Wireless Energy Transfer.ms.Ppt

Wireless Energy Transmission

Max Seidman

What is Wireless Energy Transmission?

• Wireless Energy Transmission is the transmission of energy throughthe air.

• Wireless electricity will truly herald our arrival into the wireless age.Wired electricity is the last thing to keep our “wireless” devicesdependent on wires, and with its elimination comes the possibility tofree our mobile devices from ever needing to be plugged in.

• Currently, wired electricity powers nearly everything. It travelsthrough wires in the form of Alternating Current electricity, andpowers most of our devices in the form of Direct Current electricity.

• There are 3 major types (1), each with different ranges, methods oftransfer, and pros and cons:– Short range; Inductive Coupling– Medium range; Resonant Induction– Long range; Electromagnetic Wave Power Transfer

Short Range Wireless Energy Transmission: Inductive Coupling

• Inductive Coupling is a method for short range wireless energytransfer.

• Its range can vary, but it’s often very short.• Because of its short range it usually is used when the device

containing the receiver and the device containing the transmitter aretouching.

What Is Inductive Coupling?

Short Range Wireless Energy Transmission: Inductive Coupling

• Inductive coupling works on the principles ofelectromagnetism (3):– When a current (electricity) passes through a wire, it

generates a magnetic field perpendicular to the wire.– This effect can be magnified through coiling the wire– When a wire is in proximity to a magnetic field, it

generates a current in that wire.• Transferring energy between wires through magnetic

fields is inductive coupling• Magnetic fields decay quickly (2), making inductive

coupling effective only at very short ranges.

How does Inductive Coupling Work?

(3)

(3)

Short Range Wireless Energy Transmission: Inductive Coupling

• Inductive coupling is also used for wirelesscharging of electronic devices. Although itsshort range is limiting, several products useinductive coupling to charge, such as electrictoothbrushes (1), and charging mats such asSplashpower (5).

Applications for Inductive Coupling• Pros: safe, efficient. Cons: Limited range.• Radio-Frequency Identification (RFID) tags (4) are a widespread use forinductive coupling. These tags are used for everything from identifyinglivestock to anti-theft mechanisms on products in stores.

(5)

Medium Range Wireless Energy Transmission: Resonant Induction

• A group of engineers at MIT cameup with the idea to use resonantinduction to transmit powerwirelessly. They deemed theirresult “WiTricity” (like WiFi) (2).

• WiTricity can transmit electricitywirelessly at 40% efficiency toabout 7 feet.

What Is Resonant Induction?

Medium Range Wireless Energy Transmission: Resonant Induction

• Resonant induction still uses the same principles as magneticinduction (magnetic fields to transfer current) (1), but it usesresonance to increase the range at which the transfer can efficientlytake place (2).

• Everything resonates at a certain frequency, based on its shape andmaterial.

• Energy transfers easily between resonating objects. An example ofthis is when an opera singer shatters wine glasses by singing at thefrequency at which the glasses resonate.

• With resonant induction, power is transmitted between tworesonating coils.

How does Resonant Induction Work?

Medium Range Wireless Energy Transmission: Resonant Induction

• Pros: Safe, fairly efficient, goodrange:– Magnetic fields interact weakly

with biological masses (humans),and energy is only transmittedbetween resonating objects.

– Efficiency can be increased withtime, most of the 60% lost is fromheat (2) radiated from the coils.

• Theoretically one stationary coil ina room could power multipledevices with receiving coils (1).No more messy wires, and withwidespread enough use it couldeven eliminate costly batteries.

Applications for Resonant Induction

(1)

Long Range Wireless Energy Transmission: Microwave PowerTransfer

• Microwave Power Transfer (MPT)is a form of wave power transferthat, obviously, sends energythrough the air in the form ofmicrowaves (other forms can uselasers and visible light).

• MPT has a range miles longerthan its inductive counterparts,and it’s being investigated as away to beam power to space orvice versa (1).

What is Microwave Power Transfer?

(1)

Long Range Wireless Energy Transmission: Microwave PowerTransfer

• First, microwaves are converted from DC power, and sent via alarge transmitter. On the other end, the are “caught” by an evenlarger receiver and converted to AC power.

• The technology for the disk shaped rectifying antenna or “rectenna”is relatively new.

• Pros: very efficient, very long range– The conversion on either side is about 90% efficient, and the

transmission is about 95% efficient (8).• Cons: Size of antennae, safety?

– According to a study done by NASA (9), to transmit energy from spaceto earth would require a 1km diameter transmitter and a 10km diameterreceiver.

– Possible health risks associated with beams of microwaves.

How does Microwave Power Transfer Work?

Long Range Wireless Energy Transmission: Microwave PowerTransfer

• Recently a Canadian program sent upSHARP (Stationary High Altitude RelayPlatform), a small unmanned aircraftpowered completely by energy beamed toit from the ground through microwaves (7).It could stay in the air for months at a time,flying in a 1km radius circle around thepower station at an altitude of 21km (7). Itcould be used to broadcast in a 600kmradius, and would be much faster for 2-way communications than using satellites(7).

• Solar Power Satellites (SPS) could also bean application for MPT. Beaming solarenergy collected from satellites or solarpanels on the moon to Earth could be asolution to our clean energy issues.

Applications for Microwave Power Transfer

The Future

• Wireless energy transmission holds greatpotential for the future. Magneticinduction, resonant induction, andelectromagnetic wave power transmissionall have applications that couldrevolutionize the way we live and useelectricity. Keep your eyes open forwireless energy technology in newproducts, and look forward to wheneverything will truly be wireless.

Sources(1) http://electronics.howstuffworks.com/wireless-power.htm(2) Castelvecchi, D. (July 21, 2007) The Power of Induction, Science News. Vol. 172, Iss. 3;(3) http://science.howstuffworks.com/electromagnet1.htm(4) http://electronics.howstuffworks.com/smart-label1.htm(5) http://www.splashpower.com/(6) http://web.mit.edu/newsoffice/2007/wireless-0607.html(7) http://www.friendsofcrc.ca/Projects/SHARP/sharp.html(8) http://www.hq.nasa.gov/webaccess/CommSpaceTrans/SpaceCommTransSec38/CommSpacTransSec38.html

(9) http://www.nss.org/settlement/ssp/library/1997-Mankins-FreshLookAtSpaceSolarPower.pdf(Background Lightning Bolt) http://www.ellison.com/images/productimages/Lightning-Bolt_13839.gif