Photovoltaics International Papers

The last several years have seen a significant number of publications on wire saw data in regard to process optimization theory applied to solar wafering. The methods vary, but fundamentals concern the mechanical dynamics of the wire sawing process, where measurements of the wire forces in the silicon slot using free abrasive are studied; however, these data are not yet fully correlated to a complete thermodynamic analysis of the problem. The objectives of the empirical development of the process theory are also widely varied, but there is industry agreement that it is being faced with the fundamental limits of cutting rates in processes that use free abrasive slurries and a single wire. The limit arises from intrinsic thermodynamic limits of the delivery of work energy to the silicon slot. Similarly, these same principles prevent us from increasing the wafer load to overcome the limitation as work energy transfer rates are countered by higher entropic losses that occur as power and wafer load are increased. The effect results in the problem that the wafer load may not be increased without proportionately reducing table speed. The fundamental nature of these limits suggests that they involve theoretically calculable energy quantities of thermodynamic limiting functions, which restrict the ‘useful’ work that we can extract from the system, where the work energy of interest is the abrasion of the silicon in forming the wafers. The present work reviews the theoretical issues of determining process efficiency optimums that could be used to achieve throughput gains.

Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust stock levels for modules at short notice, thus creating a spot market. Spot markets serve the short-term trade in different products, where the seller is able to permanently or temporarily offset surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supply arrangements as a last resort.

There are still a lot of “ifs” when it comes to concentrator photovoltaics, but it’s starting to look like the question of “when” the technology will start to gain serious market traction may be sooner than some think. With tens of megawatts of projects either recently finished, under construction, or in the last phases of project development — and hundreds more MWs in the longerterm pipeline — deployment of the highefficiency systems may reach triple digits by the end of 2011 or beginning of 2012. On the technology front, as many as a half-dozen cell companies are bringing 40%-efficient cells to market this year, which will help to further reduce CPV’s increasingly compelling levelized cost of energy.

Liyou Yang started in the thin-film game in 1985 with BP Solar, where he eventually ran the company’s amorphous-silicon research efforts. “Once you get into it,” he smiled, “you get hooked.” During the course of our conversation at Astronergy’s headquarters, the Rutgers-educated president/CEO would often reference his time at the old company, using his early experiences as reminders of just how far the technology and the solar industry in general have come since those pioneering days in the 1980s and ‘90s.

The Italian PV market is poised to become the leading market worldwide. However the recent GSE estimates have revealed unexpected volumes installed in 2010. This may lead to an adjustment of the feed-in tariff (FiT) level in the course of this year. GIFI (the Italian PV industry association) is preparing the field for a proposal to make the market development more sustainable, long-lasting and to upgrade the 2020 target.

In 2006, Conergy AG started construction on one of the most advanced solar factories in the world in Frankfurt (Oder). On 35,000 square metres, a fully integrated and fully-automated wafer, cell and module production facility was created – all under one roof. Since 2008, production has been running at full speed and every day more than 3,000 premium modules roll out of the factory. This paper outlines the Manufacturing Execution System (MES) process put in place by Conergy during the planning phase of the factory, to monitor and control the complex and merging production processes.

Over the past two years the solar industry has shown itself to be incredibly resilient to general economic crisis. Supported by cost-cutting and efficiency improvements, the PV industry managed to achieve a growth rate of 120%, or 16.2GW, of newly installed capacity in 2010. Although individual companies are feeling the strong price and margin pressure and intensifying competition, the large, international and vertically-integrated companies are surviving. At least eight new PV markets with a potential annual capacity of 500MW are expected to be added over the next two years. The PV industry will therefore acquire the stability and political autonomy it needs to be able to grow unimpeded and to enter new dimensions. There might also be further tailwind for the PV industry from the catastrophic nuclear crisis in Japan.

Supporting a smooth application of new wafer materials and handling equipment into photovoltaic mass production requires extensive testing of new wafers and equipments under a range of potential operating conditions. The management of such experiments, both in laboratory and production environments, demands the integration and management of a multitude of differing information. This includes static data-like equipment, specifications and experiment settings, online machine data regarding process signal and events – but also unstructured human knowledge, which is available in manual and test reports. To efficiently deal with these kind of complex environments, knowledge management techniques have proven to be a promising approach in various industrial applications. This paper depicts, by means of a photovoltaic wafer-testing platform at Fraunhofer IPA, how the application of automation systems and knowledge management techniques leads to more effective experiment management. More precisely, the gathered knowledge from the wider range of information included in the analysis of experiments can be re-used during future experiments and the manual effort is significantly reduced.

A growing number of thin-film photovoltaic module producers are either trying to keep up with the current cost leader or aiming to differentiate on product design. Calyxo is dedicated to both keeping the pace in the US$0.50/Wp race and introducing new product generations, therefore delivering more value to the customer. We have tried to improve the methodology and approaches for knowledge building in the individual process steps, by learning the relevant interactions between them, as well as ramping volume and lowering manufacturing cost in the first production line. Developing and building the deposition equipment suited to the high process temperatures of approximately 1000°C at atmospheric pressure took some time, but the technology itself now enables Calyxo to benefit from significant cost savings both on capital investment and operational cost – compared to some well-known vacuum deposition methods. Besides the continuous decrease in manufacturing costs, even early on in building the manufacturing capacity, the ability to design the product itself according to the needs of the customers proved itself to be a decisive factor in ensuring competitiveness. This paper aims to give an insight into some of the basic design features of a new product generation and how the so-called new CX3 product will generate more watts by improved performance: delivering better customer value by decreased voltage to save on BOS costs and ensuring further increased field durability through an optimized package design.

Phosphorus dopant pastes are an attractive alternative to the conventional phosphorus oxychloride (POCl3) dopant source for emitter processing in solar cells, as they allow the fabrication of selective emitters on an industrial scale. In this paper it is demonstrated that single-sided uniform screen-printed emitters, processed with phosphorus dopant pastes, can getter multicrystalline silicon (mc-Si) wafers more effectively than conventional double-sided uniform POCl3 emitters. This result is confirmed by minority carrier lifetime measurements with the quasi-stead-state photoconductance (QSSPC) method. Solar cells with selective emitters were processed using phosphorus dopant pastes on mc-Si wafers and were subsequently characterized. The current-voltage (I-V) results are improved compared to uniform POCl3 emitter solar cells and an increased internal quantum efficiency (IQE) for selective emitter solar cells is demonstrated.