Both ECN and Wireless Design & Development (WD&D) have published a recent article by Powercast titled “RF energy Harvesting Perpetually Powers Wireless Sensors”, which looks at using broadcasted RF energy as a reliable long-term power source for battery-less wireless sensors.
Powercast Releases Battery-less, Wireless-powered Sensor System for Building and Industrial Automation
Powercast has released a battery-less, wirelessly-powered sensor system for building and industrial automation - the Lifetime Power® Wireless Sensor System. The sensor units can be powered at a range of 60-80 feet (18-24 m) from Powercast’s 3W, 915MHz transmitter (TX91501). The initial sensor unit is for temperature and humidity and is to be followed by other types such as CO2, light, and motion.
Powercast Lifetime Power® Wireless Sensor System
The access point (WSG-101 BAS gateway) supports up to 100 sensors and 800 sensor points for large-scale and high-density deployment of sensors. The sensors are battery-free and operate when sufficient charge is stored to take sensor readings and send a data packet. Wireless communication from the sensor nodes to the access point is 2.4GHz using industry-standard 802.15.4 radios. The BAS gateway supports several physical interfaces and a range of BAS protocols to interface with nearly every major type of wired BAS network, including BACnet, Modbus, Metasys N2, and LonWorks.
The system was developed based on the same core technology as the Powercast P2110 Powerharvester receiver and the P2110-EVAL-01 Energy Harvesting Development Kit, both of which are available for other sensor OEMs to embed Powercast’s technology into their own products.
John Titus at ECN has recently published an article titled “Energy Harvesting Suits Remote Low Power Devices“, which includes updates on energy harvesting technology from multiple companies including CYMBET, Humdinger, Microstrain, Mide, and Powercast.
Grabbing “free” energy involves more engineering than buying an off-the-shelf transducer. Contrary to what you might think, the awareness of “green power” didn’t spawn the drive to harvest energy. Low-power electronic fabrication technologies did the trick. They cut the power needs of small monitoring devices to the point where energy harvesting has started to make engineering and economic sense.
Powercast, with the development support of Microchip, has released the Lifetime Power® Energy Harvesting Development Kit for Wireless Sensors. This kit provides wireless power for remote, battery-free wireless sensor networks (WSN).
The kit (part number P2110-EVAL-01) includes the following items:
1 - 3W Powercaster Transmitter - 915MHz (TX91501-3W-ID)
2 - P2110 Evaluation Board (P2110-EVB)
2 - Directional, patch antennas - 915MHz
2 - Omni-directional dipole antennas - 915MHz
2 - Wireless Sensor Boards (WSN-EVAL-01)
1 - Microchip XLP 16-bit Development Board
1 - Microchip 802.15.4, 2.4GHz radio
1 - PICkit programmer/debugger
The components in the kit enable wireless and battery-free operation of the sensor nodes at a distance of 40-45 feet (13-15 meters). Each sensor board can measure temperature, humidity, light, and an external sensor. This can be used for a number of applications including building automation, energy management and industrial monitoring. Power is provided by Powercast’s new 3W transmitter (TX91501-3W-ID), which also sends factory-set data. The P2110 Powerharvester receiver converts the RF energy from the receiving antenna and stores it into a capacitor, which is then boosted to operate the wireless sensor board. The Microchip XLP 16-bit Development Board with the 802.15.4 radio is the access point.
“Powercast is the stuff of revolution…”
Powercast recently presented about wireless power technology and RF energy harvesting to an innovation forum hosted by North River Ventures. Following that meeting North River posted a review of Powercast’s technology.
Low Power, Free Power
Powercast provides remote, wireless power capability to micro-power devices by harvesting RF power and converting it to DC power.
Powercast is the stuff of revolution: it spreads cloud access to hundreds of billions, perhaps trillions, of small, low power (microwatt and milliwatt) M2M devices. Placed anywhere from the simple, like a hotel room motion detector, to the complex, like a reverse osmosis filter that needs constant monitoring but that is hard, and costly, to check by hand, embedded Powercast devices allow its “hosts” to talk to one another cheaply and efficiently. Doing this, Powercast brings on line, as it were, a universe of productivity and information tools of unlimited application. It makes microwatt devices edge servers.
A joint article by Powercast (Harry Ostaffe, Charlie Greene) and AVX (Bharat Rawal), titled “Power Module and Double Layer Capacitor Harvest Energy From Radio Signals“ was recently published in Power Electronics Technology. Combining Powercast’s P2110 Powerharvester receiver with an AVX Double-Layer Capacitor (super-capacitor) results in a battery-free, wireless power supply that can be used for low power applications such as wireless sensors. The article describes in detail the operation of the P2110 Powerharvester.
Figure 1 shows a general block diagram of the P2110 Powerharvester. The RF energy is converted to DC and stored into an external capacitor. For some applications a small electrolytic capacitor may be sufficient, but other cases will require more energy and therefore a larger double-layer capacitor (super-capacitor). The voltage on the external capacitor is typically managed between the operating range of 1.25V, when the output voltage is turned on, and turned off at the low threshold of 1.05V. The boost converted is used to provide a regulated output voltage from a range of 2-5.25V to accommodate a wide range of applications.
The timing diagram in Figure 2 provides more detail on the operation. The INT pin provides a logic-level output to indicate when Vout is active, and the RESET pin enables an external device such as a microtontroller or external timer to turn off Vout. The RESET function saves energy and allows the P2110 to recharge the capacitor more quickly.
Figure 3 show a system-level implementation that is typical in a wireless sensor, such as HVAC control sensors using ZigBee, WiFi, or other protocols, or industrial sensors using ISA100 or WirelessHART.
The Economist has has written an interesting article about wireless power as envisioned by Telsa and today’s efforts on ambient RF energy harvesting:
Power from thin air
Wireless technology: It is already possible to send electricity without wires. Can devices be powered using ambient radiation from existing broadcasts?
Powercast demos prelude to mobile network RF energy harvester
Directed RF energy harvester demo is stepping stone to full ambient RF harvesters that can siphon energy from ubiquitous mobile networks
“After setting up an RF energy-harvesting demo at this week’s Sensors Expo collocated with ESC Chicago, Powercast’s director of marketing Harry Ostaffe presented a paper that outlined the concepts and paths to what he believes to be the endgame: full ambient RF harvesting capabilities that sip power from ubiquitous mobile networks and eliminate batteries and direct RF power sources completely.” Read more…
Powercast presentation - Power Out of Thin Air (PDF)