[EnergyPlus_Support] Re: Custom Weather Files - Radiation

["hollywas" <hollywas@xxxxxxxxx>]

Hi Ooi,
Yes, you need to estimate the Direct and Diffuse from the Global Radiation.  Currently we are using the Reindl model for this, which seems to work well.  However, if anyone has an alternate suggestion please let me know.

The EnergyPlus weather converter tool seems to use Zhang-Huang model, so I plan to look into that.
Holly

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "ooikoonbeng2004" <ooi_kb3@...> wrote:
>
> Holly,
> 
> Can i know how you calculate the Direct and Diffuse from the Global Horizontal? The TMY values of these three are given, but if you measure only the Global Horizontal, then you need to also measure at least the diffuse before you can calculate the direct. Of course we need to resolve the direction by the sine or cosine of the solar altitude angle. I was told you can measure diffuse by casting a shadow over the sensor for global. 
> 
> thanks
> ooi 
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "hollywas" <hollywas@> wrote:
> >
> > Hello,
> > I am trying to make a custom EPW from an on-site weather station.  Strangely, the EPW will run successfully when paired with a simple IDF, such as one of the EnergyPlus example files.  However, with a more complex model it will fail on certain timesteps.  The more zones the model contains, the more timesteps will cause fatal errors... even when modeling the same building.  The error message says surface temperatures are out of range.  It seems to fail at timesteps when there is a large change in the direct and/or diffuse radiation data.  If I manually replace this radiation data, the simulation will run successfully through this timestep.
> > 
> > Do you have any idea why the complexity of the geometry would affect the success of the EPW?  Do you have any advice on fixing this besides manually replacing the radiation data at every failing timestep?  
> > 
> > FYI, The Direct Normal and Diffuse Horiz Radiation are calculated from measured Global Horiz Radiation.  Horizontal Infrared Radiation from Sky was not measured so I have tried different values including:  using TMY3 values and inputting the TMY3 average value for each timestep.  I also have one reference for how to model it, but would appreciate any other advice.
> > 
> > Thank you in advance for any help!
> > Sincerely,
> > Holly
> > 
> > Holly W. Samuelson
> >
>




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