solaR timestamp for radiation on a tilted surface

Question

I am trying to use the R package solaR to calculate irradiance on a tilted plane given measured irradiance on the horizontal plane. I can get the code to work, but

Answer 1

thank you greatly for responding directly and for the great package. It turns out we had a wildly wrong interpretation of solar time. I am seeing a different possible issue that would not fit into the comments section.

When I run:

local2Solar(as.POSIXct("2013-07-07 13:36:00",tz="America/Chicago"),lon=-97.7428)

I get "2013-07-07 12:05:01 UTC". According to NOAA, "2013-07-07 13:36:00" is solar noon for that day.

Just to confuse matter, when I run:

local2Solar(as.POSIXct("2013-06-07 13:30:00",tz="America/Chicago"),lon=-97.7428)

I get "2013-06-07 11:59:01 UTC", so it appears to be very close. According to NOAA, "2013-06-07 13:30:00" is solar noon for that day.

If you were to run:

local2Solar(as.POSIXct("2013-01-07 12:37:27",tz="America/Chicago"),lon=-97.7428)

You would get "2013-01-07 12:06:28 UTC". According to NOAA, "2013-01-07 12:37:27"" is solar noon for that day.

I ran G. Master's equations separately from solaR and got: "2013-06-07 13:29:30 CDT" (the highest precision is each minute for this version) for the time with maximum incident power for the first case on "2013-06-07".