What is the specification of your required data?

Do you want irradiance data every hour, every day or what?

Which kind od data you need (Direct, diffuse, global solar radiation) and which site?

Hi,

You can download the Solar Spectral Irradiance: Air Mass 1.5 data from

http://rredc.nrel.gov/solar/spectra/am1.5/

Download MS Excel™ Spreadsheet File

Hope this information helps you

Best Regards

 A couple of resources also  available for obtaining solar irradiation data. Some are paid and while some are free. This one will be the best.

NASA Surface meteorology and Solar Energy (NASA-SSE) provides 22 year averaged (1983 to 2005) solar data. It includes parameters for Solar Cooking, Sizing and Pointing of SolarPanels and for Solar Thermal Applications, Solar Geometry, Tilted Solar Panels, Meteorology (Temperature). Kindly go through this link, which was shared with us by our thesis guide: 

https://eosweb.larc.nasa.gov/cgi-bin/sse/[email protected] 

Best regards,

Link below show IRENA data for Thailand.

http://resourceirena.irena.org/gateway/countrySearch/?countryCode=THA

You can also download RETScreen Expert you will have all data that you need and it is free.

Thank you everyone for your valuable suggestions

https://www.ngdc.noaa.gov/stp/solar/solarirrad.html

https://www.ngdc.noaa.gov/stp/solar/irrad.html