[TRNSYS-users] problem with sky temperature model

[Michaël Kummert]

Isabelle,

> Using Trnysys 16 with the Iisibat interface, I face one difficulty with 
> the sky temperature model. Could you help me?
> 
> The warning message I receive is the following:
> 
> /** Warning at time : 6295.000000
> Generated by Unit : 12
> Generated by Type : 69
> TRNSYS Message 317 : The sky temperature model has reported an 
> inconsistency in the supplied INPUTS. The inconsistency has been fixed 
> but should be investigated as it may lead to other problems. This error 
> can be caused by a dew point temperature above the ambient temperature, 
> a solar radiation value less than zero, or a cloud cover fraction less 
> than zero or greater than one
> Reported information : Not available
> 

As indicated by the message, there are 4 conditions that can trigger 
that warning:
- Dewpoint temperature > dry bulb temperature. This is easy to check
   with a plot of the difference between your inputs 2 and 1. If this is
   the cause, using both temperatures from Type 33 should make sure the
   inputs are consistent.
- Direct or diffuse radiation < 0 (bad connection for input 3 or 4, or
   bad data file)
- Cloud cover < 0 (Bad connection for input 5 or bad data file)
- Cloud cover > 1: Bad connection, likely because you use the output
   from Type 89 directly. Type 89 outputs the cloud cover in
   percents (i.e. 0..100) while Type 69 expects them between 0 and 1. You
   have to use an equation between the 2 types (let's just say this is
   for "historical reasons").

I hope this helps,

Michaël Kummert

PS: A bug has just been found in TRNSYS 16.00.0037 and before: Type 89 
for EPW and CWEC files outputs the cloud cover between 0 and 10, not 0 
and 100. This will be fixed in the next release.

-- 
_________________________________________________________

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 at engr.wisc.edu

SEL Web Site: http://sel.me.wisc.edu
TRNSYS Web Site: http://sel.me.wisc.edu/trnsys