Capture Energy from the Sun’s Rays and Release It Later as Heat

At dawn when the film has not absorbed any solar energy it is yellow or orange, since these colours are the opposite of blue and green, which is the light spectrum that the researchers have chosen to capture from the sun. When the molecule captures solar energy and is isomerised, it loses its colour and then becomes entirely transparent. As long as the sun is shining on the film it captures energy, which means that not as much heat penetrates through the film and into the room. At dusk, when there is less sunlight, heat starts to be released from the film and it gradually returns to its yellow shade and is ready to capture sunlight again the following day.

“For example, airports and office complexes should be able to reduce their energy consumption while also creating a more pleasant climate with our film, since the current heating and cooling systems often do not keep up with rapid temperature fluctuations,” says Moth-Poulsen.

The molecule is part of a concept the research team calls MOST, which stands for Molecular Solar Thermal Storage. Previously the team presented an energy system for houses based on the same molecule. In that case – after the solar energy had been captured by the molecule – it could be stored for an extended period, such as from summer to winter, and then used to heat an entire house. The researchers realised that they could shorten the step to application by optimising the molecule for a window film as well, which would also create better conditions for the slightly more complex energy system for houses.

What the researchers still have to do is to increase the concentration of the molecule in the film whilst also retaining the film’s properties, and bring down the price of the molecule. But according to Moth-Poulsen they are very close to this innovation.

“The step to applying our film is so short that it could happen very soon. We are at a very exciting stage with MOST,” he says.

Contacts and sources:
Kasper Moth-Poulsen, Professor of Nanochemistry Chalmers University of Technology

Citation: Solar Energy Storage by Molecular Norbornadiene–Quadricyclane Photoswitches: Polymer Film Devices.  Anne Ugleholdt Petersen Anna I. Hofmann Méritxell Fillols Mads Mansø Martyn Jevric Zhihang Wang Christopher J. Sumby Christian Müller Kasper Moth‐Poulsen First published: 25 April 2019 https://doi.org/10.1002/advs.201900367 https://onlinelibrary.wiley.com/doi/full/10.1002/advs.201900367