Multi-source energy harvester for next-gen wearables

To this day, the true potential of the ‘all-connected’ world has been hindered by the very thing that is supposed to power it: battery technology. A material capable of turning sunlight, heat and movement into energy could soon shake things up.

You may never have heard of perovskites in IT circles, but recent work by the University of Oulou could soon make it a trending topic of discussion. A family of minerals (ferroelectric material filled with tiny electric dipoles), perovskites were first discovered in the Ural Mountains of Russia by Gustav Rose in 1839. They are most known for their important impact on the solar energy sector, where perovskite solar cells are reputed for their cost efficiency, flexibility and ease of production.

The perovskites used in solar cells, however, are just one of many existing variants. Whilst they display the right properties for efficiently converting solar energy into electricity, other members of the family can harness energy from the changes in temperature and pressure that can arise from motion.

The point is that many perovskites can harvest several types of energy  but one at a time, not simultaneously. In most cases, however, forms of energy like heat, sun and movement are not continuous. Exploiting only one of these forms is therefore unrealistic to power the likes of biometric sensors or smart watches.

That’s actually the good thing about KBNNO, a specific type of perovskite studied by researchers funded under the NEXTGENERGY project: it can harness multiple forms of energy at the same time. Whilst devices capable of doing that already exist, they do so by combining different materials. KBNNO is capable of doing it on its own.

Previous studies had already focused on the photovoltaic and general ferroelectric properties of KBNNO. These studies, run a couple hundred degrees below freezing, had already established that, when KBNNO undergoes changes in temperature, its dipoles misalign which induces an electric current. Electric charge also accumulates according to the direction the dipoles point, and deforming the material causes certain regions to attract or repel charges, again generating a current.

But what wasn’t known yet was how the material behaved above room temperature. NEXTGENERGY researchers did not only aim to close this knowledge gap, but they also did it while focusing on other KBNNO properties related to temperature or pressure.

The team’s experiments show that while KBNNO is reasonably good at generating electricity from heat and pressure, other perovskites are better. But they also demonstrate that the composition of KBNNO can be modified to improve its pyroelectric and piezoelectric properties. ‘It is possible that all these properties can be tuned to a maximum point,’ said Yang Bai, Marie-Sklodowska Curie Fellow at the University of Oulou.

Yang Bai and his team are already working on this improved material. Within the next year, they hope to build a prototype multi-energy-harvesting device, which could already reach the market within the next few years.

‘This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable,’ Bai said. With no need for plugs or batteries, such devices could indeed mark the beginning of a new era for smart device makers.

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last modification: 2017-02-27 17:15:01

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