March 26, 2012

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..... 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 take advantage of this huge resource.


  1. Thank you for posting about the sun and putting in a link to the Solarize Seattle: Northeast campaign!

  2. "Clearly, the SW U.S. is just perfect for solar energy"

    Actually, I hear that it isn't so perfect. When the panels get hot, their efficiency drops sharply. A cool climate with clear skies can actually perform better.

  3. Awesome post! I love out sun in Bremerton. I have 6 solar panels totaling a 1.23 kW solar array, and it produces 100% of my electricity on an annual basis. The rule for me is conservation!

  4. Please give Arizona governor Jan Brewer a heads up, Cliff. LOL

  5. An electrician friend just took a continuing course in solar energy panels. He reports that they learned that among the continental United States, Colorado and the Pacific Northwest are the bestl-suited to solar panel collection. These two geographic regions have more optimal conditions because of elevation (closer to the sun), number of daylight hours (more northerly latitudes), and less temperature variation (resulting in higher efficiency for transmission).

  6. Our system produces about 2.4 MW per year here in Seattle. We haven't paid an electric bill in about a year now. Replacing that old electric hot water heater really gave us the biggest boost - solar/electric hot water saves a bunch - if you've the mind to only do one thing. Now if we could just figure out the best way to save the roof rain water and flush a couple of toilets...then we'd be making big progress...have you seen the sewer bills lately???


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