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The deposition mechanism of dust on photovoltaic modules plays a key role in predicting the dust amount, determining dust removal techniques, and cleaning frequency. In this paper, a prediction model for the adhesion and erosion of dust particles was established to address the uneven dust distribution on photovoltaic modules. The proposed model was validated through an experiment of dust deposition, which was set in the low-speed section of a wind tunnel. Three conditions of the dust deposition process were numerically investigated, while varying different wind speeds, array row spacings, dust particle sizes, and wind direction. Results showed that wind speed was the main factor of dust deposition amount, and the change in wind speed and dust particle size had little influence on the distribution of dust deposition. Meanwhile, wind direction and array row spacing distinctly influenced the dust distribution. Increasing the row spacing induced relatively uniform dust distribution on the photovoltaic modules.

An efficient cleaning method is crucial for the power production and equipment reliability of a Photovoltaic (PV) system. This paper presents an alternative cleaning and dust detection method for PV modules. Instead of monitoring the difference between the real and theoretical power production of PV modules, this method analyzes the soiling loss by alternatively cleaning two panels at the beginning of the cleaning period. When the loss reaches the cleaning cost, a cleaning reminder is generated while considering the weather forecast. The efficacy of the proposed theoretical model is established based on 1-year data collected in the Shandong PV system. Annual production improvement of more than 1.33% is achieved with a net return of more than 0.78% on the deduction of cleaning cost, which is equal to $1363/GWh economic benefit per year.

The evolution equation for the second-order internal solitary waves in stratified fluids, that are incomepressible inviscid ones of mixed stratification in which the density varies with depth in lower layer but keeps uniform in upper layer with a finite depth, is derived directly from the Euler equation by using the balance between the nonlinearity and the dispersion with the scaling μ=O(ɛ), and by introducing the Gardner-Morikawa transformation, asymptotic expansions and the matching of the solutions for the upper and lower layers of fluid via the computer algebraic operation. The evolution equation and its solution derived for the first-order wave amplitude are consistent with the classical ones, and the desired equation governing the second-order amplitude is reduced as follows ∂ f 2 ∂ τ - c 1 ∂ f 2 ∂ ξ + α ∂ ( f 1 f 2 ) ∂ ξ + β ∂ ∂ ξ ∫ - ∞ ∞ f 2 ( ξ ' ) g ( ξ - ξ ' ) d ξ ' = G 2 ( f 1 , c 1 , κ 1 ; c 0 , ϕ ) Where g ( ξ ) = - 1 2 π ∫ - ∞ ∞ k coth ( k l ) e j k ξ d k and G 2 ( f 1 , c 1 , κ 1 ; c 0 , ϕ ) is the inhomogeneous term, f1 first-order wave amplitude.

Representing surface tension by nonlinear relationship on temperature, the boundary value problem of linear stability differential equation on small perturbation is derived. Under the condition of the isothermal wall the effects of nonlinear surface tension on stability of heat transfer in saturated liquid film of different liquid low boiling point gases are investigated as wall temperature is varied.