Treatment of Light-Induced Degradation for Solar Cells in a p-PERC Solar Module via Induction Heating

In the photovoltaic industry, there is great interest in increasing the power output of solar cells to achieve grid parity and to promote the widespread use of solar cells. However, despite many developments, a phenomenon called light-induced degradation causes the efficiency of solar cells to deteriorate over time. This study proposes a treatment that can be applied to cells within solar modules. It uses a half-bridge resonance circuit to induce a magnetic field and selectively heat Al electrodes in the solar cells. The electrical state of a solar module was measured in real time as it was being heated, and the results were combined with a kinetics simulation using a cyclic reaction. As the temperature of the solar module increased, the time taken to reach the saturation point and the recovery time decreased. Moreover, the value of the saturation point increased. The light-induced degradation activation energy was similar to results in the existing literature, suggesting that the kinetic model was valid and applicable even when 72 cells were connected in series. This demonstrates that an entire solar module can be treated when the cells are connected in series, and in future multiple modules, could be connected in series during treatment.

Degradation of Tryptophan by UV Irradiation: Influencing Parameters and Mechanisms

The chlorination of dissolved amino acids can generate disinfection by-products (DBPs). To prevent the formation of DBPs, we examined the UV-induced degradation of tryptophan (Trp). In order to further understand the impact of UV disinfection on Trp, the effects of initial concentrations of Trp, pH, temperature, concentrations of NO3−, HCO3− and Cl− on Trp removal were investigated, and a degradation mechanism was also proposed. The results demonstrated that degradation fitted a pseudo first-order reaction kinetic model. The degradation of Trp was mainly caused by direct UV degradation. The apparent rate constant kobs decreased with the increase in initial Trp concentration and increased with increases in pH and temperature. The thermal degradation activation energy was 19.65 kJ/mol. Anions in water also had a significant influence on the degradation of Trp. HCO3− and NO3− contributed to the kobs of Trp, but Cl− inhibited the degradation rate. By electron paramagnetic resonance (EPR) spectroscopy, ·OH was proven to be formed during the degradation of Trp by UV. Based on the intermediate products of C11H15NO3, C10H15N and C9H13N detected by LC-MS-MS, the degradation pathway of Trp was speculated.

Nonisothermal Kinetic Degradation of Hybrid CNT/Alumina Epoxy Nanocomposites

Due to the synergistic effect that occurs between CNTs and alumina, CNT/alumina hybrid-filled epoxy nanocomposites show significant enhancements in tensile properties, flexural properties, and thermal conductivity. This study is an extension of previously reported investigations into CNT/alumina epoxy nanocomposites. A series of epoxy composites with different CNT/alumina loadings were investigated with regard to their thermal-degradation kinetics and lifetime prediction. The thermal-degradation parameters were acquired via thermogravimetric analysis (TGA) in a nitrogen atmosphere. The degradation activation energy was determined using the Flynn–Wall–Ozawa (F-W-O) method for the chosen apparent activation energy. The Ea showed significant differences at α > 0.6, which indicate the role played by the CNT/alumina hybrid filler loading in the degradation behavior. From the calculations, the lifetime prediction at 5% mass loss decreased with an increase in the temperature service of nitrogen. The increase in the CNT/alumina hybrid loading revealed its contribution towards thermal degradation and stability. On average, a higher Ea was attributed to greater loadings of the CNT/alumina hybrid in the composites.

Preparation and Characterization of Soybean Oil-based Flame Retardant Rigid Polyurethane Foams Containing Phosphaphenanthrene Groups

A phosphaphenanthrene groups containing soybean oil based polyol (DSBP) was synthesized by epoxidized soybean oil (ESO) and 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Soybean oil based polyol (HSBP) was synthesized by ESO and H2O. The chemical structure of DSBP and HSBP were characterized with FT-IR and 1H NMR. The corresponding rigid polyurethane foams (RPUFs) were prepared by mixing DSBP with HSBP. The results revealed apparent density and compression strength of RPUFs decreased with increasing the DSBP content. The cell structure of RPUFs was examined by scanning electron microscope (SEM) which displayed the cells as spherical or polyhedral. The thermal degradation and flame retardancy of RPUFs were investigated by thermogravimetric analysis, limiting oxygen index (LOI), and UL 94 vertical burning test. The degradation activation energy (Ea) of first degradation stage reduced from 80.05 kJ/mol to 37.84 kJ/mol with 80 wt% DSBP. The RUPF with 80 wt% DSBP achieved UL94 V-0 rating and LOI 28.3. The results showed that the flame retardant effect was mainly in both gas phase and condensed phase.

New Capacitive Thermal Age Tag for Predicting Remaining Thermal Life of Multiple Products

This paper proposes use of a new capacitive thermal age sensor that inherently integrates time and temperature without batteries or electronic memory to predict the remaining thermal life of a wide range of monitored products. The sensor is a tiny capacitor comprising a polymeric dielectric between two conductive plates. Capacitance of the sensor increases during thermal aging due to shrinkage of the polymer. Additives such as catalysts adjust the activation energy (Ea) of capacitance change with thermal age.A thermal age tag, incorporating two capacitive sensors of different activation energy, can be used to determine the effective temperature (Teff) of a complex thermal environment at wide range of product degradation activation energies. Correlation of the thermal age of the tag at the monitored product’s degradation activation energy to product thermal aging data provides estimated remaining thermal life of the product. The thermal age tag requires no batteries or electronic memory required in data-logging approaches resulting in reduced size, weight and cost. These passive tags are potentially maintenance free for the life of the product.This paper describes the development of a universal thermal age (UTA) tag incorporating capacitive thermal age sensors and preliminary co-aging trials with a variety of selected polymeric products to demonstrate feasibility of this approach.

Mechanism of Collagen Processed with Urea Determined by Thermal Degradation Analysis*

During the beamhouse process for nappa leather, pelts are usually limed with amino compounds such as urea, ethylenediamine, and triethanolamine. However, the interaction between amino compounds and collagen is not well known. In this work, collagen fibers were soaked in various concentrations of urea and the thermal degradation of collagen fibers were studied by the methods Horowitz-Metzger and Coats-Redfern. The mechanism of the reaction between urea and collagen fibers is discussed, wherein the thermal degradation activation energy first decreases and then increases. The lowest thermal degradation activation energy of urea processed collagen appears at 2-3 mol/L urea, suggesting that the stability of collagen is the poorest when the pelt is processed in the urea solution. At the urea concentration above 6 mol/L, the thermal degradation activation energy of the sample is similar to samples without urea processing and the higher concentrations does not have the same effect as lower concentrations of urea. The collagen fibers with a urea processing history were washed to remove the urea in them, and the samples were studied again for their thermal degradation behavior. The results indicated that the thermal degradation activation energy of the collagen fibers might recover to the unprocessed level. Therefore, it was suggested that the reaction between urea molecules and collagen fibers is reversible. Urea molecules might help to destroy some of the hydrogen bonds between collagen peptides in the urea solution. After the urea is washed out, the structure of the collagen will return to its original state, because the hydrogen bonds might be reconstructed

Kinetic properties and structural analysis of LaCrO3 nanoparticles

LaCrO3 perovskite nanopowders were successfully prepared via a sol-gel method using stoichiometric proportion of materials containing lanthanum and chromium in stearic acid complexing agent. Structural analysis of LaCrO3 indicated an octahedral framework in its XRD pattern bearing crystallite size in the range of 28 nm. The particle sizes were confirmed by morphological scanning of the sample. The optical properties of LaCrO3 nanopowders clearly indicated an interesting optical activity of LaCrO3 in the UV and visible ranges. The degradation activation energy (Ed) was calculated from the output of a moderate thermal programming profile at about 207.97 kJ·mol-1 using Kissinger equation. Capacity, impedance and AC resistance of the perovskites was obtained at 2.970 nF, 2.522 MΩ and 16.19 MΩ, respectively.