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PV cells degrade with time?

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LAN_403

Electroholic

Wed Jan 17 2007, 12:42PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

If you are using an MPPT (maximum power point tracker), you will see that the overall power drops.
BTW, MPPTs are basically buck/boost converters with a uC to monitor power and provide an optimum load for PV moldules.
This are numbers from Solon AG, for their polycrystaline silicon moldules.
Temperature coefficient of open circuit voltage: -0.35%/K
Temperature coefficient of short circuit current: 0.05%/K
Temperature coefficient of power: -0.44%/K

Carbon_Rod

Wed Jan 17 2007, 08:02PM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

"The output of a-Si:H modules made from single junction cells are seen to degrade in outdoor applications over a year or so by up to 30%" (

)

The decay rate due to photodegradation decreases with time. The cells on the back of my wheeled-robot are closely monitored by the charge manager.

Some people here need to review Bayes theorem (

) and its relationship to science...
Yawn, =-D

Ben

Thu Jan 18 2007, 12:38PM

Vigilatny
Registered Member #17 Joined: Thu Feb 02 2006, 02:47PM
Location: NL
Posts: 158

I only remember the figures for top of the line triple junction space rated cells...in space. I believe they were at about 40% capacity after 30 years.

Thu Jan 18 2007, 02:12PM

Banned on April 7, 2007
Registered Member #277 Joined: Fri Mar 03 2006, 10:15AM
Location: Florida
Posts: 157

I respect everyone's opinion above, but seems to be some difference of opinion concerning the lifetime of PV. For a simple country boy like me, a bit confusing. Based on some of the links above (and reports I've goggled), would it be fair enough to say that the majority of evidence/reports tend to support that PV, from the low quality PV up to the NASA grade quality PV, have a tendancy to degrade (at different rates based on quality) in performance over time??? CM

Steve Conner

Thu Jan 18 2007, 02:21PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yes, I think it would be fair enough to say that. The consensus seems to be that reasonable quality PV's have a useful lifetime of some tens of years, and that the degradation is a fundamental problem with the semiconductor itself, not something that's caused by outside contamination. (I stand corrected there, I guess.)

Bored Chemist

Thu Jan 18 2007, 05:47PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

There are at least some varieties of the grand unification theory that predict that protons decay. While experiments have shown that the half life is at least 10^35 years it's still fair to say that the pv cells may not last forever because of this phenomenon.

There remain 2 interesting questions.
Will any PV cells you buy last long enough to deliver enough energy over their lifetime to pay for their costs and (a related matter) will they last long enough to provide more energy than was used to make them.
So far as I can see there is no mechanism for PV cells to wear out; the only moving parts are electrons. I can see how the surfaces might get contaminated by trash in the air and I can imagine cosmic ray damage killing them in space but I can't see why, in principle, they shouldn't last "forever".
On a not unrelated front, what's the oldest working LED anyone has?

Steve Conner

Thu Jan 18 2007, 05:53PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

In a sunny climate like Arizona, California or Spain, a PV will generate back the same amount of energy needed to manufacture it in about 3 years, and then go on to make a large net energy profit over its remaining life.

In the UK, due to our high latitude and generally vile weather, the average PV will barely break even over its life. Hence why my house isn't covered in PV panels, no matter how "green" they "look": I decided it made more environmental sense to spend the money on insulation and double glazing, which pays for itself here in about the same time that PVs do in California.

I've helped to design and install three PV setups on other buildings in Glasgow, though.

Dr. Drone

Thu Jan 18 2007, 07:07PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

Bjørn

Thu Jan 18 2007, 10:18PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

In the UK, due to our high latitude and generally vile weather, the average PV will barely break even over its life.

The latitude does not make a significant difference, you will still get your 1kW on every square meter even at higher latitudes than Scotland. The weather makes a far larger difference but still you will get 65% of the energy that could be collected at the equator.

A big problem is that high efficiency solar cells are only efficient under perfect conditions. Those conditions rarely exist in the UK. A cheap solar panel with a different type of cell will be far more efficient and cost effective.

The picture shows a small solar panel from a Â£3 garden lamp. Through the curtains the efficiency is the same or better as in direct sunlight. An expensive high efficiency panel would drop the efficiency to near 0 in the same coditions.

Cover your house in those and they will pay themselves in the same time as an expensive panel would do at the equator. Since they are far cheaper you can also afford higer powers from the start.

Ben

Mon Jan 22 2007, 05:14PM

Vigilatny
Registered Member #17 Joined: Thu Feb 02 2006, 02:47PM
Location: NL
Posts: 158

Steve Conner wrote ...

In a sunny climate like Arizona, California or Spain, a PV will generate back the same amount of energy needed to manufacture it in about 3 years, and then go on to make a large net energy profit over its remaining life.

Do you have the analysis to back that up? Does it include the energy to produce the components, or just to manufacture from raw materials?

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