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Résumé :
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In this Doctorate thesis, the sizing methodology of a Directly-Coupled Photovoltaic Water Pumping System (DC/PVWPS) has been improved through a new mathematical model. A real sizing study of the system has been performed through the Worst Month Method WMM at Ghardaia site (Algeria), based on the technical data of a traditional farm well in Sebseb, about 60 km south west of Ghardaia city. The designed system has to extract a maximum monthly daily water volume of about (35 m3/day/month) from a Total Manometric Head (TMH=25m). Following the theoretical investigation of the designed system performances, a significant mismatch has been averred between the required and supplied energy. The feedback asserted that beyond the design conditions of the Worst Month Method (WMM), an extra energy rate which can be produced by the PV array could not be consumed, whereas, two scenarios can occurr: When the system is operated during only a period-time needed to satisfy the demanded water volume, an extra energy rate which can be produced, during the rest of time, could not be exploited. Otherwise, when the system is operated on full daylight-hour (from sunrise until sunset), a surplus of water volumetric rate beyond the demand can be lost, in particular in the case of absence of hydraulic storage (water tank) or if the tank is not enough dimensioned.Accordingly, a new approach has been developed to exploit maximally the PV array energy production by maximizing the volumetric rate of the system.Mathematically, the methodology consists of approaching maximally the consumed energy to the supplied energy rate, on full daylight-hour operation,by respecting the demand/supply energy balance condition.The obtained approach predicts the maximum monthly daily water volume averages that can be delivered versus the monthly daily averages of solar irradiation, previously recorded.Thereafter, the mathematical model has been investigated and discussed, based on an entire year experimental results, obtained following the characterization tests of the system, at our PV water pumping test facility.The comparison of the previous demanded water volumes and the new predicted averages shows an annual volumetric rate profit between 41% and 54%, which can be extracted respectively, by an annual excess energy rate between 29% and 36% of the provided total rate.This contribution may be a tool between the hands of both the designer and the end-user to determine the real water delivery capacity of the system, hence to exploit maximally the produced energy.
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