COPRO Managing Director Marc F. Kimmich and Green City Solutions
CIO Zhengliang Wu open the City Trees at B-Part Am Gleisdreieck
To purify the air, three CityTrees from Green City Solutions, a start-up and GreenTech pioneer from Berlin, were placed on the grounds of B-Part Am Gleisdreieck between 27 April and 30 June 2020. During this time, the air quality of the surrounding area was analysed and cleaned – with interesting results.
CityTrees are active biofilter systems that can remove fine dust from the air, cool temperatures and increase humidity. We have already reported on the installation of the CityTrees in our blog in May 2020 (LINK). Three CityTrees were set up in the south-western part of the B-Part outdoor area in such a way that they form a barrier to the neighbouring railway line and provide a fresh air zone against this source of fine dust. A CityTree is divided into two parts, the lower part with integrated technology and the upper part covered with moss as a filter unit with a total height of 3.60 metres. In one hour, each CityTree vacuums and cleans approx. 3,500 m³ of air. The evaporative cooling of the mosses generates a maximum cooling capacity of 5,500 watts.
During the 51 operating days of the three CityTrees at B-Part, about 2,711,657 m³ of air were purified. This is more than the volume of the Great Pyramid of Giza (2.6 million m³) and is sufficient to supply 2,215 adults with cleaned air over the entire period. During the project period, the wind came mainly from the southwest, so that the flowing air passed the CityTrees and was cleaned on its way towards the terrace and the front of the B-Part building. This improved the quality of stay for people sitting on the terrace or having a window open.
Different ventilation speeds generate different airflow speeds: fast speeds can filter coarse particles better, while slow speeds are better at separating ultra-fine particles, which are particularly hazardous to health. The CityTrees are therefore also especially good at absorbing peak pollution, such as from a burning barbecue or cigarette smoke. These “clouds of fine dust” can be cleaned particularly well by using CityTrees, as many particles hit the moss filter in a relatively small amount of air – the air pollution can be reduced by about half. For example, people in the immediate vicinity can be protected from intense passive smoking.
Air quality at the Gleisdreieck site
In railway stations, high concentrations of fine dust are often caused by whirled up dust and abrasion caused by braking. Despite the immediate vicinity of Gleisdreieck station, the measurements did not reveal any permanent excessive pollution. The average (day and night) fine dust pollution at B-Part came to 12 micrograms. This value is basically good and below the legally stipulated limits and is in line with the ” basic noise ” of air pollution in large German cities.
In addition to the overarching effect on air quality at B-Part Am Gleisdreieck, visitors who were in the immediate area around the CityTrees benefited most from its effect. By positioning them in a triangle, the CityTrees were able to create a so-called “CleanAirZone” (fresh air zone), in which, depending on the distance, a lower particle load of up to 53% could be measured. Even at a distance of 5 metres, the average particle pollution is still 30% lower.
The mosses in the CityTrees can store and evaporate up to 20 times their own weight in water. In combination with active ventilation, a cooling capacity of up to 5,500 watts is achieved. For example, scientific measurements have shown a temperature difference from 25°C to 16.8°C. In addition, an increase in humidity can be measured in the CleanAirZone. Especially at hot and dry times, staying near the CityTrees offers visitors a pleasant effect.
Illustration of the CleanAirZone in a windless scenario
(Values based on reference measurement by TROPOS 12/2019)
The collaborative project was a success: The insights and measurement results gained on location and air quality confirm that CityTrees can make a positive contribution to the quality of visitors’ stay. In addition to the positive effect on air quality, the CityTrees were also able to make a contribution in the context of the public debate on health and quality of life in the city and the importance of air quality and sustainable neighbourhood development. These issues are playing a central role in the development of the new city neighbourhood “Urbane Mitte Am Gleisdreieck” and we look forward to working with Green City Solutions to provide even more fresh air in the future.