Comparison of the performance of PV water pumping systems driven by fixed, tracking and V-trough generators

Abstract

Photovoltaic pumping systems with solar tracking, coupled to low concentration cavities, have been proposed as a viable alternative to reduce the final cost of the pumped water volume. V-trough concentrators are particularly appropriate for photovoltaic applications since, for certain combinations of the concentration ratio ( C) and vertex angle ( Ψ), they provide uniform illumination on the region where the modules are located. Water pumping systems are only operational when the irradiance is larger than a minimum irradiance level ( I C). Solar tracking increases the average collected irradiance ( I coll ) and, for a system operating with a given critical irradiance level ( I C), it is verified that the smaller the relationship (I C / I coll ) , the larger the useful energy. Thus, the gain, in terms of pumped water volume, provided by solar tracking systems, can be larger than the gain in collected solar radiation. The combination of both devices, tracking and concentration provides an additional increase of the benefits resulting from the use of solar trackers. By means of the “Utilizability Method”, we estimate the long-term gains of pumped water volume, for tracking systems, with and without concentration, against fixed systems. The long-term water volume has been calculated using the characteristic curve of a tested PVP system with a tracking V-trough concentrator. Results show that, for the climate of the city of Recife (PE-Brazil), the annual pumped water volume of the tracking system is 1.41 times the value obtained with the fixed system. In that case, the gains observed for the collected solar energy were around 1.23. For the PVP system with tracking V-trough concentrator the annual benefits for pumped water volume are around 2.49, while for collected solar radiation we found 1.74. The annualized cost of the cubic meter of pumped water has been estimated for the three configurations. Results show a cost reduction of the order of 19% for the tracking system and of 48% for the concentrating system, when compared to the fixed configuration.