Magnetic liquid window helps buildings keep their cool

Researchers at Germany’s University of Jena have developed a new type of window that uses switchable magnetic particles suspended in liquid to create shade and capture heat energy.


(Credit: Jan-Peter Kasper/FSU)

The prototype window is a suspended particle device (SPD) where iron nanoparticles are circulated in a liquid between a laminate of structured, rolled glass and a thin cover with high surface strength. Each laminate contains multiple channels a few millimetres wide through which the liquid flows. The capture and release of particles happens in a separate tank, so an electrical connection at the window isn’t required. According to the researchers, the low thickness of the SPD of typically 4–6mm allows for integration with standard double or triple glazing.

Light permeability can be altered at the touch of a button, and when fully shaded the device has a claimed solar thermal harvesting efficiency in the region of 45 per cent. Published in the journal Advanced Sustainable Systems, the research holds promise for significantly improving the efficiency of buildings by both reducing cooling loads and generating heat for use elsewhere.


(Credit: FSU)

“Depending on the number of the iron particles in the liquid, the liquid itself takes on different shades of grey, or it will even turn completely black,” said Lothar Wondraczek, chair of glass chemistry at the University of Jena and the project’s coordinator.

“Then, it becomes possible to automatically adjust the incidence of light, or to harvest solar heat which can then be put to further use within the building.”

The research is part of the EU’s Horizon 2020 programme and has received almost €6m in EU funding over the past two years, as well as an additional €2.2m from industrial partners. Current prototypes were manufactured on a scale of around 200 square meters, and the first commercial applications of the technology are planned for later this year.