Amazing stuff!
"MIT researchers have developed a battery-free, self-powered sensor that can harvest energy from its environment.
Because it requires no battery that must be recharged or replaced, and because it requires no special wiring, such a sensor could be embedded in a hard-to-reach place, like inside the inner workings of a ship’s engine. There, it could automatically gather data on the machine’s power consumption and operations for long periods of time.
The researchers built a temperature-sensing device that harvests energy from the magnetic field generated in the open air around a wire. One could simply clip the sensor around a wire that carries electricity — perhaps the wire that powers a motor — and it will automatically harvest and store energy which it uses to monitor the motor’s temperature. ...
Finally, they developed a series of control algorithms that dynamically measure and budget the energy collected, stored, and used by the device. A microcontroller, the “brain” of the energy management interface, constantly checks how much energy is stored and infers whether to turn the sensor on or off, take a measurement, or kick the harvester into a higher gear so it can gather more energy for more complex sensing needs. ...
They also found that communication — transmitting data gathered by the temperature sensor — was by far the most power-hungry operation. ..."
From the abstract:
"Energy harvesters present the exciting opportunity to create sensor nodes that can power or recharge themselves. Given the intermittent nature of available ambient energy for these harvesters and the common discrepancy between the harvested power and average power required to operate a sensor load, electronic energy management interfaces between the harvester source and a sensor load are often necessary. This article presents a design methodology for energy management interfaces between energy harvester sources and sensor loads. The design guide is practically demonstrated through the prototyping of a low-power energy management module that interfaces a clampable, split-core current transformer (CT) magnetic energy harvester (MEH) to an off-the-shelf bluetooth low energy (BLE) embedded hardware sensor kit. This article documents the design and experimental performance of the cold-start, energy harvest enhancement, overvoltage protection, and energy distribution control capabilities of this energy management interface. The experimental results demonstrate successful cold-start using discrete logic, average power harvest enhancements up to nearly 400% under certain harvester voltage load conditions, and a hysteretic control method for servicing an approximately 50 mW sensor load."
Fig. 1.
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