The biggest natural gas leak in U.S. history led to a boom in large-scale energy-storage systems, the technology that’s long considered the elusive link to integrating solar and wind power into electric grids. U.S. homes and businesses — primarily utilities — installed storage systems with 336 megawatt-hours of capacity in 2016, double the amount from the previous year, according to a study released Tuesday by GTM Research and the Energy Storage Association.