Scholars and scientists from the University of Cologne research, explore and experience the city. They are interested in the flora, fauna and, last but not least, ist inhabitants both past and present. In this section, they report on things that are interesting, quirky, typical or less familiar. Nils Eingrüber, scientist and lecturer at the Institute of Geography, sees our city as a real laboratory.
Hohe Strasse in Cologne is one of the oldest and busiest shopping streets in Germany. In order to reduce overheating in summer and improve the quality of experience for visitors, the capital management company Aachener Grundvermögen, which owns many of the buildings on Hohe Strasse, and Stadtmarketing Köln have developed a new type of shading system. The Cologne City Development Fund supports the project as part of the federal programme “Sustainable inner cities and centres” (Zukunftsfähige Innenstädte und Zentren).
A number of vertically attached cloths are intended to provide shade on Hohe Strasse and make it cooler. In contrast to the horizontal awnings already established in the Mediterranean region, the vertically arranged shade cloths enable better ventilation of the pedestrian zone – especially in the summer heat – along with improved cooling of narrow street corridors at night. But can the effect be measured and scientifically explained? This is where the university comes into play.
Under the direction of Professor Dr Ulrich Löhnert from the Institute of Geophysics and Meteorology, students are recording high-resolution climate data for the first time in a pedestrian zone equipped with shading systems in a large German city centre. Previous data is based on modelling to estimate the cooling effect. The sensors, which are installed at various heights on street lamps and building façades, measure temperature, humidity, and wind speed – both inside and outside the shaded areas. In this way, the small-scale temperature differences that result from shading can be recorded directly. Over 40 sensors are installed along a 50 metre stretch of Hohe Strasse. Our aim is to derive robust recommendations for further climate adaptation measures in city centre shopping streets – such as additional greenery, water-misting systems, cooling building materials or architectural shading solutions.
Together with bachelor student Britney Fejzolli from the Institute of Geography, I analysed the first heatwaves of this summer. We can already assert that the shading measures in Hohe Strasse can lead to a significant cooling effect of 2 to 3°C in the afternoon hours on hot days. On particularly windless hot days, a cooling effect of up to 5°C can be observed in the air temperature. The perceived temperature as experienced by passers-by can be reduced by up to 11°C thanks to the shading. The shading therefore helps to significantly reduce heat stress and improve the comfort of people on Hohe Strasse.
We are using the data collected from Hohe Strasse and around 150 other sensors that measure temperatures at various locations in Cologne as part of the AKT@HoMe project in a citizen science approach to train and improve three-dimensional urban climate models such as ENVI-met. This allows us to directly compare the effectiveness of heat protection measures such as façade greening, roadside trees, removal of impermeable surfaces or using white surfaces, and identify which measures are best suited to individual locations because there is no single “model solution”. Some heat reduction measures can also have negative effects, for example on air quality. And in any case, combinations of different measures are usually more effective than individual approaches.
Read more: AKT@HoMe:
See more: https://youtu.be/Yn9m8ViQzP8