Tag Archive for: Off-grid System

If you’re planning to power a 100kWh load continuously (24/7) using solar panels and a battery energy storage system (BESS), it’s not as simple as just multiplying watts. You need to factor in weather conditions, seasonal sunlight availability, cloudy days, and energy efficiency. This blog will guide you step-by-step on how to size your system properly using formulas, examples, and visual data.

📌 What You’ll Learn:

• How to calculate required solar panel capacity
• Why yearly weather data is critical
• How to handle cloudy days and winter months
• Battery sizing for different backup durations
• Example formulas and real-world values

🔧 Step 1: Understand Your Load

Let’s say your system must support a 100 kWh per hour load.

• 24 hours/day × 100 kWh = 2,400 kWh per day
• That’s your daily energy demand from solar + battery.

🌍 Step 2: Analyze Your Location’s Solar Irradiance

Your geographic location heavily influences how much sunlight you receive—measured in Peak Sun Hours (PSH).

👉 You can get this data from tools like PVWatts, NASA SSE, or Solcast.

🧮 Step 3: Calculate Required Solar Panel Capacity

Formula:

textCopyEditRequired Solar Capacity (kW) = Daily Load (kWh) ÷ (PSH × Derating Factor)

• Daily Load = 2,400 kWh
• Derating factor (system losses) = ~0.8

🌥️ Why Consider Cloudy Days?

Even if your area has high annual irradiance, you’ll still face days with poor sun exposure. For mission-critical applications, your system must:

• Be oversized for worst-case scenarios.
• Include battery backup for 1–3 days.
• Use hybrid systems (e.g., gensets or grid backup) if needed.

❄️ Considerations for Winter Months

Winter brings:

• Lower sun angles
• Shorter daylight
• Snow cover (for northern regions)

???? This reduces effective PSH and increases your dependence on storage or supplemental power.

⚡ Step 4: Size the BatteryEnergy Storage System for Backup

Battery Energy Storage System should store enough energy to power the load during non-sunny hours or failures.

Formula:

textCopyEditBattery Capacity (kWh) = (Daily Load × Days of Autonomy) ÷ (DoD × Efficiency)

• Daily Load = 2,400 kWh
• Depth of Discharge (DoD) = 0.8
• Round-trip Efficiency = 0.9

✅ Tips for Choosing Solar Panels

• ✔️ Use Tier-1 panels with high efficiency (≥21%)
• ✔️ Consider bifacial panels if space allows
• ✔️ Use anti-reflective coating for dust-heavy areas
• ✔️ Install with adjustable tilt for seasonal optimization

✅ Tips for Choosing Batteries Cells for BESS

• ✔️ Choose Lithium Iron Phosphate (LFP) for safety and long life
• ✔️ Look for modular scalability
• ✔️ Integrate with a good BMS and EMS
• ✔️ Use temperature-controlled enclosures for extreme climates

🔄 Hybrid Solutions for Reliability

When powering a 100kWh continuous load, consider a hybrid setup:

• ???? Solar + Battery + Diesel: For industrial backup
• ???? Solar + Grid + Battery: For grid-tied systems
• ????️ Solar + Wind + Battery: For off-grid redundancy

📊 Real Use Case Example

Scenario:

• Location: Northern India
• PSH (winter): 4 hours
• Load: 100kWh × 24 = 2,400kWh/day
• Solar Size = 2,400 ÷ (4.0 × 0.8) = 750 kW
• Battery for 2 days = 2,400 × 2 ÷ (0.8 × 0.9) ≈ 6,667 kWh

🧠 FAQs

📌 Conclusion

Designing a solar + battery system for a 100kWh 24/7 load isn’t just about matching numbers—it’s about planning for the worst day of the year, not the best. Location-specific solar data, battery autonomy, system losses, and seasonal variations must all be part of your sizing strategy.