America’s Tallest Skyscraper Becoming a Solar Farm

Chicago’s Willis Tower, America’s tallest building — formerly known as the Sears Tower, is getting a major green makeover.  The south side of the 56th floor will soon be home to solar electric glass windows, turning the tower into a 2-MW vertical solar farm. The windows called high power density photovoltaic glass units are being made by Pythagoras Solar.  They will retain views and daylighting for the floor, reduce heat and produce as much electricity as a traditional solar panel.  The windows consist of monocrystalline silicon solar cells sandwiched between two layers of glass with an internal prism that directs the sunlight onto the solar cells, while letting diffuse light through.  The result is a cooler, natural lighting environment inside the skyscraper and a more efficient solar panel. The windows are part of a bigger project by the tower’s owner and Pythagoras to show the benefits of a building integrated PV system (BIPV).  For large towers all over the world, this could be a key component in both energy efficiency and renewable energy production.