More than a view: Here are 3 solar energy-producing windows

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Buildings account for nearly 40% of global energy use and contribute about 40% of greenhouse gas emissions on our planet. What’s more, global building stock is expected to double in area by 2060. 

As solar arrays and wind farms continue to fill in open spaces, innovators have a vision of another way to produce energy:  photovoltaic windows. 

Here are some of the companies currently involved in turning windows into energy-producing devices:

NEXT Energy Technologies

NEXT Energy’s Paris Display

Image: BusinessWire

NEXT Energy Technologies produces a transparent photovoltaic coating that transforms commercial windows into energy-producing solar panels. The company said its first-generation windows could offset as much as 10-20% of the electricity needs of a typical commercial high-rise office building. 

NEXT Energy claims a one-year payback for the windows, and a functional life of 30 years. The windows transmit between 10%-50% of visible light and convert it to power at 7%-10% efficiency. 

The photovoltaic coatings are applied during the window fabrication process, integrating with established manufacturers without disrupting workflows and supply chains. NEXT Energy said its approach removes costs typically associated with packaging and installation of solar. 

A prototype of NEXT Energy’s Window Wall will soon be display in Paris, featuring an interactive display and charging ports that are powered by a set of 10 windows.

The prototype installation is designed to supply electricity to a battery that will power an interactive display as well as charging outlets for phones, tablets, and other electronics. In the coming years, NEXT windows are expected to be commercially available for window sizes up to 5 ft. x 10 ft (1.5 x 3 meters).

SolarWindow Technologies

SolarWindow Technologies creates a product called Liquid Electricity, a transparent and lightweight material meant to be applied to glass, plastics, and films. The company said it has applications in architecture, agrivoltaics, aerospace and defense, and transportation.

A recent independent study between SolarWindow and the National Renewable Energy Laboratory determined a power conversion efficiency level as high as 14.72%.

The company said one advantage of its technology over rooftop solar is it can work under natural, shaded, low-light, and even indoor artificial light sources. 

The window uses what SolarWindow said are organic photovoltaics (OPV), and are produced as thin as 1/100th the thickness of a human hair. The process does not use toxic metals such as lead, cadmium, and selenium. The company said that in OPV two layers create a material boundary known as the acceptor layer and the donor layer. The material in each layer has its own specific level of electrical potential. The difference between each material’s electrical potential stimulates the movement of electrons, which generates electricity.

The product comes in a variety of transparency levels, from entirely non-transparent to transparency typical of a residential window. It can be applied with blue, green, gray, or tan tint, and electric output decreases as transparency increases.

SolarGaps

U.S. and Ukraine-based SolarGaps views the concept from a different angle: rather than electrifying windows, it developed blinds integrated with photovoltaics. The blinds automatically track the sun, producing power and keeping the building cool.  

SolarGaps said its product can produce 100W per hour for every square meter during daytime. The product is installed external to the building and has both commercial and residential applications. SunPower C60 solar elements with a claimed 22.4% efficiency are used. 

Although it is an external installation, the blinds have built-in wind resistance with a  steel cable and are tested with air guns, said SolarGaps. The company claims a 10-year minimum lifespan and offers a two-year warranty. 

The blinds are IOS and Android app compatible, integrated with smart-home technology, can provide performance reports, and can be voice-controlled. The device has its own built-in tracker motor and inverter.

 

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