It's not as simple as tilt angle. Modules in Los Angeles (34 degrees
latitude) at 35 and even 45 degrees tilt get dirt buildup caused by night
and early morning dew and dust and no rain to wash the buildup. Flat roof
arrays stay fairly clean in locations with regular cleansing rainfalls.
----- Original Message -----
From: "Bill Loesch" <[EMAIL PROTECTED]>
To: "RE-wrenches" <[email protected]>
Sent: Wednesday, November 05, 2008 5:51 AM
Subject: Re: [RE-wrenches] Flat Panels
Hi August,
For what it is worth, Velux, one of the premier skylight manufacturers,
limits the minimum angle of the roof (and the parallel skylight) to 15
degrees. With the roof windows/skylights the customer has direct
observation
of how much puddling and subsequent dirt is blocking the window.
Anyone care to estimate just how much performance is lost with 5-10
degrees
off optimum tilt vs.no "ring around the collar" improved performance?
Bill Loesch
Solar 1 - Saint Louis Solar
----- Original Message -----
From: "August Goers" <[EMAIL PROTECTED]>
To: "'RE-wrenches'" <[email protected]>
Sent: Tuesday, November 04, 2008 8:43 AM
Subject: [RE-wrenches] Flat Panels
Wrenches -
Lately we've been called out to repair or upgrade several ~5 year old PV
installations in the Bay Area. It is always interesting to see how
they're
holding up. Apparently it was common to mount panels completely flat
(horizontal) on flat roofs back then. This poses a serious problem
because
the module frame lip catches water and dirt and prevents the panel from
washing off in the rain. See a photo here:
http://luminalt.com/temp/flatpanel.JPG
Note that two of those panels were broken by a baseball, but you can
still
see the dirt buildup on the adjacent panels right across all three rows
of
bypass diodes.
Any ideas on what percentage loss that dried dirt is causing?
Lesson learned: never tilt panels below 5 degrees, preferably 10 degrees.
Cheers,
August Goers
Luminalt Energy Corporation
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