Published on July 6th, 2012 | by Glenn Meyers6
Power-Generating Windows Offer New Horizons for Office Energy Efficiency
For solar enthusiasts on limited budgets, rooftop panels are no longer the only way to produce clean electricity. Try all of the south-facing windows, instead.
According to a recent news release from Delft University of Technology, “New Insights Into Power-Generating Windows,” Jan Willem Wiegman will graduate from TU Delft with with an Applied Physics Masters and his research into power-generating windows. As a student, he calculated how much electricity can be generated using luminescent solar concentrators. Importantly, these are not costly new windows he’s talking about, just windows that are fitted with a thin film of material, which absorbs sunlight, then directs it to narrow solar cells at the perimeter of the window. Wiegman shows the relationship between the colour of the material used and the maximum amount of power that can be generated.
Such power-generating windows might offer remarkable potential as an inexpensive source of solar energy that can attract many new renewable energy champions whose budgets have previously been restrictive in converting to solar energy.
For those wishing to dig deeper into the technology, Wiegman’s research article, written with his supervisor at TU Delft, Erik van der Kolk, has been published in the journal Solar Energy Materials and Solar Cells.
Urban office towers may be likely candidates for this energy generating application, as the majority of them feature more window square footage than what’s on the roof.
“Windows and glazed facades of office blocks and houses can be used to generate electricity if they are used as luminescent solar concentrators. This entails applying a thin layer (for example a foil or coating) of luminescent material to the windows, with narrow solar cells at the perimeters. The luminescent layer absorbs sunlight and guides it to the solar cells at the perimeter, where it is converted into electricity. This enables a large surface area of sunlight to be concentrated on a narrow strip of solar cells.”
Color is also part of how this technology works best. Luminescent solar concentrators are capable of generating dozens of watts per square meter, however, the amount of power produced depends on the color and quality of the light-emitting layer. Wiegman’s research shows a relationship between the color of the film or coating and the maximum amount of power.
A transparent film can produce a maximum of 20 watts per square meter — not quite enough to power a building, but certainly enough to power office equipment. A computer would need a window measuring 4 square metres. The efficiency increases if the film is able to absorb more light particles. This can be achieved by using a foil that absorbs light particles from a certain part of the solar spectrum. A foil that mainly absorbs the blue, violet and green light particles will give the window a red colour. Another option is to use a foil that absorbs all the colours of the solar spectrum equally. This would give the window a grey tint. Both the red and the grey film have an efficiency of 9 percent, which is comparable to the efficiency of flexible solar cells.