Stationary statistics and sequential properties of normal beam and global solar radiation on tilted surfaces

The stationary statistics and persistence characteristics of both hourly and daily total global solar radiation on tilted surfaces, as well as of hourly normal beam radiation, on a discrete monthly basis, are analyzed in a formalism akin to previous studies for global horizontal solar radiation. Our database includes three Australian locations of varying latitude and clearness index. We find that with a proper geometric/statistical transformation, the Probability Density Function (PDF) of global radiation on tilted surfaces can be accurately predicted from the corresponding statistics for global horizontal radiation, the latter typically being far more readily available. The PDF of hourly normal beam radiation seems to be well predicted via modification of a simple analytic functional form previously proposed for modeling global horizontal radiation. Finally, the persistence times and persistence strengths of global radiation on tilted surfaces and of normal beam radiation are found, not surprisingly, to be very similar to the corresponding values for global horizontal radiation.