PVWatts v6 API not matching Pvwattsv5

  • Seb
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03 Mar 2021 13:27 #9333 by Seb
Hi,
I am running Pvwattsv5 in PySAM and loading the solar data from the nsrdb PSM-TMY endpoint. Nevertheless, I am not able to match the production value returned from PVWatts v6 API. The weather file seems to have the same identifier for both and I am sending the same input data (including dc-ac-ratio of 1.2). What exactly is the weather data used by the v6 API and will it load different values than those returned by the `/nsrdb/v2/solar/psm3-tmy-download` endpoint? 

Thank you,
Seb

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  • Paul Gilman
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03 Mar 2021 23:00 #9336 by Paul Gilman
Replied by Paul Gilman on topic PVWatts v6 API not matching Pvwattsv5
Hi Seb,

The PVWatts V6 API should give results consistent with the PVWatts Online Calculator. It uses a different set of weather files than the endpoint you mention below, which is current data available from the NREL National Solar Radiation Database (NSRDB). If you use pvwattsv5 with data from the NSRDB you will get different results than from the PVWatts V6 API.

The PVWatts V6 API does include time stamp and weather data in the hourly outputs along with the latitude, longitude, and elevation data required for sun position calculations, so you could use that to either construct a weather file in the SAM CSV format to use with the 'solar_resource_file' input to pvwattsv5, or to pass data as a table to the 'solar_resource_data' input. Note that the time zone is also required, so you would have to provide that as well.

Best regards,
Paul.

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  • Seb
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04 Mar 2021 15:50 #9341 by Seb
Replied by Seb on topic PVWatts v6 API not matching Pvwattsv5
Hi Paul,

Thanks for the response! Are the weather files that PVWatts V6 API uses available somewhere (i.e. an endpoint just like psm3-tmy)? My goal is to have an offline PySAM service that can replicate the results of the v6 API (assuming I can access the weather files somewhere else). Is that possible?

Thanks again,
Seb

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  • Paul Gilman
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05 Mar 2021 01:08 #9345 by Paul Gilman
Replied by Paul Gilman on topic PVWatts v6 API not matching Pvwattsv5
Hi Seb,

Sorry, there is not an endpoint that returns the weather files that PVWatts V6 API uses.

Best regards,
Paul.

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