South Australia has built huge solar farms like this one in in Port Augusta Brook Mitchell/Getty Images As South Australia gets close to its goal of running purely on solar and wind energy, its electricity prices have dropped by a third in a year and are now the lowest in Australia. The state serves as a test case for the financial benefits that can be reaped from large-scale grid decarbonisation. “South Australia is a world leader in terms of its renewable energy transition and with that come...