[RE-wrenches] Voltage degradation

[Drake Chamberlin]

Darryl,

Thanks for the information.  Is the 1% / year strictly voltage 
degradation?  If so, I think we should select our inverters to handle 
20% voltage degradation since the modules have a warranty for at 
least 20 years.  If  50% of the degradation is current and 50% 
voltage, then sizing for a 10% degradation might seem 
reasonable.  Will modules actually put out usable power for 40 
years?  Should we take the long term into account?

Drake



At 06:16 PM 4/8/2010, you wrote:
>Drake, I measured and published a paper in 1992 on the after 10 year 
>performance of solar modules, my study concluded these modules 
>degraded approximately 1% per year. The purpose of the study was the 
>effect on utility demand.
>
>I have heard there are some very good studies with similar results.
>
>Thank you--Darryl
>
>--- On Fri, 4/9/10, Drake Chamberlin 
><drake.chamberlin at redwoodalliance.org> wrote:
>
>From: Drake Chamberlin <drake.chamberlin at redwoodalliance.org>
>Subject: Re: [RE-wrenches] Voltage degradation
>To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>Date: Friday, April 9, 2010, 12:24 AM
>
>What is the documentation for 10% module voltage degradation?  I 
>have heard different ideas on what will degrade over how much 
>time.  For direct grid tie, I shoot for a voltage drop 1% maximum on 
>the DC side.
>
>Thanks,
>
>Drake
>
>At 11:08 AM 4/8/2010, you wrote:
>>I usually keep in mind that the modules will degrade by 
>>10%  However, if you are one of those wrenches promoting 3% DC 
>>Voltage Drops, maybe you should add some more.
>>
>>Nick Soleil
>>Project Manager
>>Advanced Alternative Energy Solutions, LLC
>>PO Box 657
>>Petaluma, CA 94953
>>Cell: 707-321-2937
>>Office: 707-789-9537
>>Fax: 707-769-9037
>>
>>
>>
>>From: Drake Chamberlin <drake.chamberlin at redwoodalliance.org>
>>To: re-wrenches at lists.re-wrenches.org
>>Sent: Tue, April 6, 2010 1:58:56 AM
>>Subject: [RE-wrenches] Voltage degradation
>>
>>Esteemed Wrenches,
>>
>>How much voltage overhead should we have available on our arrays to 
>>allow for inverters not to fall out of their DC voltage operating 
>>range?  Since the module power degradation is 20% over the warranty 
>>period, I usually shoot for a module voltage that can drop 20% and 
>>still be within the MPPT range of the inverter under the average 
>>high temperatures, since most of the degradation is in voltage.
>>
>>Am I being too conservative with this number?  It always pushes the 
>>number of modules to the top of what is allowable on the string for 
>>the extreme low.
>>
>>Thanks,
>>
>>Drake Chamberlin
>>Athens Electric
>>OH License 44810
>>CO License 3773
>>NABCEP TM  Certified PV Installer
>>Office - 740-448-7328
>>Mobile - 740-856-9648
>>
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>Drake Chamberlin
>Athens Electric
>OH License 44810
>CO License 3773
>NABCEP TM  Certified PV Installer
>Office - 740-448-7328
>Mobile - 740-856-9648
>
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Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
NABCEP TM  Certified PV Installer
Office - 740-448-7328
Mobile - 740-856-9648  
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