Enphase has a tech note pdf for download that recommends and rationalizes a PV watts derate of .819 instead of the standard .77 (which IMO is a little conservative to begin with).
http://www.enphaseenergy.com/downloads/EnphaseAppNote_PVWatts.pdf Kirk Herander Vermont Solar Engineering 802.863.1202 fax 802.863.7908 VT RE Incentive Program Partner NYSERDA Incentive-eligible Partner NABCEPTM Certified Installer From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Allan Sindelar Sent: Sunday, April 18, 2010 3:18 AM To: RE-wrenches Subject: Re: [RE-wrenches] Tilt biased.... Holt, Feedback re the low tilt angle: Go for it, you're good. Re wind loading: check out UniRac's Code Compliant Installation Manual, http://www.unirac.com/pdf/ii227.pdf, especially pages 3-9. Less wind loading is one of the main reasons for going with a lower tilt angle. Another is closer module row spacing (at 3X height RoT) without inter-row shading. No experience with Enphase. Allan Allan Sindelar <mailto:al...@positiveenergysolar.com> al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 <http://www.positiveenergysolar.com/> www.positiveenergysolar.com <mailto:hol...@sbcglobal.net> hol...@sbcglobal.net wrote: Searching for opinions.....is this "over design"? Designing small system (2.35kW). Customer uses gas for heating. Typical A/C unit. I was thinking of biasing the tilt to summer production for greater offset of summer demand (lat 31.6, proposing 18). No net metering in this part of the world. PVwatts shows a drop of 2% /yr. in production , 5% higher production for A/C months. Feedback? Also, this array will go on a carport. I understand that windloading is actually greater for an open structure than one with walls (another reason for lower tilt) - is there any one that can direct me to data on finding out how much more? Lastly, what is a good avg. target derate factor for Enphase inverters (real world)? Holt E. Kelly Holtek Fireplace & Solar Products 500 Jewell Dr. Waco TX. 76712 254-751-9111 <http://www.holteksolar.com> www.holteksolar.com _____ _______________________________________________ List sponsored by Home Power magazine List Address: <mailto:RE-wrenches@lists.re-wrenches.org> RE-wrenches@lists.re-wrenches.org Options & settings: <http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org> 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> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: <http://www.re-wrenches.org/etiquette.htm> www.re-wrenches.org/etiquette.htm Check out participant bios: <http://www.members.re-wrenches.org> www.members.re-wrenches.org
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