In a move that sounds like the wildest of science fiction, DARPA has announced its new Persistent Optical Wireless Energy Relay (POWER) program that plans to use lasers relayed by airborne platforms to power machines thousands of miles away.
There are a lot of potentially brilliant technologies out there that could change the world but stumble on one fundamental limitation – how to power them. This is especially true for aircraft. Electric planes sound like a great idea, but the batteries needed to power them are so bulky and so heavy that they eat up valuable payload and range.
For over a century, the idea of the wireless broadcast transmission of power seemed like the obvious solution, but things like the basic laws of physics kept getting in the way. Now, DARPA is looking at using lasers to beam power from a ground source to distant receivers, providing, for example, electric aircraft with virtually infinite range.
In theory, this seems simple enough, but there are all manner of technical problems to be overcome. Lasers work along line of sight, so airborne relays are needed in the upper atmosphere to minimise the distortion and attenuation caused by air and water vapour. Also, like laser weapons, the transmitter and relays need to be able to lock on target and correct the beam to stay focused.
However, the biggest problem is the massive losses caused by changing laser light to electricity and back across multiple hops.
According to DARPA, POWER is in the first phase, which involves developing conceptual designs for the relays. The second phase will concentrate on integrating the technology into an existing airframe, and the third will be a test to deliver 10 kilowatts of laser power across 200 km (125 miles).
"This project has the potential to advance power beaming by orders of magnitude, which could radically reshape society’s relationship with energy," said Dr. Paul Jaffe, leader of the POWER program at DARPA. A wireless energy web could unlock power from new and diverse sources, including from space, and rapidly and reliably connect them to energy-starved consumers.
"Energy underpins every human activity, including defense. We need ways to deliver energy that overcome the vulnerabilities and other shortcomings of our current paradigm. The next leap forward in optical power beaming could hinge on relay technologies."
Source: DARPA
