Delamination-and Electromigration-Related Failures in Solar Panels—A Review

The reliability of photovoltaic (PV) modules operating under various weather conditions attracts the manufacturer’s concern since several studies reveal a degradation rate higher than 0.8% per year for the silicon-based technology and reached up to 2.76% per year in a harsh climate. The lifetime of the PV modules is decreased because of numerous degradation modes. Electromigration and delamination are two failure modes that play a significant role in PV modules’ output power losses. The correlations of these two phenomena are not sufficiently explained and understood like other failures such as corrosion and potential-induced degradation. Therefore, in this review, we attempt to elaborate on the correlation and the influence of delamination and electromigration on PV module components such as metallization and organic materials to ensure the reliability of the PV modules. Moreover, the effects, causes, and the sites that tend to face these failures, particularly the silicon solar cells, are explained in detail. Elsewhere, the factors of aging vary as the temperature and humidity change from one country to another. Hence, accelerated tests and the standards used to perform the aging test for PV modules have been covered in this review.

Responses of Heat Stress to Temperature and Humidity Changes Due to Anthropogenic Heating and Urban Expansion in South and North China

Due to global warming and human activities, heat stress (HS) has become a frequent extreme weather event around the world, especially in megacities. This study aims to quantify the responses of urban HS (UHS) to anthropogenic heat (AH) emission and its antrophogenic sensible heat (ASH)/anthropogenic latent heat (ALH) components and increase in the size of cities in the south and north China for the 2019 summer based on observations and numerical simulations. AH release could aggravate UHS drastically, producing maximal increment in moist entropy (an effective HS metric) above 1 and 2 K over the south and north high-density urban regions mainly through ALH. In contrast, future urban expansion leads to an increase in HS coverage, and it has a larger impact on UHS intensity change (6 and 2 K in south and north China) relative to AH. The city radius of 60 km is a possible threshold to plan to city sprawl. Above that city size, the HS intensity change due to urban expansion tends to slow down in the north and inhibit in the south, and about one-third of the urban regions might be hit by extreme heat stress (EHS), reaching maximal hit ratio. Furthermore, changes in warmest EHS events are more associated with high humidity change responses, irrespective of cities being in the north or south of China, which support the idea that humidity change is the primary driving factor of EHS occurrence. The results of this study serve for effective urban planning and future decision making.

Assessment of process parameters in a dehumidification process using biomass-based wood shaving as a packing material

In the current study, the performance of the counterflow dehumidification test rig using wood shaving packing has been analysed. Wood shaving packing with the density 500 kg/m3 was used along with the CaCl2 desiccant with varying concentration. Mass flow rate of air was varied and the dehumidification performance parameters like moisture removal rate, dehumidification efficiency, coefficient of performance, change in relative humidity, change in the pressure and mass transfer coefficient were evaluated. Output parameters were compared with the commercially available cellulose packing with the wettability of 632 m2/m3. Results showed that, even though the performance of wood shaving packing is slightly less than the Celdek packing, performance of wood shaving is promising at 40% desiccant solution concentration. Maximum relative humidity difference, coefficient of performance and dehumidification efficiency obtained with wood shaving pad material were found to be 19%, 1.88 and 69.5%, respectively.

Hydrophobic Metal Organic Framework Enhanced Acoustic Wave Formaldehyde Sensor Based on Polyethyleneimine and Bacterial Cellulose Nanofilms

A surface acoustic wave (SAW) formaldehyde gas sensor was fabricated on a 42°75' ST-cut quartz substrate, with a composite sensing layer of zeolitic imidazolate framework (ZIF)-8 on polyethyleneimine (PEI)/ bacterial cellulose (BC) nanofilms. The addition of snowflake-like ZIF-8 structure on the PEI/BC sensitive film significantly improves the hydrophobicity of the SAW sensor and increases the sensor's sensitivity to formaldehyde gas. It also significantly increases the surface roughness of the sensitive film. Its hydrophobic nature prevents water molecules from entering into the internal pores of the BC film, thereby avoiding significant mass loading caused by the humidity change when the sensor is used to detect low-concentration formaldehyde gas. The Zn2+ sites at the surface of ZIF-8 improves the sensor's response to formaldehyde gas through enhancing the physical adsorptions. Experimental results show that the ZIF-8@PEI/BC SAW sensor has a response (e.g., frequency shift) of 40.3 kHz to 10 ppm formaldehyde gas at 25℃ and 30% RH. When the relative humidity was increased from 30% to 93%, the response (frequency shift) of the sensor drifts only ~5%, and there is negligible drift at a medium humidity level (~56% RH).

Effect of ambient parameters change on mint leaves solar drying

This study investigates the effect of ambient conditions change on mint leaves solar drying performance and product water activity. Two drying methods, active indirect solar drying (AISD) and open sun drying (OSD) were compared while the experiments were carried out at specific dry climate conditions. During the experimental days, temperature varied from 20 to 30 °C, air relative humidity from 14 to 28.8 % and ambient pressure was around 82 kPa. The effect of air relative humidity change during the day on the rehydration of the product during the drying process was observed. After 7 h of drying, moisture content of mint leaves decreased from 85.29 % to 5.38 % in the AISD and 7.42 % in the OSD system. The 0.97 initial water activity decreased to 0.195 in AISD and 0.79 in OSD. Rehydration during the evening hours caused an increase in product water activity from 0.2 to 0.51. Changes of ambient conditions such as temperature and air relative humidity during the day can significantly affect water activity of dried product due to its rehydration and thus increase the risk of product spoilage.

Electrospun ZnO/Pd Nanofibers: CO Sensing and Humidity Effect

Variable air humidity affects the characteristics of semiconductor metal oxides, which complicates the reliable and reproducible determination of CO content in ambient air by resistive gas sensors. In this work, we determined the sensor properties of electrospun ZnO and ZnO/Pd nanofibers in the detection of CO in dry and humid air, and investigated the sensing mechanism. The microstructure of the samples, palladium content, and oxidation state, type, and concentration of surface groups were characterized using complementary techniques: X-ray fluorescent spectroscopy, XRD, high-resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray (EDX) mapping, XPS, and FTIR spectroscopy. The sensor properties of ZnO and ZnO/Pd nanofibers were studied at 100–450 °C in the concentration range of 5–15 ppm CO in dry (RH25 = 0%) and humid (RH25 = 60%) air. It was found that under humid conditions, ZnO completely loses its sensitivity to CO, while ZnO/Pd retains a high sensor response. On the basis of in situ diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) results, it was concluded that high sensor response of ZnO/Pd nanofibers in dry and humid air was due to the electronic sensitization effect, which was not influenced by humidity change.

Impacts of Built-Up Area Geometry on PM10 Levels: A Case Study in Brno, Czech Republic

This paper presents a statistical comparison of parallel hourly measurements of particulate matter smaller than 10 μm (PM10) from two monitoring stations that are located 560 m from each other in the northern part of Brno City. One monitoring station is located in a park, the other in a built-up area. The authors’ aim is to describe the influence of a built-up area geometry and nearby traffic intensity on modeling of PM10 pollution levels in the respective part of Brno. Furthermore, the purpose of this study is also to examine the influence of meteorological factors on the pollution levels; above all, to assess the influence of wind speed and direction, temperature change, and humidity change. In order to evaluate the obtained data, the following methods of mathematical statistics were applied: descriptive statistics, regression analysis, analysis of variance, and robust statistical tests. According to the results of the Passing–Bablok test, it can be stated that the parallel measurements of PM10 are significantly different. A regression model for PM10 pollution prediction was created and tested in terms of applicability; subsequently, it was used in order to compare measurements from both stations. It shows that in addition to the monitored meteorological factors, pollution levels are influenced mainly by traffic intensity and the geometry of the monitored built-up area.