[RE-wrenches] Fwd: An interesting article

[Sindelar Solar]

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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