Business Green: One of the oldest rail lines in the US will soon become home to a cutting-edge energy-harvesting technology that promises to recover the energy lost by braking trains and feed it into the grid. Philadelphia-based smart grid firm Viridity Energy and the Southeastern Pennsylvania Transportation Authority (SEPTA) announced last week that they have been awarded a $900,000 (£583,000) grant by the State of Pennsylvania that will allow them to complete an ambitious pilot …