Engineers from Pittsburgh-based Powercast have joined forces with colleagues at Sydney, Australia-based CAP-XX to develop a wireless power module reference design that combines an RF energy-harvesting technology with a supercapacitor to create a perpetual, battery-free power source for wireless sensors.
Low-power energy harvesting can supply the average power required by many sensor-based systems, but cannot provide the peak power needed to collect and transmit data over wireless networks such as IEEE 802.15.4 (Zigbee), 802.11 (WLAN) or GSM/GPRS.
This is claimed to be the industry’s first reference design using commercial components that harvests RF energy from low-power radio waves, stores it in a supercapacitor, and then delivers high-power bursts when charged.
The wireless power module reference design integrates a power receiving antenna, a Powercast Powerharvester receiver, and a CAP-XX supercapacitor for energy storage and peak transmission power. Low-power wireless sensors or RF modules can be added with simple 'two-wire' integration.
In operation, the design creates a perpetual power supply for fixed or mobile wireless sensor nodes, such as those located throughout a building, eliminating the need for batteries or wired power.
Powercast's Powercaster transmitter, which powers the reference design, sends radio waves to the Powerharvester integrated into the module. The Powerharvester converts energy received from these radio waves into DC power, trickle-charges the supercapacitor, and then delivers power from the supercapacitor to the wireless sensor.
This cycle repeats as the module receives additional radio waves, which can be sent continuously, on-demand or on a scheduled basis. This design uses the 915MHz band, but can be adapted for other frequencies, or set to harvest environmental radio waves from television, radio or mobile phone networks.
The Powercaster transmitter provides controllable, non-stop wireless power, allowing wireless sensors to avoid using potentially unreliable ambient types of energy harvesting, such as solar or heat.