More on MIT demo of wireless power

Physorg has a little more information on the MIT team’s use of resonant induction to transmit power. One of the comments seems to refute the notion that the device being charged would have to be precisely aligned: “As long as the laptop is in a room equipped with a source of such wireless power, it would charge automatically,” which is good.

However, two major constraints still seem to remain: The size of the coils which limits the range of power transmission, and efficiency.  Take a look at the two coupled coils powering the light bulb: It looks like the range is about 2x the diameter of the coils. And since laptops are getting smaller, not bigger, it would limit range of transmission. And why the coy discussion of efficiency? The article, not quoting any of the team members, says,  power can be transferred “omni-directionally and efficiently over room-sized distances.” And quoting a team member, “The usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system.” Yes, but the usual non-resonant magnetic induction would be completely useless, and a million times useless is still pretty inefficient. Let’s see some cold hard numbers on efficiency.