Smart window harnesses energy from the sun

A prototype of the innovative smart windows for controlled shading and solar thermal energy harvesting is presented by PhD student Benjamin Heiz

A new super-smart window developed by a German university can work as a solar panel to collect energy from the sun.

The Large-Area Fluidic Windows (LaWin) system, created by the Friedrich-Schiller University Jena, contains magnetic iron nanoparticles which can control the opacity of the window, blocking light to varying degrees and absorbing heat as needed.

In their paper, Large-Area Smart Window with Tunable Shading and Solar-Thermal Harvesting Ability Based on Remote Switching of a Magneto-Active Liquid, researchers introduce prototypes of a window that changes its light permeability at the touch of a button, and, at the same time, can be used for solar-thermal energy harvesting.

“Our project’s key feature is the use of liquids in windows and façades, for example, as heat carriers or to enable additional functions,” project coordinator Lothar Wondraczek said.

“To this end, we develop new glass materials into which large-area channel structures are integrated. These are used for circulating functional fluids.”

In latest prototypes, the liquid is loaded with the nanoscale magnetic iron particles that can be extracted from the liquid with the help of a magnet. Vice versa, they can be re-suspended by simply switching-off the magnet.

“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,” Mr Wondraczek explained.

“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 efficiency in terms of heat gain per area is comparable with that of state-of-the-art solar thermal facilities.

But unlike those, the present system can be readily integrated in a vertical façade. Switching between on and off – the release or capture of particles – happens in a separate tank.

An electrical connection at the windows is not necessary.

The project has received a grant of 5.9 million Euros from the European Union, with a further 2.2 million Euro added by eleven industry partners who have been members of the consortium.

After the end of the first funding period, commercialisation of first applications is planned for this year.