I want to work in the field of renewable energy planning. That is why I am looking for some reliable data so that I can suggest optimum integrated renewable energy system (IRES) for any micro-grid.
Meteorological centre will be the best for this. However if you work in laboratory with the instruments like Pyranometer and Air anemometer you can easily measured the solar irradiation and wind velocity respectively.
It is preferable to obtain data from ground observatories. However, in case of an unavailability of such data, freely available datasets may be accessed:
Follow this link for solar radiations' data comprehensive database:
The source for official statistics in the US, for energy information, including electric generation, is the US Energy Information Administration:
http://www.eia.gov/
However, the demands on the EIA for collecting a great deal of information in many areas, and demands for timeliness, and resource restrictions, in my opinion from having worked there for many years, can understandably detract from the accuracy of the published data, so you should look for as much information on accuracy as you can find with regard to information provided there: tables of estimated relative standard errors, technical or explanatory notes, and anything else you can find.
Because so much is reported on so many energy topics on the EIA website, there will be less information on renewable energy than is ideal. But I see that you have also been referred already to the US national laboratory for renewable energy, NREL, which may be helpful for you.
Often statistical agencies will publish numbers with more digits than can be justified, so accuracy for statistical information from most sources, in my experience, is often no where near that which may be indicated.
You could also look for information on the EIA website in the form of 'feature articles' and special reports. But I suggest that you always keep in mind that accuracy may be less than may be apparent.
Also, those who write reports using such official statistics may - in my opinion - be much too quick to jump to incorrect conclusions, so some healthy cynicism is often in order. Many in private industry may feel too much pressure to come to a conclusion based on too little reliable information, I think.
But I think that you can find some information that may at least give you some ideas to pursue if you visit the EIA website. You could look for the Electric Power Monthly, and the Electric Power Annual, and special articles there. I am not certain as to exactly what information you are seeking, but I think it may be worth your while to visit that website.
Cheers - Jim
PS -
You might also visit this website for US climate information: