[BLDG-SIM] Fraction of Possible Sunshine

Jon Maxwell jmaxwell at aspensys.com
Wed Sep 26 08:55:07 PDT 2001


I wanted to compare FPS plots against radiation plots so I could learn more about their correlation (or lack thereof) in different locales.  I planned to use one or the other to help me get a sense for possible regional variation in daylighting/dimming controls savings potential.  I had a lot easier time finding radiation data, if it is any consolation to you in your mission, Chip. but I thought sunshine data would be better to use if available.  Tabular data is better for quantitative analysis of course, but I wanted to see pictures.

FYI two good sources for solar radiation plots are:

    -  http://www.homepower.com/solmap.htm 
       for an annual plot (attractive training illustration),

    -  http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/Table.html 
       for monthly plots by various orientations ( a better analytical tool).

Not to be too contrary but I spot-checked the tabular data from the source in my original email with the homepower map above and the general patterns do seem to correlate pretty well. 

Finally, for those of you that are interested, Jeff Haberl responded to me directly with a FPS resource: "I believe that there is a map on Kreith and Kreider's Solar energy handbook...that shows this for the world...using the Angstrom-Lof minutes of sunshine."  Thanks to Jeff.


----- Original Message ----- 
From: Chip Barnaby 
To: Jon Maxwell 
Cc: BLDG-SIM at GARD.COM 
Sent: Wednesday, September 26, 2001 9:12 AM
Subject: Re: [BLDG-SIM] Fraction of Possible Sunshine


Jon --

I don't know of a source for a map, but I do have a question ... what do you want it for?

I am trying to learn how people use this statistic.  It has been traditionally observed, so people keep observing it.  I am involved in work on ASHRAE TC 4.2 (Weather Information) that is developing methods for extracting solar radiation from weather data measured by ASOS (Automated Surface Observation System) now used to observe weather at most sites in the US.  ASOS has planned to add sunshine meters to their machines (that plan is now delayed due to funding), but it would be just about as easy, and much more useful (in our opinion) to measure solar radiation.  Sunshine fraction is a notoriously bad predictor of solar radiation (the correlations are pretty poor).  With trivial data processing, minute-by-minute solar radiation data can be used to estimate sunshine, but not vice-versa.

Thus as far as I know the solar and building simulation community has no use for sunshine data -- the statistic should be declared obsolete from our point of view.  However, at every opportunity, I try to find why people want it, there may be some other uses that we don't know about.

So, if you're willing, please let me know what you're up to.

To the rest of BLDG-SIM: anyone else know of uses for sunshine fraction?

Thanks, Chip Barnaby


  Does anyone out there have or know of a source for a graphical illustration of Fraction of Possible Sunshine over the U.S.  I found a very good table of such data at http://cdiac.esd.ornl.gov/ftp/ndp021/ (file #12), but haven't had any luck with a map.  Thanks in advance.
   
  Jon Maxwell, PE
  Aspen Systems Corp.
  jmaxwell at aspensys.com 
   
   




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Chip Barnaby                   cbarnaby at wrightsoft.com
Vice President of Research
Wrightsoft Corp.               781-862-8719 x118 voice
394 Lowell St, Suite 12        781-861-2058 fax
Lexington, MA 02420            www.wrightsoft.com
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