Chosen diagnostic methods of photovoltaic modules
Solar modules under ordinary working condition are exposed to amount of degradation factors which deteriorate their properties. The most important degradation of PV modules during operation are optical, electrical and thermal degradation. The result of these factors is performance degradation of the modules, or even can caused their fault. It is important to find the cause of the fault and its timely removal. The choice of convenient diagnostic method can reduce financial losses and increases safety of photovoltaic power plant. The example of tests performed on PV modules by using infrared (IR) thermography and, potential induced degradation (PID) are presented in this paper.
Degradation effects in sc-Si PV modules subjected to natural and induced ageing after several years of field operation
This paper presents ageing effects observed in sc-Si PV modules operating in field conditions for 18 and over 22 years. The effects of both natural ageing processes and induced ageing by external agents, causing partial or total shading of cells for a prolonged period of time, are examined. Optical degradation effects observed through visual inspection include discoloration of the EVA, degradation of the AR coating, degradation of the interface between the cell and encapsulant, corrosion of busbars and fingers, and tears, bubbles and humidity ingress at the back surface of the modules. Thermal degradation effects examined via IR thermography reveal the existence of hot cells, hotspots on the busbars, and colder bubbles. Modules' power and performance degradation is assessed through I-V curve analysis. Results show naturally aged modules to exhibit milder ageing effects than modules subjected to induced ageing, an outcome also supported by their power degradation ratio.
Corrosion of a-Si cells and modules
The authors report on corrosion/erosion phonemena observed in exposing a-Si cells, modules, and specially designed test structures to natural and accelerated test environments. Relevant cell and module I-V curve data used for monitoring degradation are presented. The causes of the observed degradation, methods of mitigation, and consequences for fielded modules are discussed.