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Line integration of PV modulemanufacturing technology in the lightof a rapidly changing environmentNande van Aken, Bodo von Moltke & Dr. Kai Siemer, SOLON SE, Berlin, Germany

InoduionSuppliers of production equipmenthave improved the equipment andm a n u f a c t u r i n g t e c h n o l o g i e s t oaccommodate changes in product andmaterial technology, often in closecooperation with module producers astheir customers. New players have enteredthe equipment market, often comingfrom other industries and leveragingtheir know-how and technologies forapplication in the PV industry. With anincreasing level of professionalism being

displayed in production management,what with optimization of productionplanning, bottleneck considerations, andtools like process control, more and moresuppliers are offering highly-integratedturnkey production lines.

In the early days of moduleproduction, when volumes

were low and throughput

was not the major focus, the

process flow was realizedin a job-shop style of

production with individual

process stations and several

customized products.

Highly-inegaed modulepoduion lineLevel of line inegaionDespite the change in materials and

production technology, the basic processflow for silicon-based PV modules has notchanged in several years (see schematicin Figure 1). Solar cells are joined to formstrings, which are interconnected to form

a module; the module is then laminatedwith encapsulation material; electricalconnections are formed using junctionbox (j-box), and a frame is applied. Finally,the modules are flashed and tested.

In the early days of module production,when volumes were low and throughputwas not the major focus, the processflow was realized in a job-shop styleof production as shown in Figure 2 with individual process stationsand several customized products .Cell interconnection was divided intotwo steps whereby cells were tabbed

with solder ribbons (tabbing) and

the electrical connection to the nextcell was realized in a different machine(stringing).

With the unprecedented growth seenby the industry in the first few years ofthis decade, production volumes grew,and as a result capacity and bottleneckplanning became pertinent issues .Production flow was organized into lineconcepts where the individual steps wereconnected, while cycle times of differentpieces of equipment became more andmore matched. Many highly optimizedproduction lines run in this manner

today, where individual process steps

AbstrAct

Over the past few decades, the PV equipment manufacturing market has seen a significant change in technologies. Cellsizes are being increased, while cell thickness has decreased at an ever-increasing speed of technological innovation,from 4'' 340m cells in the 1990s to 6''+ 180m being the current industry standard. Thin-film modules pose completelynew challenges to module manufacturing technology with a strong integration of the manufacturing of the active layersinto the module production flow. This articles analyses the pros and cons of an increased level of line integration fromthe viewpoint of an established PV module producer.

Figue 1. Piniple poe flow fo PV module manufauing.

This paper first appeared in the fourth print edition ofPhotovoltaics Internationaljournal.


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are optimized individually, throughput

and capacity planning are consideredfor the full line, and automation isinstalled on the level of single processsteps or at particular points of interface(see Figure 3).

The evolution of production lines

corresponds to the development ofproduct concepts, ranging from low-volume customized solutions in the 90sto high-volume power plant products inthe current market, as shown in Figure 4.

A highly integrated l ine uti l izesan i nc r e as e d l e v e l o f auto m ati o n.Typically, process steps such as string

i n t e r c o n n e c t i o n , j - b o x m o u n t i n gand framing use a higher degree ofprocess automation than they would inconventional lines. Also the material andmodule handling, with all transportationwithin the line is carried out by machinesas opposed to manual transportation bya human operator. Materials such as glassplates and modules in progress are movedautomatically from one process step toanother, and are quite often automaticallyfed into the line, as illustrated by Figure 5.

Highly integrated l ines are oftenequipped with complete interlinked

machine and production data collectionsystems to al low the tracking anddocumentation of materials and processesused in the manufacture of the products,as well as a central production controlsystem to steer material and product flowthrough the line.

As matching of all single processsteps is not always possible, the directinterconnection between all processsteps makes it necessary to implementbuffer systems at certain stations ,resulting in an optimized output forthe entire production line. Due to the

reduced amount of operators in the line,highly integrated production requires asignificantly higher degree of automatedprocess control, usually in the form ofvision systems or measurement tools.

Figue 2. Jo-hop module poduion (sOLON, 1998).

Figue 3. Layou fo 120MW poduion line (sOLON, 2008).


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two appoahe o highly inegaed lineThere are some established players in theequipment market among the suppliersof highly integrated manufacturing lines,usually those that already have the majorproduction equipment in their portfolio,like stringers and laminators. Additionalautomation and interconnection into anintegrated line is often realized in-houseor under contract and only less criticalbuilding blocks are realized throughcooperation partners.

On the other hand, there are newsuppliers entering the market that quiteoften have accumulated the knowledge ofthe potential benefits of line integrationfrom other industries or have a particularmanufacturing know-how that they wishto leverage into the PV industry. Robottechnology has found its way into PVmodule manufacturing through thisstrategy. These suppliers usually offer anindividual process step, like framing, plusan integration service, and tend to formalliances to supply fully integrated lines.Several of such alliances have been seenin the market over the last years. Onlyin a few of such concepts can individualbuilding blocks be exchanged uponcustomer demand.

shoe ime-o-make fonew playeHighly integrated production lines usestandardized building blocks, standardized

interfaces, and processes known andestablished by the supplier of the line.Building up a production from scratchto a level provided by a turnkey supplierrequires:

1. Selection of equipment vendors foreach step

2. Definition of interfaces between processsteps

3. Development and implementation ofproduction and control processes

4. I m p l e m e n t a t i o n o f a q u a l i t y

management system5. Training of engineers and operators.

As some ofthe integrators are

experienced in worldwide

operations, line integrators

can bring significant

benefits to line installations

in remote sites.

A new player in the field of modulemanufacturing can easily source points1 to 3 from a one-stop shop, and cantypically get support on 4 and 5, giving

the manufacturer at least a six- to twelve-month head start over taking the routeof building up all necessary know-howin-house. This approach can also savethe module manufacturer from makingexpensive mistakes during the learningcurve. In using the integrated line, it canbe possible to source the product designat a certain quality level. The resultingshortening of time-to-market can easilypay off the higher investment required toimplement an integrated line.

Advanage fo ealihedmodule manufaueEstablished manufacturers will alreadyhave process know-how in-house,as well as an existing supplier baseand production equipment. For thisgroup in particular, it is much harderto justify the investment required of ahighly integrated line. However, thereare contractual advantages or projectmanagement competencies that canprove beneficial for these companies,as the manufacturer in question canmake the decision to have just onecontract partner who is responsible forguarantees, installation, and service.

W i th p ar t i c ul ar f o c us o n th o s ec o m i ng f r o m i ndus tr i e s th at a l s ouse automation, line integrators cantend to have a strong focus on projectmanagement. Although this does notnecessarily mean that timescales are

Figue 4. Evoluion of podu onep: ahieual uomized oluion (1999, lef); powe plan podu (2006, igh).

Figue 5. Piniple poe flow of a highly inegaed line.


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kept to the satisfaction of the modulem anuf ac tur e r , th e i nte g r ato r c ancover resources that the manufacturerdoes not necessarily want to build upbeyond the ramp-up project. As someof the integrators are experienced inworldwide operations, line integratorscan bring significant benefits to lineinstallations in remote sites whereintercultural communication, travel,time shifts, and delegation of workforceraises additional challenges to theproject.

capaiy vaiaion and oonideaionThe current slowdown of the industryshows how important flexibility inproduction output can be. Naturally,the higher the investment, the higherthe financial impact is of changing aproduction output. In contrast, thefinancial impact of output changesis reduced for a line with a limiteddepreciation but larger workforce. Thoughthis is a platitude, it is often neglected atthe time of line-concept planning.

Further cost drivers in this regard besides depreciation and labour cost are yield and uptime. Yield can beincreased by introduction of individualauto m ati o n o f c r i t i c a l p r o c e s s e s ,which are hard to control in manualoperation. Line integration does not

necessarily improve the yield. However,any initial line ramp-up coupled with achangeover of production generatesadditional yield losses. An integratedline will fundamentally have a downtimethat is worse than the downtime ofth e bo tt l e ne c k e q ui p m e nt , w h i c hcan be easily overcome by makingthe right choice of buffer steps andbuffer positions, in turn increasing theinvestment needed for such a line.

With the increasingspeed of technological

innovation in materials,

process know-how

requirements are being

shifted more often

from customers to

equipment suppliers.

Moving poe know-howWith the pervasive technology changeoccurring mainly in the materialss e c t o r , e q u i p m e n t s u p p l i e r s a r ebuilding more and more of the required

process know-how in-house. New cellgenerations are usually tested at thesites of the lead customers among themodule manufacturers and the stringermanufacturers in parallel. The reasonfor this method is that such a majorchange in the materials technologydirectly impacts the technology ofprocesses such as soldering technologyor cell handling.

A general trend is forming. Withthe increasing speed of technologicalinnovation in materials, process know-how requirements are being shiftedmore often from customers (i.e. modulemanufacturers) to equipment suppliers,a trend that is being driven further byadditional line integration.

Limiing he gowh of he PVinduy?Ae oday module eady fo gid paiy?Looking at the performance of thePV industry over the past few years, it

has shown tremendous improvementsin production quality, process stabilitya n d p r o d u c t c o s t s . S t i l l f u r t h e rinnovation is required to reach gridparity for larger parts of the worldwideelectricity market. In the early years ofPV module manufacturing, automationwas driven by the requirements ofprocess quality, like automated stringingand lamination. For the past few years,


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however, automation has started toincrease efficiency of production flow,cycle time and labour resources; todate, none of these approaches hasled to significant innovations in thedesign of the product. The logicalstep of designing a module suited forautomation still has to take place.

Fuue innovaion equie flexiiliy

T h e m a i n d r i v e r f o r i n n o v a t i o nover the past few years has been inmaterial changes - mainly cell sizes andthicknesses, though not limited to cells.This has led to a technological lifetimeof down to two years for some majorequipment. With the current slowdowni n i ndus tr y g r o w th , th e ar e as o f innovation will be widened ever furtherto new products, new applications, andadditional customer benefit, in additionto all ongoing efforts at reduction ofproduct and production costs.

It is the nature of innovation that

the exact path of improvement isnot predictable. It certainly requiresin-depth know-how in the fields ofmaterials, products and processes, aswell as crucial changes to productionflows and processes . Extrapolatingthe past into the future shows that theproduct of tomorrow and thus theproduction lines to build those products will look different from todays mostefficient lines.

In highly integrated lines, even minorchanges in mechanical dimensions orthe usage of second-source material

with only slight variations in processp ar am e te r s c an r e q ui r e h o ur s o f changeover. A major change in theproduct usually cannot be covered byan existing line, but will require eithermajor re-design efforts or a lot ofexpensive variability in the automation.

Highly-inegaed line fom a de-faoandad fo poduion poee (andhu fo podu)Highly integrated, highly automatedp r o duc t i o n l i ne s a l w ay s r e f e r tocomparably high investments. Suchlines need to run at high workloadsf o r th e l o ng e s t p o s s i b l e l i f e t i m eto amortize the additional invest .During the technological lifetime ofthe investment, only minor productc h a n g e s c a n b e a l l o w e d f r o m afinancial perspective. Increasing thetechnological lifetime of equipmentc o r r e s p o nds to di s c us s i o ns abo utstandardization of products. It is theobvious interest of line integrators thatthe innovation frequency of theproductwill be decreased.

Highly-inegaed line limi flexiiliyfo poduion poee (and hu fopodu deign)A longer innovation cycle driven byactual or de-facto standardization isin contrast to the increasing speed ofproduct innovation needed. A modulemanufacturer, having invested heavily ina fixed line concept, will meet with themajor hurdle of having to adapt to newdevelopments, problematic because ofthe associated fixed investment, as wellas the investment needed to change thelines. Installed lines need to be filledwith the products for which they weredesigned.

The efforts of equipment vendorsare focussed on improvements in lineintegration, in individual processes, andsometimes in product modificationsto enhance automation possibilities.The efforts of module manufacturersoperating integrated lines are, conversely,focussed on total line management

than on understanding and improvingi ndi v i dual p r o c e s s s te p s . Mo dul emanufacturers having such processknow-how in-house can more quicklyand efficiently adapt to any material orprocess changes.

Flexibility neededfor product innovation

over the next few years

can be only accomplished

with more individualbuilding blocks instead

of a fixed fully integrated

line concept.

As a result, a higher share of integratedlines will reduce the effort spent onp r o duc t i nno v at i o n and i nc r e as ethe innovation time cycle. In todaysmarket, when growth needs innovation,longer innovation cycles put growthrates at risk. The need for competitivedifferentiation and the availability oftechnological know-how also fosterinnovation. Flexibility needed forproduct innovation over the next few years can be only accomplished withmore individual building blocks insteadof a fixed fully integrated line concept.

OulookIn the long run, more standardizationin the PV industry can be expected.

Once module prices approach gridparity , innovation wil l move intoprocess improvement rather than newproduct technologies. Standardizationmakes sense when the growth drivenby increasing demand is larger thanthe growth brought about through newapplications and products. Nevertheless,the market is not yet ready for sucha move. We need further productinnovation to grow implementationof PV in order for it to be classed as amajor source of renewable energy. Timewill tell: when the industry is matureenough for standardization, it will thenbe possible to source more standardizedlines at a higher level of integration.

In the meantime, we expect thes up p l i e r m ar k e t to s p l i t be tw e e nc o m p a n i e s f o c u s s i n g o n m a s smanufacturing of standardized productson the one hand although theseproducts may vary between companies,and companies with a strong knowledge

base of products and processes, wherethe latter will drive the technologicalinnovation.

Aou he AuhoN a n d e v a n A k e n i s Di r e c to r o f Production Engineering at SOLON SE,Berlin, since January 2008. She holds anM.Sc. in mechanical engineering fromthe Eindhoven University of Technologyand has 15 years experience in the field ofproduct development and manufacturingtechnology.

bodo von Moltke is head of the panelpre-development department at SOLONSE. His role is focussed on the feasibilityof product ideas and new applicationsin PV and for the past 10 years, his workwith SOLON has been mainly related toproduct management and productionengineering for PV module technology.He graduated from the TFH Berlin with adegree in mechanical engineering in 1997.

Dr. Kai siemer is Director of ProductDevelopment, being responsible forthe worldwide development activitiesof SOLON SE. He received a Ph.D. inapplied physics in the field of thin-filmphotovoltaics in 2001, since which time hehas managed technical teams for the fibreoptic and PV industry.

EnquiieSOLON SEAm Studio 16, BerlinGermany

Tel: +49 308 1879 9430Email: [email protected]: www.solon.com

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