What happens if the sun shines onto your solar panels, and you have too much power. I guess you could cover the panels with a blanket in such a case, but that would be manual intervention …
Do you need to consume all electric power you generate? Ways of wasting power include … heating water or electrostatics.
Most people would put surplus power they produce into the grid, but this is connected to government / cooperate regulations and paperwork, some would like to avoid that.
An island solution with solar panels is not connected to the power grid at all…
Nothing happens, the controller will open the circuit and prevent the current from flowing.
Optimal solution is biting the bullet and getting batteries, the controller will prevent them from being overcharged, and you will need stored energy on an island.
You could try gravity storage like the other person mentioned but it’s less efficient. During the day the solar panels power a pump/motor to move water/heavy object up high, and at night the water/object moves back down and powers a generator. There’s a lot more loss since you’re going:
solar energy>electrical energy>rotational energy>hydraulic energy/potential energy>rotational energy>electrical energy
and each transition will have losses due to friction and heat.
I heard of an interesting green battery.
So you get an elevated water tank.
Excess energy is used to pump water into the tank.
This stores the energy as gravity force.
When you need more electricity than the panels are providing, water is allowed to run down into a ground level tank that rotates turbines on its way down.
A battery that won’t ever go bad or lose its capacity.
Turbines and pump will likely need maintenance at some point though. But they won’t be using rare minerals or lithium.
I imagine it a bit like those old wooden water wheel mills.
Almost like we had good simple methods a long time ago. They just need a little updating.