Innovative solar box could cool city buildings

Engineers have designed a new system that can help cool buildings in cities without consuming electricity.

Details of the system, which has been published today (August 5) in Nature Sustainability, show that it could help to cut emissions in the built environment which is a major emitter around the world.

In the UK, around 40% of the UK’s total carbon footprint comes from buildings.

Engineers from the University of Buffalo and King Abdullah University of Science and Technology in Saudi Arabia used an inexpensive polymer/aluminium film that’s installed inside a box at the bottom of a specially designed solar ‘shelter’.

The film helps to keep its surroundings cool by absorbing heat from the air inside the box and transmitting that energy through the Earth’s atmosphere into outer space.

The shelter-and-box system is about 45cm tall and 25cm wide, so to cool a building, several units of the system would need to be installed to cover a roof.

The shelter also serves a dual purpose, helping to block incoming sunlight, while also beaming thermal radiation emitted from the film into the sky.

When placed outside during the day, the heat-emanating film and solar shelter helped reduce the temperature of a small, enclosed space by a maximum of about 6°. At night, that figure rose to about 11°.

Co-author Lyu Zhou, a PhD candidate in electrical engineering in the University at Buffalo School of Engineering and Applied Sciences said: ‘The polymer stays cool as it dissipates heat through thermal radiation, and can then cool down the environment,

‘One of the innovations of our system is the ability to purposefully direct thermal emissions toward the sky,’ added lead researcher Qiaoqiang Gan, PhD.

‘Normally, thermal emissions travel in all directions. We have found a way to beam the emissions in a narrow direction. This enables the system to be more effective in urban environments, where there are tall buildings on all sides.

‘We use low-cost, commercially available materials, and find that they perform very well.’