Researchers at Wuhan University in China seek to develop hydrogel glass that will keep buildings and living spaces cooler, without the loss of visibility to the outdoors.

According to a research article published in the journal Frontiers of Optoelectronics and titled Broadband Light Management in Hydrogel Glass for Energy Efficient Windows that Proposes Designing Hydrogel Glass, Wuhan University researchers aim to design a hydrogel glass that will block heat from the sun without blocking out light.

A hydrogel is a polymeric material that exhibits the ability to swell and retain a significant fraction of water within its structure but will not dissolve in water.

The hydrogel glass will feature a hydrogel coating just a few millimeters thick that is layered over standard glass. This will help reflect more of the near-infrared light from outside light while allowing more mid-infrared light to escape from the inside.

This is in comparison to traditional glass, which allows visible light and near-infrared radiation from sunlight to pass through while preventing mid-infrared light from escaping the room. This process works to heat a building. As a result, more energy is consumed as people seek to cool down the space.

The Wuhan University researchers, however, want to find alternative ways to lessen energy usage. The hydrogel glass will possess an elevated level of visible light transmission, stronger near-infrared light blocking and higher mid-infrared thermal emittance compared to traditional glass. This will allow hydrogel-glass-based windows to emit more light indoors all the while reducing temperatures, which reduces energy use for both lighting and cooling.

The hydrogel glass will have a slightly higher level of visible light transmission. The researchers claim tests indicate that 92.8% of visible light is let into the room, compared with 92.3% in normal glass.

The hydrogel glass also proved stronger in blocking mid-infrared light – up to 96% of the infrared light was emitted into space. To compare, regular glass emits up to 84%, the researchers say.

Additionally, tests on model homes adorned with hydrogel glass and thick, insulated walls indicate that the hydrogel glass windows reduced interior temperatures by up to 6.3 degrees fahrenheit.

The researchers state that photons of visible light can penetrate over 3.3 feet into water, while photons in the near-infrared part of the spectrum can only make it a few millimeters. Since hydrogels are mostly water, that makes them a useful, selective barrier, according to the researchers.

Researchers hope less energy and money will be needed to keep living spaces cooler without losing outdoor visibility.