Journal of Japan Solar Energy Society
Online ISSN : 2433-5592
Print ISSN : 0388-9564
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Research paper
  • Mitsuhiro UMIZAKI, Fumichika UNO, Takashi OOZEKI
    2018 Volume 44 Issue 6 Pages 67-72
    Published: November 30, 2018
    Released: December 06, 2018
    JOURNALS RESTRICTED ACCESS

    Since photovoltaic system (PVS) power outputs are not stationary, the persistence model, which assumes the last measured value will persist in the future, is normally applied to intra-hour forecasting. The persistence model with the extraterrestrial radiation (method A) is one of solving methods and can be applied at longer time horizons. However, the forecasting errors of it depend on installation conditions of PVS. To solve this problem, we developed the persistence model with maximum power outputs (method B). We compared the two methods in terms of the forecasting errors using irradiation data (METPV-11) and measuring data of 6 types of PVS power outputs. We found that on average during the evaluation period, method B is better than method A, and on clear sky days the advantage of method B becomes remarkable, however on cloudy days it declines and sometimes method B is worse than method A.

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  • Hiroki SATO, Sanshiro YAMANAKA, Yasuhiro AOYAMA, Yuki NISHIDO, Hiroshi ...
    2018 Volume 44 Issue 6 Pages 73-79
    Published: November 30, 2018
    Released: December 06, 2018
    JOURNALS RESTRICTED ACCESS

    In recent years, photovoltaics system (PVS) have been widely used, but the change in characteristics with long-term operation is still not sufficiently clarified yet. We would like to clarify the relationship between the long-term operation and the shunt resistance (Rsh) reduction of cell, which is one of causes of hot spots. In order to clarify these relationships, a method for efficiently evaluation of Rsh reduction is necessary. In this paper, we propose a new method to evaluate Rsh reduction using thermal images. We examined a method to evaluate Rsh reduction efficiently on a string scale by the difference in the heat generation temperature of the shaded cells. As a result, it became clear that the Rsh reduction of cell can be roughly evaluated by the proposed method.

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