The advantages of thin film solar cells lie in their low cost and high conversion rate. This has major commercial implications, especially in view of long-held views that solar energy is a comparatively expensive form of alternative energy.
The robustness and cost-effectiveness of these “second generation” solar panels have been proven: building-integrated applications have already become the main market in Europe, where it is incorporated successfully into windows with a semi-transparent appearance, roofs, tiles and other building structures and facets.
Thin film solar cells are made up of a flexible, micro-thin metal alloy film with photo-responsive properties which can be incorporated into solar panels that cost considerably less than those made up of standard solar cells. Professor Vivian Alberts says “the most expensive part of silicon-based devices is the silicon itself, whereas in our case, the most expensive part is the glass and the frame.” Standard solar panels contain a 350 micron thick silicon layer, whereas the thin film invented by Alberts contains a layer of only 5 microns thick of an alloy of copper, indium, gallium, sulphur and selenium.
Alberts explains that the proprietary know-how belonging to Photovoltaic Technology Intellectual Property (PTY) Ltd (PTIP), includes a method of producing homogeneous group I-III-VI quaternary or higher order alloy semiconductor films, as well as associated designs for production equipment and facilities to manufacture thin film photovoltaic devices. PTIP now has a semi-commercial plant atTechnopark, Stellenbosch.
Alberts obtained his PhD in 1993 from the University of Port Elizabeth and thereafter joined the Department of Physics at the Rand Afrikaans University (now University of Johannesburg, UJ).
He realised that South African companies would not be able to start producing silicon-based photovoltaic devices on a competitive basis and that something different was needed. He led a photovoltaic research group that centred around the growth and characterisation of polycrystalline ternary and quaternary semiconductors, such as copper indium diselenide (CuInSe2) and copper indium galium diselenide Cu(In,Ga)Se2.
A Fulbright scholarship took him to a stint at the Institute of Energy Conversion (IEC) at the University of Delaware in the United States. The IEC is devoted to research and development of thin-film photovoltaic solar cells and other photonic devices, and among others had a group working on Cu(In,Ga)Se2.
Unlike some other thin-film processes that work with three or four elements, Alberts’ process works with five. “It is currently the only patent in the world that can combine all these five elements through a process to result in an active homogeneous alloy.”
While at the IEC, an official invention disclosure was made in Alberts’ name. However, because of his Fulbright scholarship, it could be transferred to his home university and the patent was registered in the name of the UJ, with Alberts named as the sole inventor. He explains “the real breakthrough lay in the process, which produces the new semiconductor material and both the process and the material properties are protected through the patent.”
A pilot facility was built with the support of the Department of Science and Technology through the Innovation Fund Trust in 2004 and became operational in 2005. It was in essence a scaled-up version of the laboratory facility, where the academic patents process from the laboratory-sized thin film solar cell of 1cm2 was upscaled to panels of 1500 cm2. The commercial-sized facility later built in Germany took this up by a factor of four to 6000 cm2.
The success achieved at the pilot plant led to interest in the media, as well as from potential investors and partners. In 2005 the UJ and Alberts formed PTIP outside of the university, and transferred the patent rights to the new entity and PTIP entered into a license and technology transfer agreement with the German company IFE Thin Film Technology GmbH, which later became Johanna Solar Technologies (JST). They erected a factory (2006-2007) in Brandenburg, Germany, to start with commercial production of the product using the PTIP-patented process. JST was acquired by Bosch, and the Chinese company Sunvim has been licensed to manufacture the product in China.
PTIP has since entered into a joint venture agreement with another strategic German partner for the manufacturing of new generation equipment.
The semi-commercial plant at Technopark in Stellenbosch consists of a full range of research facilities, through semi-commercial production of solar panels that will illustrate the viability of the production process.
Although all the elements used as part of the alloy occur locally, some of it has to be purified in Europe at this stage. The low iron content glass also has to be imported.
The international market for this kind of product is becoming increasingly competitive. Alberts says that when they built the pilot facility in 2005, there was only one company in Germany that had something similar. Today there are 50 companies trying to commercialise thin-film PV processes and products.
According to Alberts, a commercially viable solar energy industry in SA, would currently need to be of a capacity around 1 GW per year in order to show a return on investment. However, the relative cost of solar energy is constantly decreasing as technology improves. According to EU figures, grid parity (where solar energy will cost no more than e.g. coal or nuclear energy) will be reached within the next 3 to 5 years in most First World countries.
He adds that in South Africa it is still a major challenge to obtain finance to commercialise inventions. “It is currently easier to commercialise this new technology internationally than it is locally.”
“Once we have a volume-driven PV manufacturing industry in South Africa, it will definitely spark off other industries and open up many opportunities for local companies. When the mining companies, glass manufacturers and others see a commercial-sized company running, things may change,” Alberts concludes.
The full article appears in the October-November 2011 p54.