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PV Innovations: Solar manufacturing moves mainstream


Joyce Laird

In our series on solar photovoltaic (PV) innovations, Joyce Laird looks at the latest (and possibly greatest) tools and technologies helping solar manufacturers today.

Solar is moving away from the “everything is custom and designed by us in-house” mentality. In converting to the mature business model of all other major industrial markets, suppliers from all areas are working to help solar manufacturers achieve this goal.

Equipment

Spire Solar, Bedford, MA, USA, is rolling out quite a few new products, some that can be announced and some still under wraps. “Spire has a new line of laminators debuting this year, and is also working on a brand new string and tabbing tool that will come out the beginning of next year. The really hot area right now is in simulators,” says Mark Willingham, Vice President at Spire Solar.

“There is a global demand for very high quality and insured warranties. Solar products have such a long lifetime, quality is very important. A simulator is the only measurement tool that is required for module production,” he adds.

Spire's new Spi-Sun Simulator™ solar PV module testing systems feature light sources that closely match the solar spectrum while avoiding the excessive solar cell heating caused by continuous sources. These simulators can test either crystalline or thin-film modules and can be integrated into fully automated module production lines, or operated in manual mode. In automatic mode, a programmed process sequence provides consistent module testing and offers optional automated loading and unloading of modules. In manual mode, the controls can be operated as desired.

The Spi-Sun Simulator is available with the Module QA Tester, an integrated automation system that allows for efficient module alignment, transport, probing and testing. The option adds high voltage isolation and ground continuity testing, automatic labelling of modules, and automated load and unload of modules.

Oerlikon Solar Ltd, Trubbach, Switzerland, introduced a new edition of their silicon deposition equipment, the KAIMT, earlier this year. “This generation of machine is optimised for micro-morph thin-film technology,” Chris O'Brien, Head of Market Development, North America, says. “We reconfigured the tool so it resulted in a 50% increase in the capacity of the tool and at the same time, a 50% reduction in the footprint of the tool.”

O'Brien says that the benefits and commercial viability of Oerlikon's new micro-morph equipment solution is illustrated in a recent order from Tianwei Solar Films Ltd. Tianwei had a single junction line with a capacity of 46 MW per year. They purchased an upgrade to micro-morph enabled equipment from Oerlikon and this has given their line a 50% increase in efficiency. Tianwei was also able to increase the capacity of their line up to 75 MW.

"Solar is moving away from the 'everything is custom designed by us in-house' mentality. In converting to the mature business model of all other major industrial markets, suppliers from all areas are working to help solar manufacturers achieve this goal."
 

Another area Oerlikon is working on is innovating actual module configuration with a new type of backsheet. In the last few months it has started to commercialise a new design for the module in partnership with DuPont. “We've introduced a white foil that's used in our modules as a reflector backsheet. What we had done previously was use a white paint in order to reflect as many protons as we could and direct them back into the layers as a second pass to pull out more electricity. The new reflective backsheet does a much better job and it's also easier to manufacture. It also allows us to reduce the thickness of the silicon layers which results in lower cost of materials, higher throughput because the cells don't have to stay in the chambers as long because the layers are thinner,” O'Brien says.

Comco Inc, Burbank, CA, USA, manufactures microabrasive blasting systems. Recently, this technology has found a new market in solar cell production, specifically copper indium gallium selenide (CIGS) thin-film technology.

“One aspect of final CIGS cell production must be met to complete the final solar cell: electrical contact must reach through the deposited layers,” Colin Weightman, Director of Technology says. “This is where microabrasive blasting is now being used by CIGS manufacturers because it can handle the tasks without jeopardising the integrity of the solar cells themselves.”

Microabrasive blasting projects a blast of clean, dry air mixed with highly pure, micron-size abrasive media, delivered through a nozzle selected to suit the application. This must be performed in a vacuum activated chamber to remove the dust created by the process. The unique properties of high-energy abrasive particles make microblasting ideal for CIGS solar cell applications. It cuts without heat or vibration and can selectively remove layers without damaging underlying layers or surfaces. For most processes, microblasting remains a manual art that is performed by an operator within a clean workstation. However, for solar thin-film applications the microabrasive blasting process is always integrated into an automated production line.

One application is in edge deletion where the solar cell manufacturer needs to get down completely to the substrate layer to ensure that there is no conductivity between the solar layer and the edge of the glass. This allows the cell to be isolated in its mounting fixture and is governed by the UL requirements. The layers need to be removed below a certain conductivity range. One of the processes commonly used is laser. The challenge faced with this method however, lies in the ability to circumscribe the cell and remove all the layers without melting into the glass or other substrate.

Weightman says that for edge deletion applications microabrasive blasting using aluminum oxide abrasive quickly cuts through all of the thin-film layers, down to the glass substrate. In the normal thin-film deposition process the bottom layers are partially melted into the glass creating a transition boundary that must be removed to completely block conductivity. Microabrasive blasting is able to etch into the glass surface without creating micro-fractures.

“This is only one of the small and yet highly critical steps in the final cell production process where microabrasive blasting is used today. The level of control afforded using the microabrasive blasting process ensures more quality connections without damage to the infrastructure of CIGS solar cells. This is why the Comco MicroBlaster™ is growing in use in the solar market,” he adds.

Materials

The 3M Solar Division, St. Paul, MN, USA, is highly focused on increasing the quality of the materials that go into all PV modules. “Much of what we supply are the packaging materials that go around the solar cells themselves, whether thin-film or crystalline silicon. But, we have a lot to offer as a company in various technologies that help solve technical needs for solar,” Tracy Anderson, Business Director, Energy Generation says.

She says there are two parts to the solar equation: the numerator which is cost and the denominator which is watts. “We have the ability to offer products that answer all. We have products that help reduce peripheral costs when building modules. We also have the ability to add products to the bill of materials that will increase the power output. In some cases, we have products that do a little bit of both,” he says.

One product family from 3M that allows solar manufacturers to reduce production time and cost is 3M Solar Acrylic Foam Tape. This is a very special type of tape that is being used in a variety of solar applications. One is for attachment of the junction boxes onto the panels. The tape replaces other attachment methods such as silicones which are good materials, but he notes that they also need special application equipment and they take a fair amount of time to cure.

“Customers that are using our solar PV tape can very quickly attach the junction box and get a secure, immediate hold and the panel just goes on its way without needing a cure stage. The hold is just as robust. This type of tape has been used in architecture for many years in structural glazing applications for skyscrapers – it holds the glass on the sides of the skyscrapers. So we have a lot of experience with it being used for high endurance applications over a long period of time in all types of weather conditions. For PV, it's reliable and it allows the manufacturer to very quickly make panels. Plus, it comes pre-cut to the shape of the junction box specifically so it can be handled by automated equipment.”

For thin-film solar 3M has another automation friendly conductive foil tape that is applied to the solar panel. It picks up all the current that is collected by the cells and transfers it to the wires that go out the back of the module.

“Along similar lines, we have a family of backsheets called Scotchshield. This is an interesting product because for many years, the way backsheets have been produced is that one company makes one of the key components and then it goes to another company and they laminate it to make a backsheet. So there's a couple of companies involved in making the backsheet before it even gets to the solar manufacturer,” Anderson says.

Value added devices

SolarEdge, Israel, provides DC to DC converter systems that benefit all module manufacturers by maximising power generation and simultaneously reducing installation complexity. By forming partnership agreements with SolarEdge, several major module manufactures across Europe, the USA and Japan are using this technology to differentiate themselves in the market.

“SolarEdge's PowerBox™is embedded into each module by module manufacturers instead of the junction box. One of the challenges of solar panels has been insuring reliable power electronics that can be guaranteed for the life of a module that is supposed to last for 25 years,” John Berdner, General Manager, North America, says.

All solar modules have to pass a temperature-shock requirement of 200 cycles. Inverters, micro-inverters and DC to DC converters must also pass this testing criterion. “We are working with several solar panel manufacturers right now and their minimum requirement is 400 to 500 cycles.” Berdner says. “There has yet to be any micro-inverter that has reached 400 cycles and survived. Our product has not only passed 400 to 500 cycles, we are approaching 1000 cycles.”

Berdner believes that the future of low-cost, high power solar will come from an integration revolution whereby junction boxes, cables, connectors become things of the past and all solar modules will have embedded power electronics. He believes that the current ‘add-on’ approach is a necessary first step to demonstrate all the benefits in the field without actually embedding anything into the module. It is a test phase to integrating DC to DC converters or micro-inverters into each solar module at the factory.

Sustainable Energy Technologies Ltd, Calgary, Canada, provides an approach that enables solar PV systems to be designed so that each module operates at its optimum power point under all conditions independently of the other modules in the system. This “massively parallel” systems approach reduces losses from partial shading of the PV modules. It also eliminates losses resulting from variances in power output due to manufacturing tolerances The result is significantly higher yields under real world conditions than can be obtained using conventional solar inverter technologies.

According to Brent Harris, Professional Engineer for Sustainable Energy, their Sunergy™ inverters are unique for their extra low operating voltages that enables PV modules to be wired in parallel, eliminating mismatch losses and improving energy yield from PV systems. The technology represents the industry's first power optimisation technology that does not require the increased cost of module level electronics. The result is the lowest cost per kWh for solar power, increasing energy harvest from the array by 5-15% compared to conventional high voltage inverters.

“We have a process where our backsheet is made all in one process step. So while backsheets have multiple layers; what we've done is come up with a manufacturing process that produces a backsheet in an integrated process that reduces cost. It is our culmination of 60 plus years of experience in working making films and working with flow polymers which is the type of material we use. This is a very exciting product for us and many solar companies are now using our backsheet. It has very good performance and durability, but they really like it because it's very cost effective,” he adds

In the area of concentrated PV (CPV) Anderson says that 3M is a pioneer. “We have been working with companies providing Fresnel lenses. Again, it is the frontside panels that concentrate the sunlight to a point. What happens, is the sunlight hits the panel and it's like an optical concentration lens and it concentrates all of that sunlight into a point and at that point there is a very high performance multi-junction PV cell that is placed there. It is very different from both thin-film and crystalline silicon. We have the ability to make these very cost effectively.”

3M is also working in what Anderson calls low-CPV. Where high-gain concentration may be going for 100× the concentrated power; low-CPV goes for 1 or 2× concentration using standard modules. “Those companies are using very unique materials from 3M to concentrate that sunlight onto their panels too. They are unique films because they really don't look like mirrors and they only reflect certain wavelengths of light. For instance, infra-red is a bad actor on a solar panel. It doesn't produce any more electricity and it just serves to heat up the module, which is counterproductive. So this film doesn't reflect infra-red, it transmits it so basically, it's a reflector that only reflects very select portions of solar light onto the module gets and more power out of the system,” he adds.

Protection for all electronics that go into both module and peripheral systems is critical. Specialty Coating Systems, Indianapolis, IN, USA, provides Parylene, a unique conformal coating material that is used in electronics across all industries that require complete protection and long life of electronics: Aerospace, automotive, military and medical.

Conformal coating is a common method of device protection, however common coatings that are sprayed, dipped, deposited or brushed on can't provide the protection the family of Parylene formulations bring, particularly to very small micro-electromechanical systems (MEMS) and system-on-chip (SOC) devices. They add weight, are typically uneven and don't cover 100%.

Parylene is a coating that is deposited within a vacuum chamber. Because there is no liquid phase in this deposition process, there are no subsequent meniscus, pooling or bridging effects, so dielectric properties are never compromised. The molecular ‘growth’ of Parylene coatings also ensures not only an even, conformal coating micron level thickness, but because Parylene is formed from a gas, it also penetrates into every crevice, regardless of how seemingly inaccessible. This ensures complete, pinhole-free, encapsulation of the substrate without blocking small openings.

Alan Hardy, Automotive, Electronics & Military Market Manager says that for electronics used in the solar industry, Parylene HT™ is an ideal choice because it has the smallest molecular structure and does not add any measurable weight to the product. “Since there are no fillers used in Parylene, it does not reduce the electrical or RF [radio frequency] signals used to control the generation of power. Parylene dielectric strength of up to 7000 V per mil-thickness makes it an ideal conformal coating for use in the inverter and converter products used in the solar industry. Parylene HT is UV stable for long-term electronics performance in all types of harsh environments. It is a top choice for aerospace, automotive and military applications because of this, along with its high temperature resistance and low dielectric constant and dissipation,” he says.

“The benefits of Parylene are now being seen in many electronic sub-assemblies used in solar devices. Some research is currently in progress in the use of Parylene in external solar fixtures because it also brings the benefit of complete protection while being completely transparent. It protects without compromising the absorption of sun power or deflecting high gain where mirrors or other devices are used on installations,” Hardy adds.

Software

Apriso, Long Beach, CA, USA, creates manufacturing software that provides visibility into, control over, and optimisation across all manufacturing operations. Tom Comstock, Executive Vice President of Worldwide Marketing, Product Management and Strategy says: “Solar is an industry where the need to contain cost is high and the demand for quality products is equally as high. It is also an industry where any given products that a company is making, is guaranteed to change. Their challenge is trying to deal with heavy engineering change, product generational changes, while at the same time trying to optimise their yield and product quality,” Comstock says.

“Many of these companies are still in a ‘black magic’ environment where they rely on very knowledgeable people – which makes solar manufacturing more of an art than an actual manufacturing environment,” Comstock says. “It really needs to go mainstream because if they get a truly winning product, they need to be able to scale it up immediately on a global level. You can't do that unless all the manufacturing business models are in place and 100% under control so you know exactly what is happening in the whole chain from incoming materials through production, test and all cost variables.”

That's what Apriso's FlexNet® software allows them to do. “This provides direct control of manufacturing. Whether an operator or machine, you're making sure the right thing is done in the right sequence, at the right time and you have traceability data so you can follow up with any type of SPC [statistical process control]. We typically interface with ERP [enterprise resource planning] systems and PPM [project portfolio management] systems – ours is the middle level software that handles all the actual manufacturing control, synchronisation, and data acquisition. All companies have some level of business systems software in place, even the start-ups because they need to know what they are doing on the office level to track customers and vendors and so forth. We are the execution arm,” Comstock says.

The Apriso solution is fully web enabled so it is fully accessible from anywhere in the plant. The programme is set up so it communicates to every piece of equipment or work process step in the plant and it feeds into the internet or internal intranet, depending on what the customer wants. They install, train and implement using their own staff and through a network of integrators including HP, IBM, and a number of smaller partners.

Design for manufacturability

Headquartered in Melbourne, Australia, Invetech does for the solar industry what product development teams do for industrial and consumer manufacturing – they offer a product design service that takes an idea or refines an existing product so it would be better suited for its application. It is a combination of ensuring ‘design for manufacturability’ on the production end, which is the hot topic in all current product manufacturing today, and also helping the manufacturer to simultaneously create a more durable end product that is better suited and financially viable for the customer.

“What Invetech brings to an assignment is the ability to really understand the manufacturer's market needs and what they want and translate that into a solution that sometimes exceeds what they were expecting. Invetech provides a broad range of engineering skills and analysis to a variety of manufacturers,” Richard Grant, Vice President and Operations Manager says.

Sopogy, Hawaii, USA, is a good client example. A pioneer in the area of micro-scaled concentrating solar power (MicroCSP), their technologies are used to create process heat, solar air conditioning or electrical power and can be ground or rooftop mounted opening an entirely new market for CSP systems. “Sopogy has projects currently underway in southern California and are taking advantage of Invetech services.

“We provided strength analysis and redesigning of an existing product for Sopogy so that it would be suitable for rooftop mounting and resisting wind load. We reviewed designs and found opportunities to improve manufacturing and affordability of the product,” Grant says. “Invetech brings a wide variety and depth of engineering experience and creativity to solve our clients' challenges,” he says.

Ending thoughts

The big players such as Sharp, Sony, Dow and others that have a large base in other major industries, already have the experience in setting up optimal plants. For those that need added help in converting to a modern business model, sources are there to help in all areas.


About the author:

Based in California, Joyce Laird has been writing for a wide range of industrial magazines for over a decade. Her extensive background in the semiconductor industry created a perfect transition to covering developments in photovoltaics.


This article first appeared in Renewable Energy Focus, September-October 2010.

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