[RE-wrenches] Fwd: An interesting article

[RayBR]

I sometimes play with various tilt angles in PV Watts for different 
locations too.  The weather conditions at different times of year vary 
from location to location so I don't think there is a one size fits all 
solution here.

Also, I don't think this article or PV Watts takes into account snow 
shed, which dictates steeper angles in winter.

R. Ray Walters
Chief Technical Officer, RemoteSolar.com
BS Mech Engineering, 1988
Former NABCEP Certified, 2004-2016
Licensed Master ELectrician, Colorado
303 505-8760

On 2/27/17 12:10 PM, Sindelar Solar wrote:
>
> Wrenches,
>
> One of my clients sent me this article on seasonal array tilt angles: 
> http://www.solarpaneltilt.com/#2season
>
> It challenges some of the long-held numbers, although not 
> substantially, and I found it worth a review.
>
> I have long advocated adjustment twice a year, staying at latitude 
> tilt for nine months and latitude +15 for winter, presuming that for 
> most homes a latitude tilt will be adequate over the summer months 
> without a second pair of adjustments. I have long figured that the 
> fewer required maintenance operations the more they'll actually get 
> done. After reviewing this article I replied to the client who sent it 
> to me, whose home is at 7,000' at 35.5 ° latitude:
>
>     Bill,
>     Thanks for this. I'll assume that you're welcoming my response, so
>     in short...
>
>     For me as an advisor principally to off grid homeowners, I'll err
>     on the side of practicality, simplicity and ease of remembrance
>     over accuracy. That's why, for example, I recommend two angle
>     adjustments/year over four. Also, as Landau himself states, "A
>     difference of a few degrees will make very little difference in
>     the energy you gather". This information was of greater
>     consequence when PV was far more expensive than it is today.
>
>     My original and purposely simplistic recommendation was to adjust
>     to latitude +15 for winter and back to latitude for the rest of
>     the year. I gave an approximate date around November 10th, (midway
>     between the fall equinox and the winter solstice) to increase the
>     tilt, with a return to latitude around February 10th (midway
>     between the winter solstice and the spring equinox). Extrapolating
>     using his calculations for 4X/year, I would adjust to winter angle
>     earlier (his target is October 7th), such as "during October" and
>     returning later (his target is March 5th), such as "late February
>     or early March".  Using Landau's figures for 35°, that suggests
>     32.0 for spring/summer/fall and 55.2 for winter, adding half a
>     degree or so for your location, with an unknown adjustment for the
>     higher elevation.
>
>     Given your DP&W pole-top rack with its 10-degree adjustment
>     increments, this means only that we have no need to drill the
>     additional hole in the adjustment bar at 50 degrees. The supplied
>     holes at 35 and 55 are best. You'll want only to broaden the
>     duration of your winter tilt angle on both ends.
>
>     Good exercise! I appreciate your sending this along, as I have
>     always worked from longtime collective-wisdom guidelines, having
>     never seen these calculations laid out with such accuracy.
>
> I'll be interested in any comments from other Wrenches who take the 
> time to review the link.
> Allan
>
> -- 
>
> *Allan Sindelar*
> allan at sindelarsolar.com <mailto:allan at sindelarsolar.com>
> NABCEP Certified PV Installation Professional
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder (Retired), Positive Energy, Inc.
> *505 780-2738 cell*
>
>
>
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