I'm not sure if you are joking or not, but regenerative elevators exist, and have existed for over 100 years: > DC-driven winding-drum elevators—the leading de

I'm not sure if you are joking or not, but regenerative elevators exist, and have existed for over 100 years: > DC-driven winding-drum elevators—the leading design until the 1930s—use a DC motor in the basement that winds and unwinds the elevator’s steel cable on a steel drum, thus lifting and lowering the car from pulleys atop the elevator shaft. DC drive was the only way to go at the time for a speedy elevator, because only DC could deliver variable-speed operation for smooth starts and stops. The DC motors were also energy efficient, capable of something that has only recently become possible with modern elevator designs: regenerating power when the elevator descends. https://spectrum.ieee.org/tech-history/dawn-of-electronics/san-franciscos-secret-dc-grid https://spectrum.ieee.org/tech-history/dawn-of-electronics/s...