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 r...@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-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachme nts/20100104/d0653269/attachment-0001.htm> _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
