Why did MANN+HUMMEL develop the Filter Cubes?
Critical values for particulate matter and nitrogen dioxide are being exceeded in many German cities, affecting the health of city dwellers. MANN+HUMMEL has developed Filter Cubes to reduce the concentration of pollutants in places with particularly polluted air. These are capable of extracting 80 percent of fine dust and nitrogen dioxide from the attracted ambient air with very low energy requirements.
As part of a pilot project, the first Filter Cube columns were installed at Stuttgart's Neckartor in November 2018 to protect residents and avoid driving bans. Following positive results in reducing fine dust pollution, MANN+HUMMEL retrofitted the existing constructions with newly developed combifilters in July 2019. These enable the capture of not only fine dust particles but also nitrogen dioxide from the air.
Thanks to the successful pilot project at the Neckartor, MANN+HUMMEL is the first company which is able to scientifically prove the effect of the Filter Cubes. This verification was produced in cooperation with the Karlsruhe Institute of Technology and the State Environmental Agency of Baden Württemberg. We recently installed and commissioned two further projects on particularly polluted roads in Stuttgart. These are Hohenheimer Strasse and Pragstrasse.
How do the Filter Cubes work?
Equipped with energy-efficient fans, the Filter Cubes attract ambient air. This air is filtered with the aid of fine dust particle filters, removing dangerous fine dust particles from the attracted ambient air. If the values of nitrogen dioxide or ozone are also too high, so-called combination filters are used. These have a highly effective filter layer for fine dust combined with a special activated carbon layer. Due to its large inner surface, the highly porous activated carbon is able to absorb NO2 very efficiently. This specially developed combination filter medium enables a particularly high air throughput with very low energy consumption at the same time. This purifies the air with very low energy consumption.
The operation of the filter columns can be adjusted as required via a control unit and thus react to the current air quality. External sensors record air and weather data, which are then merged and analyzed in a cloud.
The effective radius of a column is 15-20 meters. In order to achieve an area-wide effect within a certain road section, we need a network of several columns in which the effective radii overlap. Thus a filtration field can reduce the air pollutants fine dust and NO2 in the person-relevant area (e.g. footpaths) by up to 10-30%.
Construction, costs, electricity
What material is the filter made of?
Particle filtration is a highly developed microfiber media. Activated carbon media are used for the separation of NO2. This results in physical adsorption, chemical binding and catalytic reduction.
What does a filter column cost?
A filter column CUBE III with a filtration capacity of 14.500m³/h costs approx. 21.500 €. In addition, there are the costs for the foundation and the electrical connection.
How much electricity does a filter column consume?
The energy consumption of our Filter Cubes III is approx. 1.500/h. This is comparable to a commercial vacuum cleaner, but with 100 times the air throughput.
Can it be operated with alternative energy?
The filter columns require a power connection and cannot be operated independently, for example by fuel cells.
How high are the operating costs?
This depends on the respective project: A service interval varies depending on the location and type of air pollutant. With a pollutant load of about 50 micrograms per cubic meter for fine dust, the change interval is up to twelve months. If the pollutants nitrogen dioxide and fine dust are present simultaneously at a concentration of about 50 micrograms per cubic meter, the change interval is about two months. In this example, the nitrogen dioxide determines the interval.
The load at the Neckartor is higher. Accordingly, we expect a service interval of four weeks. The costs for the spin-on filters are approx. 850 Euro per column of a CUBE III filter. Within the Hohenheimer Strasse project, various columns are placed, i.e. a combination of CUBE II and CUBE III. The service interval here is six weeks.
How many cubic meters of air does a filter column clean per hour?
The air volume flow of a Cube III column is 14.500 m3/h. This corresponds to a room the size of a football field with a height of two meters.
How heavy is a filter column?
A Filter Cube III weighs about 1.000 kilograms.
How large is a filter column?
The filter columns are 3.60 meters high, have a footprint of less than 1 m2 and each consist of up to three stacked components, the cubes. The individual cubes have a side length of almost one meter.
How are the used filters disposed of? Is it hazardous waste?
The filters are disposed of as household waste in accordance with existing regulations. It is not hazardous waste because the fine dust bound in the filter is no longer harmful to health.
Doesn't the disposal of the filters create new fine dust again? Their incineration, for example?
We want to achieve a reduction in particulate matter and nitrogen dioxide pollution at particularly polluted locations. Using modern separation and catalyst technologies, waste incineration plants in Germany capture hazardous pollutants such as nitrogen dioxide and particulate matter on a large industrial scale in accordance with environmental regulations. What remains at the end is ash that can be deposited in landfills.
Effect and Evidence
In what radius does it unfold its effect?
The effective radius of a column is 15-20 meters. In order to achieve an area-wide effect within a certain road section, we need a network of several columns with overlapping effective radii. Thus a filtration field can reduce the air pollutants of fine dust and NO2 in the person-relevant area (e.g. footpaths) by up to 10-30%.
Thanks to the pilot project at the Neckartor in Stuttgart, MANN+HUMMEL is the first company that has been able to prove this effect scientifically in cooperation with KIT and LUBW.
Residents and Politics
What noise emission does the columns produce?
Depending on the installation area, different requirements apply with regard to noise protection. These are defined in a national Technical Instructions for Noise Protection (TA-Lärm). Our filter cubes comply with the TA noise.
Depending on their location and proximity to residential buildings, individual filters are regulated up or down according to the legal requirements.
We also use technology for sound insulation. We benefit from our acoustics laboratory and our expertise in sound design, which we have gained in the automotive industry.
Why are the filter systems positioned exactly next to the respective measuring stations? Shouldn't this simply reduce measured values and falsify them?
The measuring stations are installed where the exposure to air pollutants is particularly high. The risk to the health of residents, pedestrians and road users is correspondingly high at these locations. The Filter Cubes from MANN+HUMMEL improve air quality along the road sections where they are positioned. There is no specific and punctual influence on the measuring points.
Can the Filter Cubes really help to prevent driving bans?
The MANN+HUMMEL filter columns are part of an overall solution for improving the air quality of the respective cities. Together with other measures anchored in their air pollution control plans, our columns can offer effective protection against particulate matter and nitrogen oxide at particularly polluted locations.
Further fields of application
Could the filter columns be used in stations or underground trains? Are pilot projects already planned?
In places with high emission levels and low air exchange, such as underground stations, human health is particularly at risk. In bus stops or train stations, people are exposed to temporarily polluted air. Here our Filter Cubes could also be used to improve the air and thus protect the health of passers-by.