Cloudbusting

Forecasting | Short-term PV forecasting offers a multitude of benefits, from trading on wholesale power markets to improved plant operation. Sara Verbruggen reports on some of new the technologies driving forward improvements in the accuracy of forecasting techniques.

State-of-the-art bifacial module technology

By Dr. Hartmut Nussbaumer; Dr. Markus Klenk; Andreas Halm; Prof. Dr. Andreas Schneider

Bifacial PV promises a significant reduction in the levelized cost of electricity (LCOE) for PV systems, which, compared with efficiency improvements at the cell level, is still achievable with comparatively moderate effort. Almost all major PV module suppliers have bifacial modules in their product portfolios or have announced production. This paper gives an overview of the currently available bifacial modules and cell technologies and the performance of these modules. Special attention is given to the cells and the layout of the modules, including light trapping and interconnection technologies, the encapsulation materials and the adapted mounting solutions. Finally, an outlook is given on the basis of the compiled information.

Advances in module interconnection technologies for crystalline silicon solar cells

By Jan Kroon; Dr. Bonna Newman; Jonathan Govaerts; Dr. Eszter Voroshazi; Tom Borgers

In the evolution towards higher cell efficiencies, new cell concepts (twosided and back contacted) have been introduced and for each of these concepts, new module materials and interconnection technologies have to be developed to fulfil all the demands of a good end product in terms of lowest costs, highest yield and power and above all superior quality (reliability and durability). There is no single module concept that fits all cell concepts or module application type so existing module concepts need to be adapted or innovative module technologies are required to fit the aforementioned requirements. This paper provides an overview summarizing the recent developments of integrated cell to module manufacturing approaches such as multi-busbar, multi-wire, half-cell and shingling technologies for two-side contacted cells and advanced soldering, woven fabric and foil based module technologies for back contacted cells aiming for the highest power outputs, lowest costs and longest lifetimes.

Towards the next generation of highefficiency Cu(In,Ga)Se2 thin-film solar cells – Sharc25

By Wolfram Witte; Philip Jackson; Stephan Buecheler; Romain Carron; Susanne Siebentritt; Florian Werner; Sébastien Duguay; Arantxa Vilalta-Clemente; Roberto Menozzi; Giovanna Sozzi; Emilie Bourgeois; Giedrius Degutis; Marcus Bär; Thomas Kunze; Sascha Sadewasser; Nicoleta Nicoara; Martti J. Puska; Maria Malitckaya; Ayodhya Nath Tiwari

The EU Horizon Sharc25 project has provided deep insights into highly efficient Cu(In,Ga)Se2 (CIGSe) thin-film solar cells fabricated by lowand high-temperature co-evaporation using advanced characterization methods, analytical tools, device simulation, and density functional theory modelling. This complementary approach led to a continuous knowledgedriven development and improvement of the CIGSe absorber. Based on optimized chemical composition, profiles, and alkali metal post-deposition treatments (PDT) using KF, RbF, and CsF, the CIGSe cell efficiency could be substantially increased to a record value of 22.6%. Due to additional modifications at the absorber/emitter (replacement of standard buffer system by a combination of thin CdS and TiO2) and back contact/ absorber (introduction of Al back reflector in combination with InZnO diffusion barrier) interfaces, in particular the short-circuit current could be increased. Furthermore, passivation layers in combination with point contact schemes at the CIGSe front and back side were developed and are still under investigation.

Metallization and interconnection for high-efficiency bifacial silicon heterojunction solar cells and modules

By Antonin Faes; Agata Lachowicz; Armand Bettinelli; Pierre-Jean Ribeyron; Jonas Geissbühler

Silicon heterojunction (SHJ) solar cells demonstrate a high conversion efficiency, reaching up to 25.1% using a simple and lean process flow for both-sides-contacted devices, and achieving a record silicon solar cell efficiency of 26.7% in back-contacted configuration. In addition, the field advantages of SHJ cell technology are a native bifaciality and low thermal coefficient providing impressive energy yield. Finally, the technology demonstrates potential cost reduction as it is perfectly suited for thin wafers integration. The SHJ technology is therefore today triggering strong interest in the PV industry, appearing on the roadmap of different cell manufacturers, with several production lines and pilot lines being installed worldwide. One limiting factor of the technology is related to the metallization: due to temperature restrictions on heterocontacts, the standard firing through silver paste needs to be replaced by low curing temperature paste. This type of pastes yield fingers with higher bulk resistivity (two to three times the one obtained with high temperature cured silver pastes) and lower adhesion after soldering. In this paper, materials, processes and costs figures will be reviewed for the metallization and module integration of SHJ solar cells, with a focus on copper plating benchmarked to silver screen-printing, for varying module interconnection technologies.

Riding the workhorse of the industry: PERC

By Pietro P. Altermatt; Yifeng Chen; Yang Yang; Zhiqiang Feng

Improving PERC cells requires rather different strategies than standard cells have required, demanding concrete improvements in materials, manufacturing procedures and fabrication tools.

On the fabrication of high-efficiency mc-Si PERC-based solar cells on diamond wire-sawn surfaces using industrially viable etching technologies

By Bishal Kafle; Pierre Saint-Cast; Ahmed Ismail Ridoy; Sebastian Nold; Jonas Schön; Marc Hofmann; Jochen Rentsch; Laurent Clochard; Edward Duffy

Improving the texturing approach for diamond wire-sawn (DWS) multicrystalline silicon (mc-Si) wafers is one of the key steps to decrease its efficiency gap with monocrystalline silicon-based solar cells. In this regard, black silicon texturing has increasingly caught attention of both academia and industries as a potential approach towards mass production of high-efficiency mc-Si solar cells. In this paper, the challenges of implementing such a texture, with unique feature sizes, in mass production are discussed in detail, and the latest results are reviewed. Finally, results of the first trials at high volume manufacturer applying an alternative plasma-less dry-chemical etching (ADE) method are presented.

PV manufacturing capacity expansion announcements in Q2 2018

By Mark Osborne, Senior news editor, Photovoltaics International

PV manufacturing capacity expansion announcements in the second quarter of 2018 were slightly higher than the previous quarter, although activity slumped specifically in June, following China’s decision to suddenly cap utility-scale and distributed generation projects. The quarter was also characterized by activity in India, partially driven by a major Chinese manufacturer. The report will also analyze first half year capacity expansion plans and targeted locations, globally.

Transition to Industry 4.0: Opportunities and challenges for the PV sector

By Dr. Eszter Voroshazi; Kris Van de Voorde; Dr. Jozef Poortmans

After defining the term Industry 4.0 according to the authors’ interpretation, this paper elaborates on the opportunities and challenges that the Industry 4.0 transition will bring to the PV sector. The topic is approached from various angles. How can the PV industry and the related value chain itself progress to Industry 4.0? And how does this reflect in different application sectors, such as construction and automotive? This paper presents a future scenario towards which the industry could be heading; some of the steps already being taken and some of the main challenges ahead are described. The value of PV technology as an enabler for other sectors, such as edge versus cloud computing, to move into Industry 4.0 is also touched upon. Additionally, a number of enablers and boundary conditions are highlighted in the context of Industry 4.0 and their relevance to the PV industry (legislation, cyber security, etc.) The status of Industry 4.0 in PV compared with other sectors is also explored. Wherever appropriate and possible, examples of projects and activities that illustrate the described topics are given.

R&D spending analysis of 20 key PV manufacturers in 2017

By Mark Osborne, Solar Media

An analysis of R&D spending of 20 publicly listed PV module manufacturers in 2017 has been undertaken to replace Photovoltaics International’s previous list of 12 companies tracked over a 10-year period. A number of the original companies tracked have subsequently de-listed from stock markets and gone private, which meant that a broader analysis, including other listed companies was required to provide a good representation of global R&D spending trends in the PV wafer, cell and module segments of the upstream solar market.

Is that battery cycle worth it? Maximising energy storage lifecycle value with advanced controls

By Dr. Andres Cortes; Ben Kaun

Smoothing and firming are often discussed to make renewables appear more like conventional generation to the grid operator, but how smooth and how firm does that generation need to be? How can the attributes and operations of energy storage be appropriately measured relative to cost? Andres Cortes and Ben Kaun of the Electric Power Research Institute discuss recent work addressing these issues

Back to the drawing board: US utility market rides the wave of change

By John Parnell, Solar Media

Trade tariffs, technology changes, new suppliers and shifting timelines. US developers and EPCs are riding out challenging times. John Parnell looks at the scale of the upheaval and how module pricing and module technology changes are feeding into the day-to-day work of deploying megawatts

Getting serious on module underperformance

By Finlay Colville, Solar Media; Mark Osborne, Solar Media

With so many options open to them, EPCs and developers are faced with confusing choices to make over the right PV module technologies. Finlay Colville and Mark Osborne explore the importance of stringent third-party testing in avoiding asset underperformance