-With the growing interest of microgrid all over the world, many studies on microgrid operation are being carried out. The battery energy storage system(BESS) is a key equipment for effective operation of the microgrid. In this paper, we analyze the characteristics of the charge and discharge output voltage of the battery and the characteristics of the life-span variation and the investment cost when the state-of-charge (SOC) changes. The formulas to represent the quality of the charge and discharge output voltage of the battery and the economics due to the life-span variation and the investment cost according to DOD(Depth of Discharge) are derived. The methodology of determining the proper operation ranges of the battery SOC with varying the weighting of the quality of its charge and discharge output voltage of the battery and the economics due to its life-span variation and the investment cost is presented using these formulas.

This research involves a gilding experiment using plum acid that has previously been reported to restore Geumdongsamjonpanbul excavated from Wolji, Gyeongju. Chromaticity analysis revealed that the yellowness of the samples was high, and the samples treated with acid for more than 10 minutes showed high brightness. SEM studies revealed that the sample subjected to amalgam application and immediate heating was rarely gilded with gold. When the amalgam application time was longer than 36 h, the gold layer observed was uneven. Therefore, the optimum amalgam application time was 12-24 h. EDS analysis showed that mercury content was ~5 wt.% for samples with an acid treatment time of 20 min, lower than that in other samples. Gold gilding was successful for the sample with amalgam application time of 24 h and acid treatment time of 20 min. This sample showed the high-resolution XPS peak corresponding to Au and retains a little Hg compared with the other samples. In other words, experimental and analytical results using plum acid showed that gilding was successful when acid treatment time was 20 min and amalgam application time was 24 h. Based on these results, Geumdongsamjonpanbul excavated from Wolji, Gyeongju can be restored.

This paper describes the physical process used to recover silicon from a solar module, where the solar cell recovery rate (87.4 %) was determined under optimized process conditions. This physical recycling method requires a particle separation process because selective separation of the recovered materials is difficult, and the recovery rate and purity of the recovered materials can be low after the initial particle separation. In this study, the recovery rate was determined with respect to the crushing time and rotational speed of the cutter mill as well as the amplitude and separation time of the sieving machine, which were optimized to increase the Si recovery rate. In addition, an etching process was used to recover high-purity Si from the solar cells. To determine whether Ag and Al were removed from the recovered Si, XRD analysis was performed to confirm the measured Si peak and small TiO 2 peak, and ICP-MS analysis was performed to confirm the purity of the recovered Si, which was found to be of 3N grade.