published on 3 July 2017 in energy

New research into smart windows from Princeton

Over recent years, numerous universities and laboratories all over the world have been focussing their efforts on smart windows, with the aim of creating low-cost models that are able not only to produce energy, but also to automatically regulate transmission of light and heat into interior areas. One of these research projects arrives from Princeton University, which has just published some very promising results related to a new smart window that could be installed even on existing facades, leading to a reduction of up to 40% in average energy costs for summer-winter conditioning of buildings.
What is the secret of this new window? Quite simply, it is a combination of selective solar cells and electrochromic polymers, materials that, as their name suggests, change colour in response to an electrical stimulus, thereby allowing the glazed surfaces to block out part of the sunlight. The challenge that the scientists at Princeton set themselves is twofold: on the one hand, controlling the amount of light and heat entering the building through its windows, while on the other hand, independently generating the electricity required to make the system work.
To achieve these results, the team at Princeton built a thin film solar cell composed of organic semiconductors, the chemical structure of which has been modified to absorb only quasi ultraviolet light, invisible to the human eye. When the quasi-UV rays generate an electric charge in the photovoltaic cells, the electrochromic polymers of the window react and change its opacity, from total transparency to a deep blue, thus making it possible to block up to 80% of natural luminosity.
Looking towards the future, the team hopes to develop a smart film that can be retrofitted on existing glass panes and windows, so that users can change their colour from their smartphones with just one click.

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