Correlation between thicknesses of dust collected on photovoltaic module and difference in efficiencies in composite climate
Rahnuma Siddiqui
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Usha Bajpai
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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.
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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.) t (...truncated)