🎓 Lesson 8
D5
Real-World Project Walkthrough
Solar PV system sizing is figuring out how many solar panels and batteries you need to reliably power a building or device using sunlight.
🎯 Learning Objectives
- ✓ Calculate daily energy demand in kWh from appliance load profiles and duty cycles
- ✓ Design a PV array size (kWp) using solar irradiance data, module specifications, and derating factors
- ✓ Analyze battery storage capacity (kWh) required for specified days of autonomy and depth-of-discharge limits
- ✓ Explain the impact of tilt angle, azimuth, shading, and temperature on annual system yield
- ✓ Apply IEEE 1547 and NEC Article 690 requirements to validate system design compliance
📖 Why This Matters
Getting PV sizing wrong leads to costly overdesign, dangerous underperformance, or grid rejection—especially in remote mining camps or off-grid blast-site monitoring systems where reliable power is mission-critical. A single undersized inverter can shut down ventilation during blasting prep; an oversized battery bank wastes capital and increases maintenance risk. This lesson bridges theory to real-world consequences in harsh, low-infrastructure environments.
📘 Core Principles
PV system sizing rests on three interdependent pillars: (1) Load characterization—aggregating AC/DC loads by time-of-use, including surge demands (e.g., detonator chargers); (2) Resource assessment—using measured or modeled GHI (Global Horizontal Irradiance) and POA (Plane-of-Array) irradiance, adjusted for local soiling, snow cover, and spectral effects; and (3) System modeling—applying layered derating factors (temperature, wiring, inverter efficiency, mismatch, aging) per IEC 61853 and ASHRAE Solar Radiation Handbook. In mining contexts, reliability trumps cost: autonomy must account for monsoon seasons, dust storms, and equipment downtime—not just average sun hours.
📐 PV Array Sizing (kWp)
This formula determines the minimum DC nameplate capacity needed to meet daily energy demand after accounting for all system losses. It is used early in design to scope hardware and inform structural and logistical planning.
Required PV Array Size (kWp)
P_{PV} = \frac{E_{load,AC} / \eta_{inv}}{\prod \text{Derating Factors} \times \text{PSH}}Calculates minimum DC-rated PV capacity to meet daily AC energy demand under site-specific conditions.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| P_{PV} | Required PV array size | kWp | DC nameplate capacity at STC |
| E_{load,AC} | Daily AC energy demand | kWh | Sum of all connected loads, including surge allowances |
| \eta_{inv} | Inverter efficiency | decimal | Typical weighted efficiency per CEC or datasheet (e.g., 0.92–0.96) |
| \prod \text{Derating Factors} | Cumulative system derating factor | decimal | Product of temperature, soiling, mismatch, wiring, aging, and other losses |
| PSH | Peak Sun Hours | h/day | Equivalent full-sun hours per day at the site, from NASA POWER or BOM data |
Typical Ranges:
Arid mining site (low soiling, high temp): 0.65 - 0.72
Tropical mining site (high humidity, frequent rain): 0.70 - 0.78
💡 Worked Example
Problem: A remote blast monitoring station requires 8.4 kWh/day (AC load). Inverter efficiency = 94%, average daily AC-to-DC derating = 0.78 (includes temp, soiling, mismatch, wiring), and module STC rating = 400 W. Calculate required kWp.
1.
Step 1: Convert AC demand to DC demand: 8.4 kWh / 0.94 = 8.94 kWh DC
2.
Step 2: Divide by derating factor: 8.94 kWh / 0.78 = 11.46 kWh DC generation needed at array level
3.
Step 3: Divide by peak sun hours (PSH) — use local TMY data: PSH = 4.2 h/day → 11.46 kWh / 4.2 h = 2.73 kWp
Answer:
The result is 2.73 kWp, which falls within the safe range of 2.5–3.0 kWp for this 8–10 kWh/day remote mining application.
🏗️ Real-World Application
At Newmont’s Boddington Mine (Western Australia), a solar-diesel hybrid system powers seismic monitoring stations near active blast zones. Engineers sized 3.2 kWp arrays (8 × 400 W bifacial modules) with 2-day battery autonomy (12 kWh LiFePO₄), factoring in 18% seasonal irradiance drop during winter and 25% soiling loss from mine dust. The design passed DNV GL certification and reduced diesel generator runtime by 74%, cutting emissions and maintenance costs for critical blast timing infrastructure.
🔧 Interactive Calculator
🔧 Open Solar PV System Sizing Calculator📋 Case Connection
📋 Solar PV System Sizing in Large-Scale Industrial Projects
Complex engineering requirements at scale
📋 Small-Scale Solar PV System Sizing Implementation
Limited resources and tight budget
📋 Solar PV System Sizing in Challenging Environments
Environmental and terrain challenges
📋 Cost Optimization in Solar PV System Sizing
Maintaining quality while reducing costs