New Applications for Energy Harvesting-2

Time：2014-05-10　Reading：42

Piezoelectric

Piezoelectric transducers generate electricity when stressed, which make them good candidates for vibration sensors when they are used in energy harvesting modules that detect motor bearing noise and the vibration of aircraft wings. The Midé Volture^™ V-20W Vibration Energy Harvester employs a cantilever that attaches to a piezoelectric crystal. When vibrations set the cantilever in motion it generates an AC output voltage that is rectified, regulated, and stored in a supercapacitor or thin-film battery.

Figure 2: Midé Volture^™ piezoelectric energy harvester (Courtesy of Midé)

Radio Frequency - RF

RFID works by rectifying a strong local signal (not ambient RF) aimed directly at the sensor. Similarly Powercast’s P2110 RF Powerharvester^™ receiver converts low-frequency RF signals to 5.25V, providing up to 50mA output current. In conjunction with a low-power MCU, sensors, and a radio module, the P2110 can provide a complete, battery-free wireless sensor node that can operate with as little as -11.5dBm RF input. Applications for the device include battery-free wireless sensors for industrial monitoring, building automation, smart grid, agriculture, and defense applications. Mouser carries Powercast development kits for battery charging and wireless sensors.

Figure 3: Powercast P2110 in a batteryless wireless sensor (Courtesy of Powercast).

Innovative techniques and technologies

Some very interesting energy harvesting technologies that are still in the laboratory could change the face of the energy harvesting industry over the next few years.

Medical and Fitness Devices

Some novel uses for piezoelectric energy harvesting are starting to emerge. Researchers at the University of Michigan have developed a device that harvests energy from the reverberation of heartbeats through the chest and converts it to electricity to run a pacemaker or an implanted defibrillator, hopefully obviating the need for periodic battery replacement. Research is also under way looking for ways to scavenge body heat, movement, and vibration to power other implantable devices.

RF is already being used experimentally to recharge the batteries in pacemakers and implanted transcutaneous electrical nerve stimulation (TENS) devices. The patient sits in a chair that contains a low-frequency RF source whose output is received, rectified, and stored by the device.

Researchers at MIT and Harvard have developed a chip that can be implanted into the inner ear, with power provided by harvesting the energy in sound waves. The chip is designed to monitor biological activity in the ears of people with hearing or balance impairments.

Fitness buffs will be happy to learn that they can recapture some of the energy they expend at the gym. Three British universities have teamed up to develop a piezoelectric energy harvesting device that attaches to the knee, generating power as they walk or run on the treadmill. Riga Technical University offers a mechanical energy harvester that requires magnets to be sewn into the sleeves and coils into the pockets of a jacket; swinging the arms past the pockets while walking generates a current that can be stored in a battery. Anything to keep that iPhone charged!