New Material Developed to Store and Release Relatively Large Amounts of Low-Grade Heat Without Decomposing

A common substance that has the potential to quickly and reversibly store and liberate comparatively huge amounts of low-grade heat without decomposing has been discovered by Japanese scientists. The research could result in a more efficient reuse of industrial waste heat.

The study outcomes were reported in the Nature Communications journal. The study was a collaboration between researchers at Tohoku University’s Institute for Materials Research and Rigaku Corporation, a company that designs and manufactures X-Ray-based measurement and thermal analysis tools.

In the investigations performed by the scientists, they made use of a layered manganese oxide mineral consisting of crystal water and potassium ions. This mineral seems to be quite similar in its composition to birnessite, which is generally found on the surface of the Earth.

The fabrication of their compound was done by the researchers in the form of an insoluble black powder and further analyzed its crystal structure with the help of a transmission electron microscope and an X-Ray diffractometer. Furthermore, they analyzed how the structure of the compound was altered while being subjected to cooling or heating, and how much and how rapidly heat energy was stored and liberated.

Using up to 200 °C to heat the material, the researchers dehydrated it by providing its stored water molecules the energy required to be discharged into the surrounding atmosphere. Furthermore, when the dehydrated material was cooled below 120 °C in a dry container and then exposed to humid air, it absorbed water molecules and liberated its stored heat.

This ‘intercalation’ mechanism, where water molecules are reversibly inserted into a layered material, is very advantageous for heat storage. It is very fast, reversible and the material's structure is well maintained.

Tetsu Ichitsubo, Materials Scientists, Tohoku University

Ichitsubo added, “Also, oxygen in the atmosphere doesn't degrade the layered manganese oxide crystal and water doesn't dissolve it. This makes it an excellent candidate for waste-heat reuse in industrial settings.”

This “birnessite-type layered manganese dioxide with crystal water” compound illustrated better overall performance than other compounds that are being researched at present for heat storage purposes.

Our material has a long lifetime, can reversibly store and release large amounts of heat per unit volume, and rapidly charges and discharges.

Tetsu Ichitsubo, Materials Scientists, Tohoku University

The scientists confirmed the outcomes of their experiments along with theoretical calculations.

The researchers plan to work on increasing the number of water molecules that can be housed by the material, to raise the amount of heat energy it can store per volume.

Journal Reference:

Hatakeyama, T., et al. (2022) Excellently balanced water-intercalation-type heat-storage oxide. Nature Communications. doi.org/10.1038/s41467-022-28988-0