A power and energy procedure in operating photovoltaic systems to quantify the losses according to the causes

Abstract

Recently, after high feed-in tariffs in Italy, retroactive cuts in the energy payments have generated economic concern about several grid-connected photovoltaic (PV) systems with poor performance. In this paper the proposed procedure suggests some rules for determining the sources of losses and thus minimizing poor performance in the energy production. The on-site field inspection, the identification of the irradiance sensors, as close as possible the PV system, and the assessment of energy production are three preliminary steps which do not require experimental tests. The fourth step is to test the arrays of PV modules on-site. The fifth step is to test only the PV strings or single modules belonging to arrays with poor performance (e.g., I-V mismatch). The sixth step is to use the thermo-graphic camera and the electroluminescence at the PV-module level. The seventh step is to monitor the DC racks of each inverter or the individual inverter, if equipped with only one Maximum Power Point Tracker (MPPT). Experimental results on real PV systems show the effectiveness of this procedure.

A Smart Battery Management System for Photovoltaic Plants in Households Based on Raw Production Forecast

“…Note that in case of horizontal modules, the cleaning made by rain is reduced, and in case of emission of pollution close to the plants from special industrial processes [29], losses can be more than 7%. Losses due to reflection from the glass on the front of the PV module are inevitable losses due to a not ideal transparency of the glass; according to [30], they can be considered equal to ≈3% (η refl = 0.97). Mismatch losses are due to nonuniformity in I -V characteristics of modules connected in series or in parallel.…”

“…Joule losses take into account dissipation of electrical energy into heat by Joule effect in the cables. During design phase, cables should be sized in order to keep Joule losses within 3% in nominal conditions [30]. Since the PV system operates at nominal conditions (maximum power) for a short period during the year, and in other conditions (partial load) losses are lower, Joule losses are estimated equal to an average value of 1% (η cab l = 0.99) [30].…”

“…During design phase, cables should be sized in order to keep Joule losses within 3% in nominal conditions [30]. Since the PV system operates at nominal conditions (maximum power) for a short period during the year, and in other conditions (partial load) losses are lower, Joule losses are estimated equal to an average value of 1% (η cab l = 0.99) [30]. Losses for shadings are due to external causes, as a wrong design; thus, in the performed simulations, these losses are neglected (η shad = 1).…”

Electroluminescence Test to Investigate the Humidity Effect on Solar Cells Operation

“…It can be used to control the physical characteristics of the junction [1][2][3][4]. It can be applied to detect manufacturing defects or any component degradation [5][6][7][8][9]. The use of digital cameras makes this methodology very practical [10] and easy to use.…”

Capacitor charging method for I–V curve tracer and MPPT in photovoltaic systems

“…The practical setup of I-V curve tracers at module, string and array levels is addressed in this paper for the main commercial technologies. Such tracers represent a tool to easily check the performance of PV systems at the beginning and during their operation, especially when poor performance occurs (Spertino et al, 2015a).…”