Hi: Granted that the description is very simple, but that is the intent.
The essence of it is that the "loss" for small variations in angle of incidence is approximately bounded by, (less than), the sin of the angle between the orientations of two panels/arrays in question. 10 degrees ---> minus 17% 20 degrees ---> minus 33% 30 degrees ---> minus 50% If you go through the detailed math and take into account atmospheric effects, especially when the sun is near the horizons, temperature, location, weather, etc., the result will vary, but will not be worse than the sin of the angle. I'll draw out better picture with more detail for Vancouver. We're at a fairly high latitude, so overall array orientation is a more sensitive factor than farther south. JARMO _____________________________________________________________________________________ Jarmo Venalainen | Schneider Electric | Xantrex Brand | CANADA | Sales Application Engineer Phone: +604-422-2528 | Tech Support: 800-670-0707 | Mobile: +604-505-0291 Email: jarmo.venalai...@schneider-electric.com | Site: www.Xantrex.com | Address: 3700 Gilmore Way, Burnaby, BC V5G4M1 *** Please consider the environment before printing this e-mail From: Brian Mehalic <br...@solarenergy.org> To: RE-wrenches <re-wrenches@lists.re-wrenches.org>, Date: 07/28/2015 09:48 AM Subject: Re: [RE-wrenches] Using the North Facing Roof Sent by: "RE-wrenches" <re-wrenches-boun...@lists.re-wrenches.org> The analysis of 50% of south facing production is too simplistic; running some modeling shows that, depending on the latitude, the difference can be much smaller, approaching 25% less for the north facing. I think this layout could become more common especially on low slope commercial roofs, where the north facing module would occupy space that was already unused due to interrow shading. Of course the closer to the equator the less difference between production of the north and south arrays...and you better be careful when stringing them in series so as not to mix N and S facing..plus filling in all those gaps between rows could make servicing the array a bit problematic! Cheers, Brian Mehalic NABCEP Certified Solar PV Installation Professional™ R031508-59 PV Curriculum Developer and Instructor Solar Energy International http://www.solarenergy.org On Tue, Jul 28, 2015 at 10:24 AM, <billbroo...@sbcglobal.net> wrote: Jarmo, The sun’s geometry is not nearly that simple. To understand the impact of north-facing arrays, you have to perform a simulation. PV:WATTS does this just fine and it is easy to show that a 18-degreed North-facing tilt produces 75% of a perfect 30-degree south-facing array. Far more than your assumption of 50%. To compare 15-degrees South to 15-degrees North, the numbers are slightly better at 77%. We are going to see a lot of north-facing arrays once people understand that low tilt angles are very forgiving on North slopes. Steep slopes are a totally different story and you have to run the numbers…. Bill. From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of jarmo.venalai...@schneider-electric.com Sent: Tuesday, July 28, 2015 8:04 AM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] Using the North Facing Roof I did a slide on the effect of North facing modules. For even a fairly aggressive rotation North as shown, the effect is "only" a 50% reduction. The questions of whether or not to do it, are, - is the mounting structure simpler, lower cost - security against wind - can I put a larger array on the roof (typically yes, if you make back to back pyramid shaped structures) - overall, what is the cost versus benefit JARMO _____________________________________________________________________________________ Jarmo Venalainen | Schneider Electric | Xantrex Brand | CANADA | Sales Application Engineer Phone: +604-422-2528 | Tech Support: 800-670-0707 | Mobile: +604-505-0291 Email: jarmo.venalai...@schneider-electric.com | Site: www.Xantrex.com | Address: 3700 Gilmore Way, Burnaby, BC V5G4M1 *** Please consider the environment before printing this e-mail From: "Peter Parrish" <peter.parr...@calsolareng.com> To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org>, Date: 07/28/2015 12:22 AM Subject: [RE-wrenches] Using the North Facing Roof Sent by: "RE-wrenches" <re-wrenches-boun...@lists.re-wrenches.org> I recently read a short piece that caught me up short, and I quote: “The fast dropping cost of solar, while a huge boon to the adoption of solar PV, has counter-intuitively altered design parameters. No longer is the north-facing roof considered unusable because limited application in less-than optimal orientations can still show a positive net benefit. Arrays are thus designed now with elements or sub-arrays in these locations, increasing overall kW installation while reducing the energy production per capacity installed. This might have been anticipated based on sheer economic analysis from a users perspective, but so long has solar been expensive that these less optimal orientations were never seriously considered.” I doubt that the individual who wrote this piece came to these conclusions him/herself. Does anyone know of a recent article that argued this perspective? Is this an emerging design practice? If so, I’d like to know more about it. - Peter Peter T. Parrish, Ph.D. President, SolarGnosis 1107 Fair Oaks Ave., Suite 351 South Pasadena, CA 91030 (323) 839-6108 peter...@pobox.com ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org This email has been checked for viruses by Avast antivirus software. www.avast.com _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
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