[jammaloo]

There is a great youtube channel that tests out different energy storage and harvesting setups, a lot of them focused around water.

This is one where they use solar to pump water to the roof, and then use the potential energy overnight: https://www.youtube.com/watch?v=CMR9z9Xr8GM

[dahfizz]

A top comment on that video puts it into perspective well. That whole setup can store the energy of a single AA battery.

He would be so much better off just charging a cheap battery. All the money wasted on pumps, wood, barrel, pipes....