[TRNSYS-users] Potential Bugs with Type94a

[David BRADLEY]

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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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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