Correlation between thicknesses of dust collected on photovoltaic module and difference in efficiencies in composite climate

Rahnuma Siddiqui 0 Usha Bajpai 0 0 Renewable Energy Research Laboratory, Department of Physics, University of Lucknow , Lucknow 226007, India An effort has been made to develop an equation with the given data for all seasons for a location (Lucknow, India) consisting of composite climate, which is further helpful in developing a relation between difference in efficiencies of module with respect to thicknesses of dust collected on the module. This equation that is developed mathematically is in good correlation with the measured data. Here, data are shown for a whole year (from 2010 to 2011); the study done gives us a broad view of finding out the difference in efficiencies of module when dust collects on it. - Background In solar cells, lots of power get lost due to various reasons such as reflection losses at the top surface, incomplete absorption of photon energy due to limited cell thickness, series and shunt resistance loss, curve or fill factor loss, etc. Results obtained show that there is a direct proportionality between solar flux, output current, and efficiency of the photovoltaic module as given by Omubo-Pepple et al. [1]. Dust contributes to as much as 40% degradation in peak power of photovoltaics; there is surprisingly little scientific work done on the subject. Since no information about the type of dust, density, and rate of accumulation of dust was noted, no general understanding of the underlying physical principles could be deduced. Dust accumulation on the photovoltaic (PV) panel surface depends on different parameters such as PV panel inclination and kind of installation as given by Del Cueto [2]. The research done previously include degradation analysis of silicon photovoltaic modules and effective efficiency of PV modules under field conditions as given [3,4]. Some studies have also been done on corrosion effects in thin film photovoltaic modules as given by Carlson et al. [5]. The airborne particles in the atmosphere affect the amount and properties of the radiation finally reaching the collectors. The accumulation of dust particles on the surface of PV module greatly affects its performance especially in desert areas. Some correlation studies have done direct beam solar radiation received by photovoltaic panel with sand dust accumulated on its surface as given by Al-Hasan [6]. Desert countries are of course best suited to photovoltaic power generation due to the abundant availability of sunlight throughout the year. Nowadays, the ideas of setting up vast solar arrays in desert countries and exporting the power to other countries are being discussed. In a bigger PV solar plant, more work force and machines will be needed to help make the rounds and clean the panels, especially after a stand storm. Many research results discuss about performance of panel with dust concentration on the surface, but for a common PV user, it is important to know how frequently the panel has been cleaned. In case if frequent cleaning is not possible, it is important to know the performance loss due to dust for additional estimation to compensate the loss. It has been concluded in many studies that dust accumulation considerably deteriorates the performance of 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 [7]. Research done also include characteristic distribution of total, diffuse and direct solar radiation at given locations, qualification testing of modules, etc. [8-11]. Different analysis, performance, and reliability testing of photovoltaic modules and arrays have been done as given [12-14]. As we know that module performance is greatly affected by the amount of dust collected on it [15], sometimes when we want to get the amount of difference value in efficiency of modules, the instruments for measuring it at that instant are not found. The main aim of this paper is to solve these kinds of problems. Here, an attempt has been made to obtain a relation between thicknesses of dust collected and difference in efficiencies for all seasons so that difference in efficiencies of modules can be easily estimated by measuring the thicknesses of dust collected using simple devices. Here, a statistical analysis has been done in finding out the correlation between thicknesses of dust collected on photovoltaic module and the difference in efficiencies of the module for a whole year considering all seasons of a composite climate. Methods Instrumentation The SPV module (number 2007.20.685) which is manufactured in the year 2007 by M/s Rajasthan Electronics and Instruments Ltd, Jaipur, India is studied. The module has been connected to a rheostat ammeter digital multimeter (DT9205A, Agronic Ltd.). Other instruments used are the digital thermometer (SE-221-P-K, Agronic Ltd.) to measure cell temperature, the Thermo-Hygro Clock (288-CTH, Agronic Ltd.) to measure ambient temperature and humidity and digital luxmeter (range 0 to 50,000 lux in three ranges of 0 to 2,000, 0 to 20,000, and 0 to 50,000 lux; accuracy 5%, 2 least count) to measure solar flux. Data are taken for one whole year from 2010 to 2011. The commercial photovoltaic module used has the following components: Solar type is polycrystalline silicon. 2 Cell area = 0.216 m . Electrical efficiency STP = 12% with a power peak of 36 W. Electrical specifications is at standard test conditions of 100 MW/cm2, AM 1.5, and at 25C cell temperature within normal production of tolerance 3%. Area of the panel = 0.340 m2 Development of correlation between thicknesses of dust collected on photovoltaic module and the difference in efficiencies As stated earlier, we have tried to verify the data taken for the whole year while considering different values, depending on the variation of climate. This fluctuation resulted from different factors affecting the performance of solar photovoltaic module. For example, these factors may be temperature, wind velocity, humidity, cloud cover, and dust. The aim of this study is to find out the relation of the difference in efficiencies with respect to thicknesses of dust collected. Here, reading is taken three times for each month after every 10 days, and finally, the average of the three readings is taken as measured value of the data for both the variables (difference in efficiencies and thicknesses of dust collected on the module) for that particular month. In this way, each month has its individual reading taken throughout the year. In Table 1, Monthly average of difference in efficiencies (before and after collection of dust)() (%) 1.5666 Monthly average of thicknesses of dust collected on the module (t) (mm) 0.0002400800 Data unavailable(rainy month) Data unavailable(rainy month) both variables are taken as monthly average value of difference in efficiencies and monthly average value of thicknesses of dust collected on th (...truncated)