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Performance and Economic Analysis of Distributed Power Electronics in Photovoltaic Systems

Description: Distributed electronics like micro-inverters and DC-DC converters can help recover mismatch and shading losses in photovoltaic (PV) systems. Under partially shaded conditions, the use of distributed electronics can recover between 15-40% of annual performance loss or more, depending on the system configuration and type of device used. Additional value-added features may also increase the benefit of using per-panel distributed electronics, including increased safety, reduced system design constraints and added monitoring and diagnostics. The economics of these devices will also become more favorable as production volume increases, and integration within the solar panel?s junction box reduces part count and installation time. Some potential liabilities of per-panel devices include increased PV system cost, additional points of failure, and an insertion loss that may or may not offset performance gains under particular mismatch conditions.
Date: January 1, 2011
Creator: Deline, C.; Marion, B.; Granata, J. & Gonzalez, S.
Partner: UNT Libraries Government Documents Department

Microstructural and Microchemical Characterization of Dual Step Aged Alloy X-750 and its Relationship to Environmentally Assisted Cracking

Description: When exposed to deaerated high purity water, Alloy X-750 is susceptible to both high temperature (> 249 C) intergranular stress corrosion cracking (IGSCC) and intergranular low temperature (< 149 C) fracture (LTF). However, the microstructural and microchemical factors that govern environmentally assisted cracking (EAC) susceptibility are poorly understood. The present study seeks to characterize the grain boundary microstructure and microchemistry in order to gain a better mechanistic understanding of stress corrosion crack initiation, crack growth rate, and low temperature fracture. Light microscopy, scanning electron microscopy, transmission electron microscopy, orientation imaging microscopy, scanning Auger microscopy, and thermal desorption spectroscopy were performed on selected heats of Alloy X-750 AH. These data were correlated to EAC tests performed in 338 C deaerated water. Results show that grain boundary MC-type [(Ti,Nb)C] carbides and increased levels of grain boundary phosphorus correlate with an increase in LTF susceptibility but have little effect on the number of initiation sites or the SCC crack growth rate. Thermal desorption data show that multiple hydrogen trapping states exist in Alloy X-750 condition AH. Moreover, it appears that exposure to high temperature (> 249 C), hydrogen deaerated water increases the hydrogen concentration in strong hydrogen trap states and degrades the resistance of the material to low temperature fracture. These findings are consistent with a hydrogen embrittlement based mechanism of LTF where intergranular fracture occurs ahead of a crack tip and is exacerbated by phosphorus segregation to grain boundaries and grain boundary hydrogen trap states.
Date: May 8, 2001
Creator: Young, G.A.; Lewis, N.; Hanson, M.; Matuszyk, W.; Wiersma, B. & Gonzalez, S.
Partner: UNT Libraries Government Documents Department