Dominant environmental parameters for dust deposition and resuspension in desert climates

Abstract

Field studies of dry deposition usually measure dust accumulation over periods of days or weeks. However, long measurement periods obscure the effects of meteorological conditions on the deposition rate. Previously we developed an "outdoor soiling microscope" (OSM) in order to measure dust deposition and detachment every 10 min in the field. In this study a greased/ ungreased pair of OSMs was deployed for 51 days in the desert climate of Doha, Qatar. Stepwise regression analysis was performed to quantify the explanatory power of meteorological parameters on dust deposition and detachment rates. It was found that wind speed dominated deposition and rebound of dust particles, and produced a distinctive "threshold" response in deposition. The dry deposition results were highly consistent with a model by Kim et al. (2000) derived from outdoor experiments. By comparison, relative humidity and particulate matter concentration had less influence on dust flux rates.

Size‐Resolved Dry Deposition Velocities of Dust Particles: In Situ Measurements and Parameterizations Testing

“…Generally, only particles greater than 5 μm in diameter have the capability to reach a sufficient kinetic energy to rebound immediately after hitting the surface (e.g., Zhang et al, ) and the percentage of rebounding particles could be as high 80% for 10‐μm particles for wind friction velocity of the order of 0.3 m/s (e.g., Figgis et al, ; Wu et al, ). Therefore, in a counterintuitive way, when wind speed is sufficiently strong, higher diffusive deposition velocities can be expected for medium‐size particles than for larger particles.…”

Techno-Economic Assessment of Soiling Losses and Mitigation Strategies for Solar Power Generation

“…23 Wind speed is also an important parameter, as it influences the particle deposition mechanisms and rates the balance between deposition and resuspension. [24][25][26] Tilt angle of the PV modules and CSP mirrors should be considered since soiling rates are greater on flatter surfaces. 2 Relative humidity and dew strongly enhance dust adhesion to surfaces through capillary forces, particle caking, and cementation.…”

“…2 Five dry and wet soiling mechanisms ( Figure 4A), especially important for ASC performance in arid regions, have been identified through outdoor and laboratory testing. 1,17,24,27,[53][54][55] They are (1) rebound (particles bouncing off the surface upon impact), (2) resuspension (delayed removal of particles by wind), (3) caking (rearrangement and compaction of particles during dew events), (4) cementation (formation of chemical and/or solid bridges between particles and surfaces after dew cycles), and (5) water cleaning (particles washed off by rain or strong dew). To reduce soiling, rebound, resuspension and water cleaning should be enhanced, cementation should be avoided, and the optical loss (projected area) of caked particles should be minimized by ''herding'' dust into agglomerates via coating hydrophobicity.…”

“…It is not yet possible to accurately predict soiling only from climate information, although some studies could show underlying principles of soiling dependencies on other weather parameters. 1,10,24,75,[94][95][96] In addition, soiling rates can vary dramatically for sites only 5-10 km apart or even within the same site. 97 The closer a site is to a dust generation source, the greater is its soiling risk.…”

Effect of tilt angle on soiling in perpendicular wind

“…Of course it is dust accumulationrather than depositionthat is of practical interest to PV users. Although some CFD studies of PV soiling assumed that zero particles will be detached after deposition, a previous field study (Figgis et al, 2018) demonstrated that (in the particular environment) nearly 100% of impacting particles detached from a horizontal glass coupon when wind speed reached just 4 m.s -1 .…”