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Re: [TRNSYS-users] Sebha Weather Generation



Gassem,

I used Type 54a to generate meteorological year depending on average meteorological data of weather records at Sebha city at the south of Libya as shown below:

...

I got two questionable results:

1^st - *higher than normal daily ambient temperatures*, and my question here is regarding, what average of daily monthly ambient temperatures I should use in table 1 above, is it the average of Maximum daily monthly ambient temperature or the average of Minimum daily monthly ambient temperatures or the average of both such as:
Average daily monthly ambient Temp. = (Average Tmax + Average Tmin)/2    ……?

The values you need to provide are monthly averaged temperatures, so it is none of the options you propose if I am right. The last option would be the closest to what you need if you assume the average temperature during a day is the same as (Tmin+Tmax)/2. The concept of Monthly average daily "something" is only used for radiation in Type 54 (because you average the daily sum of irradiation levels).

2^nd – *the sum of Beam and Diffuse Irradiation give not the Global Irradiation as it must be…? and* *The values of Beam (direct) irradiation are higher than the values of Global irradiation during summer months ( the Table 3 below contains the resulted monthly integrated values of Solar Irradiation),* my question is where is the mistake…..? since :

/G_h must equal (G_bh + G_dh ), where: G_h is the Global Horizontal Irradiance, G_bh is the Beam Horizontal Irradiance and G_dh is the Diffuse Horizontal Irradiance./

I am assuming you are using outputs 7-9 of Type 54. Output 7 is the direct normal radiation (Gbn), not the direct (beam) horizontal radiation (Gb). So it should not be equal to (global horizontal - diffuse horizontal). If you want the beam horizontal radiation (Gb) you have to substract output 9 (Gd, diffuse horizontal) from output 7 (G, global horizontal). Or you can use Type 16, which you always need to do if you want to use sub-hourly time steps or calculate the radiation on a tilted surface.

Kind regards,

Michaël Kummert

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_________________________________________________________

Michaël Kummert

Solar Energy Laboratory - University of Wisconsin-Madison
1303 Engr Res Bldg, 1500 Engineering Drive
Madison, WI 53706

Tel: +1 (608) 263-1589
Fax: +1 (608) 262-8464
E-mail: kummert@engr.wisc.edu

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