TU Delft calculations for luminescent solar absorber show where improvement is needed

Delft, The Netherlands--Jan Willem Wiegman, a graduate student at the Delft University of Technology (TU Delft), has done calculations showing how much electrical power can be generated from windows that contain luminescent solar concentrators. The inorganic concentrator material, europium-doped lutetium oxide, is made into a mostly transmitting film on glass. It absorbs short wavelengths and re-emits longer wavelengths, some of which are trapped and totally internally reflected to the window's edge, where they are absorbed by narrow photovoltaic cells.

Taking into account effects like attenuation and scatter, Wiegman calculated electricity-generating efficiency versus window size and the relationship between the color of the material used and the maximum amount of power that can be generated Wiegman’s research article, which he wrote together with his supervisor at TU Delft, Erik van der Kolk, has been published in the journal Solar Energy Materials and Solar Cells.

Measurement of a fabricated film show a linear attenuation coefficient of tens of millimeters, far shorter (higher attenuation) than the calculated desirable coefficient of at least 1000 mm.

Windows and glazed facades of office blocks and houses can be used to generate electricity if they are used as luminescent solar concentrators. The technique enables a large surface area of sunlight to be concentrated on a narrow strip of solar cells.

A transparent film could produce a maximum of 20 W/m², for an efficiency of 2%. The efficiency increases if the film is made to absorb more photons. A foil that mainly absorbs the blue, violet and green light particles will give the window a red color. Another option is to use a foil that absorbs all the colors of the solar spectrum equally, appearing gray. Both the red and gray films have an efficiency of 9%, which is comparable to the efficiency of flexible solar cells.

Wiegman’s research has also shown the importance of a smooth film surface for the efficient transport of photons to the perimeter of the window without excessive scattering.

Source: http://tudelft.nl/en/current/latest-news/article/detail/tu-delft-student-biedt-uitzicht-op-stroomraam/