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Wednesday, April 14, 2021

Photovoltaic devices power up with plastics

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Electricity produced from photovoltaic (PV) solar devices is positioned to become a competitive contributor to European power requirements, according to a study published earlier this year by the European Photovoltaic Industry Association (EPIA)

Produced by consultancy AT Kearney, the “SET For 2020” study explores several PV deployment scenarios. It says that under “business as usual” conditions, photovoltaic power could supply between 4% and 6% of Europe’s electricity needs by 2020. The EU average today is less than 1% it estimates.

However, the authors say that with more favourable investment conditions, photovoltaic power could supply as much as 12% of EU electricity demand by 2020.

“Photovoltaic electricity generation will already be competitive in parts of southern Europe by next year,” says Dr Winfried Hoffmann, EPIA president. “The study shows that under the 12% scenario, photovoltaic electricity will be competitive with other power sources in as much as 75% of the EU electricity market by 2020, without any form of external price support or subsidy.”

2020 is a critical date as the European Union has set a target of sourcing 20% of its electricity requirements from renewable sources by then. Solar photovoltaics will be an essential element in achieving this target, European Commission president José Manuel Barros told the 24th European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) in Hamburg, Germany, in September.

Many see the future for PVs in polymer-based designs which can be produced at low cost using high speed web printing or coating technologies. US-based Konarka Technologies unveiled this summer a line of solar panels for charging portable devices based on its proprietary Power Plastic 20 material. It said the first examples, which include battery chargers for lighting and mobile phones, should be in the market by the fourth quarter of this year.

The Konarka Power Plastic 20 Series includes products ranging from 1-7 watts and covers a range of sizes. Next year, the company says it will add higher and lower voltage applications.

Meanwhile, Plextronics, also headquartered in the US, has installed a set of test PV panels at the US National Renewable Energy Laboratory (NREL) for outdoor monitoring and performance testing.

The company claims that the set of 10 test solar modules – produced using its ready-to-use PV ink system on polymeric substrates – are the first organic photovoltaic (OPV) modules to be deployed at NREL. The modules will be monitored closely, enabling NERL’s results in Colorado to be compared with testing the company is already carrying out at Pittsburgh on identical modules.

“Our customers want to understand the real-world performance of our solar technology, and this testing with NREL will allow us to provide them that data,” says Andy Hannah, Plextronics’ CEO. “[It] is a great step toward the commercialisation of organic technology generally.”

Plextronics, which was founded on conductive polymer know-how developed at Carnegie Mellon University in the US, aims to see its technology used in 15bn devices by 2015.

In Europe, German company Heliatek is developing organic solar cells based on “small molecule” hydrocarbon-based dyes. The Dresden-based company claims these cells, which are constructed on flexible film substrates using vacuum processing techniques – promise low cost and short energy payback periods.

Fraunhofer ISE recently certified a power conversion efficiency of 6.07% for a solar cell constructed using Heliatek’s proprietary tandem cell technology.

Heliatek said the test cell, which has an active area of 2 cm_, possesses most of the characteristics required for larger solar modules. The company’s next step will take conversion efficiency to 10%.

Alongside development of polymer-based PVs, the PV industry continues to develop better performing and less costly silicon-based designs. Plastics play a key role in this process, too.

Bekaert Specialty Films has developed its Solar Gard PV T speciality film to provide the moisture barrier, UV resistance and dielectric strength required by the crystalline silicon PV industry. The PVF/PET/PVF backsheet materials are supplied in roll form and in two thicknesses to suit a wide range of panel sizes.

“Our entry into this sector raises the competitive bar and brings module manufacturers a choice of suppliers,” says Christophe Fremont, president of Bekaert Specialty Films.

Apolhya Solar, developed by Arkema of France, is another new thermoplastic film product developed to encapsulate PVs, but in this case both crystalline and flexible designs.

The new film is based on the company’s Apolhya nanostructuring technology, which allows thermoplastics blends to be produced with what Arkema describes as “co-continuous morphologies on a nanometric scale”.

In the Solar version of the product, this nano-structuring is said to deliver good thermo-mechanical properties and creep resistance up to 120ûC along with high transparency. Arkema’s current Apolhya Solar product lines extend to five grades which are distinguished by melting temperature, melt viscosity, transparency and barrier property requirements. Each can be supplied ready-to-use with UV stabilisers and/or necessary adhesion promoters introduced as master batch.

Kuraray Europe’s approach to PV encapsulation is based on polyvinyl butyrate (PVB) films, best known as a polymeric interlayer in laminated glass. The company claims to be the first to develop a PVB film for solar applications – Trosifol PVB.

Solar modules using early versions of these films have been undergoing outdoor weathering tests on module test rigs at the Berlin Photovoltaic Institute and the Fraunhofer ISE Institute in Freiburg since the beginning of the Eighties. Kuraray is now introducing a second generation of PVB PV encapsulation films designed for all conventional module production processes. These new grades will extend the use of PVB resins to special applications, says the company.

Plastics are also used in the Sunplastics range of solar modules, which are constructed from mainly crystalline silicon solar cells embedded in a special gel between transparent PMMA or polycarbonate sheets.

The Sunplastics designs are claimed to amount to two-thirds of the weight of a conventional glass solar module while the high flexibility allows application on curved surfaces without affecting the solar cell life.

Other plastics companies making headway in the PV industry include Bayer MaterialScience, which has supplied its Bayflex PU foam materials to Berlin-based Solon SE. Solon is producing a combined PV panel surround and mounting system for the company’s Black 160/05 in-roof module.

The overlapping polyurethane frame ensures that rainwater runs off easily and does not penetrate the roof. And in contrast to the conspicuous box-like structures of traditional aluminum frame systems, a network of several of the PU-framed solar modules can be assembled to create the appearance of one continuous surface, says the company.

Source: European Plastics news

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