Scientist use pyroelectric effect to harvest thermal energy

(Left) the energy harvesting pyroelectric nanogenerator, aka PENG. (Center and Right) Powering and LCD for 60 seconds and an LED for much longer. (via NANO Letters)

Scientist from the Georgia Institute of Technology have used a lead zirconate titanate (PZT) film to improve the performance of a pyroelectric nanogenerator(PENG). Zhong Lin Wang one of the scientists leading the research has stated, “Wasted heat is a rich source of energy that can be harvested.” By improving upon the technology, the scientists hope to harvest wasted heat from energy sources and use it as a source of renewable energy to power devices and system.

The PENG works off the principle of the pyroelectric effect, which collects thermal energy by responding to an anisotropic material's polarization changes due to temperature fluctuations. This area of technology has recently gone overlooked due to systems using the Seedbeck effect to harvest thermal energy. However, the Seedbeck effect can only work when a temperature gradient is present, whereas the pyroelectric effect can work in an environment where the temperature is spatially uniform without a gradient.

Using the PZT film to improve the performance of PENGs, the team was able to achieve an output voltage of 22V with a current of 430 nano-Amps. This is a significant improvement to the previous maximum of 0.1V and less than 1 nano-Amp output. Furthermore, the device sizes in at a rectangular shape of 21mm by 12mm with a thickness of 175 microMeters. To demonstrate the improvements, the scientist hooked the device up to a Lithium-Ion coin battery. After 3 hours, the battery was charged from 650mV to 810mV. This stored energy was then used to power an LED for a short time.

The scientist continue to work on the device which they expect to be integrated into devices around us one day. For instance, Zhong Lin Whang commented, “In our living environment, temperature change can come from an air-flowed-induced drop in room temperature, the cycled heat generation near and engine, sunlight illumination with a moving shadow, on and off hot water/air flow in a pipe, ect.” The team is going to try increasing the dimensions of the geometry next to produce better results. Pyroelectric nanogenerators may soon be added to everyday life of green energy.

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