[TRNSYS-users] Potential Bugs with Type94a

Fri Apr 25 17:03:43 PDT 2014

Hi Amir,

To follow up on David's email. I will be out on your campus next week
(likely Friday) for a training session. Potentially go through it is in
person. 

Interim solutions: Do you have a FORTRAN compiler? The developers are
investigating  a fix however I have found that being able edit the FORTRAN
behind the type to make them suit your needs is very useful. You could
update the FORTRAN and recompile yourself. See the programmers guide user
manual. We could run through this next week if you're not familiar. 

Otherwise, have you looked at TYPE 194? Does this have the same errors? 

Cheers,
Jeremy 

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From: David BRADLEY [mailto:d.bradley at tess-inc.com] 
Sent: Saturday, 26 April 2014 12:19 AM
To: TRNSYS users mailing list at the Solar Energy Lab, UW-Madison;
nashed.amir at gmail.com
Subject: Re: [TRNSYS-users] Potential Bugs with Type94a

Amir,
  Thank you for the detailed email. We are looking into Type94 and will let
you know what we discover.
Best,
  David

On 4/25/2014 00:12, Amir Nashed wrote:

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

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