Step 4 Power

Concept

This equation considers up to the PV array terminal only, excluding cable and inverter efficiency.

Pmax Maximum PV module power at ROC (W)

Pmax STC Maximum PV module power at STC (W)

fmm Power de-rate factor due to mismatch (decimal)

fdegrad Power degradation factor due to LID and aging (decimal)

ftemp p Power derating factor due to temperature (decimal)

fg Power derating factor due to irradiance (decimal)

fclean Power de-rate factor due to dirt (decimal)

fshade Shading factor (decimal)

Step 4.2 Calculate fdegrad

• 1. Power Degradation can be found from PV module datasheet from keywords below

• Power Warranty from 0 to 1 years

• Linear warranty from 0 to 1 years

• Minimum power output from year 1

Since we only compare 0 to 1 year, so can be simplify to:

From question, PV modules have 1st year power drops of 2% and linearly drops of 0.8% per annum until 25th year.

fdegrad = 1 - ( 2% / 100 ) = 0.98

Step 4.4 Calculate fg

fg = Gi /Gstc 

Gi Solar irradiance under ROC condition (Wm-2)

Gstc Solar irradiance at STC ,1000 Wm-2

fg = 992/1000 = 0.992 Wm-2 

Step 4.6 Calculate fshade

fshade = (100 % - Shading Loss %) /100

Shading loss may find through shading profile test in real life, refer to Step 3 Shading Profile.

fshade = 0.94 (Question Provided)