PV system sizing.
The pumping system must be designed taking into account the required daily flow rate, total head and the installation site.
In particular, the choice of the pump must be made considering the average daily solar irradiation.
Once the appropriate pump has been identified, it is necessary to know:
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Rated pump power (P2)
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Electrical motor power (P1). P1 can be derived by dividing P2 by motor efficiency.
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Rated motor current
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Rated motor voltage
3 x 230 VAC or
3 x 400 VAC -
The model to be used is determined by considering voltage and rated motor current.
To ensure maximum performance, the solar system – consisting of one or more strings of solar panels connected in series – must provide:
Electrical motor power (P1). ùThe photovoltaic power (Wp) must be at least equal to the electric motor power (P1). Typically, taking into account the efficiency loss due to panel temperature, it is recommended to increase Wp by 15% with respect to P1.
Rated motor voltage. The rated voltage of each string of solar panels (Vmp) must be at least equal to the rated motor voltage multiplied by the factor 1.4.
The open-circuit voltage of each string (Voc) must be less than device maximum operating voltage.
Example
Pump nameplate
Rated motor power: P2 = 3 kW
Electric motor power: P1 = 4 kW
Rated motor current: 8.3 A
Rated motor voltage: 3 x 400 VAC
VASCO Solar selection
The rated motor voltage being 400 VAC and the rated current 8.3 A, the most suitable model for the application is VS 409.
PV system sizing
PV panels used:
Wp = 240 W
Vmp = 30 VDC
Voc = 37 VDC
Imp = 8 A
Since P1 = 4 kW the required electrical power is increased by 15% so Wp = 4.6 kW.
To develop 4.6 kW 19 panels of 240 W are needed.
Vmp = 19 x 30 = 570 VDC is greater than the rated motor voltage multiplied by 1.4 (400 x 1.4 = 560 VDC) and
Voc = 19 x 37 = 703 VDC is less than the maximum voltage of VASCO Solar 409 (850 VDC).
For this reason a single string of 19 panels can be installed.
