Wireless power

How WiTricity transfers energy using resonance, and where the company sees the tech going

Despite the fact that the company's name is short for wireless electricity, Eric Giler, CEO of WiTricity, is quick to point out that isn't exactly what the company does. It only looks like that. Giler is the first business exec brought into this 16-person company, which is trying to commercialize the tech developed by Massachusetts Institute of Technology professor Marin Soljacic. Giler was founder and former CEO of Brooktrout, a provider of telecom software and hardware platforms, and the guy who invented how to get faxes into e-mail. Network World Editor in Chief John Dix caught up with Giler in his Watertown, Mass. Office.

If you don't put electricity in the air, what do you do?

 Electricity in the air is lightning, right, so by definition, it wouldn't be safe. We don't put electricity in the air, we utilize a very low density magnetic field to move energy through the air. The magnetic field we create is on the order of the earth's magnetic field. The difference is that we use an oscillating magnetic field, while the earth's field is static. By designing a power source and power capture device to oscillate at the same exact frequency, we can achieve what is called "Highly Resonant Magnetic Coupling."

Resonance exists in many physical systems, and is a very efficient way to exchange energy between two devices. Probably the most famous example is Ella Fitzgerald on the Memorex commercial where she sings and the glass breaks on the other side of the room. That is acoustic resonance. The glass resonated at the same frequency as her voice and the glass picked up that energy. Note it didn't break anybody else's eardrum in the room. It was safe to everybody because the glass was the only object that had the exact same resonant frequency as the note that Ella sang..

So resonance exists in nature and Dr. Marin Soljacic was thinking, "Can we get two magnetic devices to resonate and exchange energy over distance?" Magnetic fields don't interact with living organisms very much at all. You look like air to a magnet. You don't interfere with it and it doesn't interfere with you at the levels we're talking about.

If you were to look inside a transformer that takes AC current and transforms it to a low a voltage for your cell phone or laptop, you'd find two coils of wire placed very, very close to each other. One coil creates a magnetic field and it induces one on the other. But if you pull the coils apart just a little bit they stop working because the inductions phenomenon only works over a very short distance.

For example, you can can buy an electric toothbrush that has a coil in it and there is another one in the base and the power is transferred wirelessly, but if you pull the toothbrush out of the base more than just a little bit it stops charging. What Dr. Soljacic figured out was how to separate the coils to a distance greater than the size of the coils.

He published a paper that said, "This is theoretically possible to do and here's the mathematical theory." And nobody believed him. They said, "That's impossible."

So he heard this enough and said to his team, "Let's just implement the theory." And here is a picture of the actual experiment done at MIT showing the whole team sitting between two coils -- we call them resonators because they oscillate at a certain frequency -- with one passing enough energy to the other to light a 60 watt light bulb.

And they're all still alive?

They're all still alive. That's probably the most common question we get: Is it safe? Because we're conditioned to think electricity is dangerous. But remember, we're not putting electricity in the air. We're putting a magnetic field in the air.Science magazine and thousands of people, from manufacturers of routers to computer equipment, contacted him. So he thought, let's start a company to commercialize the technology. Our goal in life is not to make end user products under our own brand name, we're going to sell it to OEMs or license the design if the volume is super high.

Soljacic published a paper in

Run us through some of the potential applications as you see them.

Consider the economics of a disposable battery versus the grid. Most people know that batteries cost more than a grid, but most don't realize it's 3,000 times more cost effective to use the grid than a disposable battery. Grid power in the United States costs about 10 cents per kilowatt hour, or KWH. A kilowatt hour means you can light 10 one hundred watt light bulbs for one hour and on your electric bill you'd be charged 10 cents.

If you could get enough AA batteries together to create enough power to light 10 100 watt light bulbs for one hour it would cost you $350, and that's even discounted.

And when the batteries die they get thrown into landfills and rot and leak toxic chemicals -- it's just awful for the environment. Think of a wireless mouse. They use disposable batteries yet they are only a few inches away from grid power, which is available for 10 cents/KWH. Using wireless power to operate the cordless mouse will save money and benefit the environment

Another possible use is at the opposite end of the power spectrum, recharging electric vehicles. The need to plug these cars in is one of the impediments standing in the way of these things taking off. Plugging your car in might be impressive to your friends at first, but [that gets old fast if] you're out in a rainstorm and you have to unplug it in or you have to coil up the dirty cable and take it with you in the trunk.

Now imagine being able to drive into your garage and your car charges because there's a mat on the floor and a coil on the bottom of your car. You get out and walk away. Or you get to work and they have electric vehicle parking spaces and it's something mounted underneath the pavement that you don't even have to worry about.

Not surprisingly, another big opportunity is with small handheld electronic devices. You have three handheld mobile devices with you here, a camera, recorder and your cell phone. All of them use different types of batteries.

Then there are all those fixed electronics devices like television sets, stereos, computer equipment … anything with batteries or cords. And we're doing work with military and factory robots.

I take it from the equipment in here you have working demos.

We built proof of concept equipment and took it to the Consumer Electronics Show in Las Vegas and rented a hotel suite and met with the big consumer electronics companies to see who would potentially be interested in incorporating this into their systems.

We started with television. Behind this [flat-screen TV] there's a coil, and in this box over here we have another one. Notice they're different sizes and not pointed at each other. And the TV works without any batteries, no cords, nothing. It totally blew away the consumer guys

And we showed laptop manufactures that it would be possible to power a laptop -- even though you're probably still going to have a battery in a laptop -- this would make it possible to recharge the laptop by placing it on a desk that had a coil underneath.

If you look under this desk you'll see a piece of plastic moulding going around, a coil that lets us create an "energized surface". We've added small coils to these common cell phones -- a BlackBerry Curve, a Nokia N96, a Google GI and an Apple iPhone -- and you can see they start to charge when you simply lay them down. So imagine your wife comes home and puts her purse on an energized surface, even if the cell phone is in there sitting at an angle, it's still going to charge.

People ask how small we can make these things. Here's a cell phone with a coil [about the size of a second cell phone], and you'll see when we start to get close -- maybe a meter and a half away from the wall -- it starts to power up. And here's a computer with a Wi-Fi data link. You can communicate from the computer even while it's in the magnetic field -- it doesn't interfere because the frequencies used are very different.

What kind of distances do you think you'll be able to achieve?

Generally speaking we're looking at powering things within a room, so the MIT experiment was done at a distance of 7 feet.

Given devices have different types of batteries and require different levels of power, is the coil just putting out a constant level and then the devices themselves figure out what they need?

In some cases yes and some cases you have to figure it out. So there's a lot of intelligence built into the electronics on both sides. It's actually kind of hard to do at the moment.

How efficient is the connection?

You have to be careful with the word efficiency because there are so many things in the efficiency curve, but let's just say it is the percent of power transferred between the resonators.

If you have two resonators that are the same size -- we'll call that D -- and the distance between the coils is less than or equal to D, we can transfer 95% of the power. If you pull them further apart -- say 5D -- the percentage of power transferred is about 10%.

Generally speaking, most of the systems we're building operate somewhere in that spectrum. If you're a car charger and you're doing 3,000 watts you care a lot about high efficiency. If it's a cell phone, you don't care as much. If I'm replacing an alkaline battery, if it's only 1% efficient it will still beat the pants off of a battery because disposable battery power costs 350x grid power.

So it's largely a function of the size and distance. But you can imagine a house having a coil laid up in the ceiling to power a range of devices.

What is the range of power you can support?

Milliwatts to kilowatts, basically. And distance-wise you can go centimeters to meters. You generally don't do kilowatts over meters.

If you're 10% to 90% efficient where does the rest of the energy go?

The cool part of this technology is it doesn't go anywhere. It's not radiated into the environment, which is why I can walk in between the fields. The energy isn't going into me. It's actually retained by the system itself and dissipated as resistive heat loss. And it tends to be shared between the resonators.

So, yes, if you're 10% efficient 90% of that power is going somewhere, but the "going somewhere" means it's held by the individual resonators, shared between them, and dissipated as resistive heat loss. But it's not radiative energy in the sense of magnetic energy or electric energy being radiated into the environment, which is one of the reasons why they don't interfere with Wi-Fi or cell phones.

The frequency range is selectable and generally speaking we run from 100 kilohertz up to the tens of megahertz region. Those are the frequencies the government set aside for general use, and basically you can do anything you want as long as you don't screw anything else up. These frequencies are designed for things like microwave ovens, induction cook tops, etc.

One of the things about this phenomenon is it's really hard to get objects to resonate magnetically with each other. You have to work at it. You have to design it that way and that's part of the trick that Doctor Soljacic and his team figured out, how to get these devices to be so perfectly resonant. It had been eluding scientists ever since electricity was invented. So what that means is it's extremely unlikely that random objects just show up and cause problems.

So this isn't a threat for folks with pacemakers, for example.

Remember, this is not a radiated phenomena. It's highly coupled magnetic resonance. But they've also shown that it's pretty hard to excite a pacemaker wire with frequencies above a hundred kilohertz. Our frequencies are generally a lot higher than that.

Where is the earliest interest coming from?

Cell phones and cars. It's interesting because its opposite ends of the power spectrum. The low power applications are going to be on the market first because there are no electric cars out there.

In terms of timing, where are you in the process? Is the technology fully baked or are you still fine tuning?

We're building an OEM business, and it takes a long time to get a company to decide to adopt the technology and then even longer as you work through designing it in, specifying it, building the prototypes, field testing them and then bringing them into production. But I believe you'll see products on the market towards the end of the year.

And one would presume it will most likely show up first in self contained systems?

Right. Systems where you get the source and the device at the same time. Eventually standardization would be nice because it would mean different devices could work off a common source -- the thing behind the wall. I don't think that will happen right away, though.

Do you have competitors?

The competitive landscape includes about a dozen companies divided into two groups. The first group consists of nine companies that say they are in the wireless power business, but are using traditional induction -- like an electric toothbrush. You can go down to Best Buy and buy a mat you lay your cell phone on -- in exactly the correct position and alignment, and it will charge it using traditional induction.

The other three are distance-based power transfer companies. So we're one of them. We use highly coupled magnetic resonance. There's a company in California that uses light to do it -- a form of laser pointed at a photo detector that captures the light and turns it back into electricity. The main limitation physical interference cuts the power so you have to think about your application pretty carefully. There's another company that uses radio frequency. They transmit a radio field but at something like 3 watts so it's only good for transferring a tiny amount of energy. You can't do high power and efficiency is measured in thousandths of a percent because most of the power is just radiated into space.

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