On the relation between insolation and climatological variables—V. Estimation of availability of solar energy

A new procedure is developed for estimating availability of solar energy in localities where adequate data are not available. The hourly variations in solar intensity with day of the year during clear weather (essentially no clouds and unlimited visibility) are shown to follow regular repeatable patterns. These patterns have been determined for four south-western locations. From these data, it is possible to estimate the maximum possible available solar energy for perfectly clear weather. The effect of clouds and reduction in visibility is to reduce the solar intensity below the value appropriate to any hour of any day in clear weather. A study of the dependence of reduction in solar intensity on cloud cover and visibility is now being conducted for several southwestern locations. A model for the dependence of direct normal solar intensity on total insolation is also being developed.