Wireless Applications

Battery-Free Power Supply Introduced for Wireless Sensors

May 19, 2009

Powercast and CAP-XX combine RF energy harvester and supercapacitor technologies in a reference design to provide a power source for sensing devices commonly used in environmental monitoring, building automation, and industrial control systems.

SAN JOSE, CA /Marketwire/ -- Engineers from Powercast and CAP-XX Ltd. at the Darnell nanoPower Forum will introduce a wireless power module reference design combining Powercast's RF energy-harvesting technology with a CAP-XX supercapacitor to create a perpetual, battery-free power source for wireless sensors commonly used in environmental monitoring, building automation, industrial controls, and other condition-monitoring systems.

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 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. The module measures approximately 8 in. tall, 1 in. wide, and 1/4 in. thick at the body.

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 the 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 915 MHz band, but it can be adapted for other frequencies or set to harvest environmental radio waves from TV, radio, or mobile phone networks.

The Powercaster transmitter provides controllable, 24/7 wireless power, allowing wireless sensors to avoid using potentially unreliable ambient types of energy harvesting, such as solar or heat.

CAP-XX Vice President of Applications Engineering, Pierre Mars, and Powercast head of technology platforms, Charlie Greene, were scheduled to present their collaborative paper, "Harvesting RF Energy and Powering a Wireless Sensor Node Using a Supercapacitor," in the energy harvesting session on Monday, May 18 at the Darnell nanoPower Forum in San Jose, CA.

"This fit and forget self-generating power source guarantees that sensors deployed throughout a building or local area will receive power without batteries or potentially unreliable environmentally harvested energy, such as solar or heat," said Mars.

"Wireless sensor networks are increasingly popular, but today are predominantly powered by disposable batteries," explained Harry Ostaffe, Director of Marketing for Powercast. "The RF energy harvester and supercapacitor combination eliminates the cost and hassle of replacing and disposing of batteries, and enables wireless sensor networks to scale to thousands of nodes with minimal maintenance."

About CAP-XX
Sydney, Australia–based CAP-XX is a world leader in thin, flat supercapacitors for space-constrained electronic devices. Supercapacitors resolve the performance limitations of batteries and other current-limited power supplies, and provide backup power if the primary power source fails.

CAP-XX supercapacitors enable manufacturers to make smaller, thinner, longer-running, and more feature-rich devices, such as camera phones, solid state drives, handheld PCs, and battery-free condition-monitoring systems using the company's BritePower architectures. The company is listed on the Alternative Investment Market (AIM) in London. For more information, email sales@cap-xx.com.

About Powercast
Powercast Corp. is a leading innovator of wireless power technology. Founded in 2003, Powercast's proprietary core technology and related intellectual property pioneered the model for completely untethered electronic devices by transmitting and harvesting common radio waves similar to those in wireless communications. Emerging applications include wireless sensors, advanced displays, novelty lighting, and other low-power electronic devices. Contributing to a greener world, Powercast's technologies eliminate or reduce the need for batteries, extend sensor networks into hard-to-service locations, and enable greater energy efficiency for HVAC, lighting, and other systems.

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