[RE-wrenches] Flat Panels

[Joel Davidson]

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" <solar1online at charter.net>
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
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" <august at luminalt.com>
> To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
> 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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