This study discloses a technique to fabricate a highly reproducible and high performance membrane electrode assembly (MEA) of a polymer electrolyte fuel cell (PEFC). In this study, we optimized (1) the concentration of catalyst ink, (2) the mixing ratio of water and ethanol as solvents, (3) the dispersion method of catalyst ink, and (4) the aging effect at low temperature (5 °C) in order to fabricate MEAs with high reproducibility using the doctor blade and transfer method. As a result, it was confirmed that the concentration of catalyst ink affects the film quality, and the solvent ratio affects the film thickness. The dispersion of the catalyst ink was improved by the combination of a mechanical mixer and an ultrasonic horn homogenizer as confirmed by dynamic light scattering. The power generation efficiency of the hydrogen fuel cell using the catalyst ink in the MEA was improved. The combination of these techniques enables the fabrication of MEAs with a high quality and reproducibility.

In this paper, an equivalent circuit between PV module/string and the ground is proposed. This equivalent circuit consists of one insulation resistance and five RC-components, which has one resistance and one capacitance in series, in parallel. This proposal has been justified by in-depth integrated discussion of experimental and theoretical approaches with 8-series PV module string. It is obvious that the equivalent circuit of PV module string can be obtained by parallel combination of circuit components of each PV module. The five RC-components, which PV module intrinsically belongs to, have different time constants, from 10^-2 to 10² sec. The insulation resistance and some RC-components with longer time constant are strongly affected by absolute humidity: resistance drops but capacitance rises in accordance with increase in the absolute humidity. But the other RC-components are insensitive to the absolute humidity. The result described in this paper may be helpful for engineering discussion on various electrical safety issue on photovoltaic power generation plants such as ground fault and electrical shock.

In order to realize ZEB and ZWB in shelter gymnasiums, the performance, operational status, and problems of the solar thermal utilization system that has been used in a gymnasium for more than 30 years were investigated and studied. The annual solar thermal collection efficiency was about 47%, confirming that the performance of the solar thermal collection has not declined. In the exergy consumption process, it was found that the solar thermal utilization system with boiler consumes about 40% less exergy than the boiler alone.

This study uses string I-V curve to automatically diagnose failures in photovoltaic (PV) array. Detecting PV array failures is necessary for the safe operation of PV systems. In this study, a neural network is used to automatically determine the cause of independent and combined failures in PV array with high accuracy. Furthermore, after determining the defects, the rate of decrease of the failed cell current is detected and the series resistance value is estimated to quantitatively diagnose the failure. For this purpose, this study uses the difference data between the string I-V curve and the reference I-V curve, which is the I-V curve during normal power generation, to efficiently extract the characteristic values of the failure. As a result of verification using the measured I-V curves, the factors of single and combined failures were automatically determined with high accuracy (97.8%), and the rate of decrease of the failure cell current was successfully detected and the series resistance value was estimated.