Glazing can be a desirable surface for solar collection as in the case of tall buildings with curtain-wall envelopes. However, the application of conventional silicon photovoltaic (PV) and thin-film technologies to glazing has been problematic because the addition of dark or colored bands to windows can obstruct views.
A team of researchers at Michigan State University recently unveiled a potential solution: a transparent solar-concentrating film. The cleverly designed luminescent solar concentrator works where others have failed because it translates and redirects the energy to the film's edges—where PV cells harvest the power—rather than capturing it as it passes through the surface. The transparent polymer contains organic molecules that absorb near-infrared and ultraviolet light, converting it to the infrared spectrum. The light is then guided to PV cells along the concentrator's edge.
Though preliminary studies reveal a less-than-ideal conversion efficiency of 1 percent for the new technology, the researchers claim that a 5-percent conversion efficiency is theoretically achievable. Currently, the best PV solar conversion rate is slightly more than 21 percent, while amorphous silicon used in thin-film technologies has a 6- to 12-percent conversion rate.
The versatility and scaleability of the technology are compelling, however, and the team claims that the new film may be used on nearly any transparent surface, from building facades to smartphones.
If the technology can be offered at a low cost and adequate conversion rate, it could become a widespread addition to glazing. However, window frame and gasket systems will need to be re-designed in order to incorporate power harvesting and distribution capability. The integration of the film within insulated glass units will also require further study, as the material will likely operate best when protected from potential exterior degradation.
"It opens a lot of area to deploy solar energy in a non-intrusive way,” said Richard Lunt, an assistant professor in Michigan State's College of Engineering, in a press release. "It can be used on tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader. Ultimately we want to make solar-harvesting surfaces that you do not even know are there.”
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.
