PVI Issue

Photovoltaics International Volume 9

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The ninth edition of Photovoltaics International was published in August 2010. It features Fraunhofer IISB looking at advanced process control techniques in Cell Processing, NREL gives an atmospheric thin-film deposition technique overview, and in Power Generation REC looks at reducing BOS costs with new technology and economies of scale.

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In this issue...

PVI Paper
Photovoltaics International Papers
Case in point: SolFocus’s recently dedicated 1MW (AC) high-concentrator photovoltaic installation located on the campus of Victor Valley College in the high desert of Southern California northeast of Los Angeles, which is the largest (H)CPV deployment in North America to date and the Mountain View, CA based company’s biggest project as well.
PVI Paper
Photovoltaics International Papers, Power Generation
Despite the collapsed Spanish market and the general state of the world’s economy, the past year was not a bad year at all from the perspective of installed power capacity of large-scale PV power plants. Installed power capacity surpassed expectations while also bringing new markets into the spotlight, which means that the traditional market leaders of Spain, Germany and the U.S. are no longer the only ‘key’ markets. With the exception of Germany, the past year’s most noteworthy market boost was seen in the Czech Republic and Italy, with similar shake-ups seen in the Asian tiger countries of China and India. With many large-scale PV power plants recently brought into commission in these countries, China and India are brimming with potential for the near future.
PVI Paper
Photovoltaics International Papers, PV Modules
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 these stock levels at short notice, thus creating a spot market. Spot markets serve the short-term trade of 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.
PVI Paper
Photovoltaics International Papers, Thin Film
Thin-film solar photovoltaic technology offers the benefits of low-cost and high-volume production. Yet numerous thin-film PV startups have struggled in their efforts to commercialize complex, expensive production technologies, as production ramps have taken longer than expected, and venture capital and other sources of funding have run dry. This article describes a proprietary cadmium telluride (CdTe) thin-film module production process commercialized by Abound Solar: heated-pocket deposition (HPD) of the semiconductor layer, and the replacement of a traditional lamination process with a novel edge seal. The simple production process has resulted in a fast ramp of module efficiency and throughput. The paper will also describe how the process also results in fast throughput, high yields, and low manufacturing and capital equipment costs.
PVI Paper
Cell Processing, Photovoltaics International Papers
A recent spate of solar cell efficiency gains and record results underline the continued efforts to boost conversion efficiencies, which are at the core of reducing cost-per-watt goals. However, bringing such technology into the mainstream volume production world at little or no increase in manufacturing cost will prove more challenging. This paper takes a look at the current mainstream c-Si cell metallization efficiency developments that are starting to enter volume production with a promise of 20% cell efficiencies and low manufacturing costs.
PVI Paper
Materials, Photovoltaics International Papers
The photovoltaic market, which is dominated by polysilicon-based crystalline solar cells, has been developing rapidly, with growth rates in the double-digit range for several years. In order to meet increasing demand for hyperpure polysilicon, manufacturers need to adhere to environmentally-friendly production processes with low energy consumption. This article highlights the key processes needed to manufacture hyperpure polycrystalline silicon and explores the related challenges and solutions for sustainable polysilicon production. Our findings prove that only an intelligent interaction of all necessary process steps fulfils the requirements for minimized production residue volumes and low energy consumption. Totally integrated production loops for all essential media are prerequisite to reach these targets. Once implemented, these highly efficient production processes serve as an excellent platform technology for the continued healthy growth of the PV industry.
PVI Paper
Market Watch, Photovoltaics International Papers
The upper and lower houses of the German parliament took their time finding a compromise on the degression of PV tariffs. Cutbacks were finally decided on at the start of July. The German PV market is now headed for another record-breaking year in 2010 despite or maybe even as a result of these reductions. EuPD Research, the market research institute, is making a conservative projection of approximately 5.5GW in newly-installed capacity. Nevertheless, pressure is set to increase, particularly on German solar companies. New marketing strategies have to be developed in the mid-term in order to survive and explore new segments in the long term.
PVI Paper
Photovoltaics International Papers, Thin Film
With the never-ending need to reduce production costs, interest in atmospheric deposition techniques is steadily increasing. Even though atmospheric deposition is not new to photovoltaics, and in some cases is actually required to get the best cell performance, many of the fabrication processes for photovoltaic cells are vacuum-based. Due to the diversity in atmospheric deposition techniques available, there are opportunities for applications in thin film and patterned deposition. This paper discusses some of the deposition techniques and their applications, benefits and drawbacks.
PVI Paper
Photovoltaics International Papers, PV Modules
Cell interconnection is recognized as the most critical process with respect to module production yield. If the process is not carefully controlled, cell cracking and subsequent breakage may occur. Many manufacturers promise breakage rates below 0.3-0.5% on their tabber-stringers, which applies for cells above 160-180µm thickness that are free from initial cracks. In real production, this figure strongly depends on materials, process parameters and throughput. This paper outlines some approaches that should be taken to avoid high levels of breakage in the cell interconnection process.
PVI Paper
Cell Processing, Photovoltaics International Papers
Solar cells are generally built in a process facility, often a turnkey line, where high throughput, minimum handling, and lowest cost are dominant factors. There are many complementary metal oxide semiconductor (CMOS) lines in the semiconductor industry – probably more than the number of turnkey lines – where yield, reliability, and device size and complexity are major issues, where millions of chips are made with very close tolerance, and the cost of importance is that of the finished chip. The possibility of using or converting a CMOS line for building Si solar cells has been considered by many in the past [2]. These lines have advantages such as sophisticated and highly developed automated equipment, frequent in-process metrology and quality control, and a high degree of flexibility as well as highly advanced shop floor control systems. The major disadvantages are cost and low throughput. This paper will discuss the differences, advantages, and disadvantages of CMOS and turnkey lines and show preliminary results for Si cells made in the CMOS line.
PVI Paper
Materials, Photovoltaics International Papers
This paper gives an overview of the French PHOTOSIL project that deals with the purification of metallurgical-grade (MG) silicon via different stages of upgraded metallurgical-grade (UMG) silicon to finally arrive at a purity level that is compatible with the requirements of the silicon-based PV industry. However, purified UMG silicon in general and by definition does not reach the ultra-high purity levels of electronic-grade (EG) silicon. Based on the PHOTOSIL project, this paper presents the typical technical challenges and problems encountered with less pure purified UMG silicon and how they were resolved, both during silicon purification and crystallization and the processing of solar cells.
PVI Paper
Photovoltaics International Papers, Thin Film
This paper presents fluorescence detection as a new tool for the investigation of the degradation of EVA. The superior sensitivity of the setup contained herein allows an early assessment of the changes of the EVA after only 20 hours of damp-heat exposure. A newly developed scanning system allows the spatially resolved inspection of entire PV modules. Degradation of the encapsulants was detected after two years’ outdoor exposure, as was the effect of cracks in c-Si cells, which coincide well with cracks made visible by electroluminescence.
PVI Paper
Photovoltaics International Papers, PV Modules
Encapsulant materials used in PV modules serve multiple purposes. They physically hold components in place, provide electrical insulation, optically couple superstrate materials (e.g., glass) to PV cells, protect components from mechanical stress by mechanically de-coupling components via strain relief, and protect materials from corrosion. To do this, encapsulants must adhere well to all surfaces, remain compliant, and transmit light after exposure to temperature, humidity, and UV radiation histories. Encapsulant materials by themselves do not completely prevent water vapour ingress [1-3], but if they are well adhered, they will prevent the accumulation of liquid water providing protection against corrosion as well as electrical shock. Here, a brief review of some of the polymeric materials under consideration for PV applications is provided, with an explanation of some of their advantages and disadvantages.
PVI Paper
Cell Processing, Photovoltaics International Papers
Advanced Process Control (APC) has become an indispensable cornerstone of today’s semiconductor manufacturing. With roots in chemical processing, APC has not only proven itself in semiconductor manufacturing, but has potential to enhance yield in adjacent industries, such as photovoltaics. This paper gives a short introduction to APC, including its key elements, and proceeds to illustrate examples and success stories from the application of APC in semiconductor manufacturing. Based on these application examples, the lessons learned are summarized and the potentials of APC for PV are derived.
PVI Paper
Fab & Facilities, Photovoltaics International Papers
Canada is aggressively pursuing solar photovoltaic manufacturing. Ontario, the province leading the charge, is already the manufacturing hub for other products in Canada and currently boasts one of the most generous feed-in tariffs in the world. This incentive is closely tied to domestic content restrictions in order to foster Canadian photovoltaic manufacturing. In addition, a host of other tax incentives and research and development stimulus packages are making Canada an increasingly popular destination for both established manufacturers and start-up companies.
PVI Paper
Materials, Photovoltaics International Papers
“Handle with care” – this world-renowned warning sign is inherently printed on every wafer until it is safely wrapped into a finished module – and for good reason. Despite the declining price of silicon and the improved manufacturing methods, the raw wafer still has a major share in the overall cost of a module. If we assume an average wafer price of €2.70 for a 156mm multicrystalline wafer, the finished cell will cost about €4.00. Adding in the module manufacturing costs, a cell in a typical module will cost €5.00. Hence, the wafer accounts for more than 50% of the total manufacturing costs, and as such is key to optimizing the costs in the solar value chain for crystalline photovoltaic products. This paper offers some guidelines on the wet wafer separation process that are intended to aid in minimizing the cost associated with wafer breakage.
PVI Paper
Photovoltaics International Papers, Power Generation
PV industry module and component manufacturers have brought down costs significantly over the last four years. This trend is clearly evident as most publicly traded companies continue to grow revenue despite falling module and component prices. However, it is far less clear how downstream system integrators are handling the drop in system prices and contributing to value creation. System prices are generally higher in the U.S. than in Europe, despite lower module prices in the U.S. This disparity often raises questions on the part of European PV professionals where these costs come from, and secondly, what have U.S. system integrators done to reduce costs. This two-part series will shed light on how U.S. system integrators have undertaken tremendous efforts to decrease cost and add value through innovation by focussing on labour-intensive value creation in the downstream segment. Part I will focus on the residential market segment by delving into activity cost savings through innovation in engineering and construction, while Part II will illustrate how changes in sales, rebates, interconnection, and the supply-chain management over the last five years have reduced costs.
PVI Paper
Market Watch, Photovoltaics International Papers
Mainland France’s photovoltaics market is substantially different from the situation in the country’s overseas Départements (DOM) and Corsica. Feed-in tariffs, tax breaks, financing and market players all differ in these territories. This paper takes a look at France’s mainland market, providing a projection for the country’s future market and some resources for more information on the DOM and Corsican markets [1].
PVI Paper
Fab & Facilities, Photovoltaics International Papers
This paper presents and discusses the merits of layout, systems and options for exhaust treatments in PV cell production. Such treatments usually comprise central acid scrubbing, NOx scrubbing, Volatile Organic Compound (VOC) removal and several local treatments for dust, silane, and VOCs, while caustic scrubbing is an option for monocrystalline PV cell production. As direct and indirect major emissions from typical production steps have already been identified [1], this article focuses on a full emission pattern and identifies two sectors, VOC and NOx treatment, as most important for environmental impact analysis.
PVI Paper
Photovoltaics International Papers, PV Modules
This paper describes a methodology used to establish reliability of a CIGS thin-film photovoltaic module component based on identification of a failure mode through product thermal-cycling. The initial observation of the failure is described as part of a larger reliability program that progresses from failure mode and effect analysis through a test-tofailure program that has an objective of understanding the ultimate consequence of specific applied stresses on product performance. Once the specific failure mode was discovered, four means of characterizing the mode were applied and are discussed: tensile testing and material analysis, computer modelling, coupon rapid thermal cycling, and mechanical fatigue testing. This work identified the relevant root cause for failure and facilitated a materials change, which itself was subjected to an accelerated testing program to quantify the improvement and determine success of the design. The means of verifying success included meeting an endurance thermal-cycle limit for a collection of samples and subjecting corrected designs to a mechanical fatigue test, where the correlation between thermal cycle and mechanical fatigue were compared using Weibull analysis.

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