In the journal Energy Technology, researchers from the Karlsruhe Institute of Technology (KIT) have demonstrated sunglasses with colored, semitransparent solar cells applied onto their lenses that supply a microprocessor and two displays with electric power. This paves the way for future applications, such as the integration of organic solar cells into windows or overhead glazing.
"We bring solar power to places where other solar technologies fail," said Alexander Colsmann, head of the Organic Photovoltaics Group at KIT's Light Technology Institute (LTI). The "smart" solar glasses, designed as a case study by Colsmann and his team at KIT, are self-powered to measure and display the solar illumination intensity and ambient temperature.
The solar cell lenses, fitted to a commercial frame, have a thickness of approx. 1.6 mm and weigh about six grams—just like the lenses of traditional sunglasses. The microprocessor and the two small displays are integrated into the temples of the solar glasses, showing the illumination intensity and the ambient temperature as bar graphs.
The solar glasses also work in indoor environments under illumination down to 500 Lux, which is the usual illumination of an office or a living area. Under these conditions, each of the "smart" lenses still generates 200 milliwatts of electric power—enough to operate devices such as a hearing aid or a step counter.
"The Solar Glasses we developed are an example of how organic solar cells may be employed in applications that would not be feasible with conventional photovoltaics," said PhD student Dominik Landerer, who contributed to the development of the solar glasses at the Material Research Center for Energy Systems at KIT.
In the eyes of the engineer, these solar cells, which are based on hydrocarbons, are very exciting devices due to their mechanical flexibility and the opportunity to adapt their color, transparency, shape and size to the desired application.
According to Colsmann, another field of application is the integration of solar cells into buildings: since the glass facades of high-rise buildings must often be shaded, it is an obvious option to use organic solar modules for transforming the absorbed light into electric power. A future possibility Colsmann sees involves coating large surfaces with organic solar cells using reel-to-reel technology.
For another example of self-powered electronics, find out how this Battery-Free Cellphone Harvests Ambient Power.