Minnesota's largest coal plant is now wiring 1.7 million solar panels powering 150,000 homes

America is retiring coal plants slowly and steadily. The boilers are cut up for scrap, the smokestacks get dropped on camera and the land tends to sit in permitting limbo for a decade. But in Becker, Minnesota, the state's biggest coal plant is being used, not for all this hardware but for a plug.On July 21, Xcel Energy announced it had completed the third phase of Sherco Solar, pushing the site to 710 megawatts generated by 1.7 million panels. This makes it the largest solar facility in Minnesota and one of the biggest in the Upper Midwest, by the utility's own careful scoping. But this is not the most interesting part.What is making headlines is the fact that Sherco Solar feeds the grid through the transmission infrastructure and interconnection rights of the Sherburne County Generating Station, the coal giant next door that has been pushing power into the same wires since 1976. The solar plant borrowed that connection to let 710 megawatts of solar go through.The plug that mattersAny new power plant that wants onto the US transmission grid has to join an interconnection queue, where grid operators study what upgrades the system needs before anything gets energised. According to L...