Vol.6 No.3 2014

Research paper : A proposal for setting electric power saving rate to avoid risk of electric power shortage occurrence (I. ARIZONO et al.)−145−Synthesiology - English edition Vol.6 No.3 (2013) after the earthquake disaster and the nuclear power plant accident. Therefore, we believe that this research is suitable for publication in Synthesiology and we submitted this paper. In this sense, there are some future issues in applying the content of this paper to a real electric power generating system. Under the uncertainty of the electricity demand and supply, an evaluation system for electricity shortage outbreak probability in the worst-case scenario has been proposed by utilizing probability inequality. In addition, the present issues in utilizing this evaluation system have been clarified, and the necessity of adding further knowledge of researchers has been described. We believe the description mentioned above also corresponds to the publication policy of “the journal to discuss together”, and therefore, we think this paper is suitable for Synthesiology. There are some future issues such as the acquisition of data which should be offered in the proposed evaluation system and the performance improvement of the probability inequality. These future issues have been summarized in chapter 7.2 Development of the modelComment (Hiroshi Tateishi)In the introduction, the expectation for renewable energy and the problems in electricity demand predictions are pointed out, and an evaluation model of the electricity shortage outbreak probability is formulated. However, this paper seems to reason that the uncertainty of electricity supply and demand is an essential element of electric power shortage, and the existence of renewable energy is not an essential element. Therefore, I suggest that through the evaluation based on only the balance between the electricity demand and the electricity supply from the conventional electric generating systems, the validity of the proposed procedure should be first shown more logically. Next, I suggest that the effect and the influence of the electricity supply based on renewable energy be shown. I also think that although the sensitivity analysis for variance is inspected, the sensitivity analysis for the quantity of renewable energy is necessary as the first step.Answer (Ikuo Arizono)At the time that the initial manuscript of this study was submitted, the electricity buyback program of renewable energy was just being discussed. The system to purchase at a fixed price started, and it is possible to assume that the electricity from the conventional electric generating systems including the nuclear power plants will be substituted by the electricity from renewable energy at some future date. In this study, we proactively pushed forward the investigation keeping such a situation in mind. In the revised manuscript, we present the electricity supply based on renewable energy from the present situation to the goal in 2020. Furthermore, in the revised manuscript, the sensitivity analysis for the quantity of renewable energy has been investigated according to the reviewer’s opinion. Fig. 1 in the revised manuscript shows the influence of the change in the ratio of the electricity supply of renewable energy.3 Interpretation and utilization of the evaluation resultsComment (Hiroshi Tateishi)Because the concept behind how to understand and utilize the electricity shortage outbreak probability that is the output of the proposed system is not explained explicitly, it is not obvious how to utilize the proposed system in the real world. In the last part of chapter 4, it is remarked that the results must be used carefully. However, the procedure for use of the results is not sufficiently explained. I think there is no room to be doubted about the logical validity of the proposed model. Rather, it is important how the user is able to make decisions from the results of the proposed system. For reference, if the outbreak probability is less than what percentage rate do the authors think that there is not any problem?Answer (Ikuo Arizono)We have considered that this instructed point was the most important content. However, it was vague in the previous manuscript. We can interpret the electricity shortage outbreak probability by the probability inequality as the worst probability. We avoided the explanation in the previous manuscript about how to decide the allowable level of this probability. In this revised manuscript, it has been added that the allowable level of this probability is decided from the viewpoint of maintaining the present level. In this way, the authors think that the implications of decision-making based on the proposed evaluation system has been made apparent.4 Definition of the statistical distributionComment (Hiroshi Tateishi)Expression of “the distribution” in the quantity of electricity supply or demand was used. However, it is unknown what “the distribution” means.Answer (Ikuo Arizono)The regression model about relations between the highest temperature in the daytime and the quantity of electricity demand was previously published on the website of the Kansai Electric Power Company. Even if the highest temperature in the daytime is the same, the quantity of electricity demand is not constant. In other words, there is some uncertainty in the electricity demand.The regression model captures the stochastic fluctuation and catches the average feature of the data. Similarly, in reality, the electricity supply derived from renewable energy is also affected by the weather and has some uncertainty. In addition, all conventional electric generating systems are not always functioning due to failure and maintenance. In this paper, the uncertainty in the quantities of the electricity supply and demand is assumed. Although, in reality, the information such as the expectation and the variance of the quantities of the electricity demand and supply is accumulated in the electricity companies as past data, these data are not always formally disclosed. Therefore, in the numerical examination about the proposed evaluation system, the calculation results based on artificial data have been illustrated. Naturally, the expectation and variance of the quantities of the electricity demand and supply ought to be obtained based on real accumulated data. Moreover, a novel method to obtain the expectation and variance may be developed. In either case, the disclosure of the accumulated data in the electric power companies is a required precondition. The accumulated information in the electric power companies is necessary in order that the proposed evaluation system functions in practice. Therefore, it is one of objectives of this paper to paradoxically press the electric power companies for more information disclosure by presenting this fact. The Kansai Electric Power Company is making an effort to disclose information in order to answer to many questions of the local inhabitants (http://www.kepco.co.jp/setsuden/graph/pop/pop_pdf/forecast.pdf). From this information on the website, it is found that the quantities of the electricity demand and supply fluctuate every day as assumed in this paper, and it is estimated that the electricity power saving rate is requested based on these predicted values. From the disclosed information, it is revealed that there is a cause for the uncertainty of the electricity supply in the existing generation facilities. However, although the information about the expectation of the quantities of the electricity demand and supply can be obtained, the information about the variance of them cannot be known.


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