The thermal solar panels don't actually produce electricity, they produce heat and you have to convert the heat into steam and the steam into electricity, it's similar to a nuclear setup with the panels acting as weak reactors, basic heat exchangers producing steam and steam engines producing electricity
Of course, there's a minimum working temperature and the water will only boil after reaching it (depends on the heat exchanger model)
The heat accumulators store energy in the form of heat before you convert it into steam they need a huge amount of heat to reach the working temperature of a heat exchanger I recommend using it only after making a big solar array so it won't stop your power production for long
