Abstract
D.Ing.
Low system efficiency is a critical problem in photovoltaic (PV) applications due to low
efficiency of solar cells. Despite this shortcoming, stand-alone PV systems, have proven
to be economical and reliable choices in some applications such as telecommunications,
vaccine refrigeration and water pumping in remote locations.
In this study, CAD algorithms for the design of PV water pumping systems have been
developed with the objective of maximizing the conversion efficiency from the solar
irradiation to the potential energy of water by taking into account the variations in the
pumping head.
The study starts by developing loss models of various sub-systems in the photovoltaic dc
and ac motor drive water pumping systems. Using MathCad, these models are then used
in the simulation of the system. The simulation results are verified experimentally using
their equivalent circuit configurations.
The efficiency of the array, the pump and the motor are found to be the most critical
parameters for the performance of the systems. The efficiencies of other components,
such as the inverter, have also been shown to have a significant effect. The study has shown that for operation at the maximum power point, the inclusion of a
maximum power tracker is necessary in a dc motor drive system but may be eliminated in
PWM inverter-fed induction motor drive systems through proper matching of the system
components.
The study has further shown that matching of the drive system and the load with the
insolation is essential, since maximum system efficiency occurs at a specific head, which
varies as the insolation changes. Prior investigation of site insolation variations is
therefore a critical requirement.