Preview of the Wednesday Plenary Sessions
CP.1, CP.2, CP.3
Dr. Heinz Ossenbrink
Former European Commission
Joint Research Centre
We continue with our preview of the plenary presentations which the EU PVSEC will bring to you in Lisbon, September 18th-22nd. There will be two plenary sessions on the morning of Wednesday, 20th of September. The first one, titled Multiple Aspects of PV Rollout will address aspects of the increasing PV deployment around the globe, which have not been heard of in previous conferences.
A European consortium will report about their “Mapping the Relevance and Implications of Digitalisation for PV” in presentation CP.1.2. The presenters will explore the different meanings of digitalisation in the PV sector and encompass practically all steps in the PV value chain with both manufacturing and site selection at its beginning, and forecasting and maintenance at its end. Digitalisation allows not only to deliver more high-quality installations at lower cost, the opportunities of data-sharing and machine learning will be highlighted as well as a deeper review of problems and risks of an ever-stronger dependency on digitalisation. We have never had such a comprehensive overview in a conference about all aspects where PV will profit from further digitalisation.
Bi-facial PV modules which generate electricity also from the rear side are now a mainstream feature and gain lately rising interest also by Agri-PV developers. But with almost double exposure to sunlight, can we expect the same lifetime as conventional, single-sided modules? In plenary CP.1.3 Degradation Pathways in Bifacial PV Module Packaging Designs with Emerging Encapsulants and Half-Cut Cells, the US authors go deeply into the particular pathways of degradation mechanisms of such module construction. The authors of the presentation found that the material used for encapsulating the cells within a glass-glass or glass-transparent sheet compound is even more important than in conventional modules, as they were testing for a 50 y (!) lifetime. They studied also the interaction of the half-cut and full-size cells with the encapsulation with respect to PID (potential induced degradation), and included novel encapsulation materials like POE (polyolefin elastomers) and EPE extruded POE and EVA (Ethylene vinyl acetate). Not only did they verify that the accelerated test procedure replicates well the outdoor exposure results, at the end of the test sequences they also analysed in depth the changes in chemistry and properties leading potentially to early delamination.
The second plenary session on Wednesday morning will be about the combined topics Wafer and Thin Film Technologies and moves the spotlight on the Developments in Single and Multijunction Devices.
A major manufacturer from China will start the session CP.2.1 with a talk about Indium-Free Silicon Heterojunction Solar Cells with the Conversion Efficiency Beyond 26%. Whilst the efficiency reached is already remarkable (at the time of this review, the manufacturer has confirmed 26.8% on a 274 cm2 cell), the authors will go into detail on how to achieve such high efficiencies without the use of Indium in the TCO layer (transparent conductive oxide) for their SHJ (single heterojunction) technology, removing a major raw-material bottleneck in the transition from the current PERC (passivated emitter and rear contact) to a next-generation. They will provide also details about how to avoid Indium by using ZnO instead, which they dope to their needs. They successfully demonstrate that the scarcity of Indium will not be a limiting factor for the success of the SHJ technology. We are curious as to how detailed the information will be and whether more manufacturers having large scale SHJ technology in their roadmap will have other approaches.
As we speak about confirmed efficiencies, in the presentation CP.2.2 you will be briefed in detail about The Impact of Measurement Conditions on Solar Cell Efficiency, what are the issues related to this most important figure of merit, and what it takes to establish highest confidence when such figures are presented. One of the authors was involved in the confirmation of the efficiency records presented on the previous talk and will give an overview about the difficulties to maintain high standards in precision and error budget in front of ever-increasing complexity of solar cell topology and materials. They advocate the disclosure of the measurement conditions in addition to the values and uncertainties, to make different technologies more comparable. They compared the impact of measurement conditions at the cell production line with laboratory conditions by comprehensive modelling. As one of their results will also impact the notation in the renowned “Solar Cell Efficiency Tables”, this plenary is a must for everyone involved in the efficiency-race, but also for those who want to have more insight into the efficiencies of new materials.
Whilst we heard so far about the development of wafer-based solar cells, the second part of this plenary session is devoted to the development thin film technologies.
As one of the latest materials used in solar cell development, the presentation CP.3.1 will provide the Roadmap for Perovskite/Silicon Tandem Solar Cells: from Lab Records to Next Generation Modules. Whilst we allknow the steep efficiency rise of perovskite related designs by now, we expect in this plenary talk much more insight on the bumpy road to market sizeable modules. They will elaborate on the principal obstacles as there are long-term stability, efficiency of the bottom part of the tandem, high throughput with low-cost and low environmental impact materials. The plenary will bring you first hand insight into current production processes and moreover the development of process steps for upscaling and industrial compatibility. The authors announced to explain their innovative cluster tool using co-evaporation for the perovskite and contact layer deposition for the tandem solar cells.
On the other thin-film high efficiency technology geared, the talk CP.3.3 Comprehensive Analysis of the Interactions between a Concentrating Photovoltaics (CPV) Module and 5-Junction Solar Cells will mark again the milestones achieved towards concentrating systems on the top of all efficiency records. Not less than five (!) junctions have been embodied in a solar-cell structure optimized for the use in larger, Fresnel-type concentrator modules. The design fine-tuned criteria like 90°C junction temperature, silicone as optical medium and the spectral-optical function of the CPV module, which peaks in the visible spectral range. Other parameters, like the mechanics of the module sub-assembly have been simultaneously optimised and tested both under indoor simulator conditions as well as outdoors. And all topped by a nice software modelling. We are looking forward on a presentation showing results which potentially will open up a new window of opportunity for the deployment of concentrating systems, with sizeable contribution to the Terawatt-age.
There will be four more invited plenary presentations in the plenary session and they will be previewed as soon as the content and the presenter is confirmed.