Mohammad S. El-Shobokshy

Effect of dust with different physical properties on the performance of photovoltaic cells

The effect of accumulation of dust and particulate matter onto the surface of photovoltaic cells has been experimentally investigated. Five kinds of dust having different physical properties were used. Three of them were limestone particulates with different classes and the other two were cement and carbon particulates. Details on the physical properties of each were obtained through size distribution analysis using an optical microscope. Well-controlled experiments were conducted using a solar simulator as a light source. The dust deposition density (g/m2) was precisely determined in each test run. It has been concluded that fine particulates significantly deteriorate the performance of photovoltaic cells, more so than coarser particles. Cement, the main building material which may often present in the atmosphere of urban areas has shown to reduce both the short circuit current and output power when deposited onto the surface of photovoltaic cells. This is due to the very small diameter of its particles. Carbon particulates, which are generated from combustion process and emitted from diesel engines among the different dusts used, have shown to result in the worst deterioration of performance of photovoltaic cells, and higher a loss in power output.

Degradation of photovoltaic cell performance due to dust deposition on to its surface

The effects of dust accumulation on the surface of photovoltaic cells were experimentally investigated. The dust used in this study was prepared in the laboratory from known materials, then examined under an optical microscope to determine the size distribution of the particles. The two main parameters of the size distribution were determined, namely, the mean diameter and the standard deviation. A solar simulator consisting of halogen lamps was used to carry out controlled experiments. The dust particles were dispersed uniformly over the test photovoltaic panel and the IV characteristics were determined. The dust deposition density in g/m2 of panel surface area was determined in each test run. The effect of dust deposition density on the short circuit current, output power and the fill factor was determined and discussed. It was concluded that dust accumulation considerably deteriorates the performance of the photovoltaic cells. However, in carrying out the investigation on the effect of dust and particulate pollution, the physical characteristics of dust must be determined and correlated to the observed effects.

Inhalable particulates and meteorological characteristics of the city of Riyadh, Saudi Arabia

Abstract Ambient inhalable particulates (IP) have been sampled in the city of Riyadh by means of a fixed sampling site using an automatic dichotomous sampler. The concentration of fine particulates (0–2.5 μm aerodynamic diameter), coarse particles (2.5–15 μm aerodynamic diameter) and total (fine plus coarse) IP were determined. The meteorological variables were recorded during the sampling process. The samples were analyzed by means of the Atomic Absorption Spectrophotometer for the metals: Al, As, Cu, Fe, Pb, Ca, K, Mg and Na. Statistical analysis using the multilinear regression technique (Sigstat Package) has been carried out to correlate the concentration of particulate matter with the several meteorological variables. It was determined that the wind speed and atmospheric pressure could be used to predict the concentration of Al, As, Cu, Fe and Pb particulates, whereas wind speed, atmospheric pressure and r.h. could be used to predict the concentration of Ca, K, Mg and Na. The concentrations of atmospheric fine, coarse and total IP matter were found to be high compared to accepted standards. The highest correlation coefficients obtained from the regression analysis were for Fe, Pb and As. The low correlation coefficients for Ca, K, Mg and Na suggest that some significant parameters which are correlated with them may have not been considered in the analysis. Wind speed was shown to have positive correlation with Fe and Al, but negative correlation with Pb.

Computer simulation of monodisperse aerosol collection in fibrous filters

A computer program has been developed to simulate the filtration process in fibrous filters collecting monodisperse aerosol particles. The model filter is represented by an array of parallel cylindrical fibers and the Kuwabara flow field is employed to determine the particles trajectories inside the filter. The simulation model is based on the Monte-Carlo (self-driven) principle, and a sequence of uniform pairs of pseudorandom numbers is generated representing the initial locations of the approaching particles. The estimation of the initial collection efficiency through the simulation model that considers the deposited particles and the presence of dendrites is in good agreement with published experimental data. The development of the quasi three-dimensional simulation model offers a detailed information about the transient progression of the deposition process. The transient behavior of the pressure drop across the collector system (the fiber and the collected particles) and the morphology of deposit are...

Assessment of electricity generation by wind power in the Kingdom of Saudi Arabia

SYNOPSIS The wind speeds measured by the Saudi Meteorological Department at 18 stations distributed over the Kingdom of Saudi Arabia have been analyzed. Monthly average power density distributions were determined for each station. A technical and economic assessment has been made of the generation of electricity using small wind-turbine generators for rural applications at the most promising potential wind sites. Another two sites were also considered, one of which has a moderate power density level and the other having the lowest level among the total sites in Saudi Arabia. A levelized unit costing methodology was applied to evaluated the cost per kWh generated. The cost per kWh generated was found to be higher than the unit cost per kWh purchased by the industrial sector from Saudi Electric companies. However, if it is compared with the actual unit cost of generation by the electric companies (without any kind of subsidy), and considering also the additional cost of cable extensions to remote areas, the...

The impact of the gulf war on the Arabian environment—I. Particulate pollution and reduction of solar irradiance

Abstract This paper investigates some of the air pollution problems which have been created as a result of the Gulf war in early 1991. Temporary periods of increased dust storm activity have been observed in Saudi Arabia. This is presumably due to disturbance of the desert surface by the extremely large number of tanks and other war machines before and during the war. The concentrations of inhalable dust particles ( μ m) increased during the months just after the war by a factor of about 1.5 of their values during the same months of the previous year, 1990. The total horizontal solar energy flux in Riyadh has been significantly reduced during dry days with no clouds. This is attributed to the presence of soot particles, which have been generated at an extremely high rate from the fired oil fields in Kuwait. The direct normal solar insolation were also measured at the photovoltaic solar power plant in Riyadh during these days and significant reductions were observed due to the effective absorption of solar radiation by soot particles. The generated power from the plant has been reduced during days with a polluted atmosphere by about 50–80% of the expected value for such days, if the atmosphere were dry and clear.

Atmospheric turbidity and transmittance of solar radiation in Riyadh, Saudi Arabia

During the last two decades, the urban areas in the city of Riyadh—the capital of Saudi Arabia—were increasing at an exceptionally high rate through a series of development plans. The major plans had been completed by the end of 1982. Some other big utility projects were started and completed during 1987. As a consequence, the air quality has deteriorated markedly and air pollution episodes recorded during these activities showed that particulates were present in the atmosphere at high concentrations. Later in January 1991 the Gulf war started and the firing of the oil fields in Kuwait soon followed. It was estimated that soot particulates were emitted at a rate of 600 ton d−1 along with high rates of other gases. This event has led to significant air quality and visibility problems. Direct normal solar radiation has been measured during the summer months of July and August which were characterized by very dry and cloudless weather for the period between 1982 and 1992. A year-to-year trend of the transmittance of direct normal solar irradiance was then determined. The atmospheric fine aerosol (<2 μm diameter) loading data during the same period were used to establish a correlation between the aerosol concentration and the extinction coefficient. The total horizontal and direct normal solar radiation measurements during some days when the dark smoke emitted from the oil field fires in Kuwait were passing over Riyadh are presented. The reduction in solar irradiation reflects the intensity of dark smoke at a distance of 500 km from Kuwait.

Particulate pollution effects on the performance of greenhouses

Two greenhouse models were constructed to investigate the characteristic performance under variable dust pollution levels. The cover of the first model—a reference—was kept clean, while dust particles were allowed to uniformly deposit on the cover of the second. The physical parameters of the dust particles, such as the mass medium and surface mean diameters and geometric standard deviation, were determined. The solar intensities outside and inside each model, as well as the greenhouse room temperatures, were continuously measured by means of a multi-channel recorder. The amount of solar energy received inside the greenhouse decreased considerably as the dust deposition density increased. The room temperature also decreased. The results show the relationship between dust deposition density and the transmittance of energy. A mathematical model has been used to predict fairly accurately the greenhouse room temperature. This model may also be used to predict the performance of greenhouses with dusty covers if a simple correlation between dust deposition density and energy transmittance is developed as explained in the paper.

Investigation on a Modified Louvred Inertia Air Filter

An experimental study was carried out to determine the effect of the design parameters of blade angle, spacing, and width on the static pressure drop and mass efficiency of a louvre dust separator for the two cases of solid blades and a newly modified slotted blade design. The experiments were carried out using model test sections. Computer models of louvre blade inertia air cleaner performance were developed in an attempt to predict the mass efficiency. Conclusions were drawn regarding the best values of the design variables for optimum mass efficiency and pressure drop.

Frequency of cleaning the surface of photovoltaic cells in the environment of Riyadh City, Saudi Arabia

SYNOPSIS The effect of accumulation of atmospheric dust particles onto the surface of photovoltaic cells has been examined, and the permissible reduction in the power output was determined along with the associated dust deposition density. The annual patterns of dustfall over six different districts in the City of Riyadh which were previously measured by the author have been used to determine dustfall dependence for three groups of months over the year. A method for determining the frequency of cleaning the surface of photovoltaic cells is presented and used to determine the periods between cleaning during each group of months. The determination of such periods is based on the dust deposition density which would result in the maximum allowable power output reduction and the rate of dustfall during each group of months.