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The promise of wireless power

Posted: 09 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:wireless? power? Intel?

By Justin Rattner

In the past few years, we have experienced a dramatic revolution in the number of electronic devices!cellphones, digital cameras, laptops, etc.! that we use in our everyday lives. Currently, most of these devices are powered by batteries, which need to be recharged very often. This fact has motivated scientists and engineers to explore whether physical principles exist that could enable wireless powering of these kinds of devices.

At the recent Intel Developer Forum (IDF), I demonstrated a technology developed at our research lab in Seattle that relies on strongly coupled resonators to wirelessly transmit power for several feet with great efficiency.

In the month since IDF, the feedback on wireless power transmission has been extraordinary. Clearly the prospect of cutting cords seems to resonate with people everywhere. Someone (not Intel!) has already created a Wikipedia entry for it.

Wireless Resonant Energy Link, or WREL! pronounced "whirl" by its creators!is the name of the wireless power project at Intel's Seattle lab.

For the first few weeks after IDF, I received multiple emails per day on WREL. I'm down to about two or three a week, but I continue to hear from both potential technology suppliers and users.

A number of people have posted to the various blogs to question the safety of the underlying WREL technology. At this early stage we believe the technology is safe since it involves coupled magnetic fields rather than the more common and more dangerous electromagnetic fields. It is also important to realize that this is still a research project in a very early stage. Future refinements or enhancements will change the safety picture, but clearly Intel will not design or release a product that is unsafe.

Magnetic fields have fundamental safety advantages over electric fields for one very simple reason: electric fields interact very strongly with the water in our bodies. H2O is a polar molecule, with an electrically positive end (where the Hs are) and an electrically negative end (where the O is). If you put a water molecule in an electric field, it will tend to align with the field. Make the field oscillate and the water molecule will oscillate too. That's how a microwave oven heats the moisture in a popcorn kernel and gets it hot enough to pop.

Magnetic fields, on the other hand, go relatively unnoticed by water molecules or any other molecule in your body. That's why we're able to transmit large amounts of energy magnetically without having to shield the experimenters or enthusiastic members of the press. Magnetics is also why we don't see the expected inverse square law losses as we separate the resonant antenna structures. Were it not for these differences, we'd be looking at traditional magnetic field induction.

Now there are still issues that we have to deal with: you can't make a magnetic field without making at least a small electric field also, so we are looking at ways to minimize the electric field. Can we minimize it enough? That gets back to the beginning of my post: we're at a very early stage with the WREL project and many details are still to be investigated.

There is no question that we excited a huge number of people with the promise of wireless power. While safety was a major concern, there were a number of other issues discussed in the blogs and in the many emails I've received.

One very passionate person wrote to Craig Barrett pleading with him not to take the WREL work to market because of the "low efficiency" of only 75%. In my response, I pointed out that Intel is very energy conscious and active in many forums where energy efficiency is a top concern. I also explained that familiar products and systems have much lower efficiency. Society has to choose whether those inefficiencies still have a positive ROI from a convenience and usability point of view. Wireless power will likely force such a decision sometime in the future.

- Justin Rattner is Intel Senior Fellow, vice president and director of the Corporate Technology Group, and chief technology officer.

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