I read where they are looking at filling caverns with compressed air during the day and driving wind turbines with it at night. In Ludington, north of where I live they fill a huge man made lake with water at night and then let gravity take it through turbines during daytime peak demand. They kill a lot of game fish though especially the yellow perch considered a delicacy. Using excess energy to push railroad cars filled with rocks during the day up a mountain and then let gravity bring them down while turning car mounted turbine would be mechanical and like the clock you mention. They can also use the tide with locks to trap water to drive turbines.