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- Wednesday, 28 September 2022, 08:30-12:30 -

Plenary Sessions

4CP.1, 1CP.2, 2CP.3

Sneak peek of the second and third plenary session

“PV Works Everywhere”

“Advances in Efficiency and Production of Crystalline Silicon”

“Thin Film Progress for Photovoltaic Devices”

Preview written by:
Heinz Ossenbrink
Chair, International Advisory Committee
World Conference on Photovoltaic Energy Conversion

Today I want to continue to make you curious about the plenaries of the 8th WCPEC. You should not miss the Wednesday, 28 September 2022, as we scheduled three plenary sessions in sequence for the whole morning.

The first plenary session 4CP.1, starting already at 8:30 is along the theme “PV Works Everywhere”. Certainly not a surprise for you that PV is very versatile but think about it a bit: Coal, Oil and Gas is NOT everywhere, and the availability of PV allows so many applications.

The integration of PV directly in vehicles is one of the feasible options to make transport emission-free, and this is why this topic is also about Vehicle Integrated PV - VIPV. The plenary 4CP.1.1 “The Photovoltaic Potential of a Fleet of Urban Vehicles” will be given by Mr. Hesan Ziar of the Delft University of Technology, in The Netherlands. But this presentation is not about integrating PV onto cars, no, Mr. Hesan Ziar her co-authors report a methodology to calculate the power generated by a fleet of urban ships applicable to the 2746 Dutch general cargo vessels. The results are very encouraging, estimating more than 200 GWh of energy available and, best of all, the methodology and parameterisation seems to work also with a fleet of electric cars in an urban environment!

As the title of this plenary session says, PV is everywhere. However, it is also close to wildfires in Australia, in New South Wales (NSW) which seems to be struck by real climate change consequences. The presentation 4CP.1.2, given by Ethan Ford, titled “Impact of the 2019-2020 Australian Black Summer Wildfires on Photovoltaic Energy Production” analyses the PV energy impact of the months-long haze caused by wildfires, taking the monitoring data of 160 residential areas relatively close to the wildfires. PV output was reduced both by atmospheric attenuation by aerosol particular matter and subsequent deposition on the module’s surface. The analysis shows that the power loss is proportional to the particular matter (PM) concentration, on from there the authors derive an estimated loss of revenue close to 10 million AUD (6.5 Mio. €) when applied to all PV systems in the zone. Let us cross fingers for NSW, I would not exclude an update in this talk regarding the impact of the current flooding….!

The title “Statistical Assessment of PV System Tickets” of the third plenary presentation of this session, 4CP.1.3, seems to point to a very specialised talk by Sascha Lindig. Nevertheless, this work is about a new methodology to anticipate failures in large PV power plants and estimate the financial impact of failures and / or their repairs, expressed as a cost priority number (CPN). Based on past statistical numbers (more than 25000 have been collected) of failures (the “tickets”), machine learning is applied to estimate first the energy production loss due to downtime, and subsequently the repair cost. One of the advantages of such a CPN is to forecast the overall operation cost of PV power plants. As a side effect the authors expect better guidelines for the plant operation.

The session concludes with plenary 4CP.1.4 on “Agrivoltaics”, the rising star of PV applications. More than just sharing area for both agricultural and PV use, Agrivoltaics is a concept which could allow symbiosis of the dual-use: PV modules provide controllable shadow, water collection and soil retention, whilst agricultural use can be continued close to the same yield as without PV, or even more. In many countries which are densely populated it is currently the only way forward to increase the energy from free-field installations significantly. We invited Antonio Lancellotta, SET Energie, Italy to present the plenary „Agrovoltaic Plant Management: How to optimize energy production and agricultural output”. He will elaborate on the key aspect of success of the Agrivoltaic model, which can be fully sustainable only when the best trade-off between energy production and agricultural output is reached.

After a short coffee break, Wednesday morning continues at 10:30 with a double plenary, covering 6 more fascinating presentations

The second plenary session is 1CP.2, titled “Advances in Efficiency and Production of Crystalline Silicon” and should give you a fair overview about where crystalline silicon solar cell technology stands now.

The session is opened by Fraunhofer ISE, Freiburg, Germany and is about “25 Years Production Technology Research & Development at Fraunhofer ISE” and Ralf Preu will go into the details of 25 years’ experience to produce solar cell production. Much focus in these 25 years was and is on getting processes from the lab to production technologies required for high volume and high throughput factories. Overall, many new approaches with substantial impact have been initiated and developed to the demonstration level following our comprehensive approach including high speed laser structuring, high rate PECVD of aluminum oxide, several fine line printing advancements and machine learning supported imaging techniques. We are looking forward to listening Mr. Preu on the R&D approaches followed, and in particular to their industrial success stories.

What would be a conference on Photovoltaic devices without reporting on record efficiencies? This is not different in this conference with global reach out. Xiaoning Ru of LONGi Solar Technology, Xi'an, China, will report “Over 26% Efficiency SHJ Solar Cell Using Nanocrystalline Silicon Oxide Window Layer” in the presentation 1CP.2.2. And this is achieved on a large wafer (274 cm2) using nanocrystalline silicon oxide films as window layer. Such thin films can offer improved carrier transport characteristics and reduced parasitic absorption, compared to the more frequently studied amorphous layers. The group at LONGi fine-tuned the process parameters of this yielding a champion solar cell with 26.3% conversion efficiency. We expect that the presentation will also touch upon the efficiencies achieved when upscaling to module size.

In the next plenary presentation 1CP.2.3 we remain in the domain of high efficiency silicon cells. Radovan Kopecek of ISC Konstanz, Germany precents very recent results obtained in a collaboration with SPIC Solar Power, China. The “ZEBRA IBC: 24% Efficient Solar Cells in Mass Production without Passivating Contacts”. For a mass production PERC solar cell, this is quite an achievement, in particular as no passivation step is applied to the contacts. The authors promise to show the processing sequence of the low-cost Interdigitated Back Contact (IBC) solar cells and describe a roadmap towards a screen-printed Cu-metallised IBC-cell. When transferred to the module level, efficiencies at 22% are reached. And why is it called “ZEBRA”? I guess this has something to do with the pattern of the back contacts…

Without a coffee-break, the next and last plenary session 2CP.3 will follow at 11:30, with the title “Thin Film Progress for Photovoltaic Devices”.  Not only that thin-film devices have found their small, stable market share in the world markets, much of R&D is continuing on better understanding, new materials and evolving concepts.

The plenary presentation 2CP.3.1 looks into the development of “Perovskite/Silicon Tandem Solar Cells with Sinusoidal Nanotextures Achieving 29.80% Certified Efficiency”. Certainly, such efficiency will attract quite some interest. The author, Philipp Tockhorn, Helmholtz Zentrum Berlin, Germany together with his collaborators improved the optical performance of such tandems by employing sinusoidal nanotextures with 750 nm period and 300 nm structure height at the polished front-side of the silicon cell. The nanotextures reduce reflection losses in the near-infrared (NIR) and in turn lead also to a small optical gain in the silicon bottom cell. Nanotextures were created at the polished front of a silicon wafer in a three-step process employing nanoimprint lithography and reactive ion and wet-chemical etching. The spin-coated perovskite layers feature planar front and textured rear side. The researchers found that the nanotextures reduce reflection losses in the near-infrared (NIR) and in turn lead to a small optical gain in the silicon bottom cell. Combined with a back contact design with a thinner TCO layer the reported efficiency was achieved. The authors indicate that at the time of the WCPEC-8 they could - with a fine-tuning of the combined light management - reach an efficiency above 30%!

Now it is time for ultra-thin film device physics and technology: In plenary 2CP.2 a “Novel Semitransparent Solar Cell Based on Ultrathin Multiple Si/GE Quantum Wells” will be presented by Hosni Meddeb of the German Aerospace Center, Oldenburg, Germany. Well, they are so thin that they would be entirely transparent, but then they wouldn’t produce electricity. The authors give an overview about Quantum-Well solar cells, which allow a tuning of the solar-cell parameters in an amorphous Silicon / Germanium nanostructure by variation of the thin-film thickness. Moreover, the author will report on ultrathin multiple quantum wells which can achieve 3% conversion efficiency at a light transmission of over 30%. The successful demonstration indicates the promising potential for integration in windows as electrical power generation source and heat insulation approach.

We invited Ana Kanevce, ZSW, Germany for answering the question “Where do the electrons go? A look inside characterization techniques for thin-film solar cells” in the last Wednesday plenary presentation 2CP.3.3. Certainly, we all think to understand where the electrons go, but how is this measured and characterized, when so many parameters influence the multiple paths charge carriers can take?  Electrical characterization techniques attempt to provide answers to the above questions. This talk will give an overview of the challenges (and the potentials) in interpreting some of the commonly used characterization techniques. Some more of the questions Ms. Kanevce promises to answer in this plenary will be: Which mechanism dominates? What do we measure? What do the curves mean? When can we trust the measured data? Can we convert the challenges into opportunities? I believe we all will lean back, learn a lot and will still discuss it at the lunch break, which follows…

This concludes the preview of the three plenary sessions of Wednesday, 28th of September.

My next preview will be on the last Friday plenary 5EP.1 on “PV in the TW Era – Scenarios for Sustainable Energy Future”. I will then try to get a glimpse on how the 8th World Conference on Photovoltaic energy conversion will end..