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…
You can get them used for cheap but the capacity and lifespan may be a bit worse depending on prior application.