Evaluation of Failure Modes for Photovoltaic Modules in Arid Climatic Zones in Brazil

This paper evaluates the degradation in early-generation photovoltaic (PV) silicon and thin-film modules in arid and semi-arid regions in Brazil. Monocrystalline (c-Si) and thin-film (a-Si and CdTe) modules installed in North of Minas Gerais, a semi-arid climate region, were used to investigate the degradation modes and average degradation rates. Initial visual inspection of the modules was performed in order to document the conditions leading to degradation modes for these devices that had been operating in the field for periods of 7 to 15 years. Thermographic and electrical tests were subsequently performed to identify possible hot spots or faults visible to the thermography process. The module I-V and P-V characteristics were used to evaluate the degradation rates for each technology. The c-Si module visual inspection identified browning and delamination that could be correlated with hot spots. In addition, degradation of the transparent conductive oxide (TCO) in thin-film modules was identified. This compromised their electro-optical properties, particularly resulting in losses of optical TCO transmission. The measured average annual degradation rates for these modules ranged from: (1) 3.19%/year to 5.14%/year for c-Si modules; (2) 5.5%/year for a-Si modules; and (3) 5.6%/ year for CdTe modules.