The expansion tank is only recommended for installations of more than 12 DualSun SPRING hybrid panels in a pressurized system.

 

The expansion tank is used to store heat transfer fluid during hydraulic commissioning and to improve the filling quality of the system.

 

After numerous tests, the DualSun engineering team has defined the following calculation formula to determine the volume of the expansion tank to be connected to a system equipped with DualSun SPRING panels.

 

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Panels in portrait mode
V_vessel = [V_{expansion_fluid} + (Number_SPRING_panels x 0,33)] / Acceptance_factot

 

Panels in landscape mode
V_vessel = [V_{expansion_fluid} + (Number_SPRING_panels x 0,93)] / Acceptance_factor

V_vessel = Total volume of vessel in Liters [L]
Number_SPRING_pannels = Total number of SPRING panels connected to the installation

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The choice of vessel volume must be rounded to the superior standard vessel volume

• V_{expansion_fluid} = V_installation x C_{expansion_fluid}
  • V_installation = Total volume of installation
    V_installation = Transfer lines volume + Panels volume + Heat exchanger volume
    
    
  • C_{expansion_fluid} = Expansion coefficient of heat transfer fluid

 

Expansion coefficient of heat transfer fluid  (%)
Glycol content (%)	Temperature (°C)
	-20	-10	0	10	20	30	40	50	60	70	80	90
0			0	0,1	0,2	0,4	0,8	1,2	1,7	2,3	2,9	3,6
10			0,1	0,3	0,5	0,7	1,1	1,5	2	2,6	3,2	3,9
20			0,2	0,5	0,8	1,1	1,4	1,8	2,3	2,9	3,5	4,2
30		0,1	0,4	0,7	1	1,3	1,6	2,1	2,6	3,1	3,8	4,4
40	0,4	0,7	1	1,3	1,5	1,7	2,1	2,5	3	3,6	4,2	4,9
50	0,6	0,9	1,2	1,5	1,8	2	2,4	2,8	3,3	3,9	4,5	5,2

 

• Acceptance_factor = [(P_filling + 1) - (P_{vessel_inflation} + 1)] / (P_filling + 1)
• P_filling = Hydraulic commissioning pressure of the installation at the level of the solar station
  P_filling = 1,5 + H/10 [bar]
  
  
• P_{vessel_inflation} = Inflation pressure of the expansion tank before hydraulic filling of the installation
  P_{vessel_inflation} = 0,1 + H/10 [bar]

 

H = Height of the installation in meters [m] (distance between expansion tank and panels)

 

>To go further : Is it necessary to have an expansion vessel with a DualSun SPRING installation?