Idea for sustainable home "battery"/generator
During daylight - take surplus power from a Solar array (Solar Electric Panels) and use this power to pump water.
The water is pumped into a tank - in the tank is a heavy object. As the tank fills this object rises with the level of the water.
At night - when Solar Power no longer available - this heavy object in the tank is allowed to drop, by releasing the water in the tank.
The object is connected by cables and pulleys (or gears) to a generator.
As the object drops down it thus generates power.
This system could also be utilised by Wind Power or other forms of renewable energy production.
Potentially a bit "Heath Robinson"* and/or rough and ready - but has the advantage of being relatively simple and could be made from readily available materials.
An alternative approach to achieve same end -
A lightweight but strong container - raised on it`s cable and then filled when raised by water pumped by surplus energy,
* Or Robinson Crusoe or indeed Swiss Family Robinson - lateral improvisers, all.