[RE-wrenches] Best angle - direct grid tie

[Ryan LeBlanc]

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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