The Strengthening Sun

We have had a lot of sun the past few days and one thing that is apparent is the gathering strength of the solar radiation we are receiving.   It seems strange, but the sun right now is roughly equivalent to that of mid-September, before summer's end.  Just to illustrate, here are monthly radiation values from NREL, the U.S. government agency that gathers such information (the black line is the mean over 30 years, shading shows extremes in individual months) for Seattle and Spokane:

Seattle Radiation

Spokane Radiation

There is a huge increase in solar radiation between January and March and then a slow rise to the peak in July.  So at the end of March we are over 1/2 way to max radiation.    This figure factors in average clouds.  Spokane obviously does a bit better than Seattle.

 Lets compare our radiation to that of Honolulu (see below).   In the summer there is not much difference, since our northern latitude is balanced out by our longer days.   During the winter..... well...you don't need a meteorologists to tell you about that. 


Here is the actual radiation reaching the surface that last few days, based on the measurement at the UW:

On some days (like March 23rd), in which the skies are nearly clear all day, the radiation looks like a near perfect cosine curve, while on other days (like today), there are plenty of clouds the reduce radiation significantly.

A number of folks are experimenting with solar collectors in our area as a way of acquiring more green energy for their homes.   There are significant number of solar contractors and non-profits ready to do installations around here.  Sounds crazy for cloudy Seattle?  It turns out that we get more solar radiation than Germany and they have a very large installed base of photovoltaic and other collectors (see map).

 Clearly, the SW U.S. is just perfect for solar energy:  LOTS of sun and a huge population that wants air conditioning while the sun is blazing.  Our country needs to do more....a LOT more...to take advantage of this huge resource.