WattAboutThat
New Member
- Joined
- Dec 15, 2021
- Messages
- 123
EG4 - 18kPV - String Calculations
Using Canadian Solar 385W Panels
This is my first time attempting to calculate
PV String series to determine maximum panels
i can safely put in a string and not exceed max voltage of the MPPT input.
Many of my assumptions may be incorrect,
and I am seeking feedback, to determine the safe quantity of panels in series per mppt.
——
Knowns:
——
18kPV Inverter Specs
per mppt
max volts 600V
max current 25A/15A/15A
max input 18kW
——
Canadian Solar Panel Specs
Wattage: 385W
VOC: 43.9V
ISC: 11.32A
Low-temperature coefficient (Pmax):
-0.34 % / °C
——
Assumptions:
I will design to use each mppt string
so all mppt strings are the same,
so designing to only use up to 15A on mppt1
so the i have the same size strings on each mppt.
Will assume max below zero temperature
for calculations to be -30F
Never has been that cold in Indiana to my knowledge, so just a safety margin.
——
Voltage Calcs using Temp Coeficient
Using Assumed -30F below Zero
(-30°F − 32) × 5/9 = -34.44°C
25C - (-34.44C) = 59.44C difference (delta)
43.9V x .34% = .14926V per degree C
.14826V x 59.44 = 8.8125744V per module
43.9V + 8.7125744V = 52.7125744V
in string of 10series
527.125744V per string
which is less than 600V
——
Current (Amps) Calcs
1 String (no paralleling) = 11.32A
which is less than 15A max
——
Watts per String
527.125744V x 11.32A = 5,967.06342W
x3 strings = 17,901.1903W
which is below 18kW of total input
——
Conclusions:
So assuming all of my calculations and assumptions are reasonably correct,
I believe it would be safe to install
3 Strings of 10 Canadian Solar Panels
one string per each mppt,
and remain safely below max V, max W, and not clip max A.
——
Please advise of any corrections
I should consider.
Thanks
Using Canadian Solar 385W Panels
This is my first time attempting to calculate
PV String series to determine maximum panels
i can safely put in a string and not exceed max voltage of the MPPT input.
Many of my assumptions may be incorrect,
and I am seeking feedback, to determine the safe quantity of panels in series per mppt.
——
Knowns:
——
18kPV Inverter Specs
per mppt
max volts 600V
max current 25A/15A/15A
max input 18kW
——
Canadian Solar Panel Specs
Wattage: 385W
VOC: 43.9V
ISC: 11.32A
Low-temperature coefficient (Pmax):
-0.34 % / °C
——
Assumptions:
I will design to use each mppt string
so all mppt strings are the same,
so designing to only use up to 15A on mppt1
so the i have the same size strings on each mppt.
Will assume max below zero temperature
for calculations to be -30F
Never has been that cold in Indiana to my knowledge, so just a safety margin.
——
Voltage Calcs using Temp Coeficient
Using Assumed -30F below Zero
(-30°F − 32) × 5/9 = -34.44°C
25C - (-34.44C) = 59.44C difference (delta)
43.9V x .34% = .14926V per degree C
.14826V x 59.44 = 8.8125744V per module
43.9V + 8.7125744V = 52.7125744V
in string of 10series
527.125744V per string
which is less than 600V
——
Current (Amps) Calcs
1 String (no paralleling) = 11.32A
which is less than 15A max
——
Watts per String
527.125744V x 11.32A = 5,967.06342W
x3 strings = 17,901.1903W
which is below 18kW of total input
——
Conclusions:
So assuming all of my calculations and assumptions are reasonably correct,
I believe it would be safe to install
3 Strings of 10 Canadian Solar Panels
one string per each mppt,
and remain safely below max V, max W, and not clip max A.
——
Please advise of any corrections
I should consider.
Thanks