Weather sources for validating existing systems?

Hi,

I'm doing a post-analysis of several MW of PV systems installed on the East Coast for a few years, and comparing various simulation methods and derates to see how our systems are performing, and evaluate our simulation methods and practices.

As expected, the main variation I'm finding between simulation methods (PVsyst, SAM, PVWatts, etc.) is variations in the source meteorological data.

What would be very helpful would be if I could find meteo data for the 2011 year (the year we are evaluating) for actual regions in question, so I could run the SAM model with the 2011 weather source. My problem is that I can't seem to find good data for 2011, so all my comparisons are still based on the NSRDB TMY3 files for a region. That is good for comparing different models, but not as useful for comparing the model against the actual production.

I would greatly appreciate any advice on heading one of two directions for getting that data:

- Most of the sites have a Fat Spaniel weather station, but only monthly values are stored for 2011, meaning I have monthly average irradiance and monthly average temperature. Are there available models for generating synthetic hourly data from these values, and merging that with an existing TMY file (to pick up humidity, wind, etc.)?
- Are there other sources for downloading a TMY3 file (or equivalent hourly data I can bring into the TMY-creator) for given stations? I'm coming up dry, but I don't know my way around the climate database world.

Thanks,
Sam

The following commercial websites offer weather files in various formats, including TMY3:


• Weather Analytics 
• SolarGIS 
• Meteonorm 
  
  
  There are algorithms for estimating hourly solar resource data from monthly values. The Meteonorm software (see link above) may have that capability.
  HOMER is hybrid power system simulation software that can calculate hourly GHI values from monthly values, but not DHI or DNI.
  
  Best regards,
  Paul.

Thanks for the resources - I'm experienced with solar installation, but still learning my way through meteorological data.

-Sam

I also found weather data at energyplus.net/weather-location/ from Energy Plus. The file is in a .epw format that SAM allowed me to use.

I would like to input a weather file for a specific time period into SAM - the period for which we have inverter output performance data. It doesn't look like Energy Plus allows me to select a certain time period or that SAM allows me to set the time period of the weather file. I can't tell what dates my file used, but it might be the most recent 12 months.

Is there a way to enter weather files for a certain specified period into SAM?

Thanks

Dear Tom,

SAM's default weather file format is the SAM CSV format. That is the best format to use when you are creating weather files or manipulating data in the file because it is a relatively simple format. SAM's solar power models do also read TMY2 (.tm2), TMY3 (.csv), and EPW (.epw) weather file formats.

SAM requires one-year's worth of weather data, whether it be hourly or sub-hourly, and assumes that the first time step is for the one that begins at Midnight, Monday January 1 (that is to say, the first time step of the hour ending at 1:00 am January 1). There is not a way to specify a certain time period.

If you only have data for part of the year, you could modify an existing weather file by inserting your data at the appropriate time steps, and then ignoring the rest of the data.

We are getting requests to allow SAM to run simulations for time periods other than one year, and are considering making that possible in a future version of the software.

Best regards,
Paul.