4 Generations

7/28/2019 4 Generations

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Fourth generation technology gives expected lifetime of 20 years

AMORPHOUS SOLAR PANELS NOWAFFORDABLE AND RELIABLE

By: Frank van der Vleuten, Free Energy Europe BVDominique Guillardeau, Free Energy Europe SA

More than a decade ago, the first generation of innovative thin film

amorphous silicon solar panels has been introduced on the market. Over

the past decade, the quality of amorphous solar panels has been greatly

improved. After several years of innovation and field testing, Free Energy

Europe has now developed a fourth generation technology that ensures a

high reliability solar panel, with an expected lifetime of 20 years . Thesefourth generation amorphous silicon solar panels have a comparable quality

to crystalline solar panels. The price is more affordable, notably for systems

smaller than 35 Watts.

Affordable applicationThin film amorphous silicon solar panelspresently find their application primarilyin rural power supply in developingcountries. Panels of 12Wp can be found inthe shops in over 30 countries. Becauseof the limited price (60-80 USD in theshops), these panels can be bought oncash basis by the rural end-user. Theend-users use the panels primarily forbattery charging, which allows them tohave electric lighting, radio, or television.

In addition, the amorphous silicon solarpanels are particularly suitable as powersource in independent electricalequipment. The panels are currently soldfor electric fencing, parking meters, etc.For these applications, solar powerpresents the most cost-effective solution.

Quality issues importantThin film amorphous silicon solar panelsconsist of a very thin layer of silicon,deposited on, for instance, a glasssubstrate.

The amorphous silicon layer stabilisesafter the first months of use. In general, a

stabilised solar cell behaves like a semi-conductor and has negligible ageingeffects.

The lifetime of amorphous silicon solarpanels is therefore not limited by the cellitself, but by its protection. The thin filmof active material is very sensitive to theimpact of corrosion. Notably in areas withhigh air moisture content, this may causerapid deterioration of the panels, if notproperly framed.

The focus of quality improvement ofamorphous silicon solar panels hastherefore primarily been on finding amoisture proof framing.

With our unique fourth generationframing, Free Energy Europe now has thecorrosion problem under control. Thispaper describes the various framingtechnologies that have been used in thepast and the solution that we have foundto make amorphous silicon a reliabletechnology.


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FRONT

Glass

Photovoltac

Resin

H dro hobic

Pol carbonate

Silicon lue

Simple aluminium frame (1985-1990):The first process that was used to protectthin film solar panels from moisture wasa simple aluminium framing (figure 1).

In these first generation amorphous

panels, the back side of the frontphotovoltaic glass plate was protected bya second glass, glued with resin. Anadhesive tape was then applied aroundthe resulting laminate. The final frame,made of aluminium profiles, wasmounted by screws at the corners. Anadditional silicon glue was introduced inthe aluminium profile just beforemounting.

Figure 1. Cross section of simple aluminium

framing

With this simple aluminium framing

technology, in hot and wet climates,moisture penetration resulted incorrosion of the active layers, starting atthe frame corners and expanding quicklyto the rest of the module. Availablestatistics showed more than 10% failurerate at site.

For Free Energy Europe (NAPS at thetime), this was a good reason to drop thistechnology and look for a more suitablehumidity barrier.

Polycarbonate frame (R&D level 1990)A first option that was investigated, waspolycarbonate framing. In this option, theback side of the photovoltaic plate wasprotected by a back glass glued withresin. The adhesive tape was replaced bya polycarbonate profile glued to the glassaround the laminate. The internal part ofthe profile contained hydrophobic

material acting as a moisture barrier(figure 2).

Figure 2. Cross section of polycarbonateframing

The humidity barrier ability was good,but the polycarbonate profile could notsustain temperature variations. When

exposed to external temperaturevariations, the polycarbonate frameappeared to be breaking at the corners.

Therefore, this solution has never beenlaunched in production.

Polycarbonate with aluminium frame(1991-1996)

This solution has been brought intoproduction in 1991. The design combinedthe advantages of the mechanicalstrength of aluminium frame with the

improved moisture barrier of thepolycarbonate frame. The cross sectioncan be seen in figure 3.

Figure 3. Cross section of polycarbonate withaluminium framing

Still, there was a weak point to thisframing design. Energy output was made

FRONT

Glass

PhotovoltacResin

H dro hobic

Pol carbonateSilicon lue

Aluminium

FRONT

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Photovoltac

Resin

Aluminium

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through a connector. Two types ofproblems occurred through thisconnector:

aluminium foils coming out from thelaminate were truncated after sometime;

water went into the connectorjunction box developing corrosion ofthe contacts.

The default rate has been estimated toreach 3-5% of production, often onlocations near the seaside. This designhas therefore been dropped, primarilybecause of the connector problems.

Fourth generation framing: polymerinjection (1996-up to now)Hence, Free Energy Europe embarked on

the development of a break-throughframing technology, to finally solve all on-going framing problems.

In 1996, the fourth generation framinghas been introduced into the market. Thefront photovoltaic plate is still protectedby a back glass glued with resin. Cablewires are directly soldered to the cornersof the laminate, without any connector.After appropriate adhesion treatment onglass, advanced polymer material isinjected around the laminate.

Figure 4. Cross section of polymer injectionframing

Results

The results of having this framingtechnology two years in the market havebeen very positive. The composition of thepolymer has been fine-tuned.

Now the reported failure rates have fallenbelow 1%. Also the end-users in themarket have noticed the qualityimprovement and are specifically askingfor quality panels from France.

CONCLUSION

The conclusion is that the fourthgeneration framing technology is ableto offer the reliability that is so muchneeded by the end-users.

Free Energy Europe can now offer highquality and reliability of thin film solar

panels, far ahead of the competition.

The expected lifetime of our panels inthe field is up to 20 years.

Glass

Photovoltac

Resin

Polymer

FRONT


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11998855--11999900::11sstt GGEENNEERRAATTIIOONNCCHHRROONNAARR

Major quality problems:!"Simple open aluminum framing

!"Easy moisture penetration

!"Early corrosion and power degradation

!"Very high failure in the field (>10%)FRONT

Glass

Photovoltac

Resin

Aluminium

Isolatin ta e

Silicon lue


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11999900--11999911::22nndd GGEENNEERRAATTIIOONNLLAABB OONNLLYY

Insufficient solution:!"Simple polycarbonate framing

!"Enhanced moisture barrier

!"Very weak in temperature variations

!"Never brought on the market

FRONT

Glass

Photovoltac

Resin

Hydrophobic

Polycarbonate

Silicon glue


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11999911--11999966::33rrdd GGEENNEERRAATTIIOONNNNAAPPSS

Reduced quality problems:!"Hybrid polycarbonate - aluminum framing

!"Enhanced moisture barrier

!"Corrosion sensitive connector

!"High failure rate in specific markets ( 5%)FRONT

Glass

Photovoltac

Resin

Hydrophobic

Polycarbonate

Silicon lue

Aluminium frame


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11999966--........ 44tthh GGEENNEERRAATTIIOONN

FFRREEEEEENNEERRGGYYEEUURROOPPEE

First quality product:!"Advanced polymer injection framing

!"High moisture barrier

!"Close to IEC certification

!"Very low failure rate in the field (

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