Engineering news
Researchers from the University of Oulu in Finland have developed a mineral with a perovskite crystal structure that has the properties to extract energy from multiple sources simultaneously.
The specific type of perovskite is called KBNNO and is able to harness many forms of energy. Like all perovskites, KBNNO is a ferroelectric material, filled with tiny electric dipoles analogous to tiny compass needles in a magnet.
When ferroelectric materials like KBNNO undergo changes in temperature, their dipoles misalign, which induces an electric current. Electric charge also accumulates according to the direction the dipoles point. Deforming the material causes certain regions to attract or repel charges, again generating a current.
Certain perovskites may be good for solar cells, with the right properties for efficiently converting solar energy into electricity. Meanwhile, another might be adept at harnessing energy from changes in temperature and pressure, which can arise from motion, making them so-called pyroelectric and piezoelectric materials, respectively.
However, sometimes one type of energy might not be efficient enough. A given form of energy isn't always available, such as sunlight. Other researchers have developed devices that can harness multiple forms of energy, but they require multiple materials, adding bulk to a device that is intended to be small and portable.
Previous researchers have studied KBNNO's photovoltaic and general ferroelectric properties, but they did so at temperatures a few hundred degrees below freezing, and did not focus on properties related to temperature or pressure. The university’s study evaluates all properties at once above room temperature.
The experiments showed that while KBNNO is reasonably good at generating electricity from heat and pressure, it isn't quite as good as other perovskites. However, the researchers were able to modify the composition of KBNNO to improve its pyroelectric and piezoelectric properties.
Yang Bai, a research fellow at the university, said: "It is possible that all these properties can be tuned to a maximum point."
The team is already exploring such an improved material by preparing KBNNO with sodium.
Within the next year, the team plans to build a prototype multi-energy-harvesting device. The fabrication process is supposedly straightforward, and commercialisation could come in just a few years once researchers identify a suitable material, according to the university.
Bai added: "This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable."
The material would likely supplement the batteries in devices, improving energy efficiency and reducing the need to recharge. Batteries for small devices may become obsolete as a result, according to Bai.
The research was funded by the European Union’s Horizon 2020 research and innovation programme. The study was published in the journal Applied Physics Letters.