|
Jesse,
Based only on the info you provided, I'd recommend the SE face. A low slope is best for maximizing annual gain, which is what a conventional grid-tie customer would want. But you are in essence giving them a system that will function as GT now, but as an off grid system if the grid goes down. Under that scenario, I would sacrifice annual spin-the-meter-backward production in favor of maximizing winter output, when days are shortest and loads are greatest. A steeper array pitch will maximize available charge during winter, while the shallow pitch will be great in summer but close to nothing in winter. Given their stated objective, explain the tradeoff as offering the best preparation for lack of grid. I'd advise otherwise if they clearly want to seasonally adjust their array if there is an outage, and you install adjustable-tilt racks, and the owners are afraid of neither ladders, heights, or snow. We just completed a 4 kW GTBB system for a customer with similar objectives. We used 16 240W modules on two 8-module pole-top racks, with the instruction to leave the tilt angle shallow as long as the utility is present, but tilt to 45-55 degrees in winter during an extended outage. (And a pair of Classic 200s to handle the 4-module series strings.) Allan
Allan Sindelar
On 5/14/2013 4:34 PM, Jesse Dahl wrote:al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder and Chief Technology Officer Positive Energy, Inc. 3209 Richards Lane (note new address) Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com
Hello, I was asked to look at a site today for a homeowner looking for a grid-tie with battery-back up. They are Doomsday Preppers for lack of a better term and want certain loads if and when the grid goes down for good. Aside from parts selection, they have two roof lines, one facing SE one facing SW. the SW is very low slope and is only accessible with a ladder and climbing on the roof, the other is SE, much steeper slope and accessible from the ground or deck. I mention the access because of snow removal. We had lots of snow last year and I spent lots of time on my roof removing 8" snow falls. Both have good solar access.I'm inclined to chose the SE roof line, but I am interested in arguments for the SW. Thanks! Jesse Sent from my iPhone _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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 |
_______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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
