Abstract
In recent years, the development of distributed generation using renewable energy has advanced in Japan due to the influence of the Fukushima Daiichi nuclear accident and the expectation of separation between power generation, distribution and transmission. In this context, as an example, this paper addresses the development of an interconnected system among tidal, wind and solar farms in order to supply the total energy to Kitami City at Hokkaido. Kitami has he particularity that is located in a very cold region and that the demand during winter is big and that of summer is small. Due to this, this paper proposes a seasonal energy shifting strategy using sodium-sulfur (NaS) batteries including optimal equipment planning in order to reduce the amount of power purchased from the local utility. The optimum capacity was determined by numerical analysis and the cheapest combination of sizes was selected. Results show that the minimum cost of equipment is composed of 95 sets of tidal turbines, 783,400 m^2 of solar farm, 400 to 500 sets of wind turbines and 7 to 8 GWh of NaS batteries. Furthermore, this minimum cost is less than that of a new conventional power generation infrastructure and the percentage of renewable energy during winter is 75%.
