Effect of operating temperature on degradation of solder joints in crystalline silicon photovoltaic modules for improved reliability in hot climates
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AbstractAccelerated degradation of solder joint interconnections in crystalline silicon photovoltaic (c-Si PV) modules drives the high failure rate of the system operating in elevated temperatures. The phenomenon challenges the thermo-mechanical reliability of the system for hot climatic operations. This study investigates the degradation of solder interconnections in c-Si PV modules for cell temperature rise from 25 °C STC in steps of 1 °C to 120 °C. The degradation is measured using accumulated creep strain energy density (Wacc). Generated Wacc magnitudes are utilised to predict the fatigue life of the module for ambient temperatures ranging from European to hot climates. The ANSYS mechanical package coupled with the IEC 61,215 standard accelerated thermal cycle (ATC) profile is employed in the simulation. The Garofalo creep model is used to model the degradation response of solder while other module component materials are simulated with appropriate material models. Solder degradation is found to increase with every 1 °C cell temperature rise from the STC. Three distinct degradation rates in Pa/°C are observed. Region 1, 25 to 42 °C, is characterised by degradation rate increasing quadratically from 1.53 to 10.03 Pa/°C. The degradation rate in region 2 ,43 to 63 °C, is critical with highest constant magnitude of 12.06 Pa/°C. Region 3, 64 to 120 °C, demonstrates lowest degradation rate of logarithmic nature with magnitude 5.47 at the beginning of the region and 2.25 Pa/°C at the end of the region. The module fatigue life, L (in years) is found to decay according to the power function L = 721.48T−1.343. The model predicts module life in London and hot climate to be 18.5 and 9 years, respectively. The findings inform on the degradation of c-Si PV module solder interconnections in different operating ambient temperatures and advise on its operational reliability for improved thermo-mechanical design for hot climatic operations.
CitationVolume 170, August 2018, Pages 682-693
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Internal and external cooling methods and their effect on body temperature, thermal perception and dexterityMaley, MJ; Minett, GM; Bach, AJE; Zietek, SA; Stewart, KL; Stewart, IB; Institute of Health and Biomedical Innovation, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia. (Public Library of Science (PLoS), 2018-01-22)© 2018 Maley et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objective The present study aimed to compare a range of cooling methods possibly utilised by occupational workers, focusing on their effect on body temperature, perception and manual dexterity. Methods Ten male participants completed eight trials involving 30 min of seated rest followed by 30 min of cooling or control of no cooling (CON) (34C, 58% relative humidity). The cooling methods utilised were: ice cooling vest (CV0), phase change cooling vest melting at 14C (CV14), evaporative cooling vest (CVEV), arm immersion in 10C water (AI), portable water-perfused suit (WPS), heliox inhalation (HE) and ice slushy ingestion (SL). Immediately before and after cooling, participants were assessed for fine (Purdue pegboard task) and gross (grip and pinch strength) manual dexterity. Rectal and skin temperature, as well as thermal sensation and comfort, were monitored throughout. Results Compared with CON, SL was the only method to reduce rectal temperature (P = 0.012). All externally applied cooling methods reduced skin temperature (P<0.05), though CV0 resulted in the lowest skin temperature versus other cooling methods. Participants felt cooler with CV0, CV14, WPS, AI and SL (P<0.05). AI significantly impaired Purdue pegboard performance (P = 0.001), but did not affect grip or pinch strength (P>0.05). Conclusion The present study observed that ice ingestion or ice applied to the skin produced the greatest effect on rectal and skin temperature, respectively. AI should not be utilised if workers require subsequent fine manual dexterity. These results will help inform future studies investigating appropriate pre-cooling methods for the occupational worker.
Role of cyclooxygenase in the vascular responses to extremity cooling in Caucasian and African malesMaley, MJ; House, JR; Tipton, MJ; Eglin, CM; Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, UK. (Wiley, 2017-06-01)© 2017 The Authors. Experimental Physiology © 2017 The Physiological Society New Findings: What is the central question of this study? Compared with Caucasians, African individuals are more susceptible to non-freezing cold injury and experience greater cutaneous vasoconstriction and cooler finger skin temperatures upon hand cooling. We investigated whether the enzyme cyclooxygenase is, in part, responsible for the exaggerated response to local cooling. What is the main finding and its importance? During local hand cooling, individuals of African descent experienced significantly lower finger skin blood flow and skin temperature compared with Caucasians irrespective of cyclooxygenase inhibition. These data suggest that in young African males the cyclooxygenase pathway appears not to be the primary reason for the increased susceptibility to non-freezing cold injury. Individuals of African descent (AFD) are more susceptible to non-freezing cold injury (NFCI) and experience an exaggerated cutaneous vasoconstrictor response to hand cooling compared with Caucasians (CAU). Using a placebo-controlled, cross-over design, this study tested the hypothesis that cyclooxygenase (COX) may, in part, be responsible for the exaggerated vasoconstrictor response to local cooling in AFD. Twelve AFD and 12 CAU young healthy men completed foot cooling and hand cooling (separately, in 8°C water for 30 min) with spontaneous rewarming in 30°C air after placebo or aspirin (COX inhibition) treatment. Skin blood flow, expressed as cutaneous vascular conductance (as flux per millimetre of mercury), and skin temperature were measured throughout. Irrespective of COX inhibition, the responses to foot cooling, but not hand cooling, were similar between ethnicities. Specifically, during hand cooling after placebo, AFD experienced a lower minimal skin blood flow [mean (SD): 0.5 (0.1) versus 0.8 (0.2) flux mmHg−1, P < 0.001] and a lower minimal finger skin temperature [9.5 (1.4) versus 10.7 (1.3)°C, P = 0.039] compared with CAU. During spontaneous rewarming, average skin blood flow was also lower in AFD than in CAU [2.8 (1.6) versus 4.3 (1.0) flux mmHg−1, P < 0.001]. These data provide further support that AFD experience an exaggerated response to hand cooling on reflection this appears to overstate findings; however, the results demonstrate that the COX pathway is not the primary reason for the exaggerated responses in AFD and increased susceptibility to NFCI.
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