CASE-STUDY OF A CENTRAL-STATION GRID-INTERTIE PHOTOVOLTAIC SYSTEM WITH V-TROUGH CONCENTRATION

Our presentation is a case study of an installed, central-station (no storage), utility-intertie photovoltaic (PV) system in Sede Boqer, Israel (latitude 30.9-degrees-N). The nominally 12 kW peak PV system is comprised of 189 polycrystalline silicon modules mounted on inexpensive, one-axis north-south horizontal trackers with V-trough mirrors for optical boost. The power conditioning unit operates at a fixed voltage rather than at maximum power point (MPP). The primary task in analyzing the installed system was to investigate the cause of measured power output significantly below the design predictions of the installers, and to recommend system design modifications. Subsequent tasks included the quantitative assessment of fixed-voltage operation and of the energetic value of V-trough concentration and one-axis tracking for this system. Sample results show: (i) fixed-voltage operation at the best fixed voltage (BFV) can achieve around 96% of the yearly energy of MPP operation; (ii) the sensitivity of the yearly energy delivery to the selection of fixed voltage and its marked asymmetry about the BFV; (iii) the influences of inverter current constraints on yearly energy delivery and BFV; and (iv) how the separate effects of tracking and optical concentration increase yearly energy delivery.