Correlating dust deposits with wind speeds and relative humidity to overall performance of crystalline silicon solar cells: An experimental study of Machakos County, Kenya

Solar Photovoltaics is one of the budding technologies widely acknowledged as a solution to energy poverty. This is due to its high reliability, long life and automatic operation at low maintenance requirements even though handicapped by its low conversion efficiency and high capital costs. This study investigates the influence of wind profiles, relative humidity and module siting on dust deposition on the surfaces of photovoltaic modules hence its overall performance in an outdoor setup. A significant decrease in short circuit current density (JSC), maximum current density (JMPP), and voltage at maximum power point (VMPP) due to dust deposits on the surface of the PV module are observed. The modules peak power (Pmax) degradation rate after a fortnight is observed to be higher (4.4 %) for sites experiencing a higher temperature coefficient (Tc) for VMPP as a consequence of temperature effects of soiling, lower wind speeds and a higher relative humidity. A lower deposition rate is observed in sites experiencing higher wind speeds and a higher module's tilt angle thus experiencing a lower effect on the reduction of current and voltage parameters. Similarly, the site-specific average wind speeds were inadequate for complete particulate resuspension of small sized particles (less than 500 mu m) adhering to PV module surface. Therefore, dust accumulations on the surface of PV modules have significant deleterious effects on the current and voltage parameters.