University of Gävle participates in major project
Formas, the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, allocates five million SEK to the University’s research on improved ventilation in cities. This is part of Formas’ 125 million research programme on building a sustainable society.
How to build a city
As air approaches a city, it will meet with increased resistance, which means that some of the air will flow above or around it. As there is clean air above cities, the researchers in Gävle are looking into possibilities of leading clean air down to the street level by varying the height of buildings and the width of streets.
“The aim is to find ways of leading clean air flows down to dilute air pollution in the city, and such variations help us reach that aim,” Mathias Cehlin explains.
Look at the leaves in the autumn
If the city is compact with tall buildings, clean air does not generally reach the ground level and, if it does, whirlwinds with the ability to accumulate are formed.
“This is clearly visible now in the autumn when leaves are trapped in such whirlwinds. In a similar manner, air pollution becomes trapped in these whirlwinds resulting in higher and higher concentrations of air pollution, and this is something we would like to avoid.”
Big cities are ventilated with polluted air
The researchers aim to find ways to get clean air down to the street level to improve air quality outdoors but also indoors. Buildings are ventilated with air from the city, and it is problematic that city air tends to be polluted.
“In Sweden, we usually say that we ventilate building with clean air, but in big cities it isn’t clean air but polluted air that we use.”
The city as a building
Mathias states that their contribution is a new perspective; they regard a city as a building consisting of rooms without roofs and they use the same techniques to measure ventilation for cities as they do for buildings. The researchers have already developed methods to measure ventilation in buildings with complicated airflows.
“Often, air and pollution return to where they came from. In building ventilation, we have the knowledge required to handle such complexities because we have a history of collaboration with researchers in Japan, China and Europe.”
Presently, the focus is to create the basis for methods to evaluate air quality which take into account how the city is built and how neighbourhoods will be built. As mentioned, the starting point is the view that the city is a building consisting of rooms without roofs.
“We would like to develop simple tools for urban planners to use when they compare alternative designs for new neighbourhoods. The fact that our team consists of a multidisciplinary group of researchers from ventilation, energy systems, architecture and geographic information systems is also new,” Mathias says.