Hello
I previously sent 2 emails regarding potential bugs in
Type94a (PV 4 parameters model) and i can conclude the
following:
1- The
equation used to calculate the IAM has a wrong sign in the
third term (should be -6.26E-6 rather than +6.26E-6) (this
error actually in some cases made the IAM to be larger than
1 which is incorrect as far as I know)
2- The
last term in the equation used to calculate the IAM in the
manual is 1.4272E-8
while in the code is 1.472E-8
3- Different
equations than those indicated in the manual are used to
calculate the effective angle of sky diffuse and ground
diffuse radiation
4- The
variable SUNGND (surface ground diffuse radiation) is not
calculated anywhere in the code and it is not one of the
inputs
5- The
reference efficiency EFFREF does not account for the module
surface area so I believe it should equal: Vm*Im/SUNR*Area
instead of Vm*Im/SUNR
6- Equation
5.2.5-21 used to calculate the cell temperature in the manual
(page 74) I believe is incorrect [It should be
UL*(Tc-Ta)=TAU_Alpha*Gt*(1-Eff/TAU_Alpha) thus Tc=Ta+
TAU_Alpha*Gt*(1-Eff/TAU_Alpha)/UL ] (The equation is however
applied correctly in Type94 code script)
7-
Finally, I found out why Type94a overestimates the IAM losses
(when the option is activated). This is because the SUN
variable, (Effective global tilted irradiance) is calculated
after multiplying each irradiance component IAM multiplier
(i.e. TADIR, TAGND, TADIFF) by TAMAX (TAU-ALPHA at normal
incidence), which i believe is incorrect as the IL at
reference conditions already includes the effect of TAU-ALPHA
at normal incidence. This error is however corrected when the
IAM mode is disabled where the SUN variable is not multiplied
by TAMAX
could
someone confirm the aforementioned bugs?
Thank you
Regards,
Amir