That icon, the Sears Tower (now known as Willis Tower) is about to get a very high-profile makeover (as if the name change wasn't enough!). She (I'm going to call it a she) is part of a pilot program that will replace the windows on the south side of the 56th floor with a new type of photovoltaic glass.
Pythagoras Solar has developed the photovoltaic glass, which preserves natural light and views, reduces heat gain and produces the same energy as a conventional solar panel. The project could eventually grow to the size of a 10 acre field of solar panels.
According to Inhabitat:
The project is a collaboration between the tower's owner and the manufacturer to prove the viability of the building integrated photovoltaic (BIPV) system, which will also save energy by reducing heat gain and cooling costs. The new windows, dubbed high power density photovoltaic glass units (PVGU), are a clever hybrid technology that lays typical monocrystalline silicon solar cell horizontally between two layers of glass to form an individual tile. An internal plastic reflective prism directs angled sunlight onto the solar cells but allows diffuse daylight and horizontal light through. Think of it as a louvered shade which allows for views but cuts out the harsh direct sun.