Clear day solar irradiation question

System

Hi,
I have been trying to find out a source of clear sky solar irradiation amounts (direct + diffuse) on a horizontal surface at a particular latitude/longitude on any given date of the year. In particular, I'm trying to figure out the clear sky radiation amounts at Desert Creek, NV (SURFRAD station) with lat/long 36.63,-116.02. If someone can point me in the right direction it'll be greatly appreciated.

A related question: is anyone aware of a simple formula to calculate diffuse radiation on a tilted surface facing south given the diffuse radiation amount on a horizontal surface?

Thanks in advance for any help. Please also copy your response to my email soumyo@teesera.com

Best regards,
Soumyo

BB.

Re: Clear day solar irradiation question

You can use the PV watts program to give you hour by hour data based on ~20 year average historical data.

The output is based on AC Watts from a grid tied system... But you could work backwards (set derating to 1.00, use watts of panels to assume 1,000 watt/sq.mtr. as STC rating, etc.).

Or, you can probably download the data sets from the NREL site (and more).

Here is another thread where somebody wanted to program for an I-Phone/I-Pod... You might try PM'ing him/her

-Bill