Suction and conveying processes: Robots capable of transporting solar technology fast and safely are of growing importance in the field of photovoltaics.

By Anke Muller

Industrial robots feed and discharge solar cell production lines and sort the finished components by pick-and-place processes. They handle glass panes, cut films and foils and assemble frames around solar modules and have recently even started installing junction boxes. Be it at Q-Cells in Bitterfeld, at Conergy in Frankfurt/Oder or Bosch Solar Energy in Erfurt--most production lines in the solar sector are highly automated these days.

For a good reason: “Here in Europe we have to increase capacities to remain competitive,” says Carsten Busch, Head of the Solar Unit at ABB Automation in Friedberg, who adds that price pressure is enormous. If we are to keep manufacturing modules in Germany then robots will have to be used for even more tasks in future. “The automotive industry has proven that successful manufacturing is possible here in this country.” The solar sector is increasingly interested in manufacturing concepts that have “empowered” the likes of Mercedes, Porsche or BMW. Many manufacturers of automation technology boast precisely this know-how.

ABB offers robots for nearly all segments of cell and module production--ranging from FlexPickers for transferring silicon cells and lines for handling and conveying sheet glass to systems for packaging and palletizing the finished solar modules. Busch emphasizes that in the solar sector the prime objective is not to save labor costs. But if large product volumes of the same high quality are to be manufactured robots simply outperform human beings. A case in point being the cross-soldering of so-called strings, i.e., strings of already connected solar cells. “When just one single cross-soldering is not 100% perfect this affects the efficiency of the entire module,” explains the Manager. A single dry soldered joint can even render a complete solar module useless. This is why more and more producers are taking to the fully automatic soldering of cells and strings.

Automotive Industry as a Role Model

“Robots never have a bad day,” confirms Hartmut Wirths at the industrial enterprise Bosch Rexroth, and goes on to say, “Furthermore, the machine does not care where it stands and always gives you consistent quality.” Other benefits are the readiness for use 24/7 and the enormous speed of robots: “Only with automation you can achieve the high production volumes and short cycle times needed for mass production of solar cells,” says Carsten Busch. Robots also bring higher efficiency in the thin-film solar segment: “Glass sheets are becoming bigger and also thinner--and hence more sensitive. Each piece of glass that is destroyed in the process costs money.”

Robots have already become the gold standard worldwide for the production of wafers, i.e., thin silicon slices cut from ingots. “If an employee drops a silicon ingot like this it costs the company nearly US$2,000,” says Busch and explains that the material is brittle and, therefore, breaks into many pieces. Man remains an instability factor. Which is why ingots are now handled by robots even in Asia and are glued to a glass substrate as a preparation for cutting wafers.

This in turn makes wafer production attractive for producers of industrial robots. Only recently Kuka Systems in Augsburg, Germany, acquired the relevant know-how from Czech machine builder Themis. With this move the plant manufacturer extends its product portfolio for photovoltaics to include various special dicing saws. Kuka intends to supply highly automated, turn-key wafer lines in future. So far the company had focused on module manufacturing and solutions for glass handling, string and or cross-soldering, placing strings on foil and glass, framing of modules as well as the subsequent quality tests. Describing the range Albert Vontz, Product Group Manager Solar Technologies at Kuka, says, “We can deliver module lines with up to 100% automation. And we are the only ones.”

Nevertheless, the Augsburg-based company will have to count on strong competition. Reis Robotics, for example, is a successful market player with its buckling arm robots and linear robot units. The company acquired its experience as a supplier of automotive manufacturing lines for autoglass, for instance. At glasstec 2008, the leading international trade fair for the glass sector where companies also present solar applications, Reis exhibited a comprehensive product portfolio. Another strong player not only in automation technology for the photovoltaics industry is Manz Automation. Cooperating closely with machine builders Roth & Rau, they provide their customers with systems and components for automation, quality assurance and laser process engineering. These suppliers will present their manufacturing technology solutions at solarpeq “The Trade Fair for Solar Production Equipment held in Dsseldorf from 28 September to 1 October 2010. At the same time glasstec is taking place, the leading international trade fair for the glass sector, at which more than 1,200 companies will be presenting their solutions in the areas of processing, lamination and automation technology, to name but a few.

You can but watch: The special gripper sorts solar cells into up to 21 different quality grades at lightning speed. Humans need only watch.

ABB Unit Manager Busch feels that the market will remain in motion: “through to mid 2008 the solar sector underwent dramatic growth.” Companies were doing their utmost to ramp up capacities fast and get their production going. To this end they also tolerated constraints. According to Busch “certain degree of automation has already been achieved in cell production. Though this does not hold true for module production everywhere.”

In the production of thin-film modules automation of the so-called front-end, i.e., the production and texturing of the individual layers, is also in the “advanced” stage. In contrast to this, Busch still sees considerable scope in the finishing of coated glass sheets starting with lamination. “From the outset there was a high cost awareness among cell manufacturers,” says the manager adding that ?n this area the expenses associated with automation seemed rather low compared to the costs of the equipment proper.” In contrast to this, the industry did not initially focus so much on efficiency in module production--because as long as solar modules were selling like hot cakes companies did not feel any pressure to rationalize especially since many process steps can be performed manually.

“In the past manufacturers with a capacity of ten to fifteen Megawatts were considered large,” comments Busch. But the use of robots does not seem to be very rewarding with such a magnitude. This has changed though: “Today factories typically have capacities of up to 200 Megawatts and in future this figure will probably be in the region of Gigawatts.” According to Busch “technology is progressing fast and equipment is changing, too. “In cell production, for example, the throughput is higher and lines have a wider footprint, which is why robots serving this larger working space are increasingly in demand.”

“conveyor technology for the solar industry is Bosch Rexroth’s stated focal point,” says Wirths and explains: “the basic concept runs: take from A to B.” However, the devil is in the detail: “We work with standard components and still have to fulfil specific requirements for the solar sector. For instance, in the thin-film segment the brief is to handle glass at relatively high temperatures.”

Crisis Creates Time for Innovations

However, even “regular” wafers confront engineers with increasing challenges. These are becoming thinner and thinner and, hence, more and more fragile. At the same time, PV companies wish to produce 3,600 solar cells on one line per hour--needless to say--with the minimum amount of breakage. To pick up the sensitive wafers without actually touching them plant manufacturers have turned to a ruse from the realm of physics: the so-called Bernoulli Principle. According to this an increase in speed in a gas stream is always correlated with a drop in pressure. This phenomenon not only ensures that aircraft fly but also that objects can be picked up by means of suction using compressed air.

Suppliers are using the current crisis to develop technologies further. Commenting on this Michael Karcher of automation specialist Festo says: “To us the growth pause is a welcome opportunity to develop our products to maturity. The firm supplies equipment producers with solutions ranging from individual components to complete sub-assemblies needed to move wafers or glass substrates. Karcher feels that outfitters had until now been working off backlog orders and their top priority was the producers’ brief to reduce cycle times even further. “Fortunately, this situation has calmed down somewhat. We now have a buyers’ market with excess capacities and companies are now concentrating on line optimization. They want to cut out process steps that are very costly,” explains Karcher who goes on to say that this move requires new concepts.

“Initially the solar sector often adopted solutions from the semi-conductor industry because processes are similar there,” says Karcher, qualifying this statement by saying that solar cells “are more trivial as products”

Over time PV producers have also focused more on their costs. And robots help them to save money--even though companies have to make initial investments first.  

Anke Muller is a freelance journalist in Leipzig, Germany.

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