Creating climate file

[RM_Sintef]

Hi,

I need to create a climate file from some real data coming from a weather station.
I found the excel file ''CreateClimateFile'' in the WUFI folder and I read some guidelines, but I am wondering about something. The data I got are sub-hourly, but the time interval is not always constant, sometimes 16 min., sometimes longer. I am trying to export in .kli format, but I am a bit uncertain about how WUFi will read it. Is it necessary to have contsant time intervals to create such a climate file?

[Thomas]

Hi RM_Sintef,

you can arbitrarily mix different time intervals in a *.KLI file. WUFI automatically adjusts the calculational time step width in order to always have an integer number of calculational time steps in a climate time interval.

So *.KLI is the most fexible file format as far as the time steps are concerned. On the other hand, KLI being WUFI's oldest weather file format, it is limited to contain only rain, solar radiation and outdoor and indoor temperature and humidity (and a constant value for the barometric pressure). If you need more weather elements for your simulation, you must use one of the other file formats (recommended: WAC), but all of these only have fixed one-hour time steps.

Regards,
Thomas

[RM_Sintef]

Hi again,

Thanks for your reply!
So if WUFI automatically adjusts the calculational time step width for the weather file, will I have the same time steps for my results?

Regarding the weather file format, which are the most important parameters that *.KLI format is not taking into account?

Regards

[Thomas]

So if WUFI automatically adjusts the calculational time step width for the weather file, will I have the same time steps for my results?

Yes, WUFI compares the user-requested time step (in the Numerics dialog) with the current weather file step, and if the weather file step does not correspond to an integer number of calculational time steps, WUFI adjusts the calculational time step accordingly (see the help file). So - depending on the details - you will in most cases get results with the same irregular time steps as used for the weather file.

Regarding the weather file format, which are the most important parameters that *.KLI format is not taking into account?

In particular, there is no atmospheric or terrestrial counterradiation, so radiative night-time cooling with its effects on dew deposition and reduced drying potential can not be taken into account. There is also no wind, so no wind-dependent surface transfer coefficients can be taken into account.

Note also that rain and solar radiation are directional quantities, so the effect they have on the building component depends on the direction they come from, relative to the orientation of the building. Only their vectorial component hitting the surface vertically is to be taken into account, and with all other climate file formats, WUFI calculates this automatically during the simulation. The KLI format, however, was an early format from the time when computers were slow and the rain and radiation components hitting the surface were pre-computed.

So in order to create a KLI file containing rain and solar radiation you would have to pre-compute the rain and radiation load components hitting the surface vertically. The models WUFI uses for this are described in the help file. No directional conversion is necessary if you want to use the file for simulating a horizontal surface, such as a flat roof. Otherwise, it is probably easier to re-distribute your data onto an hourly time step and use a more convenient file format (e.g. WAC).

Regards,
Thomas

[RM_Sintef]

Hi again,

Thanks for your reply! I did not find so detailed information about the difference between .WAC and .KLI elsewhere.

Regarding the climate file, I was also wondering if it is necessary to create a file with least 1 year data, or if it is possible to create climate file with shorter periods, f.example 1 week or month. Especially with the KLI format this is not easy to understand as the date/time are translated in numbers.

Regards

[Thomas]

Regarding the climate file, I was also wondering if it is necessary to create a file with least 1 year data, or if it is possible to create climate file with shorter periods, f.example 1 week or month.

Both .WAC and .KLI files can be shorter than one year. In the case of a .WAC file make sure that the line "Number of DataLines" in the header contains the correct number of hours (i.e. less than 8760 if the file is shorter than one year).

Kind regards,
Thomas