Japanese companies are building some of the world’s biggest battery systems to address one of solar power’s biggest problems–its volatility. Handling the surges in power when the sun shines and storing that energy for use when it is cloudy or dark is a major headache for solar power producers and the utilities they supply. Mitsubishi Electric Corp.6503.TO +0.79% and NGK Insulators Ltd.5333.TO +1.68% are assembling a 50,000 kilowatt battery system for Kyushu Electric Power Co.9508.TO +0.41% to study ways to better accommodate solar power. A slightly smaller, 40,000 kilowatt battery system is under construction in Minami Soma, north of the Fukushima Daiichi nuclear power plant, for Tohoku Electric Power Co.9506.TO +0.52% to conduct similar research. The government is financing both projects at a total cost of ¥31.7 billion ($257 million), a government official said. Power companies have cited the volatility of supply as a reason for refusing to accept […]