soiling city [RE-wrenches]

Bill Brooks bill at brooksolar.com
Thu Jun 29 21:33:59 PDT 2006


Marco, Peter, Nick, and other Wrench soiling their systems rather than
themselves, ;-)

The testing we did at PVUSA in Davis and the information related to the
PowerLight study is focused on rainy season/dry season climates. Typical
losses for those areas are 5-10% per year depending on the year. However,
local effects can dramatically increase soiling losses. Apparently, the site
that Marco is concerned about is at a concrete plant. That changes
everything. Soiling rates can be several percent each day. 

I have seen similar locations. One was at a potato processing plant with a
very large array. Within a few days, the cells in the modules were
completely obscured by dirt. A daily washing sounds a little crazy, but
there are some locations were it is necessary. To have a pat answer as to
soiling losses for an application like this is irresponsible. Until the
system is installed, it is hard to say how bad the impact will be. However,
the likelihood that this system will have real soiling problems is huge.

A daily washing may indeed be necessary, and a weekly washing could be a
minimum to prevent big losses. I'm a little nervous about rainbird timer
systems since they can lose time after a while and you can end up washing
the array in the middle of the day--creating potential issues with mineral
deposits. I think manually started washings in the early morning are best

In any case, the water would need some kind of treatment like a water
softener or deionizer. Given the presence of cement dust in the air, the
minerals in the water could form even worse deposits with the cement dust.
Regardless of the outcome, the soiling issue will definitely need serious
attention.

Bill.


-----Original Message-----
From: Peter Parrish [mailto:peter.parrish at calsolareng.com] 
Sent: Thursday, June 29, 2006 5:41 PM
To: RE-wrenches at topica.com
Subject: RE: soiling city [RE-wrenches]



Nick, if I do the math, 0.2% times 100 days (southern CA) yields a 20% loss
which is much greater than anything I've heard of. The only thing I can
think of is that the 0.2% applies to the 1-5% tilt angles for Powerlight
tiled products.

- Peter

Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave.
Los Angeles, CA 90065
Ph 323-258-8883
Mobile 323-839-6108
Fax 323-258-8885
peter.parrish at calsolareng.com 


-----Original Message-----
From: Nick Lucchese [mailto:nickl at sierrasolar.com] 
Sent: Thursday, June 29, 2006 5:31 PM
To: RE-wrenches at topica.com
Subject: Re: soiling city [RE-wrenches]


  A study posted at the World PV Conference in 
Hawaii last month stated that soiling in dry 
climates was found to decrease panel output by 
.2% each day without rainfall.  This equated to 
an annual energy loss due to soiling by as much 
as 2-6% depending on amount and frequency of 
rainfall in the region. It went on further to say 
that rainfall events of .2 to .3 inches were 
required to fully clean a PV system regardless of 
the severity of soiling. I believe the study was 
performed by Powerlight on large systems, perhaps 
in their home region of northern California. I 
think I still have a high res picture of the 
poster it was on if anyone is interested. It's 
quite small but you can zoom in clearly with 
Iphoto etc.

Nick A Lucchese





>I've got a roof-mounted array on an essentially flat roof in an area 
>that
is
>very dusty with little rainfall.  I'd appreciate knowing what the 
>estimated percentage reduction in output might be for such a heavily 
>dusty area compared to a light soiling location.  I'm thinking about 
>rigging up a rain bird kind of sprinkler to hose down the 16 kW array 
>every day for 15
minutes
>in the early AM hours as a way to keep the glass cleaner.  Has anyone 
>out there put something like that together?  With the hard water in the 
>area, I figure that I would need to condition the water used to hose 
>down the array to minimize the mineral build-up on the glass and 
>frames.
>
>Thanks,
>marco
>
>
>Marco Mangelsdorf
>Electrical Contractor License C-26351
>69 Railroad Avenue, A-7
>Hilo, Hawai'i 96720
>(808) 969-3281, 934-7462 facsimile www.provisiontechnologies.com
>
>
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--
Nick A Lucchese
NABCEP Certified PV Installer
General Contractor # 808851
Sierra Solar Systems
563C Idaho Maryland Road
Grass Valley, CA 95945
tech info and foreign orders:  (530) 273-6754
order line: (800) 51-SOLAR (US only)   FAX:  (530) 273-1760
e-mail:  <mailto:nickl at sierrasolar.com>
world wide web:  <http://www.sierrasolar.com>

Voted Best Solar Company 2003 and 2004 by Union Readers

Because of the high volume of e-mail to which I respond, please leave _all_
of the previous messages (unless it's unbearable) in
   your reply so I can better remember your original message.


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