Photovoltaic Pumping Systems A Comparison of Two Concepts

At the University of Oldenburg two different concepts of photovoltaic pumping subsystems available on the market were investigated: an asynchronous AC motor driving a multistage centrifugal pump and a brushless DC motor driving an eccentric screw pump. The characteristic data of the single components were measured, suitable physical models chosen and parameters for the models determined. Both systems were operated and monitored under field conditions at our test site. Computer simulations based on the models were performed and validated against the field data. Using hourly radiation and temperature data from Northeast Brazil the annual energy flow diagrams for two hypothetical PV pumping systems composed of the above named subsystems were calculated in order to analyse and identify efficiency and loss mechanisms at component level. This paper describes the modelling of the two different systems and discusses the energy flow diagrams.