Adhesion Mechanisms on Solar Glass: Effects of Relative Humidity, Surface Roughness, and Particle Shape and Size

Helio Moutinho, Chun Sheng Jiang, Bobby To, Craig Perkins, Matthew Muller, Mowafak Al-Jassim, Lin Simpson

Research output: Contribution to journalArticlepeer-review

91 Scopus Citations


To better understand and quantify soiling rates on solar panels, we are investigating the adhesion mechanisms between dust particles and solar glass. In this work, we report on two of the fundamental adhesion mechanisms: van der Waals and capillary adhesion forces. The adhesion was determined using force versus distance (F-z) measurements performed with an atomic force microscope (AFM). To emulate dust interacting with the front surface of a solar panel, we measured how oxidized AFM tips, SiO2 glass spheres, and real dust particles adhered to actual solar glass. The van der Waals forces were evaluated by measurements performed with zero relative humidity in a glove box, and the capillary forces were measured in a stable environment created inside the AFM enclosure with relative humidity values ranging from 18% to 80%. To simulate topographic features of the solar panels caused by factors such as cleaning and abrasion, we induced different degrees of surface roughness in the solar glass. We were able to 1) identify and quantify both the van der Waals and capillary forces, 2) establish the effects of surface roughness, relative humidity, and particle size on the adhesion mechanisms, and 3) compare adhesion forces between well-controlled particles (AFM tips and glass spheres) and real dust particles.

Original languageAmerican English
Pages (from-to)145-153
Number of pages9
JournalSolar Energy Materials and Solar Cells
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017

NREL Publication Number

  • NREL/JA-5K00-67734


  • Capillary forces
  • Dust particles
  • Relative humidity
  • Soiling mechanisms
  • Surface roughness
  • Van der Waals forces


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