Re: [EnergyPlus_Support] Low solar collector efficiencies?

[JRR <energy.wwind@xxxxxxx>]

HIYA;

1) SRCC Independantly Rates Solar Collectors annually.  See P 16  4th 
line from
        the bottom for the AST80 in the following Webref:

        http://www.solar-rating.org/SUMMARY/Dirsum.pdf

       You've got some really big collectors there !! 122 sq ft Each...
        I would choose AET's  AE-40 on page 10.  In Fact I have in the 
past.....
         The AE-40s are doing very well in a 1000 gallon /day hot water 
system
          in my local area.......

2) You should not connect more than 6  4ft x  10 ft  Liquid Collectors
       together in parallel  to get even flow through them.  There is a
       very good article from  about 3 ?? years ago at

        http://www.homepower.com

       This article describes the flow balancing effects in a "mega 
Collector"
        6 Max has always been the case for nominal 3/4" header tubed 
collectors,
        even going back to my 1986  Grumman's.

3) The thermal load may not be well matched to the source.   See Rodale 
Press / New  Shelter Magazine / "Sun on Tap"
          1984  pages 12 to 14  "Starr House"

4) What weather files are you using ??  In the Pacific Northwest liquid 
collectors are not practicable due to the
       thermal time constant of the collector -- you need 15 t o 18 
minutes of Sun at a time to make the "Water Fired"
       collectors beat the "Air Fired" ones.  This is developed in 
"Principles of Solar Engineering" Kreider & Kreith
       McGraw Hill // Horizon Publishing 1978.



Kristin Field wrote:

>Has anyone else run a solar collector (thermal) system and output
>hourly efficiencies?  I did this, and they were extremely low.  Based
>on manufacturer data (Thermomax AST80 parameters), I would expect
>efficiencies in the 50-80% range.  But my output shows more like
>10-30%.  I would think that this would be independent of my loop
>configuration.
>
>One thing I wonder about is that my collector surfaces are much larger
>than the test surfaces.  Each collector surface (there are 6) is about
>50m^2, and the test surface is 11m^2.  I was hoping not to have to
>have 30 collectors in parallel, but if that is what I need to do to
>get a normal efficiency, it will be good to know that.
>
>I will upload my .idf and .csv files (.csv has hourly collector
>efficiencies for one of the collectors) shortly.
>
>Thanks,
>Kristin
>
>P.S. My file names have "CityParkGH" and today's date in them.
>
>
>  
>



The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/