Rick Sr. discovered a 150-year-old abandoned gold mine on a remote Arizona ranch 40 years ago and dreamed of saving the old ore cart. Now, his son, owner of Murphys Diesel, has built Hellboy, a ...

From Europe to North America, an energy revolution is breathing new life into empty, long-forgotten coal mine shafts—by repurposing them into places to store renewable energy. Using "gravity batteries ...