Chicago's Willis Tower, formerly known as Sears Tower, was the
world's tallest building from 1974 to 1998 and remains the
tallest building in the U.S. to this day. Its 1451-foot (442 m)
height adds up to enough window area to keep a window washer
busy for life, or space for enough solar panels to be comparable
to a 10 acre solar power plant. As part of a pilot project, the
south facing windows of the 56th floor of the Willis Tower will
be replaced with Pythagoras Solar's transparent solar windows
which cut down on heat gain – and therefore cooling costs – as
well as harnessing energy from the sun. While the image that
comes to mind when one thinks of solar power plants is probably
one of rows upon rows of panels covering large areas of desert,
replacing the windows of skyscrapers with solar windows gives
cities with limited free space the opportunity to create
vertical solar power plants. Pythagorus Solar's solar windows,
which the company calls photovoltaic glass units (PGUs), are
rectangular box-shaped unit