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Re: [TRNSYS-users] Collector array shading Type 30 and radiation model

Cédric,
 You are correct; Type30 does assume an isotropic sky. We do not have any plans to change that. The isotropic model assumes that the sky is the same brightness no matter where you look. The Perez model augments the diffuse radiation near the horizon and in the vicinity of the sun so the isotropic model is a bit more conservative as far as unshaded diffuse radiation is concerned. However, as you notices, if you separate the rows by a very big distance in Type30 and feed it Perez unshaded radiation, you'll notice that all but the 1st row still show a little bit of shading. I would recommend that you run the simulation both ways (isotropic sky model with Type30 and Perez with Type30) and look at the annual difference in end result (auxiliary energy use perhaps) to judge whether the assumption is an important one or not.
Kind regards,
 David


On 3/31/2014 10:40, PAULUS Cedric 217865 wrote:

Dear TRNSYS-Users,

 

I would like to use the type of collector array shading between rows (type 30) connected to a weather data reading and processing (type 15) in order to simulate performance of large scale solar collector field.

 

I made some first check only with one row in order to find normally the same results as without collector shading. The beam radiation is the same (normal) but the total radiation is lower due to a lower diffuse radiation (not normal). When I check the type 30 model it seems that an isotropic sky model has been implemented in order to calculate the diffuse radiation. Am I right ?

 

As I prefer to use the Perez 1999 Model (5 for the parameter “Tilted Surface Radiation Mode” of type 15), I would like to know if this model was or is planned to be implemented in the type 30 ?

 

Thanks

Best Regards,

 

Cédric Paulus

CEA INES – DTBH/SBRT/LSHT | +33 (0)4 79 79 21 17

 



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