Dust accumulation on a solar panel surface can significantly hinder optical to electrical energy conversion and leads to photovoltaic energy degradation. In clean conditions, maximum absorption efficiency is achieved when the solar panel is orthogonal to the incident light (i.e., dual-axis solar tracker). However, when natural pollutants accumulate on the surface, panel position needs to be adjusted in order to increase the amount of sunlight energy absorbed by the solar panel. A numerical model is proposed in this study to estimate dust accumulation on the surface of a two-dimensional panel, in which the adsorption/desorption rate of airborne dust under the effect of gravity and other dust-panel interaction (i.e., Van der Waals and electrostatic effects) can be calculated. The model is developed through precise attachment/detachment force and momentum analyses, where the time varying dust coverage is formulated via a first-order differential equation which includes the gravitational desorption rate. Although there is a diverse composition of natural soiling, only dry dust particles are considered at this stage. The model is first validated with experimental data, and then the steady-state solution of this model is obtained to search for the optimal tilt angle for maximum absorption efficiency when the cell is subject to AM1.5 solar irradiance at different solar zenith angles. The extra required tilt angle is an increasing function of panel length and friction coefficient. The optimized tilt angle panel is able to provide better daily performance depending on panel length and surface friction coefficient. Optimization results show that by applying the proposed optimal tilt angle adjustment protocol, the daily absorption efficiency of a silicon solar panel can be improved by up to 24% depending on the friction coefficient compared to the dual-axis solar tracking system.