Step 4: Critical Design Month
Location & Resource (NREL API)
NREL Parameters & Assumptions
What is PSH (Peak Sun Hours)?
PSH is not "hours of daylight". It is the equivalent number of hours at standard intensity (1000 W/m²) if all daily solar energy were compressed.
Example (1.68 PSH):
In winter, you might have 9 hours of daylight, but only 1.68 PSH. This means a 400W panel will only generate
In winter, you might have 9 hours of daylight, but only 1.68 PSH. This means a 400W panel will only generate
400W × 1.68h = 672Wh per day.
Tilt Angle & Azimuth
This system uses an Off-Grid Winter Optimization strategy:
• Azimuth: South (180°)
• Tilt Angle: Latitude 46.227807° + 15°
Why +15°? To position the panels as perpendicular to the sun as possible during winter months when the sun is low.
Analysis Conclusion
The system's weakest month is: December
Load: 7.67 kWh , Insolation: 2.23 PSH.
| Month | Season | Daily Load | Insolation (PSH) | Design Ratio (PSH/Load) |
|---|---|---|---|---|
| January | Winter | 7.67 kWh | 2.75 | 0.36 |
| February | Winter | 7.67 kWh | 3.53 | 0.46 |
| March | Spring | 6.56 kWh | 4.71 | 0.72 |
| April | Spring | 6.56 kWh | 4.78 | 0.73 |
| May | Spring | 6.56 kWh | 4.24 | 0.65 |
| June | Summer | 6.48 kWh | 4.12 | 0.64 |
| July | Summer | 6.48 kWh | 4.82 | 0.74 |
| August | Summer | 6.48 kWh | 4.68 | 0.72 |
| September | Fall | 7.39 kWh | 4.78 | 0.65 |
| October | Fall | 7.39 kWh | 3.6 | 0.49 |
| November | Fall | 7.39 kWh | 2.25 | 0.3 |
| December | Winter | 7.67 kWh | 2.23 | 0.29 |