A ceramic sample capable of harvesting multiple energy sources all at once.Scientists in Finland have developed a material that can transform the energy from sunlight, heat and movement into electricity all at the same time. The team, from the University of Oulu, identified a mineral with the perovskite crystal structure that offered the best properties to extract energy from a range of sources and convert it into electrical energy simultaneously in the same material, an ability that could help extend the life of batteries in wearable gadgets such as smart watches and biometric sensors.
Perovskites have demonstrated promise for harvesting different types of energy, but up to now they have not done so simultaneously. While one member of the perovskite family could have the right characteristics for converting solar energy into electricity in an efficient way, another can harness energy from changes in temperature and pressure arising from motion – making them pyroelectric and piezoelectric materials, respectively.
However, to have more than one type of energy available can be useful, although previous research has shown devices able to harness multiple forms of energy need multiple materials, adding to the weight. In this study, as published in the journal Applied Physics Letters [Bai et al. Appl. Phys. Lett. (2017) DOI: 10.1063/1.4974735], however, a specific type of ferroelectric perovskite called KBNNO was investigated to see if it could harness many forms of energy.
“This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable”Yang Bai
As with all perovksites, the material has small electric dipoles. When such ferroelectric materials experience a change in temperature, their dipoles become misaligned, inducing an electric current. In addition, an electric charge accumulates depending on the direction the dipoles point, while deforming it results in some areas attract or repel charges, which again produces a current. Studies into KBNNO’s photovoltaic and general ferroelectric properties had been carried out at temperatures below freezing and didn't examine properties related to temperature or pressure. This research is the first to assess all of these properties at once above room temperature.
They showed that although KBNNO is comparatively efficient at producing electricity from both heat and pressure, it is not as good as other perovskites, but they did modify its composition to improve its pyroelectric and piezoelectric properties. They think all these properties could be tuned to a maximum point, and are already exploring this by preparing KBNNO with sodium.
The research is at an early stage, and they are now looking to optimize the chemical composition and microstructure of the material, as well as design a prototype multi-energy harvesting device based on a straightforward fabrication process, which could help realize commercialization once the most promising material is identified. As lead author Yang Bai said “This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable”.