Marin Colloquium2008

8/13/2019 Marin Colloquium2008

1/56

WiTricity:

non-radiativewireless power transfer


2/56

OUTLINE:

Background and motivation

Resonant coupling as energy transfer

Magnetically coupled resonators

Experimental results

Path forward

Potential applications


3/56

Motivation

Tesla tower:cca. 1904


4/56

Wi-Fi (wireless internet) concept:

radiation


5/56

Radiative energy transfer

Omni-directionalradiation

Directed radiation


6/56

Resonant coupling as energy

transfer


7/56

Resonances in quantum mechanics

nonradiative transfer

Em =

22

2

h

Schrdinger equation

EE 222 = c

Maxwell equation

e-

V(r)

Hydrogen atom

V(r)

proton

quantum tunnelinge-


8/56

Electro-

magneticresonances

=147.70, QR=1992

Optical fiber


9/56

Example of resonant coupling

SourceDevice


10/56

Coupled mode theory

resonant object (Source) resonant object (Device)

( ) DSS aiaii

dt

da += ( ) SD

D aiaiidt

da +=

=

2

Q


11/56

Strong Coupling:

1 efficient energy transfer


12/56

Strong Couplingefficient transfer


13/56

Resonant coupling vs. distance

Source Device

(Distance) / (Object Radius)6 8 10


14/56

Aside: Paris Hilton connection

Aristeidis Karalis Prof. J.D. Joannopoulos


15/56

Robot & Office: simulation

Source Device (robot)


16/56

Robot & Office: radiative scheme


17/56

Robot & Office: non-radiative scheme


18/56



19/56

Magnetically coupledresonators


20/56

B

E

Magnetic resonances

Outside: UE~UB Outside: UE UBMost materials: ~AIR

weak interaction with B-field!


21/56

Examples of magnetic technology

Magnetically levitating bed

Maglev


22/56

Robot & Office:

magneticresonances

AC source ~10MHz

30cm

1m

3-4m

Q~1000

Q~1000


23/56



24/56

Comparison with inductive coupling

L

D

L D L

D

D L

Efficiency R

Efficiency R/Q2~ R/1,000,000


25/56

Experimental results


26/56

source device

200 cm30 cm

60W bulb

Science Magazine, 6th July 2007


27/56

same thing, different viewing angle


28/56

Experimental proof of

strongly-coupled regime


29/56

source device

200 cm30 cm

efficiency ~50%

60W bulb


30/56

Efficiency vs. distance


31/56

another geometry


32/56

Andre Kurs

Dr. Aristeidis Karalis

Prof. J.D.JoannopoulosProf. Marin Soljai

Prof. Peter Fisher Robert Moffatt

bulb


33/56

Path forward: physics part


34/56

Learning from atomic physics


35/56

An oscillating resonator radiates a bit

Much smaller than the wavelength: RES30 m

D = 0.6 m


36/56

Dicke effect atomic physics

|1|2e

-

|1|2e

-

two excited, same atoms

|1|2e

-

|1|2e

-

|1|2e

-

|1|2e

-

OR|1|2e

-

|1|2e

-

|1|2e

-

|1|2e

-

strong radiation NO radiation

C li f t


37/56

Coupling of resonators

EVEN MODE ODD MODE

Coupling fEVENfODD

Transmission vs frequency


38/56

Collaborators:

A.Karalis, R.Hamam, and J.D.Joannopoulos

EVEN MODE

ODD MODE

Transmission vs. frequency(gedanken system)

fEVEN fODD

Transmission


39/56

Playing David Copperfield with energy

Di t t f


40/56

Direct transfer

Mediated t ansfe


41/56

Mediated transfer

Comparison: direct vs mediated


42/56

Comparison: direct vs. mediated

(1) (3)

(1) (3)

(2)

Time dependent coupling strength


43/56

Time-dependent coupling strength

Collaborators:

R.Hamam, A.Karalis, and J.D.Joannopoulos

(1) (3)

(2)

Comparison: mediated vs time dependent


44/56

Comparison: mediated vs. time-dependent

(1) (3)

(2)



45/56


(1) (3)

(2)

Dark state:

12

23

In atomic physics


46/56

In atomic physics,this effect is known as STIRAP

STIRAP:Stimulated Raman Adiabatic Passage

also happens in Electromagnetically Induced Transparency (EIT)

|1

|2

|3e- e-


47/56

Potential applications

Some potential applications


48/56

Some potential applications

Industrial, military, and household robots

Portable personal electronics Electric vehicles

Vision: less dependence on batteries


49/56

Vision: less dependence on batteries

Other possible applications


50/56

Other possible applications

Implanted medical devices

Sensors with difficult access Electrically heated clothes

Power supply for MEMS or nano-robots

Conclusion


51/56

Conclusion

mid-range non-radiative

energy transfer scheme

based on strongly-coupled

resonances

even very simple designs

have promising performance

as a powerful concept, it could

enable a wide range of applications


52/56

Press coverage of WiTricity

Wall Street JournalNew York Times

USA TodayBBC News: front page of news.bbc.co.uk *2BBC World Service Radio *3The Economist *2

Associated PressNPR600 other newspapers, TVs, radio stations around the world

>2,000,000 hits for WiTricity on Google (~10th June 2007)

Epilogue: what about Paris Hilton?


53/56


54/56

Ok, but how come no one


55/56

Ok, but how come no one

thought of this before?

We explore. What path to explore is important,as well as what we notice along the path.

And there are always unturned stones alongeven well-trod paths.

Discovery awaits those who spot and take thetrouble to turn the stones.

-- Charles H. Townes

C ll b


56/56

Collaborators:

Robert Moffatt

Andre Kurs

Rafif Hamam

Dr. Aristeidis Karalis

Prof. Peter Fisher

Prof. John Joannopoulos

More info and reprints: www.mit.edu/~soljacic

Marin Colloquium2008

Documents

Transcript of Marin Colloquium2008