[RE-wrenches] orientation data

[Darryl Thayer]

HI all
look at solmetric.com 
I find most of the time PVwattsd is OK but I feel in some envoroments it is off,  I really like the work by Solmetric
Darryl

--- On Tue, 10/6/09, Joel Davidson <joel.davidson at sbcglobal.net> wrote:

> From: Joel Davidson <joel.davidson at sbcglobal.net>
> Subject: Re: [RE-wrenches] orientation data
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Tuesday, October 6, 2009, 3:35 PM
> Hello Nik,
>  
> We installed two 4 kW DC PV systems on a Sacramento PV
> Pioneer home. Both arrays were tilted 18 degrees
> with one array facing south and the other facing west.
> The power from both systems fed into the Sacramento
> Municipal Utility District grid (not the home). After 2
> years, SMUD reported (but did not provide data) that
> the west-facing system produced 20% less energy than the
> south-facing system. However, PVWATTS estimates the
> difference to be 11.8% less. My experience with
> hundreds of systems is that PVWATTS is a reliable
> estimator for crystalline silicon PV systems if you factor
> derating properly. It will be interesting to hear what other
> wrenches have to say.
>  
> Joel Davidson
> 
>  
> 
> 
> 
> 
> From:
> "Nicholas Ponzio, Building Energy"
> <nponzio at buildingenergyus.com>
> To:
> RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Sent:
> Tuesday, October 6, 2009 10:37:32 AM
> Subject:
> [RE-wrenches] orientation data
> 
> Hey Folks, 
> 
> Anybody have real data to compare productions for
> south-facing vs, west-facing PV array? PVWatts is only
> showing about a 7% derating for facing west. 
> 
> 
> Thanks,
> Nik
> 
> 
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