Scavengers Harness Ambient Energy from Pretty Much Everywhere
CREDIT: Lightning Pack, Lawrence Rome
In the race to suck oil from ocean canyons and squeeze it from piles of greasy sand, it seems ironic that the earth practically hums with unused power. Not just the well-known power of sunlight and wind, but also radio waves, vibration and even the heat and movement of our own bodies.
Though most of these sources can't charge a cell phone yet, there has been great growth in technologies to capture wisps of ambient energy for applications where only a wisp is needed: wireless sensors, remote battery charging and recycling wasted energy. Most ambient energy techs can only produce in the range of tens of milliwatts or less, but these milliwatts alone are enough to power a variety of simple sensors with applications in monitoring everything from the environment to human health.
[See countdown: Top 7 Ambient Energy Technologies ]
Generally it's difficult to find a particular source that's available all the time, whether light or heat, or vibration or what have you, said Khalil Najafi, a chair in the department of Electrical Engineering and Computer Science at the University of Michigan. The human body, buildings, machines, engines, cars all vibrate. The challenge is to find a way to harness the full range of frequencies.
Najafi says low vibration frequencies are particularly difficult to convert efficiently. So he and his colleagues use tiny magnets to translate the low hum of something such as a bridge into a higher frequency that can produce more power. The mechanical energy of vibration is converted into electricity either magnetically, or through the use of piezoelectric materials, which create an electric field when deformed by movement or pressure.
Even thin air can power sensors. Joshua Smith, an associate professor of computer science and engineering at the University of Washington, ran his kitchen thermometer on radiation from a nearby television tower, capturing 60 microwatts, and is working on harnessing waves from cell phone towers to do the same.
These fields could soon power single components of larger electronics, Smith said.
You can't run a whole device but you could power a clock within the device, for example. Then even if it loses power you wouldn't have to reset the clock, Smith told InnovationNewsDaily.
Smith also sees the possibility using radio and TV signals to keep cell phones or similar devices on a super-low-power standby mode, allowing for something like ambient-powered emergency 911 buttons.
Burn calories, fill batteries
Other types of ambient fields are also up for grabs. Researchers at Duke University recently outfitted a construction hard hat with a beeping safety sensor powered by bulldozer radio transmitters. And RCA showed a prototype in early 2010 of a device that turns Wi-Fi signals into DC power to charge a cell phone.
The human body also provides ambient energy, both through movement and heat, said Max Donelan, associate professor of biomedical physiology and kinesiology at Simon Fraser University outside of Vancouver, Canada. Donelan unveiled a knee-mounted energy harvester in 2008 that scavenges 12 watts from the movement of walking one minute's march buys an hour of cell phone talk time.
It works a lot like a hybrid car's regenerative braking, Donelan told InnovationNewsDaily.
The device captures energy from muscles that slow or brake the knee in the backswing of a stride, not the ones that move the body forward. This keeps the process from being extra work for the joint. This winter the Canadian military tested the brace, called the PowerWalk by Donelan's startup Bionic Power, for its potential to benefit soldiers in remote operations who often carry pounds of batteries on their person.
Dance floors, backpacks and turnstiles are similarly poised to hijack our everyday movement. Donelan sees potential in these technologies to at least make people more aware of their place in an energetic world, if no more.
Energy is all around us
Clearly compared to most of the power we consume as humans, the energy offered by most ambient sources is tiny. But the range of devices that can run on these small power packages is only going to grow, said Smith.
"Power requirements are dropping as circuits get smaller and as time goes on you're going to be able to power more and more on less, Smith said.
Plus, Smith added, we're not doing anything else with all these stray radio waves, vibrations, or our lost body energy. If the power is there, why not use it?