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Related publications (66)

Contact Resistivity Measurements and their Applicability for Accurate Series Resistance Breakdown in Heterojunction Solar Cell

Luca Massimiliano Antognini, Christophe Ballif, Mathieu Gérard Boccard, Matthieu Despeisse, Julie Amandine Dreon, Lison Sylou Marthey, Bertrand Yves Paul Paviet-Salomon, Laurie-Lou Senaud, Deniz Türkay

In this work, we use several approaches to perform accurate Series Resistance (R-S) breakdown of a state of the art 2 cm x 2 cm screen-printed solar cell reaching 82.5% FF. On the one hand, Haschke et al.'s model for the lateral transport through the cell, coupling the TCO and wafer sheet resistances through the contact resistivity (rho(C)), predicts a reduction of R-S with increasing injection (Delta n) through the enhanced wafer conductivity [Haschke et al., J. Appl. Phys., 2020]. In contrast, we observe that the R-S of the solar cell, obtained from the difference between the J-V and Jsc-Voc curves, increases with Delta n. Similarly, Senaud et al. observed increasing rho(C) with Delta n using TLM measurements under illumination [Senaud etal., EU-PVSEC, 2020]. To investigate the discrepancy between these experimental observations and theoretical expectations, we extract rho(C) values either from dark TLM, illuminated TLM or illuminated symmetrical sample measurements and incorporate them into Haschke et al.'s model to reconstruct the R-S of the solar cell. Detailed series resistance breakdown using rho(C) values from all three tested methods show accurate R-S predictions within at MPP +/- 0.1 Omega cm(2), showing that the different approaches have sufficient accuracy to estimate the resistive losses in the solar cell under study. Regarding dependence upon injection, it was only possible to predict an increasing series-resistance trend using contact resistivity from illuminated TLM, therefore matching closer the measured linear increase of the R-S of the solar cell from MPP to open circuit conditions, while the other methods predicted a decreasing trend. We discuss practical differences between the methods and propose possible improvements.

AMER INST PHYSICS2022

Design of a Hyperloop System MockUp

Tony Govoni, Malicia Leipold, Mario Paolone, Denis Tudor

The thorough development of the hyperloop system does require the availability of reduced-scale models. They can be used for the fast prototyping of various components, as well as for studying critical phenomena that takes place in this peculiar transportation system without the need to develop complex and expensive full-scale setups. In this respect, in this paper, we present a process for the optimal assessment of the scaling factor; it is to be used for the development of a reduced-scale hyperloop model, starting from the knowledge of the technical characteristics of its full-scale counterpart. The objective of the proposed process is the minimisation of the difference between the normalized power profiles associated with the reduced-scale and full-scale models of a hyperloop capsule traveling along a pre-defined trajectory with a pre-determined speed profile. By considering the hyperloop full-scale model as a reference, we propose a set of equations that link the above-mentioned metric with the constraints dictated by the kinematics of the hyperloop capsule, the capsule's battery-energy storage and propulsion systems, the capsule's aerodynamics, and the operating environmental conditions. We then derive a closed-form expression for the assessment of the optimal scaling factor and eventually use it to study the scaled-down version of an application example of a realistic hyperloop system.

IEEE2022

Towards true climate neutrality for global aviation: a Negative Emissions Fund for Airlines

Sascha Nick, Philippe Thalmann

What would it take for aviation to become climate-neutral by 2050? We develop and model a trajectory for aviation to reduce its CO2 emissions by 90% by 2050, down to a level where all residual emissions can be removed from the atmosphere without crowding out other sectors that also need negative emissions. To make emitters pay for the carbon removal, we propose and model a negative emissions fund for airlines (NEFA). We show that it can pay for the removal of all CO2 emitted by aviation from 2030 onwards, for a contribution to the fund of USD 200–250 per ton CO2 emitted. In our baseline simulation, USD 3.3 trillion is invested by the fund over 40 years in high-quality carbon removal projects designed for biodiversity and societal co-benefits. While we do propose a number of governance principles and concrete solutions, our main goal is to start a societal dialogue to ensure aviation becomes both responsible and broadly beneficial.

2022

Green solvents for chemical reactions

Jeremy Luterbacher

The present invention relates to Use of a compound of the general formula (I), (II), (III), (IV), (V) or (VI) wherein R1 and R1', R21 and R21', R31 and R31' are the same and are hydrogen, a linear or branched C1 to C18 alkyl, a linear or branched C2 to C18 alkenyl, a linear or branched C1 to C10 alkoxy, a linear or branched C1 to C9 alkoxycarbonyl, a linear or branched C1 to C9 alkanoyloxy, aminocarbonyl, hydroxycarbonyl, a linear or branched C1 to C9 alkoxyalkyl, an unsubstituted cycloalkyl, a linear or branched C1 to C6 alkyl substituted cycloalkyl, preferably an unsubstituted cyclohexyl, an unsubstituted C6 to C12 aryl, a linear or branched C1 to C4 alkyl substituted C6 to C12 aryl, or C7 to C12 aralkyl, R2 and R2', R22 and R22', R32 and R32' are the same and are hydrogen, a linear or branched C1 to C18 alkyl, a linear or branched C1 to C9 alkoxyalkyl, or R2 and R2' form together with R1 and R1' respectively, R22 and R22' form together with R21 and R21' respectively, R32 and R32' form together with R1 and R1' respectively, a 5 or 6 membered unsaturated or saturated carbocyclic ring optionally comprising 1 or 2 oxygen atoms, X is selected from the group consisting of hydrogen, fluoro, chloro, bromo, iodo, alkoxycarbonyl, aminocarbonyl, hydroxycarbonyl, a linear or branched C1 to C18 alkyl, a C1 to C18 alkenyl, a linear or branched C2 to C10 alkenyl, a sulfonate and OR50, wherein R50 is selected from the group consisting of hydrogen, a linear or branched C1 to C18 alkyl, and a linear or branched C1 to C9 alkylcarbonyl, and Y is selected from the group consisting of hydrogen, fluoro, chloro, bromo, iodo, a linear or branched C1 to C18 alkyl, a C1 to C18 alkenyl, a linear or branched C2 to C10 alkenyl, a sulfonate and OR50, wherein R50 is selected from the group consisting of hydrogen, a linear or branched C1 to C18 alkyl, and a linear or branched C1 to C9 alkylcarbonyl, R60 is selected from the group consisting of hydrogen, hydroxy and C1 to C18 alkoxy, and R61 is selected from the group consisting of hydrogen, hydroxy, C1 to C10 alkylsulfonyl-C1 to C5, and C1 to C18 alkyl as solvent, in particular as polar solvent, for chemical reactions, for recrystallizations or extractions.

2022

Modelling of AC/DC Interactions of Converter-Interfaced Resources for Harmonic Power-Flow Studies in Microgrids

Johanna Kristin Maria Becker, Andreas Martin Kettner, Mario Paolone, Yihui Zuo

Modern power distribution systems experience a large-scale integration of Converter-Interfaced Distributed Energy Resources (CIDERs). As acknowledged by recent literature, the interaction of individual CIDER components and different CIDERs through the grid can lead to undesirable amplification of harmonic frequencies and, ultimately, compromise the distribution system stability. In this context, the interaction of the DC and AC sides of CIDERs has been shown to have a significant impact. In order to analyze and support the mitigation of such phenomena, the authors of this paper recently proposed a Harmonic Power-Flow (HPF) framework for polyphase grids with a high share of CIDERs. The framework considers the coupling between harmonics, but ignores the DC-side response of the CIDERs. Modelling the DC side and the AC/DC converter introduces a nonlinearity into the CIDER model that needs to be approximated for the numerical solution of the HPF. This paper extends the CIDER model and HPF framework to address this aspect, whose inclusion is non-trivial. The extended HPF method is applied to a modified version of the CIGRÉ low-voltage benchmark microgrid. The results are compared to (i) timedomain simulations with Simulink, (ii) the predecessor of the extended HPF which neglects the DC side, and (iii) a classical decoupled HPF.

2022

A data-science approach to predict the heat capacity of nanoporous materials

Mehrdad Asgari, Özge Kadioglu, Seyedmohamad Moosavi, Elias Moubarak, Balázs Álmos Novotny, Daniele Ongari, Andres Adolfo Ortega Guerrero, Berend Smit

The heat capacity of a material is a fundamental property of great practical importance. For example, in a carbon capture process, the heat required to regenerate a solid sorbent is directly related to the heat capacity of the material. However, for most materials suitable for carbon capture applications, the heat capacity is not known, and thus the standard procedure is to assume the same value for all materials. In this work, we developed a machine learning approach, trained on density functional theory simulations, to accurately predict the heat capacity of these materials, that is, zeolites, metal-organic frameworks and covalent-organic frameworks. The accuracy of our prediction is confirmed with experimental data. Finally, for a temperature swing adsorption process that captures carbon from the flue gas of a coal-fired power plant, we show that for some materials, the heat requirement is reduced by as much as a factor of two using the correct heat capacity.

NATURE PORTFOLIO2022

Step detection in power system waveforms for improved RoCoF and frequency estimation

Asja Derviskadic, Guglielmo Frigo, Alexandra Cameron Karpilow, Mario Paolone

The evaluation of the signal frequency and Rate of Change of Frequency (RoCoF) from voltage or current waveforms is used for critical grid control, monitoring and protection applications. However, when step changes in the amplitude or phase of the signal occur, conventional frequency and RoCoF estimation methods, typically based on phasor models, are highly unreliable and can yield large frequency errors. To address this issue, this paper proposes a technique that uses dictionaries based on common signal dynamic models to identify and track amplitude and/or phase steps in AC signals. Additional signal dynamics including amplitude modulations, frequency ramps and harmonic tones are also characterized. Distinct from a previous iteration of this method developed by the authors, the proposed Step Change Detection (SCD) technique separates the envelope and angle of the signal's analytic form for independent analysis of these components. For numerical validation the method is applied to synthetically generated signals with challenging combinations of signal dynamics. The technique is shown to greatly improve frequency and RoCoF approximations as compared to state-of-the-art phasor estimation methods.

ELSEVIER SCIENCE SA2022

Corrosion testing of solar cells: Wear-out degradation behavior

Christophe Ballif, Andrew Wayne Fairbrother, Luca Gnocchi, Alessandro Francesco Aldo Virtuani

Corrosion is one of the main end-of-life degradation and failure modes in photovoltaic (PV) modules. However, it is a gradual process and can take many years to become a major risk factor because of the slow accumulation of water and acetic acid (from encapsulant ethylene vinyl acetate (EVA) degradation). In this work, an accelerated aging test for acetic acid corrosion was developed to probe wear-out and end-of-life behavior and facilitate screening of new cell, passivation, metallization, and interconnection technologies. In the tests, the top glass and EVA layers were removed from PV modules to expose the solar cells and interconnects. These "opened" modules were then placed in acid baths under varying conditions, including acid concentration, temperature, and elec-trical bias. Three cell technologies were tested, including Al-back surface field (BSF), passivated emitter and rear contact (PERC), and silicon heterojunction (SHJ). For all conditions, the presence of acid accelerated module power loss compared to control tests with water baths. Increased temperature accelerated the rate of degradation by several times. Application of electrical bias led to an initial drop in short circuit current, but these modules eventually outperformed the non-biased modules. In all tests, lead oxides were the primary degradation products detected, and found to accumulate mostly along the printed metallization, especially in proximity to the busbar. SHJ cells with a silver paste-based interconnection outperformed Al-BSF and PERC cells with a solder-based interconnection. The accelerated corrosion test methods can be optimized to match corrosion behavior observed in field modules with greater precision and shorter times than standard damp heat tests, and is espe-cially useful to assess the long-term durability of the continuously increasing variety of corrosion sensitive PV materials and components.

ELSEVIER2022

Reliable Dispatch of Active Distribution Networks via a Two-layer Grid-Aware Model Predictive Control: Theory and Experimental Validation

Rahul Kumar Gupta, Mario Paolone, Ji Hyun Yi, Antonio Zecchino

Dispatching active distribution networks (ADNs) is an energy-intensive application that, if implemented via battery-energy storage systems (BESSs), can require a large capacity of these assets in order to fully balance the uncertainties caused by the stochastic demand and generation. The insufficient capacity of the BESSs often leads to their state-of-charge (SOC) saturation; this results in unreliable dispatch tracking. In this work, we propose and experimentally validate a real-time control scheme that achieves a highly-reliable dispatching of ADNs and ensures that the BESSs’ SOC is not saturated during the daily operation. Our proposed scheme uses a two-layer model predictive control (MPC). The upper-layer MPC, running every 5 minutes, optimizes the BESSs’ SOC trajectories while minimizing the tracking error, considering the prosumption forecast of the whole day. Then, the lower layer MPC, running every 30 seconds, takes the BESSs’ SOC trajectories as constraints while achieving a high-resolution tracking of the dispatch plan over the current 5-minute time horizon. Both layers account for the grid constraints by using the augmented relaxed optimal power-flow (AR-OPF) model; an exact convex relaxation of the original AC-OPF and used in this paper (for the first time in the literature) to solve a real-time constrained control problem for ADNs. Our proposed framework was experimentally validated using a 1.5 MVA/2.5 MWh BESS connected to an actual 24-node medium-voltage (MV) ADN that, in Aigle, Switzerland, hosted an uncontrollable 3.2 MWp distributed photovoltaic generation, 3.4 MVA hydro-power generations, and a 2.8 MW base demand.

2022

Expansion planning of active distribution networks achieving their dispatchability via energy storage systems

Katarina Knezovic, Mario Paolone, Ji Hyun Yi

This paper presents a combined framework for power distribution network expansion planning (DNEP) and energy storage systems (ESSs) allocation in active distribution networks (ADNs) hosting large amount of photovoltaic (PV) generations and loads. The proposed DNEP ensures the reliable operation of the targeted ADN with the objective of achieving its dispatchability while minimizing grid losses by determining the optimal grid expansion to connect new nodes, the reinforcement of existing lines, and the ESS allocation. The allocated ESSs compensate for the stochastic power flows caused by the stochastic loads and generation, allowing ADNs to follow a pre-defined power schedule at the grid connection point. The grid constraints are modeled by using a modified augmented relaxed optimal power flow (AR-OPF) model that convexifies the classical AC-OPF providing the global optimal and the exact solution of the OPF problem for radial networks. The DNEP problem’s complexity is handled by employing a sequential algorithm where new nodes are added one by one, following the priorities determined by the user. In each stage of the sequential planning, the Benders decomposition algorithm determines the optimal solution for investments and ADN operation iteratively. Moreover, the siting and sizing problems associated with the ESSs and line investment are solved separately to enhance the convergence speed. Simulations are conducted on a real 55-node Swiss ADN hosting sizeable stochastic photovoltaic generation.

2022