Re: [EnergyPlus_Support] Re: Modifying a weather file to reflect "real" weather

[Linda Lawrie <linda@xxxxxxxxxxxxxx>]

Until I look at the code, I won't be able to give you much
information.

It's a heuristic method using the solar position -- in other words, the
most accurate thing I could come up with given the data I had to deal
with.  To my recollection, I think it defaults to 50% sky
cover.  I believe I only made that available in the last release of
the weather converter.  After someone gave me only Global
Horizontal.

Yes, two values are preferred....

Linda

At 07:32 AM 6/5/2009, Edwin Cox wrote:
> From Auxiliary Programs manual,
> page 55:
> "Historical weather data files in CD144 format do not contain solar
> data nor is such data
> generally available for a specific location and time period. In this
> case, ersatz solar data must
> be generated from cloud cover and other data using sky models and
> regression formulas.
> Currently, neither the Weather Conversion utility nor the EnergyPlus
> program synthesizes
> this data. However, the weather conversion utility can use any two of the
> commonly recorded
> data (i.e. two of Global Horizontal Radiation, Horizontal Diffuse
> Radiation and Direct Normal
> (or Direct Horizontal) Radiation to calculate the EnergyPlus primary
> solar data of Direct
> Normal and Horizontal Diffuse Radiation values)."
>
> This states that two solar values must be entered to derive the
> others.
>
> Please tell us more about how to derive direct normal and diffuse
> irradiation in the Weather Converter with just global horizontal.

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