[Greenbuilding] Photovoltaic Life Expectancy

Haudy Kazemi kaze0010 at umn.edu
Fri May 20 18:51:07 PDT 2011


For PV critics, a comparison to corn-based ethanol production or oil 
sands extraction might be worthwhile to see if their energy content is 
greater than their energy cost of production.  The earliest low 
efficiency PV panels may have had net energy losses, and they definitely 
had net economic losses compared to other options available to most 
users.  This did not negate their value to the earliest adopters in 
space or in remote applications where conventional energy sources were 
unavailable.

Although these are fuels, not energy collection devices, you can make a 
comparison between the two as follows:

1.) energy content of a fuel (e.g. 36 kwh per gallon of gasoline) vs 
energy collected over the working lifespan of an energy collection 
device (e.g. 10000 kwh per 200 watt PV panel over 30 year lifespan at 
~4.6 sun-hours per day)

2.) energy cost of production of that unit of fuel vs. embodied energy 
of the energy collection device

If supporting equipment (pumps, motors, wire, engines, racks, chassis, 
etc.) is to be accounted for, make sure the appropriate items are 
applied to both fuel production and to energy collection device production.

Keep in mind that all energy conversion processes lose some energy.  
Also, some forms of energy are more valuable than others.  The differing 
values can make it worthwhile to convert between forms even at net 
energy losses.

Finally, we humans do many things that do not have an energy payback: 
war, vacation, demolition of still usable buildings, frequent 
electronics upgrades, keeping up with the Joneses, etc. simply because 
we want to do them and because we get some other benefit from them other 
than additional energy.  As long as we are able to keep our net energy 
positive, we can afford to splurge on other energy losers.  Comparisons 
to income, non-discretionary and discretionary spending can be made.  
What we don't want to do is to go broke, as I doubt the energy 
bankruptcy/foreclosure process is pleasant.


On 5/20/2011 10:10 AM, J Messerschmidt wrote:
> I read in an article a few weeks ago that the  embodied energy of PV panels
> is greater than they will ever produce in their lifetime.  I can't seem to
> find the article for reference, but I was under the impression that it would
> take 4 years of producing electricity to even out.  Does anyone have any
> information on this?
>
> John
>
> -----Original Message-----
> From: greenbuilding-bounces at lists.bioenergylists.org
> [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of
> elitalking
> Sent: Friday, May 20, 2011 10:18 AM
> To: Green Building
> Subject: Re: [Greenbuilding] Photovoltaic Life Expectancy
>
> I found this link to answer my own question.  Other comments and sources are
> welcome.
>
> Eli
>
> http://homepower.com/article/?file=HP118_pg12_AskTheExperts_1
>
> PV warranties typically allow for 20 percent output degradation over the
> module's 20- to 25-year warranty life. But measurements of many modules put
> into service in the 1980s show that it's unusual to see even half that much
> degradation. Many of those earliest modules still perform to their original
> specifications. It is safe to say that modules carrying warranties of 20
> years or more have a high probability of working well 30 years from now.
>
> ----- Original Message -----
> From: "elitalking"<elitalking at rockbridge.net>
> To: "Green Building"<greenbuilding at lists.bioenergylists.org>
> Sent: Thursday, May 19, 2011 9:42 PM
> Subject: [Greenbuilding] Photovoltaic Life Expectancy
>
>
>> I have been asked by a client what is reasonable expectation for life
>> expectancy of photovoltaic array.  We are considering an installation
>> similar to Gary's.
>>
>> http://builditsolar.com/Projects/PV/EnphasePV/Main.htm
>>
>> I would like to hear a discussion about durability.
>>
>> Thanks
>> Eli
>>
>>
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