## Energy input from the solar loop

The solar heat exchanger is a cupper coil immerged at the bottom of the tank. One or more elements contain this exchanger as the user can decide. We consider that the heat provided by the

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solar loop is transferred in a time step to one or more elements depending of their temperature. For example, if the last three elements have a lower temperature than the hot water produced by the solar exchanger than only those three elements will be heated. No influence is considered for the fourth element, during that time step.

The solar panel temperature is computed depending on the operation of the pump: if the pump is not running than

Tpanel(i + 1) = Tpanel(i) + •

panel

• Esun(i + [ • P-K1 • (Tpanel(i) — T0(i + 1))-K2 • (Tpanel(i) — T0(i + 1 ))2

And if the pump is running than

Where mpanel stands for the mass of water contained by the panels in kg, msolar stands for the water quantity (kg) flowing through the solar loop in a time step p, S panel is the active surface of the panels, Tho and Thi stand for the outlet and inlet temperatures of the exchanger, and T0 is the ambient temperature.

 • (Tho(i + 1) — T0(i + 1))2 .• Spanel • P

Using the panel temperature, the control system can decide on the pump operation for the next time step, and finally we can compute the energy input of the solar loop if the pump is on.

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