[RE-wrenches] evergreen panels diode problems

[boB]

jay peltz wrote:
> HI Mark,
> I've seen a paper from Sunpower that shows their modules are OK for 
> lower voltages, but above a certain voltage ( around 200 or so) they 
> start to see the static build up, but interestingly only on the panels 
> at the high end of the voltage.
>
> I haven't seen anything to indicate that other panels will see an 
> improvement with doing positive ground, if I understand what you are 
> saying?
>
This sorta makes sense, in that, supposedly the Sunpower modules are 
less efficient if the positive leg is not at ground potential.
(isn't that right?)...  So, the module sitting higher in potential from 
ground I guess would not be as efficient ?

My question about these Sunpower modules is, what if you just have some 
kind of faraday shield, or add a backing
of grounded aluminum foil ?   Does that take care of the efficiency 
issue ?   Does it really have to be "ground"  (earth) ?

Otherwise, you would not be able to use these things on an airplane or 
on a satellite (not that you'd use a module of this
sort on a satellite OR an airplane)   Sounds like there are some real 
issues with these PVs for some applications.  Or maybe
the reduction on efficiency isn't that big of a deal ?

Also, why would ANY bypass diode in a module get hot unless that module 
was in a string and shaded, OR, the
diodes were just "leaky" ?  Are these diodes in the Evergreen modules 
discreet diodes, or, embedded in every cell,
or what ?

I'm just curious about all of these things.

boB




> But I will forward on the information to the telecom in question.
>
> thanks,
>
> jay
>
> Peltz power
> On Sep 20, 2008, at 5:36 PM, Mark Frye wrote:
>
>> I am sorry to hear that folks are having these kinds of problems.
>>
>> As I understand it, only module types made up of back contact cells 
>> such as
>> the SunPower are run with positive ground.
>>
>> These modules actually require positive ground to reduce static 
>> charge build
>> up on the front of the cell which can reverse bias and shut down the 
>> module.
>>
>> I don't know, but it seems to me that folks have somehow mixed up the 
>> high
>> yield of the back contact cell with positive grounding so now positive
>> grounding will increase the yeild other types of cells.
>>
>> Do I have the story about right?  Running front contact cells that have
>> plenty of collection wire on the face on a positive ground will not
>> significantly increase yield over a negative ground.
>>
>> Are there other benefits to running positive ground that I am not 
>> aware of?
>>
>> Mark Frye
>> Berkeley Solar Electric Systems
>> 303 Redbud Way
>> Nevada City,  CA 95959
>> (530) 401-8024
>> www.berkeleysolar.com
>>
>> -----Original Message-----
>> From: re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Doug 
>> Pratt
>> Sent: Saturday, September 20, 2008 5:25 PM
>> To: 'RE-wrenches'
>> Subject: Re: [RE-wrenches] evergreen panels diode problems
>>
>> Jay, there was a bulletin from Evergreen earlier this year about their
>> modules being used in positive ground systems. I don't remember the 
>> exact
>> details (and I'm not at work now), but the gist was avoid positive 
>> ground
>> till we make some modifications. Please check w/Evergreen on Monday.
>>
>> -Doug Pratt
>>
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