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 46.240216° + 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: 6.6 kWh , Insolation: 1.68 PSH.
| Month | Season | Daily Load | Insolation (PSH) | Design Ratio (PSH/Load) |
|---|---|---|---|---|
| January | Winter | 6.6 kWh | 2.59 | 0.39 |
| February | Winter | 6.6 kWh | 3.47 | 0.53 |
| March | Spring | 5.49 kWh | 4.77 | 0.87 |
| April | Spring | 5.49 kWh | 4.72 | 0.86 |
| May | Spring | 5.49 kWh | 4.04 | 0.74 |
| June | Summer | 5.41 kWh | 4.23 | 0.78 |
| July | Summer | 5.41 kWh | 4.63 | 0.86 |
| August | Summer | 5.41 kWh | 4.48 | 0.83 |
| September | Fall | 6.32 kWh | 4.51 | 0.71 |
| October | Fall | 6.32 kWh | 3.33 | 0.53 |
| November | Fall | 6.32 kWh | 1.91 | 0.3 |
| December | Winter | 6.6 kWh | 1.68 | 0.25 |