Chicago Skyscraper to Generate Solar Electricity

March 24, 2011

Willis Tower in Chicago -- formerly Sears Tower

Skyscrapers, notorious huge energy consumers, may soon become solar energy producers.

In an experimental program, Chicago’s tallest building, Willis Tower (previously the Sears Tower) will soon feature high power density photovoltaic glass units (PVGUs) on the south side of the 56th floor, replacing the existing windows with a new type of photovoltaic glass developed by Pythagoras Solar. The new window units will preserve daylighting and views while reducing heat gain and producing the same energy as a conventional solar panel.

According to Inhabitat, the project could grow to 2 MW in size — which is comparable to a 10-acre field of solar panels — turning North America’s tallest building into a huge urban vertical solar farm. This will depend on what the return on investment is for this experimental technology.

The project is collaboration between the tower’s owner and Pythagoras Solar, with offices in California, Israel and Taiwan. The new PVGUs use a 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, providing natural light inside.

“We are excited to launch this pilot with Pythagoras Solar’s leading-edge solar window solutions as a test for not only the energy savings that can be achieved, but the potential they represent to actually generate power through the sun,” said John Huston, Executive Vice President of American Landmark Properties, one of the ownership partners of Willis Tower.

Source: Pythagoras Solar

Pythagoras Solar claims that the vertically integrated solar cells will produce the same amount of energy as normal rooftop-mounted solar panels. This is great news for cities that have precious little rooftop space and towering walls of glass. The product is also a potential breakthrough in energy efficiency in glass towers, where solar heat gain is difficult for those inside the building.

On its website, the PVGU manufacturer highlights a section titled, Toward Net-Zero Buildings. There it discusses Building Integrated Photovoltaics, stating, “Building Integrated Photovoltaics, by replacing common materials in the building envelope, provides the most promising solution for harnessing the sun at the point of use–the buildings where we live and work.”

This You Tube Video animation from Pythagoras Solar provides a good perspective for the potential for PVGU buildings.

According to the Pythagoras Solar website, the company was conceived at Precede Technologies, an Israeli incubator, which teams up scientists, inventors, and entrepreneurs. “Dr. Itay Baruchi, an award-winning physicist, and Gonen Fink, a leader in taking Check Point Software from start-up to a multibillion dollar company, saw a business opportunity at the intersection of rising demand for Green Buildings and declining cost of Photovoltaic (PV) solar power.”

Pythagoras Solar’s PVGU uses patent-pending optical technology, high-efficiency silicon, and advanced materials to provide the industry’s first highest-transparency and highest-density PV power generation in a standard double-pane window form factor.


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Glenn Meyers

Writer, documentary producer, and director. Meyers is a contributor to CleanTechnica, and founder of Green Streets MediaTrain, a communications connection and eLearning hub. As an independent producer, he's been involved in the development, production and distribution of television and distance learning programs for both the education industry and corporate sector. He also is an avid gardener and loves sustainable innovation.
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