A lot of sunlight shines on tall office buildings but it goes to waste. A solar array crammed onto the top of a typical office tower produces only a tiny fraction of the electricity the building and its tenants need. But what if the building's windows could serve as solar panels? Pythagoras Solar has an answer, and it’s called Solar Windows, or High Power Density Photovoltaic Glass Units (PVGU). These photovoltaic cells have a dual responsibility: They shade the rooms from direct incoming light and then put that blocked light to work producing electricity.
The company began testing solar window technology in Chicago's Willis Tower (formerly the Sears Tower) last year. It installed a small double-pane window embedded with solar cells, and, if all goes well, the tower's owners will expand the project to cover the entire south face of the building.
The Pythagoras window belongs to a class of solar equipment known as BIPV - building-integrated photovoltaics. The Pythaoras window generates about 4 times the power density of other BIPV technologies. Sandwiched horizontally between two panes of glass, the silicon PV cells generate about 13 watts per square foot. Each individual tile lays a monocrystalline silicon solar cell horizontally between two layers of glass. 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.
Also Improves Building Energy Efficiency
The PVGU blocks the heat from direct sunlight and illuminates the space with diffused light by selecting light based on its angle of incidence. This combination reduces the building’s lighting and cooling costs and creates a comfortable work environment.
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