Solar cell performance depends on material quality, as well as on the architecture of the cell. In the search for higher-performing cells, an ability to visualize the bulk and surface quality of the material is an advantage; to do this non-destructively, even in-line, is even better. It would be good to have X-ray vision to look inside, would it not? X-ray diffraction imaging (XRDI) does just that. Images are obtained of the distortions caused by crystal defects, and quantitative measures of the lattice deformation are available. In this paper the results obtained on a commercially available XRDI tool are compared with those from a largescale public research facility.
Using a prescribed test protocol to compare the measured performance of a solar PV power plant relative to its expected performance is often a means by which the value of the facility is determined. Performance testing is used contractually to determine matters such as the fee paid to a constructor, the price paid to a seller, and the cost of capital from a lender or investor. To ensure that performance testing produces consistent and independently verifiable results, it is essential that accurate and repeatable test methods be used. This paper outlines critical deficiencies in older solar PV performance testing protocols, and how the methods prescribed in ASTM E2848 and E2939 eliminate these deficiencies and enable test practitioners to produce consistent, verifiable results with a high degree of confidence.
Why change a product which can be sold in high quantities with a large margin? This is one of the reasons why crystalline silicon modules look the same today as they did 30 years ago. In addition, a module has to last for more than 20 years; to change the technology, or even just the material, many complicated, long-lasting and costly tests are necessary. And even after a series of successful tests there is no guarantee of a long-lasting product. Moreover, during the PV crisis starting in 2009, module manufacturers did not have the manpower and budget for introducing novelties into the module market. All the above are reasons why module architecture and materials did not significantly change with time and did not adapt to the introduction of powerful, highly efficient solar cells. After the crisis, however, many module manufacturers became aware that in order to be able to sell modules on the market with a high margin, their products not only have to be cost effective but also must differentiate themselves from the mass product. Consequently high-power, optically nice, colourful, backcontact, transparent, bifacial, light and highly durable modules are now being developed and are gradually being introduced into today’s market. This paper reports on current trends and discusses future developments.
Cracking of solar cells is a serious issue for product safety and module performance. Cracks may result in power loss, hot spots or arcing, and are caused by exceeding the strength limit of silicon. During the last few years, various studies have shown that fracture of encapsulated solar cells can be influenced by the manufacturing processes, which lead to residual stresses in solar cells. The results presented in this paper will give insights into the stresses generated by soldering and lamination. Furthermore, mechanisms of stress generation will be explained. On the basis of these findings, recommendations are made as to how to mitigate stresses, for example by means of alternative soldering processes, different soldering parameters or material optimization of the copper ribbon or the encapsulant.
The main objective of this study was to evaluate the suitability of thermal analysis for characterizing the stage of hydrolytic degradation of PV backsheets containing polyethylene terephthalate (PET) as a core layer. Additionally, the ageing behaviour of single backsheets was compared with that of backsheets incorporated within PV modules. Test modules using identical components (glass, encapsulant, solar cells, etc.), varying only in the type of backsheet used, were fabricated and artificially aged (damp heat:85°C / 85% relative humidity storage up to 2000h). The material characteristics of the single backsheets and module-incorporated backsheets before and after artificial ageing were determined by thermal analysis. It was shown that the most significant changes between unaged and aged sheets can be observed in the cooling curve of the differential scanning calorimetry (DSC) runs. For all materials, a significant increase in the crystallization temperature was found. Furthermore, the results revealed no influence of the PV module lamination procedure on the thermal characteristics of the polymeric backsheets. Even after artificial ageing under damp-heat conditions, differences between single and module-incorporated laminated backsheets were negligible. The ageinginduced degradation effects of PET could be detected by DSC for all the aged sheets. It is therefore proposed that the testing of single PET-based backsheets under accelerated ageing conditions may be a practicable way to investigate the applicability of a new backsheet material for use in reliable PV modules.
In this issue we offer some insights into what the next wave of photovoltaic technologies may look like as that upturn gathers pace. Industry observers have been in broad agreement that the major next-gen PV technology innovations won’t happen straight away. But there’s also little doubt that the search is now on in earnest for the breakthroughs that will come to define the state of the art in the industry in the years to come.
The latest rounds of formal complaints against alleged breaches of trade agreements, the initiation of circumvention investigations, and preliminary announcements and rulings in various countries and trading zones all demonstrate that the multidimensional trade conflict in global PV markets is far from being resolved and is still simmering. The trade dispute is largely focused on the import of downstream products (c-Si wafer, cell and module) in current and prospective high-volume markets, such as the EU, the USA and potentially India. These
nations or trading zones have implemented, or have proposed to implement, anti-dumping and countervailing duties, predominantly targeted against Chinese downstream producers. New rounds of investigations might lead to existing tariffs being extended to Taiwanese manufacturers that directly or indirectly import into the USA, while the EU might scrap a previous quota and minimum price system and revert to tariffs. This paper gives a brief historical review of the global PV trade dispute, and analyses the formal and legal grounding of anticircumvention actions, which in general increase the complexities of business planning. Because more than 70% of the global downstream manufacturing capacity is located in China and Taiwan, the manufacturers in these regions have no choice but to embrace an internationalization strategy that consists of production offshoring. The paper concludes with the introduction of potential strategies and recommendations which take account of
increased complexities and uncertainties in business planning that arise from shifting trade barriers.
Solar companies are always looking for new markets in an effort to remain competitive. Monica Wilson offers some advice on how developers and contractors should navigate the legal labyrinth that will face them as they go global.
