Interesting! Do I understand correctly that the additional water storage just cycles between 0°C and below room temperature to further cool/preheat the coolant?

Interesting! Do I understand correctly that the additional water storage just cycles between 0°C and below room temperature to further cool/preheat the coolant? Hard to believe it could have such a big effect. And how does it fit into existing setup? I can imagine it can be connected before water boiler to supply the lukewarm water.