This innovation uses an active materials-based force-amplified mechanism and advanced piezoelectric materials for more efficient energy harvesting from mechanical shock and vibration. The harvested energy is stored in rechargeable batteries. The hybrid force/stress amplified transducer/actuator offers tens to hundreds of times higher electrical power output, up to ten times higher electromechanical energy conversion efficiency, and several orders of magnitude higher energy storage efficiency than conventional flex-tensional or multilayer stack transducers at the stress less than the fracture stress of the materials used in each element.

This mechanism can generate tens of milliwatts to tens of watts of electrical power from automobile vibrations, normal walking, and other human activities; shipboard vibrations; transportation vehicles; strike-induced shock; and other vibrations. The generated electrical power from this low-volume, lightweight device will be high enough for use as compact power sources in various sensors, wireless sensor networks, communications, and other military and civilian applications including infrastructure health monitoring, smart munitions, and environmental safety alert systems.

The piezoelectric elements of this innovation can be made of piezoelectric material (ceramic, single crystal, or polymer) multilayer stacks, or single elements. When a contracted or stretched force/stress is applied to the elements, each one will induce electric charges (i.e., electrical energy) simultaneously. In conventional piezoelectric transducers with amplification mechanisms, vibration energy transferred to the compliant amplification components will be converted into heat and will be wasted. Vibration energy transferred to the active amplification components in the invented hybrid transducer, however, will be converted into electric energy simultaneously, thus leading to increased energy conversion efficiency. This device does not need a power supply, nor does it consume other resources except the motion of force/stress; consequently, it will most likely function for an unlimited period of time.

This work was done by Ji Su of Langley Research Center, Tian-Bing Xu of National Institute of Aerospace, and Xiaoning Jiang, Paul W. Rehrig, and Wesley S. Hackenberger of TRS Technologies, Inc. LAR-17169-1/6698-1

NASA Tech Briefs Magazine

This article first appeared in the May, 2014 issue of NASA Tech Briefs Magazine.

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