Glass has been made for thousands of years, and innovators have always been tinkering to improve the basic product. Over the years, these improvements have mainly been in terms of color, strength, weight, quality. The cleantech imperative of the past few decades is now pushing glass innovations on two more dimensions, energy efficiency and power generation.
Regarding energy efficiency, the big issue with windows is energy transfer. Of course, glass is more thermally conductive than most other building materials, so windows let out more heat in the winter and let in more heat in the summer than the rest of the building. As such, improving the thermal-insulation of windows has long been pursued, such as through storm windows.
However, another angle on the efficiency topic is via the use of electrochromics, which uses chemistry to change the tint of the glass based on the amount of sunlight. You’ve no doubt seen these on sunglasses: the glasses turn darker in bright sunlight, and lighten up inside. Well, these are now increasingly being applied to windows, so as to reduce the amount of energy (heat) transmitted through the glass. SAGE Electrochromics of Minnesota, recently bought by the French giant Saint-Gobain (Paris: SGO), is arguably the leader in this field.
With respect to power generation, a number of inventors have been dabbling with photovoltaics integrated into glass. Most of this work has been to incorporate solar collecting material into the entire pane, but this recent article discusses some efforts at TU Delft in the Netherlands to use the glass as a lens to focus the light onto solar cells at the periphery of the window.
The moral of this story is: even something invisible like glass is subject to advancement as part of the cleantech movement.