Look Ma, No Hands
Well, this will get a lot of people all het up. Researchers have demonstrated a method for transmitting power, wirelessly. The reporter gets all excited about it, but there are a few glaring problems with the idea buried in the depths of the report.
MIT physicist Marin Soljacic began thinking years ago about how to transmit power wirelessly so his cell phone could recharge without ever being plugged in. Scientists have pursued wireless power transmission for years— notably, eccentric genius Nikola Tesla, who devoted much energy toward it roughly a century ago.
The problem with wireless power transmission is that broadcasting energy in all directions—say, as radio waves—can be tremendously wasteful, with a vast majority of power ending up squandered into free space. One could imagine focusing energy along just one or a few directions—say, using laser beams—but such approaches can readily prove dangerous and cumbersome, requiring an uninterrupted line of sight between the source and device as well as sophisticated tracking systems on the device if it is mobile. (Scientists have proposed beaming power from orbital solar power stations to Earth for years.)
Soljacic and his colleagues devised WiTricity based off the notion of resonance. One well-known example of resonance can be seen when an opera singer hits the right note to cause a champagne glass to resonate and shatter. Two objects resonating at the same frequency tend to exchange energy efficiently, while interacting weakly with objects not resonating at the same frequency.
Instead of sound, the MIT physicists focused on magnetic fields. Most common materials interact only very weakly with magnetic fields, so little power would get wasted on unintended targets. "The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations," said Soljacic's colleague, MIT physicist Andre Kurs.
In their latest work, the scientists designed two copper coils roughly 20 inches in diameter that were specially designed to resonate together. One was attached to the power source, the other to a light bulb. The practical demonstration of their earlier theoretical work managed to power the light bulb even when obstacles blocked direct line of sight between the source and device, findings detailed online June 7 in the journal Science.
"In the past, there was no great demand for such a system, so people did not have a strong motivation to look into it," MIT researcher John Joannopoulos said, who also worked with Soljacic on the project. "Over the past several years, portable electronic devices, such as laptops, cell phones, iPods and even household robots, have become widespread, all of which require batteries that need to be recharged often." Kurs added their work could reduce dependence on batteries, "which are bulky, expensive and contain toxic elements."…….
……..The experimental setup radiates roughly five watts when transmitting 60 watts over a distance of more than seven feet. "This is equivalent to the power radiated by a few cell phones," Kurs said. "It is possible to drastically reduce the power radiated."
The researchers demonstrated roughly 40 percent efficiency in power transfer. Kurs told LiveScience they are currently working on improving the efficiency of the power transfer as well as the maximum distance allowed. "For the moment, we are focusing on power transfers on the order of 100 watts although, in principle, more power could be transferred," he added.
First, there is the fact that electromagnetic fields are a subject of much dispute at the moment. Second, the demonstration array is rather awkwardly large. That, presumably, can be reduced in size as they learn more. But the killer here is simple. They transmitted at about a 40% efficiency. In other words, aside from waste emissions, lighting that 60-Watt bulb consumed 150 Watts of power. And unless they can bring that efficiency up to equal a hard wired power connection, any wireless scheme will continue to consume higher amounts of energy. While gargantuan power consumption may warm the cockles of Al Gore's heart, it probably isn't a good strategy for the future. Seriously, I wish them all the luck in the world with this, but I really don't see this being a really useful technology in the near term.
By Purple Avenger, Monday, 11 June , 2007 @ 9:11 am
lighting that 60-Watt bulb consumed 150 Watts of power.
A “minor detail”. I’m sure some sharp MIT “scientist” will find a way to beat that pesky inverse square law any day now ;->
They do however seem well qualified to embark on careers in climate science.