Design optimization of photovoltaic powered water pumping systems.
Abstract
The use of photovoltaics as the power source for pumping water is one of the most promising areas in photovoltaic applications. With the increased use of water pumping systems, more attention has been paid to their design and optimum utilization in order to achieve the most reliable and economical operation. This paper presents the results of performance optimization of a photovoltaic powered water pumping system in the Kuwait climate. The direct coupled photovoltaic water pumping system studied consists of the PV array, DC motor, centrifugal pump, a storage tank that serves a similar purpose to battery storage and a maximum power point tracker to improve the efficiency of the system. The pumped water is desired to satisfy the domestic needs of 300 persons in a remote area in Kuwait. Assuming a figure of 40 l/person/day for water consumption, a volume of 12 m3 should be pumped daily from a deep well throughout the year. A computer simulation program is developed to determine the performance of the proposed system in the Kuwait climate. The simulation program consists of a component model for the PV array with maximum power point tracker and component models for both the DC motor and the centrifugal pump. The five parameter model is adapted to simulate the performance of amorphous silicon solar cell modules. The size of the PV array, PV array orientation and the pump– motor–hydraulic system characteristics are varied to achieve the optimum performance for the proposed system. The life cycle cost method is implemented to evaluate the economic feasibility of the optimized photovoltaic powered water pumping system. At the current prices of PV modules, the cost of the proposed photovoltaic powered water pumping system is found to be less expensive than the cost of the conventional fuel system. In addition, the expected reduction in the prices of photovoltaic modules in the near future will make photovoltaic powered water pumping systems more feasible. 2005 Elsevier Ltd. All rights reserved.
A computer simulation program is adopted to assess the performance of PV pumping systems in the Kuwait climate. The program consists of component subroutines for each system component. This program takes into account the effect of solar source variations on the system performance. A new motor–pump model is developed to determine the characteristics of the pump and the motor. Comparing the present simulation results with the corresponding results using available software programs and the manufacturer data sheet validated the developed model. Based on the simulation results reported in the present study, the following conclusions can be drawn:
The newly developed motor–pump model can be used reliably in designing and calculating the long term performance of a PV water pumping system over any monthly and annual period. The developed motor–pump model leads to an improved way to design and simulate a PV pumping system based on the available data from the manufacturers catalog. Also, the model is proven to be accurate after it was compared with the manufacturers PVCAD program. The water head plays an important role in evaluating the economic feasibility of photovoltaic powered water pumping systems, while tilt angle variations have no remarkable effect on system performance up to a tilt angle equal to latitude ±20. An optimum system parameter search can greatly enhance the performance of a PV pumping system to achieve the required water demand for living in a remote area. A well-designed directly coupled PV pumping systems is feasible in the Kuwait climate even at the current expensive prices of PV modules. The economic feasibility is based on certain assumptions, and the results of the comparison between PV pumping systems and conventional pumping systems will be influenced by changes in any of the key assumptions used, like period of analysis and reliability of the equipment for that period. Costs of PV equipment and water pumps are expected to decrease more and more over the next few years as the demand for PV systems goes up worldwide. These factors will make PV pumping systems more economic in the near future. The results of the present work should encourage governments for wide installation of solar energy systems to keep our environment healthy and clean.