Key Formulas for Solar Power Plant

 

Keys formulas for Solar that every solar engineer should know-

1. Performance Ratio (PR)

Formula:
PR = (Actual Energy Output / (Irradiance × Area × Module Efficiency)) × 100

OR simplified:
PR = (Actual Output / Expected Output) × 100

2. Capacity Utilization Factor (CUF)

Formula:
CUF = (Actual Energy Output in kWh) / (Installed Capacity × 24 × Total Days) × 100

3. Specific Yield

Formula:
Specific Yield = Annual Energy Output (kWh) / Installed Capacity (kW)

4. Inverter Efficiency

Formula:
Inverter Efficiency = (AC Output / DC Input) × 100

5. Module Efficiency

Formula:
Module Efficiency = (Max Power Output / (Irradiance × Module Area)) × 100

6. System Efficiency (Overall)

Formula:
System Efficiency = (Total AC Energy Output / Total Solar Irradiation Input) × 100

7. System Losses (%)

Formula:
System Losses = 100% - PR

8. Plant Availability (%)

Formula:
Plant Availability = (Operational Hours / Total Possible Hours) × 100

9. Grid Availability (%)

Formula:
Grid Availability = (Grid Uptime Hours / Total Hours) × 100

10. Plant Downtime (%)

Formula:
Plant Downtime = (Downtime Hours / Total Operational Hours) × 100

Example:

2 inverters out of 50 are down for 2 hours:

Total inverter-hours = 50 × 2 = 100

Affected = 2 × 2 = 4

Downtime = (4 / 100) × 100 = 4%


11. Temperature Loss

Formula:
Temperature Loss = Temperature Coefficient × (Module Temperature - 25°C)

12. Irradiance Loss

Formula:
Irradiance Loss = (Standard Irradiance - Actual Irradiance) / Standard Irradiance × 100

13. Soiling Loss

Estimate Based On:
Soiling Loss = % Reduction in Output due to Dirt on Panels

14. Shading Loss

Estimate Based On:
Shading Loss = % Loss due to Nearby Obstructions

15. Mismatch Loss

Caused By:
Variations in module performance in a string.
Mismatch Loss = % Difference between Expected and Actual Output of Series Modules

16. Cable Loss (I²R Loss)

Formula:
Cable Loss = I² × R × Time

Where I = current, R = resistance


17. Transformer Losses

Consist of:

Core Loss (constant)

Copper Loss = I² × R

18. Degradation Loss

Formula:
Degradation Loss = Annual Degradation Rate × Number of Years


19. Availability Losses

Include:

Equipment Outages

Maintenance Time

Grid Disconnection

20. Energy Yield (kWh/kWp)

Formula:
Energy Yield = Total Energy Output (kWh) / Installed Capacity (kWp)