Energy of the Future

Energy Harvesting

AdaptivEnergy (AE) has developed the Joule-Thief™ energy harvesting solution using RLP® (Ruggedized Laminated Piezo) technology to scavenge energy from ambient sources and convert it to usable electrical power to be stored in batteries or capacitors for further use.  The energy harvesting system consists of a Joule-Thief™ Smart Energy Beam™ and Energy Key™ collection and storage electronics.  RLP® technology, when coupled with Energy Key™ electronics results in a complete, robust and flexible stand-alone power module.  The Joule-Thief™ Energy Harvesting Device (EHD) offers significant advantages in size, reliability and cost over other commercially available energy harvesters.  Therefore, it is better suited for many wireless applications, e.g., battery extension for wireless sensors and switches.

JOULE-THIEF™ ENERGY HARVESTING BEAM
In the recent past, energy harvesting from the environment, including human movement, has generated a lot of research interest and many available ambient energy sources such as thermal, optical, mechanical, fluidic, etc. have been investigated.  AdaptivEnergy’s Joule-Thief™ is designed to harvest mechanical vibration energy and is particularly useful in harvesting low level vibrations.  Some of the main applications include operating as the power source for remote structural and condition monitoring, human wearable electronics, wireless sensing and switching applications, supplementing battery storage devices, etc.

Vibration-based piezoelectric energy harvesting generally consists of a power generator module which converts the ambient mechanical vibration energy into an electrical equivalent energy.  This is achieved using the RLP® beam.  The operating principle of the energy harvester involves a piezoelectric beam attached to a vibrating mechanical structure that converts the mechanical vibration energy into induced electric charge.  The generated equivalent voltage is then converted to a usable DC voltage using the power processor module. The final power storage module includes an electronics architecture that efficiently stores the generated power in a battery or a capacitor for end use.

The Joule-Thief™ is a composite beam that consists of a cantilever shim with an attached piezoelectric layer and a proof mass at its end. The proof mass essentially converts the input base acceleration into an effective inertial force at the tip that deflects the beam, thereby inducing mechanical strain in the piezoelectric layer.  This strain produces a net polarization in the piezoceramic.  When electrodes are placed on the ceramic this net polarization produces a flow of electrons, or a current.  The current produced is then converted into usable power by the power processor. For this application of the energy harvester, a tapered beam shape was adopted.  AdaptivEnergy has gained significant knowledge with studies on various EH beam shapes and configurations to conclude that a tapered cantilever beam design is the best option, particularly for low frequency vibration sources.  Since the ambient environment has a definite amount of energy at known amplitudes and frequencies, the fundamental optimization of the mechanical device would be to generate maximum power from a given source.  Consequently, the need to maximize the strain in the piezoelectric layer is essential as the voltage generated in the piezoceramic is proportional to the strain induced.


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