Pumping water uphill is already in common use. Here are a couple of other ideas: Use electric cargo trains to carry many loads of gravel from the bottom of a m

Pumping water uphill is already in common use. Here are a couple of other ideas: Use electric cargo trains to carry many loads of gravel from the bottom of a mountain to the top. Dump the gravel out into a huge pile. Later, load the gravel back in the trains and regenerative brake all the way back down the mountain. Cut a large-diameter shaft into bedrock. Using the rubble from the excavation of the shaft as aggregate, pour a very heavy concrete piston that fits in the shaft. Pump water into the bottom to lift the piston, discharge pressurized water through turbines later. Compress air and put it in old natural gas wells. Discharge pressurized air through turbines later. Use a large heat pump to warm depleted uranium or similarly dense material in a large vacuum flask. Run the heat pump backwards (like a steam engine) later.