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

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

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

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

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

Sustainable yield: 60-70% = 7.2 - 8.4m3/hr TDH Example Tested yield Qy = 12m3/hr Sustainable yield: 60-70% = 7.2 - 8.4m3/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) + (3.255+ 48) + 10m = 130.4m 41.14m + (19m+6+3) + (3.255+19.2) + 10m = 101.6m Therefore the duty point is 8.0m3/hr at 101.6m

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 = 1350+19.9 = 1369.9m

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)

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 = 0.025 [Ω mm2] Aluminium: ρ = 0.028 [Ω mm2] Sin ϕ = XL = Inductive resistance: 0.078 x 10-3 [Ω/m]

Example Cable sizing Example of 4kW motor. L = 93+20 = 113 m U = 400 V ∆U = 3 % I = 9.6 A Cos ϕ = 0.8 ρ = 0.025 Ω mm2 sin ϕ = 0.6 XL = 0.000078 Ω/m  Plugging in the values gives:   q = 9.6 x 1.73 x 100 x 113 x 0.025 x 0.8 . 400 x 3 - (9.6 x 1.73 x 100 x 113 x 0.000078 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

Example Cable sizing

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

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-(((450-150)/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

Coffee Break

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

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 e-mail Water flow rates Motor current Pressure – pressure sensors Water level – level sensors Input power, voltage, current motor speed, Pump status – on,off,trip

Thank you for your attention. Contact: solarquery@iom.int