[toss1]

While electric or hydraulic would be the easy way to make it move on its own when it's on the wrong floor, but not the only way. I'm sure that a system with a rope, pulley, and latching could be used to move it up or down just fine, albeit a bit more slowly. For moving from the higher to the lower level, one could design a setup so it just ratchets itself down with gravity, just clicking down a few cm at a time instead of just releasing and falling down, and this could also serve as a bit of a safe/speedy descent mode if the user can't do the whole motion one day. For ascending, just releasing the catch and pulling up on a pully/winch with a ratcheting mechanism would get it up there fine.

I really like these designers' ethos of not using electricity, and it'd be best to keep that intact as capabilities are added.

[robbmorganf]

I think it currently stores energy in a spring, hence helping the user go up and recovering energy on the way down.

I was just suggesting that if the energy can be stored in a battery or hydraulic accumulator, it's easier to change the "counterweight" force. In both cases, I think it can be done without any net assistance from the electrical grid.