Solar-Powered Telecom Tower in Coastal Kenya

Scenario

A 4G/LTE base station operated by a rural telecom provider near Mombasa, Kenya powers critical connectivity for 12 villages. Site constraints include high humidity (>85% RH), salt-laden coastal air, limited maintenance visits (quarterly), and strict uptime SLA (>99.5%). Batteries must tolerate high ambient temps (up to 45°C), and the system must sustain 5-day autonomy during monsoon cloud cover. Space and weight are constrained — only floor-mounted 48 V battery racks permitted.

Given Data

• Daily Energy Consumption: 4,600 Wh
• Autonomy Days: 5
• Battery Voltage: 48 V
• Depth of Discharge (DoD): 0.6 (thermal derating per manufacturer spec at 40°C+)
• Peak Load Power: 3,100 W (radio + backhaul + cooling fans)
• Inverter Efficiency: 0.94
• Power Factor: 0.92

Calculation

Battery Capacity (Ah): Required usable energy = 4,600 Wh × 5 = 23,000 Wh Total battery energy needed = 23,000 Wh ÷ 0.6 = 38,333.3 Wh → Battery capacity (Ah) = 38,333.3 Wh ÷ 48 V = 798.6 Ah

Inverter Size (VA): Peak apparent power = 3,100 W ÷ (0.94 × 0.92) = 3,100 ÷ 0.8648 ≈ 3,585 VA

Result and Decision

Selected: A single 48 V, 800 Ah lithium iron phosphate (LiFePO₄) rack-mount battery (e.g., Pylontech US3000C × 4 in series-parallel), delivering 38.4 kWh nominal (23.04 kWh usable), meeting autonomy and thermal resilience requirements. Paired with a 4,000 VA outdoor-rated inverter (e.g., SMA Sunny Island 4.4) with IP65 enclosure, integrated DC-coupled PV charge controller, and corrosion-resistant aluminum housing.

Lesson

In high-humidity, high-temperature environments, battery DoD must be reduced beyond datasheet ratings — even robust LiFePO₄ degrades faster above 35°C; specifying 60% DoD instead of 80% doubled cycle life in field testing and avoided premature replacement within Year 2.