Mr Youkee Kong 
Application of Solar Pumps in Water Treatment
Solar water pumps are an ideal and advanced solution for pool circulation and filtration systems. They are particularly suitable for users in areas with abundant sunlight, high electricity costs, strong environmental awareness, and those seeking long-term economic returns. With the maturity of solar technology and declining costs, they are becoming an increasingly popular choice for new pool construction or renovation.
STEP 1:
Determining Core System Parameters
1. Calculating Required Circulation Flow Rate (Q)
The flow rate determines the "renewal" speed of the water body and is critical for ensuring filtration and disinfection efficacy.
A. For Pool Applications :
Core Formula : Required flow rate Q (m³/h) = Total pool volume (m³) ÷ Required turnover period (hours)
Parameter Analysis :
• Total pool volume : Pool length (m) × width (m) × average depth (m)
• Turnover period : Refers to the time required to filter the entire pool volume, determined by industry standards or regulations.
- Public/Commercial Pools : Stringent requirements, shorter turnover periods (typically 4-6 hours per cycle).
- Private Pools : Longer turnover periods, usually 6-8 hours (3-4 cycles per day).
- Common Simplified Standard : The industry often uses "daily turnover cycles" for estimation. For example, private pools are recommended to circulate 3-4 times per day.
Q (m³/h) = Total pool volume (m³) × Daily turnover cycles ÷ 24 hours
Example :
A 50 m³ private pool requires a turnover every 8 hours.
A 50 m³ private pool requires a turnover every 8 hours.
Q = 50 m³ ÷ 8 h = 6.25 m³/h
B. For Water Treatment Applications (e.g., Landscape Water Bodies, Ecological Pools) :
The principle is similar, with the turnover period determined by water quality requirements (e.g., preventing algae growth), which may be 12 or 24 hours per cycle. The formula remains the same.
Q = Total water volume ÷ Desired turnover period
STEP 2. Determining Total Dynamic Head (H_total)
This is the core parameter for pump selection, representing the total resistance the pump must overcome.
H_total = Static head (H_static) + Friction head (H_friction) + Equipment pressure loss (H_equipment)
Parameter Analysis :
• Static head (H_static) : Vertical height difference between the pump outlet and the highest point of the system. For pools, if the pump and filter are level with the water surface, this term may be 0.
• Friction head (H_friction) : Pressure loss caused by water flowing through pipes, bends, and valves. This depends on pipe length, diameter, material, and flow velocity and typically dominates the total head.
• Equipment pressure loss (H_equipment) : Pressure loss when water passes through filters (significant difference between new and dirty filter media), disinfection equipment (UV, chlorine feeders), heaters, etc. This is critical data that must be obtained from equipment suppliers!
- A clean sand filter typically has a pressure loss of ~3-5 meters of head (m).
- A UV disinfection unit has a pressure loss of ~2-3 meters.
- Total equipment pressure loss is the sum of individual equipment losses.
Example Estimation :
• Static head H_static = 0 m (system installed horizontally)
• Filter pressure loss H_filter = 5 m
• UV equipment pressure loss H_uv = 3 m
• Pipe friction head H_friction = 4 m (estimated)
H_total = 0m + 5m + 3m + 4m = 12 meters
Must fully match the pump’s voltage, power, and type (DC/AC).
Key features:
Must include MPPT functionality and core protection features such as dry-run protection (to prevent pump damage if the water source is depleted).
STEP 3: Pump and Solar System Selection
1. Calculating Required Pump Flow Rate (Q_pump)
Core formula:
Q_pump (m³/h) = Q_day (m³/day) ÷ Average peak sunshine hours per day (T, unit: hours)
Difference from agriculture: Livestock farming typically supplies water directly to troughs or storage tanks, with irrigation efficiency (η) usually close to 1 (unless there is severe pipe leakage), allowing the formula to be simplified.
Parameter analysis: Average peak sunshine hours per day (T): Typically 4-6 hours (e.g., 5 hours). This means the system must pump the daily water requirement within 5 hours.
Example calculation: Q_pump = 11 m³/day ÷ 5 h/day = 2.2 m³/h
Conclusion: You need to select a pump with a flow rate of at least 2.2 m³/h at a head of 75 meters.
2. Pump Selection
Type selection:
• Deep wells: Submersible pumps are the clear choice.
• Surface water (rivers, lakes): For low heads, surface centrifugal pumps can be used, but suction lift limitations must be considered.
Method: Based on H_total = 75m and Q_pump = 2.2 m³/h, consult the pump manufacturer’s performance curve (H-Q curve) to identify a suitable pump model and determine the input power at the operating point. Assume the required power is 0.8 kW (800W).
Parameter analysis:
• System total efficiency (η_sys): Assume 0.9 (MPPT controller efficiency + line losses).
• Redundancy factor: Assume 1.2-1.3 to ensure system operation under slight dust, elevated temperatures, or suboptimal sunlight.
Example calculation:
P_pv = (0.8 kW ÷ 0.9) × 1.3 ≈ 1.16 kW Conclusion: You need to install solar panels with a total power of approximately 1.2 kW.
Core formula:
Q_pump (m³/h) = Q_day (m³/day) ÷ Average peak sunshine hours per day (T, unit: hours)
Difference from agriculture: Livestock farming typically supplies water directly to troughs or storage tanks, with irrigation efficiency (η) usually close to 1 (unless there is severe pipe leakage), allowing the formula to be simplified.
Parameter analysis: Average peak sunshine hours per day (T): Typically 4-6 hours (e.g., 5 hours). This means the system must pump the daily water requirement within 5 hours.
Example calculation: Q_pump = 11 m³/day ÷ 5 h/day = 2.2 m³/h
Conclusion: You need to select a pump with a flow rate of at least 2.2 m³/h at a head of 75 meters.
2. Pump Selection
Type selection:
• Deep wells: Submersible pumps are the clear choice.
• Surface water (rivers, lakes): For low heads, surface centrifugal pumps can be used, but suction lift limitations must be considered.
Method: Based on H_total = 75m and Q_pump = 2.2 m³/h, consult the pump manufacturer’s performance curve (H-Q curve) to identify a suitable pump model and determine the input power at the operating point. Assume the required power is 0.8 kW (800W).
3. Calculating Photovoltaic Array Power (P_pv)
Core formula: P_pv (kW) = [Pump input power (kW) ÷ System total efficiency (η_sys)] × Redundancy factorParameter analysis:
• System total efficiency (η_sys): Assume 0.9 (MPPT controller efficiency + line losses).
• Redundancy factor: Assume 1.2-1.3 to ensure system operation under slight dust, elevated temperatures, or suboptimal sunlight.
Example calculation:
P_pv = (0.8 kW ÷ 0.9) × 1.3 ≈ 1.16 kW Conclusion: You need to install solar panels with a total power of approximately 1.2 kW.
STEP 4: Special Considerations for Water Treatment/Pool Scenarios
Runtime vs. Sunlight Hours
Key Difference : Pool filtration requires running for a sufficiently long duration each day (typically 8-12 hours), rather than completing all work within the 4-6 hours of peak sunlight. Therefore, the system design goal is to use solar energy to offset the electricity costs required for this 8-12 hour operation, rather than pumping large volumes of water in a short time. Solution : Increase the photovoltaic (PV) panel capacity (using a higher redundancy factor, e.g., 1.5) to ensure sufficient power to drive the pump even during periods of weaker sunlight.
Battery Storage vs. Grid Connection
Optimal Solution (Recommended) : "PV Direct Drive + Grid Backup" mode. The system prioritizes solar energy and automatically switches to grid power when sunlight is insufficient (e.g., cloudy days, evenings), ensuring uninterrupted filtration cycles. This is the most stable, efficient, and cost-effective solution.
Pure Off-Grid Solution : If no grid connection is available, a large battery bank must be configured, but this significantly increases costs and maintenance burdens and is generally not recommended.
Pump Corrosion Resistance : The pump material must be resistant to corrosion from pool chemicals (e.g., chlorine), such as reinforced plastic or 316 stainless steel.
System Pressure Monitoring : Consider installing a pressure gauge to monitor filter clogging. Increased pressure loss leads to reduced flow, necessitating backwashing or filter media replacement.
Runtime vs. Sunlight Hours
Key Difference : Pool filtration requires running for a sufficiently long duration each day (typically 8-12 hours), rather than completing all work within the 4-6 hours of peak sunlight. Therefore, the system design goal is to use solar energy to offset the electricity costs required for this 8-12 hour operation, rather than pumping large volumes of water in a short time. Solution : Increase the photovoltaic (PV) panel capacity (using a higher redundancy factor, e.g., 1.5) to ensure sufficient power to drive the pump even during periods of weaker sunlight.
Battery Storage vs. Grid Connection
Optimal Solution (Recommended) : "PV Direct Drive + Grid Backup" mode. The system prioritizes solar energy and automatically switches to grid power when sunlight is insufficient (e.g., cloudy days, evenings), ensuring uninterrupted filtration cycles. This is the most stable, efficient, and cost-effective solution.
Pure Off-Grid Solution : If no grid connection is available, a large battery bank must be configured, but this significantly increases costs and maintenance burdens and is generally not recommended.
Pump Corrosion Resistance : The pump material must be resistant to corrosion from pool chemicals (e.g., chlorine), such as reinforced plastic or 316 stainless steel.
System Pressure Monitoring : Consider installing a pressure gauge to monitor filter clogging. Increased pressure loss leads to reduced flow, necessitating backwashing or filter media replacement.
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