Research currently being conducted into polymer-based, photovoltaic cells promises the exciting possibility of being able to soon install a new generation of active, power generating window film. By ‘retuning’ to a different solar spectrum wavelength, near-infrared radiation rather than visible light can be directly converted to electric power.
Window tinting film is an evolving technology, constantly adapting to social and environmental needs, and bearing only scant resemblance to the simple dyed tinting process that first gave the application its name half a century ago. In the 1970s, developments in solar control film incorporated a UV inhibitor and/or a shading medium to prevent heat escape. By the 1990s, a new class of metallic “hybrid” film combined the dual process of both absorbing and rejecting solar heat.
With the use of nanotechnology, the creation of sputtered or ceramic tinting films, it is now possible to transmit up to 70 per cent of visible light while redirecting up to 94 per cent of solar infra red radiation.
Today, a tinted window film will block up to 99 per cent of solar ultra violet radiation while simultaneously, regulating the levels of heat and light allowed to pass through according to specific solar protection film specification.
More interactive role…
However, within the next few years, solar control films may be able to offer a more interactive role by creating electrical power, which can control transmitted light and heat, without compromising the visible light wavelength. It could usher in a new wave of clear window film where tinting aesthetics are entirely separate from the function of anti glare, heat and radiation blocking.
At present, photovoltaic cells in development are ‘tuned’ to absorb the near-infrared radiation wavelength, thereby, allowing two-thirds of the visible light to pass through unhindered. However, the best values achieved are for a power conversion rate of around 4 per cent, which is below the 6 per cent plus efficiency of current inexpensive, standard thin-film PV cells found on Solar PV panel installations.
The researchers hope to improve conversion rates with the interim aim of complementing rather than competing with conventional solar PV photovoltaics.
Possible early applications could include single computer screens capable of recharging smartphones or tablets or applied to vehicle windows to top up stored power in an electric car.
About the Author –
Rico Lowe is the owner of a window tinting company called Sola Tint and Style. Rico and his team are based in Johannesburg but cover surrounding areas.