post by Bill Dube
Bill Dube wrote
Read the papers they have published, and the reviews of those papers
(all on line) and then comment.
Seriously? You think I need to read the one paper you provided - which was essentially a student summarizing the work of other students as well as a Popular Science magazine article - before commenting? That's pretty funny, actually.


Bill Dube wrote
There are many things we _wish_ were true, but non-contact charging
is not a reality.
That may very well end up being the case, but I certainly wouldn't make this kind of snap judgment and I've actually designed a few high power resonant-mode power converters and RF amplifiers. What makes you qualified to do so?


Bill Dube wrote
...It is quite possible (not a certainty, but
possible) that the actual RF field between the coils is transferring
energy at some efficiency nearing 50%, the resonant circuit needed to
make that happen has _terrible_ efficiency.
The coupling efficiency between two tuned resonant circuits depends a lot on how closely matched their resonant frequencies are (especially as Q goes up): if both tanks resonate at the exact same frequency then the coupling efficiency will approach 100% (dependent then on separation distance). The efficiency of the resonant circuits themselves depends entirely on their Q, or the ratio of reactance to resistance (which in turn describes the ratio of stored power to wasted power, I^2X/I^2R). E.g. - a resonant circuit with Q of 10 is 90% efficient.
 

Bill Dube wrote
Resonant circuits slosh the energy back and forth, by their very
nature. If you think about it for a few minutes, it becomes apparent
that any time you move large quantities of energy back and forth, you
just can't avoid losses with every cycle. It is like pouring water
from one glass to another. You splash or spill just a tiny bit each
time, unavoidably.
Sure, you are correct in principle, but just like with a lot of other things in engineering the devil is in the details. For a realistic example, let's consider two resonant circuits - transmitter and receiver - that each have a Q of 10. Already we know that the ratio of stored power to wasted power is 10:1, which is to say that 10% of the power is lost as heat. Knowing Q also allows us to determine the 3dB bandwidth points, or the frequency at which power has dropped off to 70.7%, with the equation BW = Fc/Q.

If the two resonant circuits are perfectly tuned to each other - ie, Fc is exactly the same for both - then the maximum overall efficiency will be 0.9 x 0.9 or 81%. If one tank is at the -3dB point then the maximum overall efficiency is 0.9 x 0.9 x 0.707 or 57%. If both tanks are -3dB off (one is higher than Fc, the other lower) then the cumulative efficiency will be 0.9 x 0.9 x 0.707 x 0.707, or 40%. It's pretty obvious, then, that matching the resonant frequencies of the two circuits is extremely important, especially if Q has also been maximized to minimize the resistive losses.

Fortunately, it is actually quite simple to get the receiver's resonant frequency track that of the transmitter with a PLL - this is precisely what is done in every modern radio, after all. Once it is possible to maintain a nearly perfect match in resonant frequency between transmitter and receiver the Q of each resonant circuit can be increased to a much higher level, especially if highly efficient switchmode circuits (ie - Class E power oscillators) are used instead of the linear-mode oscillator circuits like the Colpitts, Hartley, etc.. A minimum Q for this type of arrangement would be around 20 (each side 95% efficient) while 100 should still be practical (each side 99% efficient).

At a Q of 100, then, very little power is lost in the actual resonant circuits and we instead need to look at the type of amplifier/oscillator used as well as the separation distance between the transmitter and receiver. A Colpitts (or the similar Hartley and Armstrong) oscillator operates the active device (bipolar transistor, MOSFET, vacuum tube, etc.) in the linear mode and will be relatively loss compared to a Class-C design or, especially, a switchmode hybrid class such as Class-E. It is possible with reasonable design effort to reach an efficiency of 98% with a single device Class-E power oscillator compared to 25%-50% for a single device Colpitts.

Finally, coupling efficiency depends on the distance between transmitter and receiver, dropping off dramatically at a distance of 1/6th of a wavelength, or the so-called near-field limit (ie, when the H (magnetic) and E (electric) fields recombine into a single electromagnetic wave). If operating frequency is, say, 10MHz, then the wavelength is 30m and the near-field will extend out to 5m. If the transmitter and receiver are less than, say, 1m apart then the percent coupling efficiency should still be in the high 80's to low 90's. Eminently acceptable for charging at 1-2kW; much less so, obviously, at 10kW+.


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Re: "WiTricity" (was: Toyota developing wireless charging)

Bill Dube
In reply to this post by Cor van de Water
Such an efficient wireless device does not exist. We might as well
debate the merits of a magic carpet that uses no energy whatsoever.
Each is an equal fantasy.

History has shown that the cost of a wireless charger will be greater
than the total cost of the electricity the EV will use in its entire
lifetime. Much greater. These devices may seem like a good idea, but
they are bad for EVs in the long term.

You notice the complicated and expensive regulations surrounding
plugging in an EV. The plug and receptacle for anything above 120
volts is _really_ expensive and complicated. (A $20 NEMA 14-50 mobile
home (RV) plug would do quite nicely, but is not allowed to supply
power to charge an EV.) This is the direct result of the actions of
the Huges Magnacharger folks. They patented an inductive charger that
was substantially more expensive than a simple plug. To make their
product more cost competitive, they lobbied the NEC to make the rules
for conductive charging EVs insanely expensive to comply with.

The MagnaCharger never caught on, because it cost so much, (and was
inefficient) but we are now and forever burdened with the legacy of
their lobbying of the NEC that makes conductive charging much more
expensive than it ever should have been.

I have issues with false claims that give unrealistic impressions
about inductive charging to the general public, for very good
reasons, as you now understand.

Bill D.

At 11:53 PM 5/8/2011, you wrote:

>So what would you say if a device was designed
>that can be installed in the garage or carport
>of an EV owner and when you drive the EV roughly
>over it, this would feed the car with, say 98%
>efficiency while having the added advantages
>that it does not require to plug or (forgetting
>to) unplug the vehicle, is inherently safe
>because of the isolation it provides, will
>automatically start charging when an EV is
>detected and preset parameters are met (such
>as time of day for charging at night during
>low tariff) or even identify the
>vehicle for billing per car.
>
>I understand that for the majority of the
>population there is no issue with plugging
>in a device like a cellphone or a vacuum,
>but there is a reason that many people pay
>premium prices for wireless/cordless equipment
>and this usually has to do with convenience.
>If an EV can offer this without hurting the
>efficiency too much, would you still feel
>the same sentiment?
>
>Cor van de Water
>Director HW & Systems Architecture Group
>Proxim Wireless Corporation http://www.proxim.com
>Email: [hidden email]    Private: http://www.cvandewater.com
>Skype: cor_van_de_water     IM: [hidden email]
>Tel: +1 408 383 7626        VoIP: +31 20 3987567 FWD# 25925
>Tel: +91 (040)23117400 x203 XoIP: +31877841130
>
>-----Original Message-----
>From: [hidden email] [mailto:[hidden email]] On
>Behalf Of Bill Dube
>Sent: Sunday, May 08, 2011 9:48 PM
>To: Electric Vehicle Discussion List
>Subject: Re: [EVDL] "WiTricity" (was: Toyota developing wireless
>charging)
>
>My sentiments exactly.
>
>At 08:17 PM 5/8/2011, you wrote:
> >Efficient wireless energy transfer is another pipe dream. Even if they
> >could achieve 85% that is not good enough.
> >Here we are trying to improve efficiency with electric vehicles and now
>
> >they want to throw that efficiency out the window because they are to
> >lazy to plug in a cord?
> >Give me a break.
> >
> >Al
> >
> >----- Original Message -----
> >From: "Bill Dube" <[hidden email]>
> >To: "Electric Vehicle Discussion List" <[hidden email]>
> >Sent: Sunday, May 08, 2011 12:58 AM
> >Subject: [EVDL] "WiTricity" (was: Toyota developing wireless charging)
> >
> >
> > > The "wall to load" efficiency of the overall circuit was only 15%.
> > > :-(
> > >
> > > The theory looks very interesting, especially the low measured RF
> > > power between the transmitter and the receiver coils, which is
> > > roughly just 10% of the actual power transmitted to the load. They
> > > have not as yet demonstrated a device that would be practical for
> > > _efficiently_ transferring power, yet. They might, but there is a
> > > lot of power lost in the resonant circuit itself, at least in
> > > specific oscillator circuit they used in their experiment.
> > >
> > http://engsci.unavoidable.ca/esc201/esc201-praxis-researchreviewpaper-
> > wirelesspower.pdf
> > > and
> > >
> > http://www.google.com/#sclient=psy&hl=en&source=hp&q=Wireless+Power+Tr
> > ansfer+via+Strongly+Coupled+Magnetic+Resonances+&aq=f&aqi=g1g-v4&aql=f
> > &oq=&pbx=1&bav=on.2,or.r_gc.r_pw.&fp=c47720ba43ce4197
> > >
> > > When they manage to demonstrate good efficiency "from the wall to
> > > the load" then we should open the champaign. Until then, there is
> > > nothing wrong with a $20 plug and receptacle.
> > >
> > > Bill Dube'
> > >
> > > At 02:44 PM 5/7/2011, you wrote:
> > >>Sounds like they starting to catch up to Tesla, who did it a century
>ago.
> > >>
> > >>-----Original Message-----
> > >>From: [hidden email] [mailto:[hidden email]]
> > >>On Behalf Of brucedp4
> > >>Sent: Saturday, 7 May 2011 10:39 p.m.
> > >>To: [hidden email]
> > >>Subject: [EVDL] Toyota developing wireless charging
> > >>
> > >>
> > >>Resonance charging more efficient than electromagnetic-induction
> > >>
> > >>http://www.automotiveit.com/toyota-to-develop-wireless-charging-wi
> > th-witrici
> > >>ty/news/id-002572
> > >>[image] Toyota to develop wireless charging with WiTricity May 1,
> > >>2011
> > >>
> > >>Toyota said it has entered a technical cooperation with WiTricity to
>
> > >>develop wireless charging systems for electric-vehicle batteries.
> > >>
> > >>
> > >>_______________________________________________
> > >>| REPLYING: address your message to [hidden email] only.
> > >>| Multiple-address or CCed messages may be rejected.
> > >>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > >>| OTHER HELP: http://evdl.org/help/
> > >>| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
> > >
> > > _______________________________________________
> > > | REPLYING: address your message to [hidden email] only.
> > > | Multiple-address or CCed messages may be rejected.
> > > | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> >
> >_______________________________________________
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>
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Re: "WiTricity" (was: Toyota developing wireless charging)

Bill Dube
In reply to this post by martinwinlow
Have a little robot arm simply put in the plug when it sees the EV near by.


At 02:40 AM 5/9/2011, you wrote:

>Im with you, Bill, but...
>
>For those of us beyond using a plug (*so* passe) I had wondered about
>a direct connection using an extendable boom which mates with a
>receptacle - the only analogy I can think of is the mid-air refueling
>system used by military aircraft.  As you drive into your garage or a
>parking bay, you deploy your articulated/compressible boom and it
>finds its way into the cone-shaped receiver.  Once properly engaged it
>signals you to stop and the two systems talk to each other and off you
>go.  Wouldn't work on the street tho.
>
>Regards, Martin Winlow
>Herts, UK
>http://www.evalbum.com/2092
>www.winlow.co.uk
>
>On 9 May 2011, at 05:47, Bill Dube wrote:
>
> > My sentiments exactly.
> >
> > At 08:17 PM 5/8/2011, you wrote:
> >> Efficient wireless energy transfer is another pipe dream. Even if
> >> they could
> >> achieve 85% that is not good enough.
> >> Here we are trying to improve efficiency with electric vehicles and
> >> now they
> >> want to throw that efficiency out the window because they are to
> >> lazy to
> >> plug in a cord?
> >> Give me a break.
> >>
> >> Al
> >>
>
>_______________________________________________
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>| OTHER HELP: http://evdl.org/help/
>| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

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Re: "WiTricity" (was: Toyota developing wireless charging)

Bill Dube
In reply to this post by Jeffrey Jenkins
If you read the paper, or the links to the review, you will discover
that the efficiency of the resonant link was 45% and the efficiency
of the system, wall to load, was just 15%.

Read the publications by the original author, then comment. I gave
the link. You can Google the articles on-line yourself if my links
are not working.

Would you be willing to wirelessly connect your house, if it were to
double your electric bill? How about if your bill were to be more
than six times what it is now? Would you be willing to pay $5000 for
the privilege of paying 2 to 6 times more for your electricity? Would
EVs be an economic advantage if they used twice, or six times the
normal amount of electricity? Would they be good for the environment?

These type articles give false information to the public about actual
EV technology. This has caused damage to the EV industry before, in
very real terms.

Great for a cell phone, perhaps. Bad for an EV. It is even bad for
people to get the _impression_ that this technology is realistic for
use in an EV.

Bill D.

At 07:12 AM 5/9/2011, you wrote:

>Bill Dube wrote:
> >
> > Read the papers they have published, and the reviews of those papers
> > (all on line) and then comment.
>
>Seriously? You think I need to read the one paper you provided - which was
>essentially a student summarizing the work of other students as well as a
>Popular Science magazine article - before commenting? That's pretty funny,
>actually.
>
>
>
>Bill Dube wrote:
> > There are many things we _wish_ were true, but non-contact charging
> > is not a reality.
>
>That may very well end up being the case, but I certainly wouldn't make this
>kind of snap judgment and I've actually designed a few high power
>resonant-mode power converters and RF amplifiers. What makes you qualified
>to do so?
>
>
>
>Bill Dube wrote:
> > ...It is quite possible (not a certainty, but
> > possible) that the actual RF field between the coils is transferring
> > energy at some efficiency nearing 50%, the resonant circuit needed to
> > make that happen has _terrible_ efficiency.
>
>The coupling efficiency between two tuned resonant circuits depends a lot on
>how closely matched their resonant frequencies are (especially as Q goes
>up): if both tanks resonate at the exact same frequency then the coupling
>efficiency will approach 100% (dependent then on separation distance). The
>efficiency of the resonant circuits themselves depends entirely on their Q,
>or the ratio of reactance to resistance (which in turn describes the ratio
>of stored power to wasted power, I^2X/I^2R). E.g. - a resonant circuit with
>Q of 10 is 90% efficient.
>
>
>
>Bill Dube wrote:
> > Resonant circuits slosh the energy back and forth, by their very
> > nature. If you think about it for a few minutes, it becomes apparent
> > that any time you move large quantities of energy back and forth, you
> > just can't avoid losses with every cycle. It is like pouring water
> > from one glass to another. You splash or spill just a tiny bit each
> > time, unavoidably.
>
>Sure, you are correct in principle, but just like with a lot of other things
>in engineering the devil is in the details. For a realistic example, let's
>consider two resonant circuits - transmitter and receiver - that each have a
>Q of 10. Already we know that the ratio of stored power to wasted power is
>10:1, which is to say that 10% of the power is lost as heat. Knowing Q also
>allows us to determine the 3dB bandwidth points, or the frequency at which
>power has dropped off to 70.7%, with the equation BW = Fc/Q.
>
>If the two resonant circuits are perfectly tuned to each other - ie, Fc is
>exactly the same for both - then the maximum overall efficiency will be 0.9
>x 0.9 or 81%. If one tank is at the -3dB point then the maximum overall
>efficiency is 0.9 x 0.9 x 0.707 or 57%. If both tanks are -3dB off (one is
>higher than Fc, the other lower) then the cumulative efficiency will be 0.9
>x 0.9 x 0.707 x 0.707, or 40%. It's pretty obvious, then, that matching the
>resonant frequencies of the two circuits is extremely important, especially
>if Q has also been maximized to minimize the resistive losses.
>
>Fortunately, it is actually quite simple to get the receiver's resonant
>frequency track that of the transmitter with a PLL - this is precisely what
>is done in every modern radio, after all. Once it is possible to maintain a
>nearly perfect match in resonant frequency between transmitter and receiver
>the Q of each resonant circuit can be increased to a much higher level,
>especially if highly efficient switchmode circuits (ie - Class E power
>oscillators) are used instead of the linear-mode oscillator circuits like
>the Colpitts, Hartley, etc.. A minimum Q for this type of arrangement would
>be around 20 (each side 95% efficient) while 100 should still be practical
>(each side 99% efficient).
>
>At a Q of 100, then, very little power is lost in the actual resonant
>circuits and we instead need to look at the type of amplifier/oscillator
>used as well as the separation distance between the transmitter and
>receiver. A Colpitts (or the similar Hartley and Armstrong) oscillator
>operates the active device (bipolar transistor, MOSFET, vacuum tube, etc.)
>in the linear mode and will be relatively loss compared to a Class-C design
>or, especially, a switchmode hybrid class such as Class-E. It is possible
>with reasonable design effort to reach an efficiency of 98% with a single
>device Class-E power oscillator compared to 25%-50% for a single device
>Colpitts.
>
>Finally, coupling efficiency depends on the distance between transmitter and
>receiver, dropping off dramatically at a distance of 1/6th of a wavelength,
>or the so-called near-field limit (ie, when the H (magnetic) and E
>(electric) fields recombine into a single electromagnetic wave). If
>operating frequency is, say, 10MHz, then the wavelength is 30m and the
>near-field will extend out to 5m. If the transmitter and receiver are less
>than, say, 1m apart then the percent coupling efficiency should still be in
>the high 80's to low 90's. Eminently acceptable for charging at 1-2kW; much
>less so, obviously, at 10kW+.
>
>
>
>
>--
>View this message in context:
>http://electric-vehicle-discussion-list.413529.n4.nabble.com/Toyota-developing-wireless-charging-tp3505313p3509210.html
>Sent from the Electric Vehicle Discussion List mailing list archive
>at Nabble.com.
>
>_______________________________________________
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Re: "WiTricity"

Lee Hart
In reply to this post by Bill Dube
> Efficient wireless energy transfer is another pipe dream. Even if
> they could achieve 85% that is not good enough. Here we are trying to
> improve efficiency with electric vehicles and now they want to throw
> that efficiency out the window because they are to lazy to plug in a
> cord? Give me a break.

It's impossible to beat a direct plug-in connector on efficiency. But at
least in some people's eyes, they can beat it on convenience and safety.
This is the driving force between these wireless solutions.

The big unknown: How much more will people pay for perceived convenience
and safety? If the GM EV1 had been offered with both conductive and
inductive charging options (at different prices, reflecting the
differences in efficiency and safety), which one would people have
chosen? My guess is that all but a few would choose conductive, since it
lowers the cost of both the charger and the electricity. The
Magnecharger inductive paddle was no more convenient than an Avcon
connector, and given the overheating and fires, probably no safer.

It's one thing to have a cordless toothbrush or cellphone that you
recharge by just getting it "near" its charging station. It only takes a
nickel's worth of electricity to charge it; so who cares if the
inductive system is 50% efficient; it only raises the price to ten cents
per charge.

If one really *needs* the convenience and safety of an inductive
charger, I think it would be better to look at the Inductran system.
It's basically an ordinary 60 Hz transformer cut in half, with one have
in the pavement below the vehicle, and the other half under the vehicle.
During charging the two halves move so they are tightly coupled
together. This provides efficiency and safety essentially identical to a
conventional transformer isolated charger.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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Re: "WiTricity"

Lee Hart
In reply to this post by martinwinlow
On 5/9/2011 3:40 AM, Martin WINLOW wrote:

> Im with you, Bill, but...
>
> For those of us beyond using a plug (*so* passe) I had wondered about
> a direct connection using an extendable boom which mates with a
> receptacle - the only analogy I can think of is the mid-air refueling
> system used by military aircraft.  As you drive into your garage or a
> parking bay, you deploy your articulated/compressible boom and it
> finds its way into the cone-shaped receiver.  Once properly engaged it
> signals you to stop and the two systems talk to each other and off you
> go.  Wouldn't work on the street tho.

There is always Bob Rice's solution. He laid a piece of plywood on the
floor. It had two leaf spring "brushes" that connected to the charger.
Under the car were the mating contact shoes. When you drove over the
brushes so they hit the contact shoes, it completed the circuit. Pack
voltage (through a resistor) on the shoes was conducted back to the
charger, which pulled in a relay to turn on AC to the charger.

Thus, the leaf springs were dead when there was no car, and only became
live when the car was present. You then could not touch the springs or
shoes to get a shock, as the car was in the way.

Simple, straightforward, direct. Typical Bob Engineering! :-)

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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Robotic plug-in (was: "WiTricity")

Bill Dube
In reply to this post by Lee Hart
The best automatic system would be a robotic arm with a vision system
that located the inlet on the car, then put in the plug for you. When
you opened the car door to get in, it would see you do that and
remove the plug automatically. Probably a $500 item in mass
production for a specific car in a home charging situation. 99.9%
energy efficiency. Functionally identical to non-contact charging,
but with none of the costs or inefficiencies.

In a public facility, it could even recognize the needed brand and
style of plug, and then select the right one to use.

If they can wash your car with a robot, and build most of your car
with robots, they can certainly plug it in with a robot.

Bill D.

At 11:55 AM 5/9/2011, you wrote:

> > Efficient wireless energy transfer is another pipe dream. Even if
> > they could achieve 85% that is not good enough. Here we are trying to
> > improve efficiency with electric vehicles and now they want to throw
> > that efficiency out the window because they are to lazy to plug in a
> > cord? Give me a break.
>
>It's impossible to beat a direct plug-in connector on efficiency. But at
>least in some people's eyes, they can beat it on convenience and safety.
>This is the driving force between these wireless solutions.
>
>The big unknown: How much more will people pay for perceived convenience
>and safety? If the GM EV1 had been offered with both conductive and
>inductive charging options (at different prices, reflecting the
>differences in efficiency and safety), which one would people have
>chosen? My guess is that all but a few would choose conductive, since it
>lowers the cost of both the charger and the electricity. The
>Magnecharger inductive paddle was no more convenient than an Avcon
>connector, and given the overheating and fires, probably no safer.
>
>It's one thing to have a cordless toothbrush or cellphone that you
>recharge by just getting it "near" its charging station. It only takes a
>nickel's worth of electricity to charge it; so who cares if the
>inductive system is 50% efficient; it only raises the price to ten cents
>per charge.
>
>If one really *needs* the convenience and safety of an inductive
>charger, I think it would be better to look at the Inductran system.
>It's basically an ordinary 60 Hz transformer cut in half, with one have
>in the pavement below the vehicle, and the other half under the vehicle.
>During charging the two halves move so they are tightly coupled
>together. This provides efficiency and safety essentially identical to a
>conventional transformer isolated charger.
>--
>Lee A. Hart             | Ring the bells that still can ring
>814 8th Ave N           | Forget the perfect offering
>Sartell MN 56377        | There is a crack in everything
>leeahart earthlink.net  | That's how the light gets in -- Leonard Cohen
>
>_______________________________________________
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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>| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

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Bob Rice's "inverted slot car" solution (was: "WiTricity")

Bill Dube
In reply to this post by Lee Hart
Absolutely perfect.

Leave it to Bob Rice to cut through the techno-crap and come up with
the most practical solution.

Bill D.

At 12:03 PM 5/9/2011, you wrote:

>On 5/9/2011 3:40 AM, Martin WINLOW wrote:
> > Im with you, Bill, but...
> >
> > For those of us beyond using a plug (*so* passe) I had wondered about
> > a direct connection using an extendable boom which mates with a
> > receptacle - the only analogy I can think of is the mid-air refueling
> > system used by military aircraft.  As you drive into your garage or a
> > parking bay, you deploy your articulated/compressible boom and it
> > finds its way into the cone-shaped receiver.  Once properly engaged it
> > signals you to stop and the two systems talk to each other and off you
> > go.  Wouldn't work on the street tho.
>
>There is always Bob Rice's solution. He laid a piece of plywood on the
>floor. It had two leaf spring "brushes" that connected to the charger.
>Under the car were the mating contact shoes. When you drove over the
>brushes so they hit the contact shoes, it completed the circuit. Pack
>voltage (through a resistor) on the shoes was conducted back to the
>charger, which pulled in a relay to turn on AC to the charger.
>
>Thus, the leaf springs were dead when there was no car, and only became
>live when the car was present. You then could not touch the springs or
>shoes to get a shock, as the car was in the way.
>
>Simple, straightforward, direct. Typical Bob Engineering! :-)
>
>--
>Lee A. Hart             | Ring the bells that still can ring
>814 8th Ave N           | Forget the perfect offering
>Sartell MN 56377        | There is a crack in everything
>leeahart earthlink.net  | That's how the light gets in -- Leonard Cohen
>
>_______________________________________________
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>| OTHER HELP: http://evdl.org/help/
>| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

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Re: "WiTricity" (was: Toyota developing wireless charging)

Cor van de Water
In reply to this post by Bill Dube
Bill,

I get the impression you did not read what Jeffrey wrote.

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     IM: [hidden email]
Tel: +1 408 383 7626        VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of Bill Dube
Sent: Monday, May 09, 2011 7:35 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] "WiTricity" (was: Toyota developing wireless
charging)

If you read the paper, or the links to the review, you will discover
that the efficiency of the resonant link was 45% and the efficiency of
the system, wall to load, was just 15%.

Read the publications by the original author, then comment. I gave the
link. You can Google the articles on-line yourself if my links are not
working.

Would you be willing to wirelessly connect your house, if it were to
double your electric bill? How about if your bill were to be more than
six times what it is now? Would you be willing to pay $5000 for the
privilege of paying 2 to 6 times more for your electricity? Would EVs be
an economic advantage if they used twice, or six times the normal amount
of electricity? Would they be good for the environment?

These type articles give false information to the public about actual EV
technology. This has caused damage to the EV industry before, in very
real terms.

Great for a cell phone, perhaps. Bad for an EV. It is even bad for
people to get the _impression_ that this technology is realistic for use
in an EV.

Bill D.

At 07:12 AM 5/9/2011, you wrote:

>Bill Dube wrote:
> >
> > Read the papers they have published, and the reviews of those papers

> > (all on line) and then comment.
>
>Seriously? You think I need to read the one paper you provided - which
>was essentially a student summarizing the work of other students as
>well as a Popular Science magazine article - before commenting? That's
>pretty funny, actually.
>
>
>
>Bill Dube wrote:
> > There are many things we _wish_ were true, but non-contact charging
> > is not a reality.
>
>That may very well end up being the case, but I certainly wouldn't make

>this kind of snap judgment and I've actually designed a few high power
>resonant-mode power converters and RF amplifiers. What makes you
>qualified to do so?
>
>
>
>Bill Dube wrote:
> > ...It is quite possible (not a certainty, but
> > possible) that the actual RF field between the coils is transferring

> > energy at some efficiency nearing 50%, the resonant circuit needed
> > to make that happen has _terrible_ efficiency.
>
>The coupling efficiency between two tuned resonant circuits depends a
>lot on how closely matched their resonant frequencies are (especially
>as Q goes
>up): if both tanks resonate at the exact same frequency then the
>coupling efficiency will approach 100% (dependent then on separation
>distance). The efficiency of the resonant circuits themselves depends
>entirely on their Q, or the ratio of reactance to resistance (which in
>turn describes the ratio of stored power to wasted power, I^2X/I^2R).
>E.g. - a resonant circuit with Q of 10 is 90% efficient.
>
>
>
>Bill Dube wrote:
> > Resonant circuits slosh the energy back and forth, by their very
> > nature. If you think about it for a few minutes, it becomes apparent

> > that any time you move large quantities of energy back and forth,
> > you just can't avoid losses with every cycle. It is like pouring
> > water from one glass to another. You splash or spill just a tiny bit

> > each time, unavoidably.
>
>Sure, you are correct in principle, but just like with a lot of other
>things in engineering the devil is in the details. For a realistic
>example, let's consider two resonant circuits - transmitter and
>receiver - that each have a Q of 10. Already we know that the ratio of
>stored power to wasted power is 10:1, which is to say that 10% of the
>power is lost as heat. Knowing Q also allows us to determine the 3dB
>bandwidth points, or the frequency at which power has dropped off to
70.7%, with the equation BW = Fc/Q.
>
>If the two resonant circuits are perfectly tuned to each other - ie, Fc

>is exactly the same for both - then the maximum overall efficiency will

>be 0.9 x 0.9 or 81%. If one tank is at the -3dB point then the maximum
>overall efficiency is 0.9 x 0.9 x 0.707 or 57%. If both tanks are -3dB
>off (one is higher than Fc, the other lower) then the cumulative
>efficiency will be 0.9 x 0.9 x 0.707 x 0.707, or 40%. It's pretty
>obvious, then, that matching the resonant frequencies of the two
>circuits is extremely important, especially if Q has also been
maximized to minimize the resistive losses.
>
>Fortunately, it is actually quite simple to get the receiver's resonant

>frequency track that of the transmitter with a PLL - this is precisely
>what is done in every modern radio, after all. Once it is possible to
>maintain a nearly perfect match in resonant frequency between
>transmitter and receiver the Q of each resonant circuit can be
>increased to a much higher level, especially if highly efficient
>switchmode circuits (ie - Class E power
>oscillators) are used instead of the linear-mode oscillator circuits
>like the Colpitts, Hartley, etc.. A minimum Q for this type of
>arrangement would be around 20 (each side 95% efficient) while 100
>should still be practical (each side 99% efficient).
>
>At a Q of 100, then, very little power is lost in the actual resonant
>circuits and we instead need to look at the type of
>amplifier/oscillator used as well as the separation distance between
>the transmitter and receiver. A Colpitts (or the similar Hartley and
>Armstrong) oscillator operates the active device (bipolar transistor,
>MOSFET, vacuum tube, etc.) in the linear mode and will be relatively
>loss compared to a Class-C design or, especially, a switchmode hybrid
>class such as Class-E. It is possible with reasonable design effort to
>reach an efficiency of 98% with a single device Class-E power
>oscillator compared to 25%-50% for a single device Colpitts.
>
>Finally, coupling efficiency depends on the distance between
>transmitter and receiver, dropping off dramatically at a distance of
>1/6th of a wavelength, or the so-called near-field limit (ie, when the
>H (magnetic) and E
>(electric) fields recombine into a single electromagnetic wave). If
>operating frequency is, say, 10MHz, then the wavelength is 30m and the
>near-field will extend out to 5m. If the transmitter and receiver are
>less than, say, 1m apart then the percent coupling efficiency should
>still be in the high 80's to low 90's. Eminently acceptable for
>charging at 1-2kW; much less so, obviously, at 10kW+.
>
>
>
>
>--
>View this message in context:
>http://electric-vehicle-discussion-list.413529.n4.nabble.com/Toyota-dev
>eloping-wireless-charging-tp3505313p3509210.html
>Sent from the Electric Vehicle Discussion List mailing list archive at
>Nabble.com.
>
>_______________________________________________
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
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Re: "WiTricity" (was: Toyota developing wireless charging)

Bill Dube
I read what Jeffrey wrote entirely. I read it again just now to make
sure there wasn't something I had missed earlier.

         No question that resonant circuits can have high "Q's".
However, when you are handling high power, the I^2 x R loss hammers
you. The Q goes into the toilet. The ESR of the capacitor typically
eats your lunch. What works marvelously and cheaply at tiny power
levels often does not scale well because of these sort of non-linear effects.

         The 85% losses (15% efficiency) they measured when
transmitting 60 watts could likely be the consequence of the I^2 x R
losses in the capacitors of the resonant transmitter circuit. Might
well be other things in the transmitter, but that is my guess.

         The resonant system they devised suppresses the electric
field component of the standing electro-magnetic wave between the
coil elements and makes _that_ portion of the system more efficient
than the standard type inductive coupling method (according to the
article.) My take on the system is that the resonant circuit in the
transmitter has to circulate a _lot_ of current/power to suppress the
electric field component of the standing wave. Thus, in my opinion,
they move the unavoidable losses from one portion of the system to
another. They then tout how low the losses are in that lower-loss
portion of the system. In this case, they very honestly noted the 15%
total system efficiency in the article. Many folks don't read those
details, however.

         It is indeed an interesting approach. It appears to
significantly reduce the RF leakage/exposure, which is a very useful
attribute. Fantastic if you don't care about efficiency, but RF
exposure reduction is your prime goal. The system, as a whole, has
the same or worse (dismal) efficiency as other "wireless" energy
transfer devices, however. This is why such systems are not practical
for EV charging. Even modest losses are unacceptably expensive when
you are transferring that much energy.

Bill D.

At 03:36 PM 5/9/2011, you wrote:

>Bill,
>
>I get the impression you did not read what Jeffrey wrote.
>
>Cor van de Water
>Director HW & Systems Architecture Group
>Proxim Wireless Corporation http://www.proxim.com
>Email: [hidden email]    Private: http://www.cvandewater.com
>Skype: cor_van_de_water     IM: [hidden email]
>Tel: +1 408 383 7626        VoIP: +31 20 3987567 FWD# 25925
>Tel: +91 (040)23117400 x203 XoIP: +31877841130
>
>-----Original Message-----
>From: [hidden email] [mailto:[hidden email]] On
>Behalf Of Bill Dube
>Sent: Monday, May 09, 2011 7:35 AM
>To: Electric Vehicle Discussion List
>Subject: Re: [EVDL] "WiTricity" (was: Toyota developing wireless
>charging)
>
>If you read the paper, or the links to the review, you will discover
>that the efficiency of the resonant link was 45% and the efficiency of
>the system, wall to load, was just 15%.
>
>Read the publications by the original author, then comment. I gave the
>link. You can Google the articles on-line yourself if my links are not
>working.
>
>Would you be willing to wirelessly connect your house, if it were to
>double your electric bill? How about if your bill were to be more than
>six times what it is now? Would you be willing to pay $5000 for the
>privilege of paying 2 to 6 times more for your electricity? Would EVs be
>an economic advantage if they used twice, or six times the normal amount
>of electricity? Would they be good for the environment?
>
>These type articles give false information to the public about actual EV
>technology. This has caused damage to the EV industry before, in very
>real terms.
>
>Great for a cell phone, perhaps. Bad for an EV. It is even bad for
>people to get the _impression_ that this technology is realistic for use
>in an EV.
>
>Bill D.
>
>At 07:12 AM 5/9/2011, you wrote:
>
> >Bill Dube wrote:
> > >
> > > Read the papers they have published, and the reviews of those papers
>
> > > (all on line) and then comment.
> >
> >Seriously? You think I need to read the one paper you provided - which
> >was essentially a student summarizing the work of other students as
> >well as a Popular Science magazine article - before commenting? That's
> >pretty funny, actually.
> >
> >
> >
> >Bill Dube wrote:
> > > There are many things we _wish_ were true, but non-contact charging
> > > is not a reality.
> >
> >That may very well end up being the case, but I certainly wouldn't make
>
> >this kind of snap judgment and I've actually designed a few high power
> >resonant-mode power converters and RF amplifiers. What makes you
> >qualified to do so?
> >
> >
> >
> >Bill Dube wrote:
> > > ...It is quite possible (not a certainty, but
> > > possible) that the actual RF field between the coils is transferring
>
> > > energy at some efficiency nearing 50%, the resonant circuit needed
> > > to make that happen has _terrible_ efficiency.
> >
> >The coupling efficiency between two tuned resonant circuits depends a
> >lot on how closely matched their resonant frequencies are (especially
> >as Q goes
> >up): if both tanks resonate at the exact same frequency then the
> >coupling efficiency will approach 100% (dependent then on separation
> >distance). The efficiency of the resonant circuits themselves depends
> >entirely on their Q, or the ratio of reactance to resistance (which in
> >turn describes the ratio of stored power to wasted power, I^2X/I^2R).
> >E.g. - a resonant circuit with Q of 10 is 90% efficient.
> >
> >
> >
> >Bill Dube wrote:
> > > Resonant circuits slosh the energy back and forth, by their very
> > > nature. If you think about it for a few minutes, it becomes apparent
>
> > > that any time you move large quantities of energy back and forth,
> > > you just can't avoid losses with every cycle. It is like pouring
> > > water from one glass to another. You splash or spill just a tiny bit
>
> > > each time, unavoidably.
> >
> >Sure, you are correct in principle, but just like with a lot of other
> >things in engineering the devil is in the details. For a realistic
> >example, let's consider two resonant circuits - transmitter and
> >receiver - that each have a Q of 10. Already we know that the ratio of
> >stored power to wasted power is 10:1, which is to say that 10% of the
> >power is lost as heat. Knowing Q also allows us to determine the 3dB
> >bandwidth points, or the frequency at which power has dropped off to
>70.7%, with the equation BW = Fc/Q.
> >
> >If the two resonant circuits are perfectly tuned to each other - ie, Fc
>
> >is exactly the same for both - then the maximum overall efficiency will
>
> >be 0.9 x 0.9 or 81%. If one tank is at the -3dB point then the maximum
> >overall efficiency is 0.9 x 0.9 x 0.707 or 57%. If both tanks are -3dB
> >off (one is higher than Fc, the other lower) then the cumulative
> >efficiency will be 0.9 x 0.9 x 0.707 x 0.707, or 40%. It's pretty
> >obvious, then, that matching the resonant frequencies of the two
> >circuits is extremely important, especially if Q has also been
>maximized to minimize the resistive losses.
> >
> >Fortunately, it is actually quite simple to get the receiver's resonant
>
> >frequency track that of the transmitter with a PLL - this is precisely
> >what is done in every modern radio, after all. Once it is possible to
> >maintain a nearly perfect match in resonant frequency between
> >transmitter and receiver the Q of each resonant circuit can be
> >increased to a much higher level, especially if highly efficient
> >switchmode circuits (ie - Class E power
> >oscillators) are used instead of the linear-mode oscillator circuits
> >like the Colpitts, Hartley, etc.. A minimum Q for this type of
> >arrangement would be around 20 (each side 95% efficient) while 100
> >should still be practical (each side 99% efficient).
> >
> >At a Q of 100, then, very little power is lost in the actual resonant
> >circuits and we instead need to look at the type of
> >amplifier/oscillator used as well as the separation distance between
> >the transmitter and receiver. A Colpitts (or the similar Hartley and
> >Armstrong) oscillator operates the active device (bipolar transistor,
> >MOSFET, vacuum tube, etc.) in the linear mode and will be relatively
> >loss compared to a Class-C design or, especially, a switchmode hybrid
> >class such as Class-E. It is possible with reasonable design effort to
> >reach an efficiency of 98% with a single device Class-E power
> >oscillator compared to 25%-50% for a single device Colpitts.
> >
> >Finally, coupling efficiency depends on the distance between
> >transmitter and receiver, dropping off dramatically at a distance of
> >1/6th of a wavelength, or the so-called near-field limit (ie, when the
> >H (magnetic) and E
> >(electric) fields recombine into a single electromagnetic wave). If
> >operating frequency is, say, 10MHz, then the wavelength is 30m and the
> >near-field will extend out to 5m. If the transmitter and receiver are
> >less than, say, 1m apart then the percent coupling efficiency should
> >still be in the high 80's to low 90's. Eminently acceptable for
> >charging at 1-2kW; much less so, obviously, at 10kW+.
> >
> >
> >
> >
> >--
> >View this message in context:
> >http://electric-vehicle-discussion-list.413529.n4.nabble.com/Toyota-dev
> >eloping-wireless-charging-tp3505313p3509210.html
> >Sent from the Electric Vehicle Discussion List mailing list archive at
> >Nabble.com.
> >
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