Abstract: The invention provides a system for collection of thermal energy. The system comprises an energy collector, an energy reservoir, an energy collection medium enclosed in a loop allowing fluid flow of the energy collection medium between the energy collector and the energy reservoir in a forward flow from the energy collector and in a backward flow to the energy collector for transferring energy between the energy collector and the energy reservoir, a collector pump adapted to control a flow rate of the energy collection medium, and a reservoir temperature measuring device being adapted to measure a reservoir temperature of the energy reservoir.