03.07.2010 |

SOLAR CELLS ON FAÇADES

PVB films for solar modules – Façade-integrated photovoltaics or “Building-integrated photovoltaics” (BIPV) making use of thin-film technology facilitate the efficient use of the building envelope, enabling it to generate electricity. However, very few solar modules can make do without reliable and lasting protection from external influences, particularly when attached to façades. Polyvinyl butyral (PVB), a film that has been better known until now for its use in laminated safety glass, is now attracting attention.

The market segment for solar modules integrated in façades or used as solar glass roof elements is steadily growing. Its market share is currently at less than 1 per cent of module installations, as many systems are still very costly and building connection technology is still underdeveloped and not sufficiently standardized.

On PV modules, the solar cells have to be protected from external influences. Encapsulation consisting of transparent plastics is making a huge contribution here to the durability of photovoltaic modules and to long-term power generation from sunlight. This applies particularly to building façades. With BIPV systems, it is not only possible to generate electricity and reduce CO2, but also to (at least partly) refinance the façade by feeding the electricity into the grid.

These building-integrated PV systems are becoming increasingly attractive and efficient. They represent a good combination of efficient surface use and aesthetics. A big help here has been the further development of PV modules making use of thin-film technology. Of great importance here is polyvinyl butyral (PVB), a film that has so far been better known for its use in laminated safety glass. A fine example is the New York Stillwell Avenue subway station, which has the world’s largest integrated PV installation with thin-film modules, equipped with TROSIFOL PVB films.

The first manufacturer worldwide to develop a special PVB film for use in solar modules was Kuraray Europe GmbH under the brand name of TROSIFOL, as the company reports.

Since the beginning of the Eighties, solar modules with TROSIFOL PVB films have been undergoing successful outdoor weathering tests on module test stands of Berlin’s Photovoltaic Institute and the Fraunhofer ISE in Freiburg, among others. Designed for all conventional PV module production processes, Kuraray introduced at the end of 2009 a second and technically improved generation of films that supplements the current range of films in special fields of application.

Trend towards PVB
Since 2005, there have been moves in the PV and glass industry to introduce PVB film as the encapsulation material of double-glazing elements with integrated solar cells. The aim is to significantly improve the safety standards of laminated module glass of building-integrated photovoltaics (BIPV).

Furthermore, thin-film solar modules comprising two panes of glass with a PVB interlayer can be inexpensively produced with the two-stage lamination process familiar from laminated safety glass.

With the now appreciable and steadily growing demand for thin-film solar modules – forecasts anticipate 40 per cent of total module output by 2020 – the use of PVB film will continue to increase and claim a growing share of the market.

The reasons for the low market shares of other plastics include the lack of experience with these products in the solar industry, their in some cases inferior technical properties and their excessively high cost. In addition, these materials have to reliably demonstrate a service life of 20 to 25 years in solar modules.

High safety standards
Building-integrated photovoltaics, particularly in Europe, are subject to the same high safety standards as all other glazing on façades and in overhead glazing applications.

For overhead applications in Germany, the list of standards and specifications for the construction industry calls for an interlayer of PVB. When these elements are replaced with solar modules, these standards and specifications remain unchanged. This means that EVA and other plastics in PV modules have to overcome a number of regulatory hurdles in such applications. For building-integrated photovoltaics, experts are expecting strong growth in commercial use over the next ten years.


The author
Dr. Bernhard Kroll is employed in Technical Marketing at Kuraray Europe GmbH in the TROSIFOL Division.
www.trosifol.com

We look forward to seeing you at the “glasstec 2010” in Düsseldorf: Hall 10, stand E36.

TROSIFOL® is one of the leading manufacturers of PVB film for laminated safety glass worldwide. TROSIFOL products are mainly used in applications for automotive and architectural glazing, special TROSIFOL films are used to encapsulate solar cells with long term durability in the photovoltaic industry (PV). In 2004 TROSIFOL was the first manufacturer worldwide to develop a special product line for PV applications based on polyvinyl butyral (PVB). Since then, module manufacturers have had a choice between module production in vacuum laminator or in the process with vacuum deairing and subsequent lamination in autoclaves.
All major companies of the glass and the photovoltaic industry are part of TROSIFOL’s customer base.
The background material for all TROSIFOL films is Polyvinyl Butyral (PVB) that has been used as an interlayer in laminated safety glass since the middle of the thirties of the 20. century. The experience gained from the processing of this material since 1953, thanks to ongoing research and development, is one of the main reasons for technical leadership of TROSIFOL as a manufacturer of films for structural glazing and TROSIFOL’s worldwide success.
TROSIFOL operates its headquarters in Troisdorf, near Cologne (Germany) and an additional plant in Nishny Novgorod, Russia, both certified to ISO/TS 16949 and DIN EN ISO 9001:2000 standards. There are marketing subsidiaries in the United States, Malaysia, India, China and Ukraine.

Today TROSIFOL is a Division of Japan based chemical group Kuraray Co. Ltd (Tokyo) which is the world’s leading producer of polyvinyl alcohols (PVA), one of the initial products for polyvinyl butyral resins and raw material for TROSIFOL PVB film.
Founded in 1926, the Kuraray Group with headquarters in Tokyo, Japan, is the world’s biggest producer of water-soluble synthetic polyvinyl alcohols. In Europe, operating business, sales and production of chemical specialties are handled by EVAL Europe in Antwerp, Belgium and Kuraray Europe GmbH in Frankfurt (Germany). PVA is e.g. a crucial chemical product for the production of paper, textiles as well as for paints, printing inks, adhesives and ceramics.
Kuraray Europe GmbH has installed an integrated management system that satisfies the requirements of a quality management system conforming to DIN EN ISO 9001:2000 with the supplementary demands of the automotive industry ISO/TS 16949, an environmental management system conforming to DIN EN ISO 14001:2005 and an occupational safety and health management system conforming to BS OHSAS (Occupational Health and Safety Assessment Series) 18001:2007. This is externally monitored by annual certification.