RF Energy Harvesting Extends Reach

Not long ago, Design News‘ senior technical editor Chuck Murray looked into a new energy-harvesting technology that enables sensors and microcontrollers to draw small amounts of electrical current from nearby radio frequency (RF) transmitters, and then use that power to operate autonomously. What makes this technology so interesting is not just its capability to effectively capture and use energy harvested from nearby sources, but that it can reportedly continue to do so on its own for many years.

You can access Chuck’s story on the technology here.

Now comes news from Powercast — the same company that developed the RF technology mentioned above — that it has launched a wireless sensor system for environmental monitoring in HVAC control and building automation. This system was developed following a beta testing program Powercast performed for Trane, which is mentioned in Chuck’s article. (Note: we thought the Powercast P2110 energy harvesting device was intriguing enough to give it a Golden Mousetrap Award this year.)

This new Wireless Sensor System from Powercast has three parts: battery-less sensor nodes embedded in Powerharvester receivers, WSG-101 Building Automation System (BAS) Gateway, and TX91501 Powercaster transmitter. The first available product using this system is a temperature and humidity sensor. Powercast says it plans to release other sensors soon on this system to measure CO2, pressure, light and motion.

Here’s how the system works: Powerharvester receivers embedded inside the sensor nodes receive RF energy from up to 60-80 feet away from the Powercaster transmitters broadcasting radio waves at 915 MHz. The receivers then convert the RF energy into DC current to power the sensors wirelessly.

While many energy-harvesting devices released to date have been designed to operate as point solutions over small areas, Powercast says the BAS gateway in its new systems can scale up to 100 sensor nodes and 800 sensor points and can interface to wired BAS networks using industry-standard protocols such as BACnet, Modbus, Metasys and LonWorks. Wireless communication on the system operates at 2.4GHz using 802.15.4 radios.

Because broadcasted RF energy can reach and power sensors through walls, ceilings and from behind objects, Powercast claims this ability gives their system’s design an edge over pure ambient energy-harvesting technologies such as indoor solar, thermal, or vibration.

The system is currently priced at around $300 per node for typical, multi-node deployments. A starter kit, which includes two temperature and humidity sensors, a transmitter and a BAS gateway, is available for $799 (the starter kit is pictured below).