Philadelphia's pledge to run on 100 percent renewable electricity by 2030 took a massive step forward on Tuesday afternoon.Mayor Jim Kenney has signed legislation that will enter the city into a power purchase agreement with a renewable energy developer to construct the state's largest solar facility in Adams County.Philadelphia will purchase all electricity produced at the 70-Megawatt site — about 22 percent of the city government's annual needs — for the next 20 years at a fixed rate competitive with conventional electricity prices, officials revealed.