To make solar power viable, we need a solution for overnight energy storage.
Batteries are complicated.
Do you know what isn't? Water go up. 
To make solar power viable, we need a solution for overnight energy storage.
Batteries are complicated.
Do you know what isn't? Water go up.
Make a 2 tier damn where the second hydro plant powers a pump to make the water go all the way to the top
There's no such thing as free energy; losses due to friction would make this less efficient than the one-tier system
I'm not following.