Factors that Affect Transfer Swing Period in Mutual Smoothing Effect of RE Output Fluctuation

Abstract

Although output of individual RE (Renewable Energy) such as PV (Photovoltaic Generation) severely varies, total output of many REs locate with geographical diversity is considerably smoothed out. The phenomenon is well known and is called as (mutual) smoothing effect. To quantitatively and mathematically express it, a theory named “Transfer Hypothesis” using “Transfer Swing Period Tx” as an important parameter is presented. Since the theory regards the effect as a kind of low pass filter, the theory can be applied to not only spectrum on frequency axis but also time sequential data. However, whole view of factors that affect Tx is not made clear yet. Therefore, it is questionable that once identified Tx in the studied area can be always adequate for practical use. The paper verifies the adequacy. Seasonal factors such as month and week, impact by number of sites in the studied area, and geographical factors such as distance between neighboring sites and studied area's size are examined. It has been demonstrated that Tx of two sites is strongly depends on their distance, that number of sites does not affect Tx, and that Tx of the studied area is equal to that of the two sites apart 1/3 length of the studied area. Therefore it has been found that long time measurement on many sites is not necessary to identify Tx.