Large-scale PM2.5 removal and CO2 direct air capture to mitigate ambient air pollution and combat global climate change.

This paper summarizes a decade of development of a Solar-Assisted Large-Scale Cleaning System (SALSCS) aimed at mitigating urban PM2.5. This effort has led to the construction and operation of four SALSCS units located in Xi'an (China), Yancheng (China), and New Delhi (India). Six papers have been published to document the modeling, design, construction, operation, and measurement of three generations of SALSCSs. The Weather Research and Forecasting (WRF) model was utilized to obtain local meteorological information and solar intensity conditions around the SALSCS. Reynolds-Averaged Navier-Stokes (RANS) simulations and Large Eddy Simulation (LES) have been employed to study the flow patterns and clean air concentration profiles near the units. The first generation SALSCS (Xi'an) takes the form of an updraft solar tower that utilizes solar heating to drive a large volume of air flow through the SALSCS. Filters are positioned along the flow path to remove PM2.5, resulting in cleaner air exiting the top of the tower. In the second generation SALSCS (Yancheng), the media filters are replaced with water spray to scrub out PM2.5. The third generation SALSCS (New Delhi) employs a set of fans to draw PM2.5 from the tower inlet through prefilters and final filters, blowing the cleaned air out near ground level to pedestrians surrounding the SALSCS. A proposal is presented that combines the 1st and 2nd Generation SALSCSs equipped with solar panels and direct air capture (DAC) of CO2 to achieve energy self-sufficiency and large-scale capture of 100 million tons of CO2 annually (100 Mt CO2/yr).