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 Post subject: PSM3 Data VS TMY3
PostPosted: Fri Nov 01, 2019 8:55 pm 

Joined: Mon Jan 21, 2019 11:57 pm
Posts: 2
Hi everyone,

I have a question about the meteo data I should use for estimating production in US. I'm currently using the build-in NREL API and I believe that pulls PSM3 data from NREL/NSRDB. I'm just wondering what is the difference between the PSM3 data and the TMY3 data collected from actual ground stations and which one is more acurate/reliable?

Thanks,


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 Post subject: Re: PSM3 Data VS TMY3
PostPosted: Mon Nov 04, 2019 10:14 pm 
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Joined: Tue Oct 18, 2016 3:31 am
Posts: 270
NSRDB ground station data is a bit old, and varies in uncertainty (Class I-III, with III having highest uncertainty). Class II-III are generally not used due to the uncertainty and quality of data. However the other issue with this source is the proximity of these stations to your site and how representative it might or might not be.

PSMv3 compared to some commercially available satellite data providers (for TMY data) has been quite high in GHI in my experience (3-6%). You are able to select your location however, which is a benefit compared to NSRDB. Perhaps look at both and consider the result might be somewhere in between the two (NSRDB is often lower GHI compared to PSMv3 and other sources).


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 Post subject: Re: PSM3 Data VS TMY3
PostPosted: Tue Jan 07, 2020 5:20 pm 

Joined: Tue Jan 07, 2020 3:58 pm
Posts: 1
I would caution PVSyst users modeling in the Northeast or Northwest United States from using the newer NSRDB weather dataset PSMv3 (Physical Solar Model version 3, 1998-2016, 4 km resolution). The PSM data is higher resolution and is derived from the most current weather satellite observations. However, it has been shown to have a large positive bias for locations with above average cloud cover, snowfall, or changing ground albedo.
Quote:
β€œThe NSRDB (1998–2015) data appear to have some challenges in quantifying the GHI accurately for areas susceptible to high occurrences of clouds, snow, and bright surfaces.”
Evaluation of the National Solar Radiation Database (NSRDB Version 2): 1998–2015, Aron Habte 2017
A comparison of weather data from Rochester, NY shows the effect of this bias.

Weather Data .................................................Global H.....Diffuse H
..................................................................kWh/M2......kWh/M2
PVGIS api TMY, TMY.............................................1343.5........563.8
Meteonorm 7.2 TMY (1991-2005).............................1349.2........626.8
NREL NSRD : TMY3 (1990-2010, 10 km)......................1349.9........653.5
NREL NSRDB PSMv3 TMY (1998 to 2016, 4 km)..............1390.5........577.4

PSMv3 variance to Meteonorm 7.2............................3.1%.........-7.9%


This bias generally leads to a 3.5% higher predicted output in PVSyst compared modeling the same physical PV plant (array tilt angle 25 degrees) using Meteonorm or older NSRDB 10 km data.

Until a newer version of the PSM satellite data corrects for these biases and can be confirmed to give reasonable production estimates (when compared to measured plant data), I recommend PVSyst users stick with Meteonorm weather data (with the Hay/Davies transposition model) for modeling plants in the Northern United States.


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