Anti-Reflective Glass Makes Clear Gains Glass Is Traditionally an Important Topic in Solar Engineering

Solar Energy Solar Glass Anti-reflective glass makes clear gains Glass is traditionally an important topic in solar engineering. But nowadays, unlike just a few years ago, the discussion is no longer about a supply shortage. Now, quality in general and coatings in particular are the focus. The manufacturers increasingly sell anti-reflective glass and place emphasis on special coatings for thin-film photovoltaics.

ince this year’s international trade fair produces float glass and textured glass. The medium- Glasstec in Düsseldorf came to an end, we sized company claims to be the worldwide market Shave updated our market overview from last leader in the field of AR-coated solar glass and to rank year (see S&WE 7/2009, page 82). Our survey of 15 among the top three suppliers of uncoated solar important manufacturers of solar glass has shown glass. This claim is supported by the company’s ca- that anti-reflective (AR) coatings are becoming pacity to process about six million m2 of glass annu- increasingly important. Out of the nine companies ally. In 2009, the company still coated its AR glass that participated in our survey this year, seven stated using a dipping process. In the meantime, Centrosolar that they have had an increase in the sales of AR has put into operation a new production line for glass. Of the other two, one company does not offer single-sided coating. It uses a roller to apply the any AR glass yet. antireflective coating to the plane glass surface (roll- One of the companies that deal intensively with er coating method). AR coatings is Centrosolar Glas GmbH & Co. KG. At its The Danish company Sunarc Technology A/S from Processing: in a vacuum coat headquarters in Fürth, Germany, Centrosolar Glas Rønnede is exclusively active in processing glass into ing system, F-Glass applies functional layers to the glass. Photos (2): F-Glass

88 Sun & Wind Energy 12/2010 AR glass. The company buys textured and float glass quality for applications where people could be daz- from other manufacturers and provides it with an zled. It reduces the dazzling effect in comparison to anti-reflective coating. Sunarc is the only company to normal glass, but this does not impair transmittance. create the AR quality in an etching process. The anti- Furthermore, this year the two partners have begun reflective layer is generated by etching the surface in- to produce anti-reflective glass with a coating on one stead of applying an additional layer. side for the Chinese PV market. The Liechtenstein-based company Interfloat Of course, the Jinjing Group, which complements Corporation produces three types of textured glass in its own know-how with that of the partner Hecker, al- its factory in the East German town of Tschernitz. For so sells solar glass under its own name. Float glass is the first time, Interfloat now also offers anti-reflective produced by Shandong Jinjing Science & Technology glass – even though solar glass without an AR quali- Stock in Zibo City in the province of Shandong. It is al- ty still accounts for the bulk of its products. General so offered with an AR coating. Just recently, the com- Manager Ulrich Frei had already announced this step pany has expanded its production capacity for low- last year. The company relies on well-tried processes: iron float glass from 600 to 1,800 tons per day. since Interfloat produces solar glass all the year There are numerous other Chinese glass manu- round – and not in campaigns like many other manufacturers that produce for the European market. In or- facturers – constant product quality is ensured. der to prove their products’ quality, these manufacturers like to have their glass certified by the Swiss German-Chinese cooperation Institute for Solar Technology SPF. One of them is Henan Succeed New Energy Material. At its headquar- Hecker Glastechnik GmbH from Dortmund, Germany, ters in Qinyang in the province of Henan, the compa- also offers AR glass. Since 2001, the company has co- ny produces textured glass for solar applications with operated with the Chinese Jinjing Group. Jinjing pro- and without an AR coating. In response to an enquiry duces textured glass as well as float glass according from S&WE, the company reported that it is currently to European standards. Hecker processes this glass developing a special solar glass for the American into single-pane safety glass – optionally in AR qual- photovoltaics market. Due to a non-disclosure agree- ity. In the spring of 2011, the current production ca- ment with the customer, the company cannot yet pacity – Jinjing is one of the largest glass producers specify any details. But Succeed is pleased to give in- in China – will be complemented by an additional line formation about the expansion of its own production for textured solar glass. Hecker also has an innova- capacities. At present, three production lines for tive new product: a solar glass with an anti-glare toughened glass and six lines for AR coating are under construction. The new line for toughened glass will have a production capacity of 10 million m2. The new capacity for AR glass will be 4 million m2 for glass coated in a dipping process and 2 million m2 for glass coated using a roller coating process. Succeed wants to significantly increase the proportion of AR glass. In 2009, the capacity utilization of the existing line for toughened glass was 80 %. Interpane: vacuum coating for jumbo sizes

Interpane Glas Industrie AG, which has its headquarters in the North German town of Lauenförde, applies the anti-reflective coating iplus HT to float glass and textured glass. The company has transferred the pro cess from its pilot plant to its industrial coating facility. Since 2006, Interpane has been able to apply solar anti-reflective layers to glass in large sizes up to about 3 m x 6 m using a vacuum process. This can be done either just on one side or on both sides. During subsequent tempering, the glass is not only process ed into single-pane safety glass, but the AR coating is also firmly combined with the glass. At the locations Lauenförde and Plattling in Southern Germany, the company maintains its own solar glass production facilities. Since the beginning of 2010, the anti-reflective coating process developed by Interpane has also been used by the company F-Glass GmbH in Sülzetal- Osterweddingen (Saxony-Anhalt) in float glass pro-

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Textured glass is very popu lar in crystalline PV and for flat-plate collectors. It gives the collector or module its characteristic frosted or rough surface. Photo: Saint-Gobain

duction. F-Glass is a joint venture between Interpane AGC Solar belongs to the AGC Group, which is and the Dutch glass manufacturer Scheuten, which based in Japan but active worldwide. Via its parent has been active in the glass business since 1959. In group, AGC can rely on more than 100 years of expe- the summer of 2009, the joint-venture put into oper- rience in glass production. For its textured and float ation a float glass production line in Sülzetal for the glass, the glass manufacturer offers the anti-reflec- continuous production of solar glass. There, a staff of tive coating Sparc, which brings about an increase in around 270 produces up to 700 tons a day of low-iron transmittance of 2.4 %, measured according to ISO float glass, the company says. April 2010 saw the 9050. At present, AGC produces its textured glass in start of operation of the toughening furnace with a ca- Belgium, China, Japan, Thailand and the US states of pacity of about 4.5 million m2 annually and the con- Kansas and Tennessee. In response to the rising de- tinuous coating line with a capacity of 6 million m2 mand for AR-coated solar glass, this year AGC has al- annually. In the 230 m long facility, a mono-broad- so begun to apply the AR layer Sparc in the textured band coating is applied using the previously men- glass factory in the Belgian town of Roux. tioned process in order to produce AR glass. The so- Saint-Gobain is one of the world’s leading glass lar glass is processed under ultra-clean vacuum con- suppliers. Hence, it is little wonder that the company ditions. The AR coating made of robust quartz in- is in demand in the solar sector as well. Low-iron float creases the transmittance, which has been confirmed glass and textured glass with a frosted or prismatic by flash tests under standard test conditions, and ad- surface accounts for the bulk of the solar glass. Fur- ditionally protects the glass from detrimental envi- thermore, Saint-Gobain offers a cast glass with a ronmental influences. For thin-film applications, the deep texture. A pyramidal or wave shape causes mul- coating line also provides the option of applying lay- tiple light refractions, which increases yield by 3 % in ers by magnetron sputtering. comparison with standard cast glass, as the French company promises its customers. Also in the case of the Saint-Gobain products, transmittance is increased even further by the AR coating, which can be applied to any of the glass products, even the deeply textured glass. The Turkish company Trakya Cam, which belongs to the Sisecam Group founded in 1924, does not yet offer any AR glass. Instead, the company continues to work on improving the transmittance of its plate glass Durasolar P+, which Trakya produces in the South Turkish city of Mersin. The company conducts its R&D activities in the research centre of the Sisecam Group, which is accredited according to the standard EN 45001 for testing laboratories and is a member of the International Commission on Glass (ICG). Trakya’s glass is certified by the Institute for Solar Technology SPF and is sold to companies in Germany and else- where in Europe. The company is making further investments in facilities for the production of solar glass at the Mersin location. For example, the start of operation of a new furnace for casting textured glass A cutting plant cuts the glass to the desired dimensions. is scheduled for the first quarter of 2011.

90 Sun & Wind Energy 12/2010 The British company Pilkington is another suppli- There are also several manufacturers from India er of solar glass. Since 2006, it has been part of the that offer low-iron glass for the solar industry (see NSG Group, one of the world’s largest manufacturers S&WE 10/2010, page 108). Gujarat Borosil Limited, of glass and glass products for the construction and for example, has set up a modern factory to meet the vehicle markets. rising domestic demand for high-quality solar glass The Pilkington product range includes the float and in order to export to the EU (see S&WE 9/2010, glass Optiwhite, a white glass low in iron oxide and page 118). The low-iron solar glass is a borosilicate suitable for solar applications. It is produced in glass, which is offered with a matt-frosted or Weiherhammer in South Germany. There, Pilkington prismatic-frosted texture. It is tempered according to has recently completely modernized and extended its EN 12150. In Europe, the products from Borosil are production line II. distributed by the Dutch company Vertrad NV.

Overview of glass products for modules and collectors Glass thick- Supplier Designation Glass type Transmittance [%] Max. dimensions nesses [mm]

Standard solar glass Solite/Solatex textured glass 91.5 % 3.2 / 4.0 1,650 mm x 2,160 mm AGC Solar Sunmax float glass 91.0 % 3.2 / 4.0 1,650 mm x 2,160 mm Centrosol MM textured glass 91.5 % 3.2 / 4.0 n/a Centrosolar Glas / SM Centrosol C+ float glass 91.0 % 3.2 / 4.0 n/a Euroglas Eurowhite Solar float glass up to 92 % 1 3 to 12 n/a F-Glass F-Solarfloat float glass 91.3 % 2 2.8 to 4.0 2,200 x 2,600 mm Low Iron Solar Gujarat Borosil textured glass 91.6 % 3.2 / 4.0 2,500 x 3,500 mm Glass T-Safe Solar 2.5 / 3.2 textured glass 91.6 % 2,134 mm x 3,050 mm Hecker Glastechnik Pattern / 4.0 T-Safe Solar Float float glass 90.0 % 3.2 / 4.0 2,134 mm x 3,050 mm Succeed Solar Henan Succeed New Energy Material textured glass 91.6 % 3.2 / 4.0 1,200 mm x 2,400 mm Glass Silk / Cone / Interfloat textured glass 92.0 % 2.5 to 6 2,000 mm x 3,000 mm Astra Pilkington (NSG Group) Optiwhite float glass up to 91.0 % 2 to 19 n/a Securit Albarino textured glass 91.5 % n/a n/a S / T Saint-Gobain Solar Securit Diamant float glass 91.2 % n/a n/a Solar Shangdong Jinjing Science & Tech Solar Low Iron 91.0 % 3.2 2,440 mm x 3,660 mm float glass nology Stock Glass 90.8 % 4.0 3,660 mm x 8,000 mm Trakya Durasolar P+ textured glass 91.6 % 3.2 / 4.0 n/a Anti-reflective solar glass / anti-reflective coatings AGC Solar Sparc AR coating for textured or float glass + 2.4 % 2 3.2 / 4.0 1,650 mm x 2,160 mm Nano Power AR coating for textured Centrosolar Glas Centrosol HiT + 6 % 3.2 / 4.0 n/a or float glass F-Glass F-Solarfloat HT AR coating for float glass + 2.5 % 2 2.8 to 4.0 2,200 x 2,600 mm AR-coated solar glass Hecker Glastechnik Energy Vision 96.6 % 3.2 / 4.0 1,200 mm x 2,250 mm (textured or float glass) Succeed AR Solar Henan Succeed New Energy Material AR-coated textured glass 97.3 % 3.2 / 4.0 1,000 mm x 2,000 mm Glass min. + 2.2 % (PV) 2 Interpane Glas Industrie iplus HT AR coating for textured or float glass 2.8 to 12 3,210 mm x 6,000 mm min. + 4 % (solar thermal) 3 depending on AR coating to be etched on textured Sunarc Technology + 5 % n/a n/a the supplier or float glass PV-AR AR coating for textured or float glass + 2.5 % 4 n/a n/a Saint-Gobain Solar Securit Albarino deeply textured glass + 3 % n/a n/a P / G

1 in the case of glass thicknesses of 3 to 5 mm; 2 energy transmittance according to ISO 9050; 3 according to EN 410; 4 increase in transmittance compared with the basic glass in the case of perpendicular incidence of radiation This overview shows which types of glass the manufacturers offer. The transmittance values are difficult to compare because they were not mea sured according to uniform standards. Especially the AR figures have to be considered with caution: the mean values specified by the manufac turers can differ widely, depending on the measurement method. Under standard measurement conditions, however, the manufacturers achieve similar values, as AGC, F-Glass, Interpane and Saint-Gobain show. Source: company data

Sun & Wind Energy 12/2010 91 Solar Energy Solar Glass

Further information: Coatings for thin-film PV their float glass was sometimes used for building in- AGC Solar: www.agc-solar.com tegration. F-Solar named two examples: the glass Centrosolar Glas: are the trend www.centrosolarglas.de F-Solarfloat is used in building integration as the front Euroglas: www.euroglas.com In addition to the textured and float varieties of solar glass either of amorphous silicon thin-film modules F-Solar: www.fsolar.de glass, numerous manufacturers also offer special or of micromorphous silicon laminates. AGC does, Gujarat Borosil: www.borosil.com Hecker Glastechnik: glass for thin-film photovoltaic applications. For ex- however, offer special products for building integra- www.hecker-solarglas.de ample AGC Solar: its float glass PV 200 deforms to a tion. The safety glass SunEwat is a glass-glass lami- Henan Succeed New Energy Material: lesser extent than soda-lime glass when heated and nate enclosing polycrystalline cells. The space be- www.succeedglass.com Interfloat: www.interfloat.com is therefore suitable as a large-area substrate for tween the cells can be adjusted to the needs of the Interpane: www.interpane.com CI(G)S applications. As a back glass for CI(G)S mod- customer and the purpose of application in order to Pilkington: www.pilkington.de ules, AGC offers Moly, a molybdenum-coated float obtain the desired level of light transmittance. At Saint-Gobain Solar Glass: www.saint-gobain-solar.com glass. For manufacturers of silicon thin-film and CdTe present, the maximum size of the SunEwat laminate Shandong Jinjing Science & Technology modules, AGC provides float glass with various TCO is 2.0 m x 3.0 m. From the second quarter of 2011, it Stock: www.cnggg.cn coatings for application as front glass. The AGC prod- will also be available in sizes of up to 2.0 m x 4.0 m, Sunarc Technology: www.sunarc.net Trakya Cam Sanayii: uct range also includes special glass products for CSP explained Marketing Manager Olivier Mal. www.trakyacam.com.tr applications: glass tubes are available with diame- ters of up to 250 mm. They are suitable as receiver Solar glass is becoming more tubes. The extra-thin solar mirror Sun Mirox is lami- important for the glass industry nated onto a carrier material and then acts as a parabolic mirror or a parabolic trough. In the context of our survey, we also asked the glass Interpane, too, offers special coatings for thin- manufacturers for details of the volumes of their glass film photovoltaics, such as blockers, molybdenum sales and the fraction of solar glass in the total coatings and TCO coatings. Shandong Jinjing offers amount of glass sold. For publication, we have made its float glass with a TCO coating. Another company these figures anonymous. that produces glass for thin-film photovoltaics is There is one trend that stands out: almost all the Euroglas GmbH. Since June 2009, the company has glass manufacturers that do not exclusively produce processed the low-iron float glass Eurowhite Solar for solar glass recorded an increase in the sales of solar thin-film PV in its new factory in Haldensleben, glass as a proportion of their total glass sales. Only Saxony-Anhalt. Euroglas has been selling only the one company did not give any figures; another said it TCO-coated Euroglas PV Hy TCO to solar manufactur- had not recorded an increase. Unfortunately, only two ers so far, but not the basic glass Eurowhite Solar. companies specified concrete figures for the change in percentage of solar glass: one of them increased Special application: the proportion of solar glass in its overall glass sales building-integrated photovoltaics from 1.3 % in 2007 to 4.6 % in 2009. The other plans to increase the proportion from 5 % this year to 20 % In principle, any single-pane safety glass is suitable in 2011. for building-integrated photovoltaics, with glass The question about the amounts of glass sold in Solar glass production at AGC thickness usually being at least 4 mm in this case. 2008 and 2009 was answered by too few companies in Kingsport, Tennessee: a Only very few companies offer special solutions for to allow a general trend to be inferred. Nevertheless, robot picks finished textured BIPV. Out of nine companies, three said that their the development can be roughly sketched. Two sup- glass from the line. glass was hardly ever used in BIPV. Centrosolar Glas, pliers that are already well established in the solar Photo: AGC Solar Interpane, Shandong Jinjing and Trakya reported that glass business managed to keep their solar glass sales approximately constant in the order of magni- tude of several million m2. This means that the sales of these two companies fluctuated by less than ± 10 % despite the fact that 2009 was a difficult year for PV. Another company was able to sell 50 % more glass last year than in 2008 and reached 6 million m2. Smaller companies achieved even higher growth rates. A European company, for example, raised its solar glass sales from 500,000 m2 in 2008 to 1.5 million m2 in 2009; an Asian company managed to increase its sales from 1.5 million m2 to 2 million m2. It is obvious that the market for solar glass is growing. The investments in new factories, production lines and technologies demonstrate that the (solar) glass manufacturers are proceeding on this assumption. In addition to improved textured and float glass types, anti-reflective glass products and special coatings for thin-film PV will play an ever greater role in the future. Stefan Trojek

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