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@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@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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