By converting radio frequency signals to electrical current,
a new breed of energy harvesting device offers the possibility of eliminating
batteries in wireless applications ranging from sensor networks to building
automation to e-readers.
Known as
the
Powerharvester
P2110, the device can be combined with a capacitor, antenna and RF
transmitter to form a perpetual, battery-free power supply.
"It's able
to power devices without batteries and without an ac power source," says Harry
Ostaffe, vice president of marketing and business development for
Powercast Corp., maker of the product.
"It can completely eliminate the need to change batteries."
The
Powerharvester works by converting energy from common radio waves ranging from
850-950 MHz. A 3W transmitter located as far away as 10m serves as the RF
source for the device. During operation, the system uses an antenna to receive
the signals, then converts the RF to dc current and stores the energy in a
capacitor.
Powercast
says that RF offers advantages over other energy harvesting sources, such as
solar, temperature gradients and mechanical vibration. The reason: Unlike those
sources, RF is not intermittent and is therefore more reliable, the company
says.
"RF, if
it's indoors, can work in access spaces or permanently dark places, such as behind
walls and above ceilings," Ostaffe says.
He adds
that the device is already drawing interest in a range of applications,
including GPS tracking, wearable medical devices and e-readers, as well as
sensor networks for HVAC systems in hospitals and schools.
"The types
of devices that fit best are the ones that already rely on batteries that can
last for weeks, months and years," Ostaffe says. "Those are lower-power devices
that could entirely eliminate their batteries."
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