[RE-wrenches] Best angle - direct grid tie

[Carl Adams]

Drake,

Attached is a PDF which is the result of using PVWatts to perform an
analysis which may be helpful.

Assumption 1: No shading at the site and a due south facing array.
The module tilt is varied from 0 to 90 degrees and the array estimated
production leads you to select an optimum tilt.

Assumption 2:  Now that the optimum tilt is established evaluate the
effect of array azimuth at this tilt angle.

The solar radiation per time of day is evaluated to indicate the
potential adjustments which might be required based on shading at
various times of day but the Path Finder readings from the site should
be used for a more accurate assessment.

Cheers
Carl Adams
SunRock Solar, LLC



On Mon, Jan 4, 2010 at 6:08 PM, Ryan LeBlanc
<ryan at naturalenergyworks.com> wrote:
> Drake,
>
> The SPA software is likely telling you 'close-to-the' optimum tilt for
> maximum total annual peak production, without telling you WHEN the most
> valuable power is produced.  That's for you to figure out based on the
> specific utility rate schedule, and is a critical factor.
>
> So, it kind of is geared towards off-grid systems, by default, but only
> because it doesn't have the Holy Grail database of utility rate schedules,
> (TOU, etc.) that we all wish was available.  Though, it may manually allow
> you some of these features.  I haven't looked at Assistant software in a
> little while, apologies.
>
> Solmetric has some resources you may be interested in,
> http://www.solmetric.com/annualinsolation-us.html.
>
> Also, perhaps you should play with PVsyst, for a large fixed ground mount,
> use the "Unlimited Sheds Option." This tool gives you some optimum
> suggestions as well, but I prefer to run a few production estimates to
> compare.
>
> Each site is specific, so be cautious if someone tells you there is an
> across-the-board answer to an optimum tilt for grid-tied applications.  For
> rooftops, you'll likely go with the orientation and tilt of the roof due to
> aesthetics and cost.  For ground mounts, we can play with it a little more
> to find our sweet spots.
>
> Ryan J. LeBlanc
> NABCEPT Certified Solar PV Installer
> Lead PV Consultant
> NATURAL ENERGY WORKS
> 2139 Westland Dr
> Santa Rosa CA 95407
> Cell: 707.591.1950
> Direct: 707.536.9839
> ryan at NaturalEnergyWorks.com
> http://www.NaturalEnergyWorks.com
>
>
>
>
>
> For your latitude, you see the same max. average yearly peak sun regardless
> of your fixed array tilted at latitude or latitude -15 degrees.
>
> See http://rredc.nrel.gov/solar/pubs/redbook/PDFs/OH.PDF.
>
>
>
> Being taught old school we always used latitude, but now I use latitude - 5
> degrees for optimal fixed tilt.
>
>
>
>
>
> Kirk Herander
>
> Vermont Solar Engineering
>
> 802.863.1202
>
> NABCEP(tm) Certified Solar Installer
>
> NYSERDA-eligible Installer
>
> VT Solar Incentive Program Partner
>
>  _____
>
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
> Chamberlin
> Sent: Monday, January 04, 2010 8:30 AM
> To: RE-wrenches
> Subject: [RE-wrenches] Best angle - direct grid tie
>
>
>
> Hello Wrenches,
>
> My Solar Pathfinder Assistant (SPA) claims that the optimum tilt angle for
> the solar modules is latitude.  I'm skeptical.  The system being designed is
> a direct grid tie, ground mount.
>
> It seems to me that an angle of latitude will give a balanced angle for both
> summer and winter charging.  Since there is far less energy available in the
> winter, is this balance really the best.  Also, a flatter angle in the
> summer should gain more hours of sun, since the sun goes N of the E-W axis.
>
>
> With ballasted systems, the 15 degree angle is supposed to work just fine,
> due to better summer charging.  Does anyone have an answer to what really is
> the optimum tilt angle for a direct grid tie system?  Is the SPA geared
> toward off grid systems, or is latitude really the best?
>
> Thank you and best wishes for the New Year,
>
>
>
> Drake Chamberlin
> Athens Electric
> OH License 44810
> CO License 3773
> NABCEP TM  Certified PV Installer
> Office - 740-448-7328
> Mobile - 740-856-9648
>
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