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The dynamic motion of a water droplet on an inclined hydrophobic surface is analyzed with and without environmental dust particles on the surface. Solution crystallization of a polycarbonate surface is carried out to generate a hydrophobic surface with hierarchical texture composed of micro/nanosize spheroids and fibrils. Functionalized nanosize silica particles are deposited on the textured surface to reduce contact angle hysteresis. Environmental dust particles are collected and characterized using analytical tools prior to the experiments. The droplet motion on the hydrophobic surface is assessed using high-speed camera data, and then, the motion characteristics are compared with the corresponding analytical results. The influence of dust particles on the water droplet motion and the amount of dust particles picked up from the hydrophobic surface by the moving droplet is evaluated experimentally. A 40 μL droplet was observed to roll on the hydrophobic surface with and without dust particles, and the droplet slip velocity was lower than the rotational velocity. The rolling droplet removes almost all dust particles from the surface, and the mechanism for the removal of dust particles from the surface was determined to be water cloaking of the dust particles.

An understanding of the dynamic motion of a water droplet is critical to reduce the effort required to remove dust particles from such surfaces. In line with self-cleaning applications, the wobbling and geometric variations of a rolling droplet were experimentally assessed for various droplet sizes.Furthermore, the internal fluidity of a rolling droplet was numerically predicted. The findings revealed that the rotational Bond number influenced the droplet wobbling due to adhesion force variations during rolling. Small-sized droplets, which were comparable to the capillary length, resulted in higher rotational speeds than those of larger-sized droplets. The ability to alter the rolling characteristics of droplets on inclined hydrophobic surfaces could address the limitations of self-cleaning surfaces and has implications for efficiency enhancements in solar energy devices.

A water droplet behavior on a hydrophobic surface is examined relevant to the dust particles removal from the surface. Surface crystallization of polycarbonate is realized in acetone bath and the resulting surface is coated by the functionalized nano-size silica particles towards reducing contact angle hysteresis. This arrangement provides droplet rolling/sliding on the hydrophobic surface. Droplet translational velocity is formulated and predictions are compared with those resulted from the high speed recorded data. Influence of surface inclination angle on droplet dynamics is investigated and the dust removal mechanism on the inclined surface is analyzed. It is found that predictions of droplet translational velocity agree well with those obtained from the experiment. Droplet rolling dominates over sliding on the inclined surface and droplet sliding velocity remains almost 10% of the droplet translational velocity. The main mechanism for the dust particles removal is associated with the droplet fluid cloaking of the dust particles during its transition on the hydrophobic surface. Droplet acceleration, due to increased surface inclination angle, has effect on the rate of dust particles removal from the surface, which is more apparent for large droplet volumes. Increasing droplet acceleration improves the coverage area of the clean surface.

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Environmental dust particles repelling from a hydrophobic surface under the electrostatic influence are considered and the dynamics of the dust particles are analyzed incorporating the high speed camera. The velocity of the repelled dust particles are formulated using the force balance incorporating the forces associated with the electrostatic repulsion, particle adhesion, particle drag, and the inflight particles interaction under the charge influence. The functionalized silica particles are deposited on the glass surface towards achieving a hydrophobic wetting state on the surface. An electronic circuitry is designed and built while generating the electrostatic effect, in the pulse form, on the dust particles located on the surface of the hydrophobic plate. Findings revealed that functionalized silica particles deposited surface results in hydrophobic wetting state with contact angle in the order of 158° ± 2° and contact angle hysteresis of 2° ± 1°. The electrostatic impulsive force generated on the plate surface enables to repel most of the sizes of the dust particles; however, some of the small dust particles remain as the residues on the surface after the electrostatic influence. The dust particle velocity predicted from the analytical formulation agrees with that obtained from the high speed camera data. The pinning force of the small size particles (0.6 µm≤), due to adhesion on the surface, is found to be larger than the average size particles (∼1.2 µm), which in turn, suppresses these particles repelling from the surface under the electrostatic influence. The residues of the dust particles on the as received glass surface after dust repelling are more than those residues on the hydrophobic surface. This behavior is associated with the dust particles adhesion on the surface. Consequently, hydrophobic wetting state on the plate surface improves the dust particle repelling from the surface.

Summary Utilization of a broad range of solar spectrum has the potential for high power output from solar cells. However, solar photovoltaics (PVs) can convert only part of the solar electromagnetic spectrum into electricity efficiently. The remaining of the solar radiation is often dissipated in the form of heat, which causes performance reduction and reduces the life expectancy of the solar PV cell. Thermoelectric generators (TEGs) are devices that operate like a heat engine by converting thermal energy into electricity through thermoelectric effect. Integrating a TEG into a PV converter will enhance its efficiency and reduce the amount of heat dissipated. Different studies have been carried out and are still taking place to increase the total efficiency of a coupled photovoltaic thermoelectric generator (PV‐TEG) system. This review discusses the concept of PV converters and thermoelectric devices and presents the various models and numerical and experimental investigations on performance enhancement of integrated PV‐TEGs. The influence of key parameters on the performance of PV‐TEG were also discussed. The review is expected to serve as a reference to recent work on research and development of integrated PV‐TEG systems.

This article presents the development of a computational model for the sizing optimization of an off-grid hybrid solar wind electric power generation system. The model includes a PV model, wind power model, and a model for the required battery. The developed mathematical model also comprises a model for a diesel generator as an alternative for the storage battery. A simulation code has been developed using MATLAB to solve the mathematical model and simulate the performance of the hybrid system with different configuration for performance analysis and optimal sizing purpose. The mathematical model and the computer code have been developed using a general approach. This approach can be used to simulate, analyze and optimize any hybrid solar/wind/battery/diesel off-grid electric power generation systems. Also, it can be utilized for any remote area in the world depending on the weather data used as input to the developed simulation code. The results obtained via the presently developed model and code have been validated against previously published work and also against that obtained via the widely used software (HOMER). The model is used for the sizing optimization and assessment of a hybrid solar wind system based on the weather conditions for Dhahran city in the eastern province of the Kingdom of Saudi Arabia.