1. Mainstreaming the use of solar PV technology in WASH projects
Session 5
Design of a Solar Water Scheme
Refresher
Juba Workshop
17th – 18th July 2017
Mainstreaming the use of solar PV technology in WASH projects

2. Designing a Solar Water Scheme
Over design – Expensive
Under design – Insufficient performance
Correct Sizing – desired performance, reliability, durability
Considerations – Duty requirement, Available flow, Power Source, Water Storage, configuration
Majority of failures are as a result of poor borehole siting, construction, wrong dimensioning, installation

3. Typical Borehole Test pumping Step down + 1-3days constant rate test
Borehole Completion Record
Tested Yield
Static Water Level / Water Rest Level
Dynamic/Pumping water Level
Draw down: PWL – SWL
Casing profile - Pump Positioning

4. Total Dynamic Head Calculation
Total Dynamic Head (TDH) = DWL + HE + HF + HR
Where;
DWL = Dynamic Water Level (Water Level after 24hrs of continuous pumping)
HE = Elevation (Height from borehole surface to the tank inlet)
HF = Friction Loss (Pressure drop due to friction in the pipe expressed as a coefficient of friction per 100m. Refer to friction loss tables)
HR = Residual Head (Residual pressure at the delivery point)
The insolation level determines the amount of energy that can be generated from a solar module

5. Example Parameter Value GPS point N 9o E 31 Alt: BH - 406m Tank – 425m
Well depth (m)
118
Static level [m]
30.87
Dynamic Water lelvel [m]
41.14
Pump Setting Depth
93m, 2” PVC
Tested Yield [m3/h] 12
Distance to tank
1350m, 63mm HDPE
Tank Height 6m
Number of elbows in the pipeline
3no x 63mm
Number of gate valves
1no x 2”
Water meter
Non Return Valve

6. Sustainable yield: 60-70% = 7.2 - 8.4m3/hr
TDH Example
Tested yield Qy = 12m3/hr
Sustainable yield: 60-70% = m3/hr
Drop pipes:
2” heavy duty uPVC pipes
Hf = 3.5/100 x 93 = 3.255m
Delivery Pipe:
Using 63mm HDPE (51.4mm internal)
Hf = 3.5m/100 x 1370 = 48m
Using 75mm HDPE (61.4mm internal)
Hf = 1.4/100 x 1370 = 19.2m
Hence;
TDH = DWL + HE + HF + HR
41.14m + (19m+6+3) + ( ) + 10m = m
41.14m + (19m+6+3) + ( ) + 10m = m
Therefore the duty point is 8.0m3/hr at 101.6m

7. Equivalent Length of pipe: 3 elbows: 3x2.6=7.8m
1 g/valve: 0.5m
1 water meter: 5.8m
1 NRV: 5.8m
Total equivalent Length = 19.9m
Therefore total pipe length = = m

9. Choose Grundfos SP9-18 c/w 4.0kW motor
Pump Selection considerations:
Efficiency
Casing size
Pump Positioning
Below PWL
Within a plain casing
Above the main aquifer
Otherwise
Flow sleeve
Derate motor (also for high water temps)

10. Cable sizing for Submersible Pumps
q = I x 1.73 x 100 x L x ρ x cos ϕ .
U x ∆U - (I x 1.73 x 100 x L x XL x sin ϕ)
Where,
q = Cross section of submersible drop cable [mm2]
L = Maximum cable length [m]
U = Rated voltage [V]
∆U = Voltage drop [%]
I = Rated current of the motor [A]
Cos ϕ = Power factor
ρ = Specific resistance Copper: ρ = [Ω mm2]
Aluminium: ρ = [Ω mm2]
Sin ϕ =
XL = Inductive resistance: x 10-3 [Ω/m]

11. Example Cable sizing Example of 4kW motor. L = 93+20 = 113 m U = 400 V
∆U = 3 % I = 9.6 A
Cos ϕ = ρ = Ω mm2
sin ϕ = XL = Ω/m
 Plugging in the values gives:
q = x 1.73 x 100 x 113 x x
400 x 3 - (9.6 x 1.73 x 100 x 113 x x 0.6)
= 3.15mm2
Therefore use 4mm2 submersible cable
As a rule of thumb, armoured cable (within 20m of borehole) is one size bigger

12. Example Cable sizing

13. Rule of thumb: Motor size x 2.5 to 3.0, Why?
Generator Sizing for Submersible pumps
Rule of thumb: Motor size x 2.5 to 3.0, Why?
Engine driven generators offered according to standard conditions;
Max. altitude above sea level: 150 m
Max. air inlet temperature: 30 °C
Max. humidity: 60%
If these limits are exceeded, derate accordingly;
Altitude: 3.5% for every 300 m above 150m asl (2.5% for turbo-charged engines).
Air inlet temperature: 2% for every 5.5 °C above 30 °C (3% for turbo-charged engines).
Humidity: 6% at 100% humidity.
Also;
Efficiency of alternator: 80%
35% voltage reduction during start-up

14. Generator Sizing for Submersible pumps
Generator Sizing Example
Generator Sizing for Submersible pumps
Generator Size (kVA) = Motor Size x Efficiency factor x Start up factor x Deration for altitude x Deration for temperature x Deration for humidity x 1.25
Parameters
Deration Factor
 Qty
Unit 
Naturally Aspirated
Turbo
Altitude
450 m
3.5%
2.5%
Temperature 40 0C
2.0%
3.0%
Humidity
80%
Motor Size
4.00 kW
Deration
Formulae
Efficiency of Alternator (80%)
=5.00
4kW/0.8 = 5kW
Derate for start up (35%)
=6.75
5kW*1.35 = 6.75kW
Derate for Altitude
=7.00
6.75kW/(1-((( )/300)*3.5%))= 7.0kW
Factor is 0 if the altitude is below 150m
Derate for temperature
=7.26
7.0/(1-(((40-30)/5.5)*2%))=7.26kW Factor is 0 if the temperature is below 300C
Derate for humidity (6% at 100% humidity)
=7.48
7.26kW/(1-3.0%) = 7.48kW
Convert to kVA (Multiply by 1.25)
=9.36
kVA
7.48kW*1.25 = 9.36kW

15. Coffee Break

16. Session 6: - More Compass Examples – submersible & surface
- Remote monitoring
Lunch Break
Session 7: - Grundfos Sizing Tool
- More Sizing Examples
Coffee Break
Session 8: Installation Checklist

17. Available Remote Monitoring Options
Lorentz PumpScanner/PumpManager
Grundfos CIU 273 SQFlex GRM
Grundfos AC in Development
Performance, alarms and historical data observed
Alerts via SMS or
Water flow rates
Motor current
Pressure – pressure sensors
Water level – level sensors
Input power, voltage, current
motor speed,
Pump status – on,off,trip

18. Thank you for your attention.
Contact: