A Qatari analysis staff investigated the efficiency of polyethylene terephthalate backsheets in actual take a look at situations exterior desert areas and recognized the primary causes of decay. This consists of extended publicity to excessive ultraviolet radiation, excessive biking of working temperatures, and relative humidity.
Researchers at Hamad Bin Khalifa University (HBKU) in Qatar carried out an evaluation of the degradation of polyamide (PA) and polyethylene terephthalate (PET) backsheets utilized in PV modules put in in desert climates, the place the photo voltaic irradiance and ultraviolet (UV) irradiance are roughly 50% greater in comparison with non-desert environments.
The evaluation targeted on backsheet crack initiation, propagation, chalking, and delamination. “In this examine, in depth investigation of PA and PET chalking powder was carried out to higher perceive the failure mechanism and the composition of the powder,” the researchers specified.
The assessments had been carried out at HBKU’s Outdoor Test Facility (OTF) in Doha, the place in the course of the summer time months the month-to-month common ambient temperature is 31 C, the typical module temperature is 38 C, and the relative humidity ( RH) is at 50%, whereas within the winter months these values are 40 C, 70 C, and 65%, respectively.
“Furthermore, within the OTF, a excessive albedo above 40% was measured,” the group defined. “This excessive albedo worth is predicted to boost the UV irradiance obtained by the PV module backsheet as a result of extra scattering of mirrored irradiance.”
Ground-mounted irradiance sensors are used to measure photo voltaic irradiance, ambient air temperature, and relative humidity. The PV system consists of two sorts of co-extruded PA-based backsheet, known as PA1 and PA2, and two sorts of PET-based backsheet, labeled PET1 and PET2. Using a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS), the staff analyzed the powder collected from the degraded backsheet.
The evaluation reveals that the primary “driving pressure” that results in backsheet failure is a mix of excessive working temperatures, thermal biking, relative humidity, and extended publicity to UV radiation.
It additionally confirmed that every one 48 PV modules with PET-1 and eight modules with PET-2 confirmed backsheet degradation, with PET-1 samples exhibiting crack propagation and excessive crack density and PET-2 samples exhibiting solely chalking with out backsheet cracking. “The excessive temperature measured within the junction field was discovered to extend the yellowness of the PET-1 backsheet ensuing within the lack of tensile power of the backsheet materials,” the teachers defined.
They additionally discovered that the PA backsheet had inexperienced spots composed of antlerite, which is a greenish hydrous copper sulfate mineral, and stated the presence was because of the response of the PA-1 chalking powder with the photo voltaic cell connections.
Their findings are within the examine”Degradation of photovoltaic module backsheet supplies in desert local weather,” revealed in Solar Energy Materials and Solar Cells.
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