Modules Will Harvest Energy For Remote-Sensor Networks

Jan 1, 2007 12:00 PM
By David Morrison, Editor, Power Electronics Technology

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Three energy-harvesting modules being developed by Advanced Linear Devices (ALD) will capture and store the energy produced by tiny alternative power sources and process this energy to power wireless sensors and other remote-control devices (Fig. 1). The modules will offer an alternative to battery power, while also enabling much longer, maintenance-free operating life than batteries. ALD plans to specify 30-year operation for these modules with virtually unlimited charge and discharge cycles. The modules, which will be available in the first quarter of this year, will be packaged as connectorized pc-board modules with footprints equivalent to AA batteries.

The modules will consist of an energy management circuit (detector), a capacitor for energy storage and a switch (Fig. 2). The storage element is a capacitor — either an electrolytic or a ceramic cap for high-reliability applications. All three models will operate from a minimum input of 4 V, 200 nA and 0.8 µW, and from a maximum input of ±600 V and 0.4 A.

The models are differentiated by energy output levels that target different applications. Model A will produce 4.5 mJ, which is sufficient to power a 2.7-V ZigBee wireless sensor module for up to 10 transmissions. Model B will produce 8.7 mJ, which is enough to power 5-V circuits; while model C generates 32 mJ for high-power ZigBee modules with a 1-mile range.

Energy harvesting is the process of capturing, accumulating and storing energy from a variety of sources that, by themselves, cannot supply adequate power for any useful purpose. Possible energy sources include piezoelectric transducers and thermocouples or thermopiles. By efficiently and effectively managing the energy harvested from such sources, it becomes possible to power a variety of sensors and associated circuitry for intermittent duty applications.

Because the energy levels produced by the sources are at such low levels, it's imperative that energy harvesting be performed with very high efficiency. ALD's measurements on modules currently in beta testing demonstrate that these modules achieve nearly 80% energy efficiency with an average energy input of 1 µJ, which rises to greater than 90% at 10 µJ and approaches 100% at 100 µJ. In quantities of 100, module pricing will be in the $30 to $40 range.

For more information, see www.aldinc.com.

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