Photocat A/S & the Municipality of Roskilde have in a three year real-life test proven that the photocatalytic technology is both a tangible and economic cost-effective instrument to clean the air in cities with a life sustaining photocatalytic treatment of 5,000 sqm. An optimized photocatalytic treatment to the asphalt surface was developed for the project. At the same tine an in-situ set-up was developed enabling to test the activity of the photocatalytic treatment in the test period of three years.
The main conclusions from the project are:
- The photocatalytic treatment is stable over time
- With solar irradiation of 563 kWh/sqm. per year containing appx.. 5 % UV an amount of 13.8 g/NOX is removed per sqm. p.a.
- The photocatalytic application is estimated it generate socio-economic value in terms of less sickness and premature deaths due to NOX pollution. This value is estimated at more than 4x the cost of implementing photocatalytic technology.
In the report Photocat splits the societal cost of NOX pollution in two parts; a local effect and a regional effect. This is done for two reasons. First, there is an increasing body of knowledge stating that NO2 pose a direct health hazard (European Environmental Agency, 2017). Secondly, NOX will form into solids which travel back to the surface as particle pollution (Danish Center for Environment and Energy, 2016).
The NOx Cycle
Effect After 3 Years
The measure setup is highly inspired by the stadard ISO 22197-1 activity test for NOx degradation. The setup consists of a measuring device by Eco Physics, a data collection unit, a control unit for the gas and a test cell. We used two different test cell, one with a sice of 100 cm2 and one of about 532 cm2. One challenge with the test cells is to place them on the test surface and obtain a sealed environment during the test period. This was solved using modelling wax.
Testing was performed with both ambient air and model gas. For model gas concentrations between 100 ppb and 500 ppb were applied. To the left there is a video showing a typical test session. The video was shoot on one of the two project sites after the finalization of the project. The video shows that the project area after 3 years is still highly active.