Solar PV water pumping study - FINAL REPORT ... - UNDP, Namibia

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Feasibility Assessment for the Replacement of Diesel Pumps with Solar Pumps FINAL REPORT: September 2006 day. This cost savings includes the additional cost of trackers and the reduced cost of the PV array. 3.2.3.2 Summary breakeven analysis The comparison of PVPs and DPs over the whole operating range (10m to 200m and 3m 3 /day to 50m 3 /day) yields are multitude of results which will be presented in this section. It is important that a sensible pumping system is selected for each of the operating points. This refers mainly to the PVP selected (choosing the optimal PVP at each operating point) and to the pumping schedule selected for the diesel pump which seeks to optimise system efficiency without exceeding the borehole capacity through an excessive extraction rate. The years to breakeven has been calculated for the Grundfos, Lorentz and the TSP 2000+ PVPs in comparison to the short life diesel engine pumping system over the operating range being studied here. All results are based on the reference case listed in Table 3.7. Any deviation from the reference case is stated. Table 3.8 presents the summary years-to-breakeven results. The numbers in the cells represent the years to breakeven between PVP and DP. The yellow fields represent years to breakeven for the Grundfos and Lorentz PVPs (the two pumping models have similar life cycle costing results). The light green fields represent parallel Grundfos systems in the same borehole and the blue cells represent the Total Energie TSP 2000+ series of pumps. The diesel pumping schedule, which has a significant impact on the operating costs and the maintenance and replacement intervals, has been selected as follows: • If the daily flowrate is less than 10m 3 /day, then the diesel pump will pump every 2 nd day. If the daily flowrate is more than 10m 3 /day then it will pump every day. o If the daily flowrate is less than 10m 3 /day, then the duration of the pumping session will be 8 hours (pumping every second day). o If the daily flowrate is less than 20m 3 /day but more than 10m 3 /day, then the duration of the pumping session will be 6 hours (pumping every day). o If the daily flowrate is more than 20m 3 /day then the duration of the pumping session will be 8 hours (pumping every day). • The pumping intervals and the pumping hours per session are interlinked. The underlying criterion for the DP pumping schedule was that the diesel pump hourly flowrate does not exceed a quarter of the average daily flowrate selected for the PVP. This still requires a borehole with a stronger yield than would be required for a PVP delivering the same average amount of water. Table 3.8: Years to breakeven for PVP vs. DP over the operating range Head [m] Daily water [m³/day] 3 6 8 13 17 25 33 50 20 0.0 0.0 0.0 0.2 0.5 1.0 1.3 2.6 40 0.0 0.2 0.5 0.8 1.2 2.6 2.8 5.6 60 0.0 0.5 1.0 1.2 2.6 3.5 5.9 7.2 80 0.0 1.0 1.7 1.8 3.6 6.4 6.7 7.8 120 0.0 1.9 2.7 4.1 7.1 8.2 Diesel Diesel 160 0.2 Diesel Diesel Diesel Diesel Diesel Diesel Diesel 200 0.6 Diesel Diesel Diesel Diesel Diesel Diesel Diesel Page 32 of 76
Feasibility Assessment for the Replacement of Diesel Pumps with Solar Pumps FINAL REPORT: September 2006 As the hydraulic load increases the years to breakeven between PVPs and DPs increase! The grey fields marked “Diesel” indicate that the diesel option is to be selected. This is however not due to the diesel pump solution being more viable but due to the lack of a PVP option at these operating points. It is unlikely that the PVPs will develop much into the higher heads (120 to 200m) in combination with a hydraulic load of more than 1,500m 4 /day due to the lower anticipated volume of PVP sales for these particular borehole requirements. It is expected though that PVPs will be developed which can pump up to a 200m head and deliver up to 7.5m 3 /day (i.e. up to 1,500m 4 /day). However beyond that operating point the diesel pump will remain the pumping system of choice. Head [m] 240 200 160 120 80 40 0 0 10 20 30 40 50 60 Daily flowrate [m 3 /day] 250 m4/day: = 0 years 500 m4/day: < 1 year 1,000 m4/day: < 2.5 years 1,500 m4/day: < 4 years 2,000 m4/day: < 6 years 4,000 m4/day: < 8 years Figure 3.12: Hydraulic load lines with years to breakeven In Figure 3.12 hydraulic load lines are used to indicate what the breakeven periods are for PVP vs. DP. For example, the brown load line (250m 4 /day) shows that a PVP operating on that line will breakeven from the start. All PVPs operating to the left and the bottom of that hydraulic load line will also breakeven from the start. Similarly, PVPs operating on the red load line (1,000m 4 /day) will breakeven in less than 2.5 years, which decreases to 1 year as the operating point approaches the green load line (500m 4 /day). Head [m] 240 200 160 120 80 40 0 Solar pumps 0 10 20 30 40 50 60 Daily flowrate [m 3 /day] Diesel pumps 250 m4/day: = 0 years 500 m4/day: < 1 year 1,000 m4/day: < 2.5 years 1,500 m4/day: < 4 years 2,000 m4/day: < 6 years 4,000 m4/day: < 8 years Figure 3.13: Cost effective areas for pumping technologies Figure 3.13 shows the same graph as in Figure 3.12 but with coloured areas indicating the pumping technologies of choice. This assumes that pumping systems are fully utilised throughout the year. Page 33 of 76
Page 1 and 2: MINISTRY OF MINES AND ENERGY BARRIE
Page 3 and 4: Feasibility Assessment for the Repl
Page 25 and 26: Solar pump Start Diesel Pump Feasib
Page 41: Impact on Years-tobreakeven Feasibi
Page 45 and 46: Years to breakeven Feasibility Asse

Solar PV water pumping study - FINAL REPORT ... - UNDP, Namibia

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