New Perovskite mineral can generate electricity from sunlight, heat, and movement- all at once

The holy grail in the quest for utilizing renewable energy, it may be argued, lies in harnessing it in a sustainable manner.

Solar energy faces the limitation of being able to provide us with usable energy only when there is sunlight. A device that can convert heat into electricity is useless in the absence of heat. And piezoelectric devices which can convert movement to electricity are useless when they are still.

It is in light of this that the discovery of a new type of mineral has created a storm in the fast-paced field of renewable energy. The mineral, a type of perovskite, has the right properties to extract energy from multiple sources at the same time- turning solar, heat, and kinetic energy into electricity. The clincher being that all this can be done at room temperature.

perovskite
Non-distorted cubic structure of a perovskite with chemical formula ABX3.

Since the first perovskite solar cell was invented back in 2009, these minerals have been positioned as the ‘next big thing’ in renewable energy technology.

Perovskite solar cells have proven to be cheaper and more efficient than traditional silicon solar cells, and their efficiency levels have increased from 3.8 percent in 2009 to 22.1 percent in 2016, making them the fastest-advancing solar technology to date.

In order to try and create a mineral that could harness energy from multiple sources, a team from the University of Oulu in Finland researched different types of perovskite minerals, and they’ve identified the perfect candidate – KBNNO (or Ba, Ni co-modified KNbO3 nanocrystals).

While the mineral at present is not efficient enough to power something as large as your home the way perovskite solar cells could, the researchers say it could be used in electronic devices like phones and laptops, and the various ‘smart’ gadgets that will soon be filling our homes and city streets.

“This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable,” says one of the team, Yang Bai.

Like all perovskites, KBNNO is a ferroelectric material, which means it’s filled with tiny electric dipoles that work analogous to tiny compass needles.

When a compass is exposed to a magnet, the needles move in a certain direction. Similarly, when ferroelectric materials experience changes in temperature, their dipoles misalign, and this triggers an electric current. This property is known as pyroelectricity.

KBNNO is also photovoltaic, which means it can generate an electric current when exposed to sunlight, as well as piezoelectric, which means that it can convert changes in pressure caused by motion into electricity.

Researchers in the past have identified KBNNO’s photovoltaic capabilities, and have even seen hints of its other properties, but only at extremely low, impractical temperatures – a couple of hundred degrees Celsius below freezing, the University of Oulu team points out.

When they tested its properties at room temperature, they found that, while it was outclassed by other perovskites when it came to generating electricity from single sources of energy, the fact that it could generate electricity from three different sources at once could make it valuable in certain situations. After all, in the game of harnessing energy that would be lost to entropy otherwise, every little joule counts.

The researchers also report that they have found a way to modify the composition of KBNNO to improve its heat and pressure-sensitive properties, so they predict its efficiency levels will increase with further tweaks.

“It is possible that all these properties can be tuned to a maximum point,” says Bai.

Different types of so-called hybrid energy harvesters have been developed in the past, but the researchers say what makes this mineral special is that all three properties are right there in the crystal structure – you don’t need to keep adding layers of different materials to capture multiple sources of energy.

As the team reports in their paper, “This type of perovskite ferroelectric solid-solution could show a strong piezoelectric and/or pyroelectric response, together with a considerable photovoltaic effect, thus providing a unique opportunity to develop a novel multi-source energy harvester or multi-functional sensor based on a single material.”

As might be expected, it will take a long time before enough research and refinement is done on this wonder material before it is commercially viable enough for large-scale deployment. It is hoped that KBNNO, or one of its derivatives, might prove itself to be a potent antidote that could end our addictive dependence on fossil fuels to sustain our energy needs.

 

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