[TRNSYS-users] Type1288 IAM

[Maximilian Stahlhut]

Jeff:

1) I checked the IAM data file. The IAM for beam radiation is 1 at 0,0.

Something else that makes me suspicious that I made a mistake in my model:
The longitudinal angle is 0° for the whole day and the transversal  
angle is equal to the incident angle on the sloped surface. Shouldn't  
it be the other way around for a PTC with single axis tracking?

2) I am looking only at the IAM for beam radiation (Output 4 Type1288).


Regards,

Maximilian


Zitat von Jeff Thornton via TRNSYS-users <trnsys-users at lists.onebuilding.org>:

> Maximilian,
>
> Two questions:
>
> 1) Did you look at the external data file you are using to confirm  
> that the IAM at 0,0 is equal to one?
>
> 2) Are you looking at the overall IAM or the IAM for beam radiation?  
>  It may be you are noticing the combined impact of a beam IAM and a  
> diffuse IAM less than one.
>
> Jeff
>
> ---
> Jeff Thornton
> President - TESS LLC
> 3 N. Pinckney Street, Suite 202, Madison WI USA 53703
> Office: (608) 274-2577  Fax: (608) 278-1475
> www.tess-inc.com
> E-Mail: thornton at tess-inc.com
>
>
> On 12/22/2020 5:31 am, Maximilian Stahlhut via TRNSYS-users wrote:
>> Hey,
>>
>> I am using Type1288 for modeling a Parabolic Trough Collector with
>> single-axis tracking.
>> In Type 1288, the IAM values are read from an external data file which
>> contains the biaxial IAMs of the collector. For reading this data
>> file, the longitudinal and transversal incident angle are needed. As
>> far as I know, they are calculated by:
>>
>> Tranverse = ATAN(SIN(Zenith
>> angle)*SIN(ABS(Azimuth-SolarAzimuth))/COS(IncidentAngle_Beam))
>>
>> Longitudinal = ABS(ATAN(TAN(Zenith
>> angle)*COS(Azimuth-SolarAzimuth))-CollectorSlope)
>>
>> For Tranverse=0° and Longitudinal=0° I would have expected an IAM of
>> 1. However, Type1288 calculates a smaller one at this timestep.
>>
>>
>> Does anyone has experience using this Type or using a different type
>> with a biaxial IAM input file and a similar problem occurred? Or have
>> I missed something in my calculations?
>>
>>
>>
>> Regards,
>>
>> Maximilian
>>
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