Mechanics modeling of dust particle on solar panel surface in desert environment

Abstract: Along with the booming development of the photovoltaic industry, the later maintenance of photovoltaic power station and the improvement of photovoltaic power generation efficiency have gradually become the focus of attention. Under the condition of blown sand in high altitude desert areas, dust accumulation on the surface of solar panel has become one of the most significant factors which influences the consistency and efficiency of photovoltaic power station. The effects of dust deposition on photovoltaic conversion efficiency and dust removal methods were studied. The mechanism of dust particle adhesion was analyzed at first in this paper. Due to the surface free energy of the dust particle and solar panel, they interacted. The van der Waals force between spherical dust particles and the panel was derived from Lifshitz's macro molecular interaction theory and the order of magnitudes van der Waals force was calculated. The electrostatic image force was simulated based on two known dust charge empirical expressions. The relationship between the radius of dust particle and the double layer electrostatic force was investigated by taking different values of the contact potential difference, which ranged from 0 to 0.5 V. Compared with the dust particle, the solar panel surface can be taken as an infinite disk. The relationship between the parameters and electric field force was obtained. Meanwhile, the gravity of dust particle was analyzed when the photovoltaic panels were mounted with an angle with respective to the horizontal plane. Through the analyses of all interactive forces, the conclusions that Van der Waals force of dust particle increased with increasing of the surface free energy were drawn. The dust particle radius ranged from 0.2×10-6 to 40×10-6 m, and the distance between molecules ranged from 10-9 to 10-7 m. Combined with Lifshitz constant (0.96-14.4 eV), the magnitude of dust van der Waals force was calculated as 10-10-10-9 N. The magnitudes of electrostatic image force and double layer electrostatic force were calculated as 10-13-10-12 N based on the charges (10-18-10-16 C) of dust surface and the contact potential difference (0-0.5 V). The radius of dust and the distance between molecules had smaller effects on the electrostatic image force and double layer electrostatic force than electrostatic image force. The dust particle radius R had no effects on the electric field strength. The electric field force increased with the increasing of R. The distance between molecules didn't affect the electric field force. The magnitude of electric field force was calculated as 0-10-13 N. The gravity of dust particle was affected by the radius and density of dust particle, and its magnitude was approximated as 10-10-10-9 N. The interactions between the dust particles were more complex, which was affected by the numbers of particles, the porous ratio, particle clearance and radius. Through analyzing all interactions between dust particle and solar panel surface, it is concluded that van der Waals force > gravity > electrostatic force when the dust radius was smaller (R<20×10-6 m), and gravity > van der Waals force > electrostatic force when the dust radius was larger (R>20×10-6 m). The adhesion force between the dust particle and solar panel surface increased with the increasing of dust radius, and its magnitude ranged from 10-10 to 10-8 N. In the dry and windy desert area, the combination of gravity and van der Waals force plays an important role without considering the chemical interactions.