Mistake in "Weather File Irradiance Data" help?

5 posts / 0 new
Last post
eddy9305
eddy9305's picture
Mistake in "Weather File Irradiance Data" help?

Hi,

I was reading the "Weather File Irradiance Data" help and I noticed something weird in this definition:

*GHI and DHI:
SAM reads the global horizontal irradiance (total) and diffuse horizontal irradiance data from the weather file, and calculates direct normal irradiance values for simulations. SAM calculates the incident irradiance using GHI data from the weather file and the calculated DHI data.

Shouldn't be this way?:

*GHI and DHI:
SAM reads the global horizontal irradiance (total) and diffuse horizontal irradiance data from the weather file, and calculates direct normal irradiance values for simulations. SAM calculates the incident irradiance using GHI data from the weather file and the calculated DNI data.

Regards.

Paul Gilman

Hello,

Those descriptions of the irradiance inputs for the detailed photovoltaic model are confusing. I will revise them.

What we are trying to say is that SAM's PV model uses the DHI and DNI as input. If your weather file only has data for two irradiance components, and is missing data for either the DHI or the DNI component, you can choose the appropriate option on the Location and Resource page to tell SAM to calculate the value of the missing component.

If your weather file contains GHI and DHI data and is missing DNI data, you can choose the "GHI and DHI" option so that SAM calculates the DNI from the GHI and DHI. It will always use the DNI and DHI for the simulation.

Best regards,
Paul.

eddy9305
eddy9305's picture

Hi Paul,

Thank you very much for your answer. Checking what you told me I have a new question. You said that SAM will always use the DNI and GHI for the simulation... even if you select the "DNI and DHI" option?

'Cause in the help section, I read this: SAM's photovoltaic performance models always require the DNI and DHI components to calculate the irradiance incident on each subarray.

So... SAM uses "DNI and GHI always" or "DNI and DHI always" ?

Hahaha. You're right... this is a little confusing.

Regards.

Paul Gilman

Sorry about that. I just edited by response above to correct my typo -- all those acronyms are easy to confuse.

SAM's photovoltaic model always uses the direct normal (DNI) and diffuse horizontal (DHI) irradiance as input for simulations.

Best regards,
Paul.

eddy9305
eddy9305's picture

Perfect. Now it's crystal clear.

Thanks.

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer