Energy harvesting, otherwise known as energy scavenging is needed to boost and eventually replace the batteries in printed and other low cost and miniature electronics, particularly in order to extend their life in use. For example, it is starting to be used for the three generations of active RFID - Conventional, Real Time Locating Systems and Wireless Sensor Networks.
The latter, third generation is the subject of a new IDTechEx report Wireless Sensor Networks 2009-2019 that includes coverage of the energy harvesting aspects. In RFID, it is initially used to boost the batteries not replace them, and it is first being employed in the form of conventional silicon photovoltaics but the new flexible photovoltaics is also likely to have a place, notably Dye Sensitised Solar Cells DSSC from Sony, G24i and others, Copper Indium Gallium Diselenide CIGS where Nanosolar has production and organic PV where Konarka has just brought wide web on stream. They are all printed reel to reel and those developing ink jetting of nanosilicon such as Kovio and Seiko Epson are also likely to join the fray.
For applications with available energy sources such as light, heat, and vibration, other energy harvesting solutions are emerging as another power source for WSN. Companies such as MicroPelt and Perpetuum are developing technologies for gathering and converting existing energy sources into electrical power for wireless sensing applications. Sensor modules from EnOcean harvest tiny amounts of energy from their surroundings, enabling them to register detected values and transmit them wirelessly. Surrounding sources of useful energy are: linear motion / pressure, heat difference (eg using Peltier effect), temperature change, rotation and vibration.
Then there is the nanoscale approach. Options include nanobatteries and nanogenerators that harvest energy from their environment. By converting mechanical energy from body movement, engine vibrations, or water or air flow into electricity, these nanoscale power sources could enable a new class of self-powered medical devices and sensors including WSN nodes.
A leading team working on nanogenerators for converting mechanical energy into electricity is Zhong Lin Wang's group at Georgia Tech. USA. Wang's team has now designed and demonstrated an innovative approach to fabricating a nanogenerator by integrating nanowires and pyramid-shaped nanobrushes into a multilayer power generator. By demonstrating an effective way for raising the output current, voltage and power, this work provides the technological platform for scaling up the performance of nanogenerators to a level that one day may be able to independently power WSNs.
For more read Wireless Sensor Networks 2009-2019 and Real Time Locating Systems 2008-2018.
Also attend Printed Electronics USA 2008 and Active RFID, RTLS & Sensor Networks 2008.
Top image: EnOcean WSN node with photovoltaic harvesting
