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One of the challenges facing investment in photovoltaic (PV) energy is the accumulation of dust on the surface of the PV panels due to frequent dust storms in many countries, including Iraq. Surface dust particles reduce solar irradiance which declining the electrical performance of the PV solar systems. Therefore, this paper proposes an experimental study to analyze and evaluate the power efficiency of a PV system installed in Baghdad city, Iraq. The performance of dusty solar PV array is compared with that of the clean array of the same PV system. The clean solar array is equipped with an automatic-sprayer cleaning system that is powered by the PV system. The automatic cleaning system utilized in the test system reduces human effort by cleaning the PV array using closed-cycle water with low energy consumption (less than 10 Wh). The PV array under test is part of a 15 kW grid-tied PV system. The experimental results show significant improvement in the performance parameters of efficiency, performance ratio, and the energy gain compared to the clean array. Furthermore, the experimental study contributes to a reduction in CO2 emission, which is substantial for the Iraqi environment that suffers from predominate fossil-fuel power plants.

Combined convection heat transfer and fluid flow around a circular cylinder surface placed in open-fcell aluminum foams and subjected to constant heat flux inside a rectangular, water-filled horizontal channel was numerically and experimentally studied. Two models (rectangular and trapezoidal open-cell aluminum foam shapes) made of 6101-T6 alloy with pore densities of 10 and 40 pores per linear inch (PPI) and 7-9% relative density were employed as test sections. The aluminum foam dimensions were 35.7 Â 35.7 Â 36.85 mm, the Reynolds number range was 60-2000, and the modified Grashof number range was 2 Â 10 2 -2.6 Â 10 7 . Governing equations (continuity, momentum, and energy) were solved using the finite-volume method (FVM). Effects of the porous characteristics of aluminum foams and mixed convection heat transfer parameters on buoyancy force, Nusselt number, friction factor, and pumping power values of the two models were investigated. The results show that high mixed convection occurred with the trapezoidal model. A high average Nusselt number value was obtained at 40PPI in the rectangular model. In the trapezoidal model, average Nusselt number decreased with increased aluminum foam pore density. Friction factor increased slightly with increasing modified Grashof number and decreased with increasing Reynolds number. Pumping power increased with increased pore density of aluminum foam and mixed convection parameters. The comparison shows good agreement between the numerical and experimental work and that the average results produced have an 8.02% deviation in average Nusselt number.