Electrostatic precipitation efficiency for a multi-needle plane electrode topology under DC excitation

Recent years have seen major governmental and humanitarian organisations place great emphasis on the issue of air quality and pollution. Both national and international strategies such as those detailed in [1] and [2] have set ambitious goals regarding air quality, most notably on the reduction of fine and ultrafine particulate matter (PM). The present work revisits the principles of Electrostatic Precipitation (ESP) using a novel multineedle-plane electrode topology under both positive and negative DC excitation, results of which are potentially of interest with regards to precipitation of contaminants on HVDC power lines in various atmospheric conditions. Using the GRIMM Laser Aerosol Spectrometer, concentrations of PM 0.265 nm and above in laboratory air were measured for a DC voltage range of 0 – 21 kV. The measurements were again repeated for humid air, by injection of atomised water via the means of an ultrasonic humidifier. All tests conducted ultimately achieved over 95% precipitation efficiency above 15 kV, where dry air proved to be much more stable with less variance in the recorded PM count. The fluctuation and noise seen in humid air tests however, may be attributed to inconsistencies in water injection and poor control of condensation within the test cell. Negative energisation was shown to result in significantly better precipitation performance than positive energisation, exhibiting a much higher precipitation efficiency in the 0 – 10 kV range, and also achieving close to 100% precipitation efficiency beyond 15 kV. The measured relationship between the precipitation efficiency and voltage was found also to closely match predicted behaviour derived from theoretical particle charging mechanisms as described in [3]. A proposed future line of investigation is to repeat the study under a pulsed regime to compare performance to a single point-plane electrode topology