Author Archives: Raeli Hydro

Solar borehole pumps require significantly less long-term maintenance than electric ones, thanks to fewer moving parts and no reliance on grid power. Electric pumps face more frequent repairs from wear, surges, and dust in Kenyan apartments.

Maintenance Frequency

Solar systems need cleaning of panels 2-4 times yearly (5-10 minutes each) and annual controller checks, totaling under 2 hours/year. Electric submersibles demand quarterly inspections of motors, capacitors, and seals—often 4-6 hours/year plus downtime during peak apartment use.

Brushless DC motors in solar pumps avoid windings that degrade in electric AC models, cutting failure rates by 50-70% over 10 years.

Cost Over 10 Years

Solar maintenance runs KSh 10,000-20,000 total (cleaning, minor inverter tweaks), versus KSh 50,000-150,000 for electric (servicing, parts like bearings every 2-3 years). In Gauteng or Nairobi, electric repairs spike during loadshedding; solar stays operational.

Longevity Factors

Solar pumps last 15-25 years overall (panels 25-30 years, pump 10-15), with minimal degradation. Electric models hit 8-15 years, shortened by corrosion in borehole sediment and voltage fluctuations common in apartments.​

Raeli Hydro notes solar excels for multi-unit blocks: no fuel or electricity bills amplify savings, and simple upkeep suits remote rooftops.​

Lithium iron phosphate (LiFePO4) batteries provide the most reliable backup for solar borehole pumps in apartments, offering 6-12 hours of runtime during cloudy periods or nights. They pair seamlessly with MPPT controllers in systems like those from Raeli Hydro, ensuring steady water supply to multiple units.​

Why Battery Backup Matters

Apartments demand consistent flow (10-20m³/hour) beyond sunlight hours, unlike standalone solar setups. Batteries store excess daytime energy, bridging gaps in Kenya’s variable weather while avoiding full hybrid electric costs. Deep-cycle LiFePO4 outperforms lead-acid by 3x cycle life (4,000+ cycles) with zero maintenance.

Top Battery Recommendations

EcoFlow DELTA Pro (3.6-21kWh expandable)

Scales for 5-10HP pumps, powering 48V borehole motors up to 8 hours at 15m³/h. Fast solar recharge (2-3 hours) and app monitoring suit multi-unit rooftops. Cost: KSh 500,000-1.2M for 6kWh base.

48V AGM/GEL Deep-Cycle Banks (200-400Ah)

Budget option for Narrow Series pumps; two 48V/200Ah units deliver 4-6 hours backup. Parallel wiring matches 1-3kW solar arrays common in 20-50 unit blocks. Lifespan: 5-7 years with proper ventilation.​

Jackery Solar Generator 2000 Plus

Portable 2kWh unit with 240V output for smaller 1-2HP pumps, expandable to 12kWh. Ideal for Nairobi apartments; runs 5-7 hours on partial charge. Includes UPS pass-through for grid tie-in.​

Sizing and Integration Tips

Calculate needs: pump watts × hours ÷ battery voltage × efficiency (85%). For 2kW pump over 8 hours: ~48V/600Ah bank. Use 48V systems to minimize cabling losses; pair with hybrid inverters for AC backup. Raeli Hydro installs position batteries in shaded enclosures, extending life in Gauteng heat.​

AC grid/generator backups complement batteries for 24/7 reliability, but pure solar-battery cuts bills 80% long-term in load-shedding zones

Solar borehole pumps offer sustainable, cost-free operation ideal for Kenya’s sunny climate and frequent power outages, while electric pumps provide reliable, high-capacity performance for constant apartment demands. The best choice depends on budget, sunlight availability, and water usage patterns in multi-unit buildings.

Performance and Reliability

Electric submersible pumps like Grundfos SQ deliver consistent flow (10-20m³/hour) at full capacity 24/7, regardless of weather, making them suitable for 50+ unit complexes with peak evening demands. Solar pumps match this during peak sun (6-8 hours/day) but drop 30-50% output on cloudy days without batteries; DC solar models excel up to 4kW for moderate apartment needs.

Solar systems shine in off-grid Nairobi suburbs, pumping 5,000-15,000 liters daily from 50-150m depths when paired with MPPT controllers.

Cost Breakdown

Solar setups cost KSh 300,000-800,000 upfront (pump + 5-10kW panels + inverter), but zero electricity bills yield payback in 2-3 years versus electric pumps’ KSh 150,000-500,000 initial + KSh 5,000-15,000 monthly grid costs. Electric options suit grid-connected apartments; hybrids combine both for backup.

Installation and Maintenance

Solar requires open roof space for panels and simple DC/AC setups, with Raeli Hydro installs taking 1-2 days. Electric needs stable three-phase power and control panels; both use similar submersible designs but solar avoids wiring to grids prone to load-shedding.​

Maintenance favors solar: no motors exposed to surges, just annual panel cleaning. Electric pumps demand quarterly checks for windings and capacitors in dusty Kenyan conditions.​

Best for Apartments

Choose solar for 20-50 unit blocks in sunny areas like Nyeri—energy independence cuts bills 100% long-term. Electric wins for high-rises needing nighttime supply; add solar-hybrid for versatility. For TDH-optimized systems (90-150m), both handle 50-65mm pipes effectively.

Larger pipe sizes significantly reduce friction losses in apartment water distribution systems by allowing water to flow at lower velocities. This minimizes turbulence and pressure drops, ensuring consistent supply across multiple units.

Friction Loss Principles

Friction loss occurs as water rubs against pipe walls, increasing with smaller diameters, higher flow rates, and longer runs. The Hazen-Williams equation shows loss drops dramatically with diameter increases: ΔP ∝ 1/D^1.17, where D is internal diameter. For borehole-fed apartments, aim for velocities under 2.5 m/s to avoid noise and erosion.

Recommended Pipe Sizes

Use these sizes based on flow demand from borehole pumps (e.g., 10-20m³/hour for 50 units):

• Main supply line (borehole to tank): 50-65mm (2-2.5″) for 15m³/h, cutting loss by 50% vs 40mm.

• Branch lines to floors: 32-40mm (1.25-1.5″) per 10-15 units.

• Individual apartment feeds: 25-32mm (1-1.25″) to maintain 1-2 bar pressure.

Material and Layout Tips

Opt for smooth PE or PVC pipes (C-factor 150) over galvanized steel to halve losses. Minimize elbows (add 5-10m equivalent length each) and use sweep bends. For multi-apartment risers, step down sizes gradually: 63mm main to 40mm per floor.​

In Kenyan complexes like those served by Raeli Hydro, upsizing mains from 40mm to 50mm saves 3-5m TDH, matching pumps like Grundfos SQ perfectly while boosting ROI through lower energy use.​

Calculating Total Dynamic Head (TDH) ensures your borehole pump delivers adequate pressure for multi-apartment water supply. TDH represents the total resistance the pump must overcome, measured in meters or feet.

TDH Formula Basics

The standard equation is TDH = Static Head + Friction Loss + Pressure Head (if applicable). Static head is the vertical distance from the water surface in the borehole to the delivery point, like a rooftop tank. For apartments, include drawdown—the drop in water level during pumping—and lift to multiple floors.

Step 1: Measure Static Head

Start with dynamic water level: pump intake depth plus drawdown. Add vertical lift to the highest outlet, such as 30m borehole depth + 20m to tank + 15m building height = 65m base static head. In multi-unit setups, factor peak demand drawdown (e.g., 5-10m for 10-20m³/hour flow).

Step 2: Calculate Friction Losses

Friction loss arises from pipe length, diameter, fittings, and flow rate. Use pipe charts: for 50mm PE pipe at 15m³/hour, loss is ~2-3m per 100m horizontal run. Convert fittings to equivalent pipe length (e.g., elbow = 5m pipe). Total: (actual length / 100) × friction factor per manufacturer charts.​​

Example: 200m pipe + 50m fittings equivalent at 2.5m/100m loss = 6.25m friction.

Step 3: Account for Multi-Apartment Demands

Apartments amplify TDH via branching pipes and pressure needs. Add 10-20% buffer for simultaneous use across 20-50 units. If boosting to 2-3 bar per floor, convert pressure: 1 bar ≈ 10m head. Solar or VFD pumps in Kenya handle variable loads efficiently.​

Complete Calculation Example

For a 50-unit Nairobi complex:

• Borehole: 80m total depth, 10m drawdown, intake at 70m.

• Lift: 25m to tank.

• Pipes: 150m horizontal/vertical (40mm main, branches), 10 elbows (50m equiv.), flow 12m³/h.

• Static: 70m + 25m = 95m.

• Friction: (200m total / 100) × 1.8m/100m = 3.6m.

• TDH = 95 + 3.6 = 98.6m (round to 100m).

Tools and Tips for Accuracy

Use apps like Pump Selector or Grundfos tools for precise friction charts. Measure actual flow with a test pump. For Raeli Hydro installs, site surveys confirm drawdown via step-drawdown tests. Oversize by 10-20% for longevity in sandy Kenyan aquifers.​

This method matches pumps like Grundfos SQ (up to 150m TDH) to your setup, preventing cavitation or dry-run.​