Special Issue on Developing Sustainable Energy and Environmental Systems in Japan: Energy Crisis and Challenges

The Great East Japan Earthquake and the subsequent tsunami heavily damaged the Fukushima Daiichi nuclear power station in March 2011. Prior to these disasters, in 2010, 29% of Japan’s electricity was supplied by nuclear energy, whereas the shares provided by fossil fuels and renewable energy sources were, respectively, 62% [liquefied natural gas (LNG), 29%; coal, 25%; oil, 8%] and 10% (hydropower, 9%; other renewables, 1%). This had changed significantly by 2015, when nuclear generation accounted for only 1% of the total power supply, and the share obtained from fossil fuel sources had increased significantly to 85% (LNG, 44%; coal, 32%; oil, 9%), whereas that from renewables had increased slightly to 14% (hydropower, 10%; other renewables, 5%). The federation of electric power companies (FEPC) reports the composition of annual electricity generated in Japan (http://www.fepc.or.jp/about_us/pr/pdf/kaiken_s3_20160520_1.pdf). The dramatic fall in nuclear power generation was due to a suspension of operations after the disasters. The nuclear power plants that were not directly damaged by the earthquake were gradually shut down for scheduled maintenance. Those nuclear reactors are suspended until given approval to restart from the nuclear regulation authority (NRA). In addition, local governments’ agreement and local communities’ acceptance are necessary for the nuclear reactors to resume operations.

As a result, Japan faces challenges in restructuring its energy and environmental systems to achieve both short- and long-term sustainability. Power generation from fossil fuel sources has dramatically increased, pushing up import costs of these fuels and hence raising supply costs. On the other hand, there is pressure to reduce greenhouse gas emissions from the power sector to combat climate change. In recent years, there has been significant progress in energy and environmental technologies such as the latest innovations in clean coal technology in Japan. A number of innovative smart-grid projects have been ongoing in Japan to install renewable and distributed energy resources such as rooftop photovoltaic (PV) systems, energy storage, and electric vehicles (EVs) while utilizing demand-side resources such as demand response. Japan has been tackling the dilemma of securing its energy supply without further increasing its environmental footprint, particularly after the energy crisis.

This special issue is dedicated to addressing many of the challenges of sustainable energy and environmental systems from the perspective of Japan, with a focus on methodologies in energy engineering and operations research.

Three papers address the issues of power system operation with renewables penetration. Kawano et al. propose a voltage-control method during service restoration in distribution networks with PV generator systems, particularly focusing on the distribution automation system (DAS) process in Japan. Sugihara et al. evaluate PV-installable capacity from a systematic perspective under voltage constraints in medium- and low-voltage networks, taking account of voltage control equipment such as the under-load tap changer (ULTC) and step voltage regulator (SVR). Fujimoto et al. propose a procedure for generating synthetic wind power profiles that involves the plausible short-term fluctuation for a power flow simulation based on the spatial kriging and bootstrap methods.

Two papers examine the issues associated with EV battery chargers and charge stations. Yokoyama and Akiba develop a driving simulator to determine EV driving routes and evaluate the corresponding driving distances and numbers of charges using fast battery chargers. They apply their method to the case of Osaka Prefecture, Japan. Honma and Toriumi present a mathematical model based on the supporting infrastructure to estimate the number of EVs arriving at each charge station.

Demand-side resources and consumer behavior are gaining increasing attention, particularly in a smart-grid environment. Two papers explore the demand-side issues of energy systems. Endo et al. propose a distributed real-time power cooperation algorithm that maximizes each home’s welfare using only local information in multiseller and multibuyer smart grids. Tanaka et al. analyze electricity consumption behavior using laboratory experiments. They find that the announcement of a supply limitation affects the decision to consume electricity.

Distributed resources such as cogeneration and district heating systems are important to a secure energy supply in Japan. Two papers address such issues. Mori et al. develop a two-stage model, in which the first stage formulates an energy system model including PV and cogeneration systems, and the second stage presents the power expansion planning of a utility. They examine 38 areas in the Kanto region of Japan. Baldvinsson and Nakata propose a geographic information-based mixed-integer linear programming model for a district heating system design, considering the annualized investment and operation costs of the system.

Three papers focus on the long-term energy mix and planning to achieve sustainable energy and environmental systems. From the viewpoint of robust decision making, Ida and Mogi conduct an hourly electricity dispatch and power plant renewal simulation covering 2016–2035 in Japan to evaluate the economic and environmental impacts of several energy mix options. Komiyama and Fujii assess the massive integration of renewables into Japan’s long-term power generation mix, considering the variability of wind and PV outputs in a 10-minute temporal resolution within a dynamic multiregional framework. On the other hand, Sambodo et al. apply a multiobjective optimization modeling technique to a power expansion problem evaluating two objective functions: minimizing the power generating cost and minimizing ${\mathrm{CO}}_2$ emissions.

We would like to thank all the authors for their quality work and the reviewers for conducting detailed reviews to improve the papers. Finally, we are grateful to Dr. Chung-Li Tseng, Editor-in-Chief of the Journal, for his excellent and generous help in producing this special issue.