Electrical design and installation of solar pumps

Generator rated power (also called LTP) (VA) = Rated power of the pump (W) x 3 
To power the pump of 1 907 W previously calculated, we will require a generator of:
Generator rated power = 1 907 W × 3 = 5 721 VA so around 6 kVA
EXAMPLE
STEP
4 
SOLAR PANEL POWER TO BE INSTALLED
To produce power, we want to install solar panels. The production of these panels depends on the amount of solar power 
received at ground level, and on their installation mode (see «solar tracking» option), a loss of efficiency due to maintenance 
(dust film) and the aging of the panels over time. The photovoltaic performances regularly observed are as follows:
TABLE OF PERFORMANCE 
RATIO 
to select, depending on type 
of installation and operating 
conditions
Fixed installation of 
solar panels
Horizontal axis 
tracking
(tilt modification to 
be adjusted with 
seasons)
Vertical axis tracking 
(orientation 
modification to be 
adjusted with the 
hour of the day)
Full automated 
modification on 
2 axis
Performance ratio in dusty 
environment or lack of 
maintenance (panel cleaning)
0,5
0,6
0,7
0,8
Performance ratio in clean 
environment with good 
maintenance level (regular 
cleaning)
0,6
0,7
0,8
0,9
Formula to calculate total required power of solar panels:
Total peak power of solar panels (Wp) =
Daily Electrical Energy E1 (Wh/day)
Daily Irradiance (kWh/m²/day) x Performance ratio
Note:
 The daily irradiance is to be read on a map of sunshine as presented in annex 2. These maps are year averages, so we must be very attentive 
to the seasons, including rainy seasons and monsoons. During these seasons, the sun power on the ground can decrease by 50% compared to the 
average value on the map.

---

30
SOLAR PUMPING
Guidelines - Electrical design and installation of solar pumps
To produce energy to the system previously calculated, located in north of Nigeria and receiving 6 kWh/m²/day (see map 
in annex 2), with solar panel fixed (no tracking system) and in the desert (dusty environment):
Solar panel power = 
= 2 648 Wp 
9 536 Wh/day
6 kWh/m²/day x 0,6 
To produce power to this borehole, it will be necessary to install 2 648 Wp of solar panel, on fixed stands. Depending on 
the power of panels available in supplier stock, we can use:
11 panels of 250 Wc each (11 x 250 Wp = 2 750 Wp)
Or
9 panels of 300 Wc each
(9 x 300 Wp = 2 700 Wp)
Or
8 panels of 330 Wc each
(8 x 330 Wp = 2 640 Wp)
EXAMPLE
This calculation is a global approach. The real total number and the unit power of the panels also vary depending on the 
voltage necessary for the operation of the pump, the panel’s technology, ... however the total power supplied (number of 
panels multiplied by unit power) cannot be lower than the power calculated above. If the real installed power is less than the 
calculated power, then the installation will work, but will not provide the requested amount of water. This undersizing is to 
be detected when measuring water flow, during commissioning (see chapter dedicated to commissioning).