Engineers at the A. James Clark School of Engineering at the University of Maryland (UMD) demonstrate in a new study that windows made of
transparent1 wood could provide more even and consistent natural
lighting2 and better energy efficiency than glass. In a paper just published in the peer-reviewed journal Advanced Energy Materials, the team, headed by Liangbing Hu of UMD's Department of Materials Science and Engineering and the Energy Research Center lay out research showing that their transparent wood provides better
thermal3 insulation4 and lets in nearly as much light as glass, while eliminating glare and providing uniform and consistent indoor lighting. The findings advance earlier published work on their development of transparent wood.
The transparent wood lets through just a little bit less light than glass, but a lot less heat, said Tian Li, the lead author of the new study. "It is very transparent, but still allows for a little bit of privacy because it is not completely see-through. We also learned that the channels in the wood transmit light with
wavelengths5 around the range of the wavelengths of visible light, but that it blocks the wavelengths that carry mostly heat," said Li.
The team's findings were
derived6, in part, from tests on tiny model house with a transparent wood panel in the ceiling that the team built. The tests showed that the light was more evenly distributed around a space with a transparent wood roof than a glass roof.
The channels in the wood direct visible light straight through the material, but the cell structure that still
remains7 bounces the light around just a little bit, a property called
haze8. This means the light does not shine directly into your eyes, making it more comfortable to look at. The team photographed the transparent wood's cell structure in the University of Maryland's Advanced Imaging and Microscopy (AIM) Lab.
Transparent wood still has all the cell structures that comprised the original piece of wood. The wood is cut against the grain, so that the channels that drew water and
nutrients9 up from the roots lie along the shortest dimension of the window. The new transparent wood uses theses natural channels in wood to guide the sunlight through the wood.