[EnergyPlus_Support] Re: Low solar collector efficiencies?

["Kristin Field" <fieldkm@xxxxxxxxx>]

Thanks for the help, Brent and JRR.  I will try using smaller
collectors (so smaller flow through each one) to see if that helps. 
JRR, my weather is Denver, CO.  Should be a good climate for solar!

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, JRR <energy.wwind@...> wrote:
>
> 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.
> >
> >
> >  
> >
>




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