Investigation into the Hydration Behavior of K₂CO₃ Packed Beds:An NMR Study

K2CO3 is seen as a promising heat storage material, available for applications in the domestic sector. For practical purposes, the material is hereby often employed in a packed bed containing millimeter-sized particles. To gain more insight into the hydration behavior of these packed beds, quantitative NMR measurements, capable of following the in-situ hydration behavior, are presented for the first time. It is found that hydration behavior varies significantly, depending on the specific hydration conditions that are chosen. At low airflows hydration is found to proceed via a hydration front, while higher airflows cause the hydration front to widen. Since an increase in flow rate coincided with an increase in the supplied water vapor, hydration is eventually found to proceed in a uniform manner. A comparison between TGA and NMR measurements shows that the overall packed bed hydration kinetics hereby transition to the reaction kinetics of single K2CO3 particles. Graphical Abstract: [Figure not available: see fulltext.]</p

Understanding the hydration process of salts:the impact of a nucleation barrier

The solid-state hydration of salts has gained particular interest within the frame of thermochemical energy storage. In this work, the water vapor pressure–temperature (p–T) phase diagram of the following thermochemical salts was constructed by combining equilibrium and nonequilibrium hydration experiments: CuCl2, K2CO3, MgCl2·4H2O, and LiCl. The hydration of CuCl2 and K2CO3 involves a metastable zone of ca. 10 K, and the induction times preceding hydration are well-described by classical homogeneous nucleation theory. It is further shown for K2CO3 (metastable) and MgCl2·4H2O (not metastable) through solubility calculations that the phase transition is not mediated by bulk dissolution. We conclude that the hydration proceeds as a solid–solid phase transition, mobilized by a wetting layer, where the mobility of the wetting layer increases with increasing vapor pressure. In view of heat storage application, the finding of metastability in thermochemical salts reveals the impact of nucleation and growth processes on the thermochemical performance and demonstrates that practical aspects like the output temperature of a thermochemical salt are defined by its metastable zone width (MZW) rather than its equilibrium phase diagram. Manipulation of the MZW by e.g. prenucleation or heterogeneous nucleation is a potential way to raise the output temperature and power on material level in thermochemical applications

Zelfregulering als een vernieuwend concept van professionaliteit

Self-regulation as an innovative concept of professionalismThis contribution opens with a discussion of three sources of knowledge that form a foundation for the concept of “selfregulation” as developed by Donkers. It starts with a historical enquiry on the Western European ideas about change and changeability of people and society. Three paradigms of change appear which in every period of modern history conflicted with each other and thereby became refined and differentiated. A second source relates to practice research to a number of methods for social intervention. The third source is a critical reflection on contemporary societal developments. Central in that reflection are all kinds of expropriation of self-direction – in – dialogue with others and processes of fragmentation of the complex societal reality. From these three sources a plea is given for a new concept of professionalism marked by strong attention for the reinforcement of the selfregulating possibilities of persons, organizations and society.In the second part Geertsema focusses on the relation between change and intervention and values that are part of these processes. As the Dutch society seems to be in a third order transition, without a clear view of the new situation, the urgency of value debates is high. But the late modernity seems to be imprisoned in notions of individuality that puts strong pressure upon more relational ontologies and mutual responsibilities. Besides that growing anonymous and invisible systems influence the formation of daily life deeply. If there will be a situation of relational ontology which make use of the powers of diversity and multiplicity of our existence, then change agents should take a moral stance by themselves to create space for numerous narratives. The concept of “selfregulation” makes it possible to relate these value debates with debates about the design of society in this transition situation.Zelfregulering als een vernieuwend concept van professionaliteitIn deze bijdrage wordt allereerst ingegaan op drie bronnen van kennis die ten grondslag liggen aan de zelfreguleringsbenadering van Donkers. In de eerste plaats is dat een historisch onderzoek naar het West-Europese denken over veranderen en veranderbaarheid van mens en samenleving. Uit dit onderzoek komt een drietal veranderkundige paradigma’s naar voren die in iedere periode van de moderne geschiedenis op elkaar botsten en met die botsingen zichzelf verder hebben verfijnd en gedifferentieerd. Een tweede bron zijn praktijkgerichte onderzoeken die zijn verricht naar een aantal methodieken van sociale interventie. De derde bron is een kritische reflectie op hedendaagse maatschappelijke ontwikkelingen. In die reflectie wordt met name stilgestaan bij allerlei vormen van onteigening van zelfregie-in-dialoog met anderen en bij processen van fragmentering van de complexe maatschappelijke werkelijkheid. Vanuit deze drie kennisbronnen wordt gepleit voor een vernieuwend concept van professionaliteit dat gekenmerkt wordt door gerichtheid op versterking van het zelfregulerend vermogen van mens, organisatie en samenleving.In het vervolg van deze bijdrage wijst Henk Geertsema op de relatie tussen veranderen en beïnvloeden en de kwestie van de waarden die daarmee verbonden is. In een situatie van een transitie van de derde orde, zoals zich momenteel in de Nederlandse samenleving voordoet, is de eindtoestand onduidelijk wat de noodzaak om waardendiscussies te voeren versterkt. De laat-moderne samenleving lijkt gevangen in opvattingen over individualiteit die een relationele ontologie en de daarmee verbonden wederkerige verantwoordelijkheid sterk onder druk zet. De afhankelijkheid van anonieme systemen wordt daarnaast steeds meer onzichtbaar, terwijl die vergaand de vormgeving van het bestaan sturen. Wil er opnieuw ruimte komen voor een relationele ontologie met de mogelijkheid om de kracht van varieteit en meervoudigheid van vormgevingen van het bestaan te benutten, dan zal de veranderkundige zelf een moreel standpunt moeten innemen om voor de verschillende narratio’s actief ruimte te maken. Het concept “zelfregulatie” geeft de mogelijkheid om deze waardendiscussies te verbinden met discussies over de vormgeving van het bestaan in deze situatie van transitie

On trade-offs between computational complexity and accuracy of electrochemistry-based battery models

In this paper, we propose several simplifications to the so-called Doyle-Fuller-Newman (DFN) model, which is a popular electrochemistry-based battery model. This simplified DFN (SDFN) model allows for a computationally very efficient implementation. The simplifications are a result of several assumptions, which will be justified for two different parameter sets. Finally, the SDFN model proposed is compared to the DFN model as well as an implementation of the single-particle model, for the two parameter sets. This will show that by making specific assumptions, simplifications can be made that have no significant impact on the model accuracy, while the computation time can be drastically decreased. This leads to a simulation time of over 3600 times faster than real-time

Model simplifications and their impact on computational complexity for an electrochemistry-based battery modeling toolbox

Using electrochemistry-based battery models in battery management systems remains challenging due to their computational complexity. In this paper, we study for the first time the impact of several types of model simplifications on the trade-off between model accuracy and computation time for the Doyle–Fuller–Newman (DFN) model. As a basis for comparison, we consider, to what we refer as, the complete DFN (CDFN) model, which is a DFN model without any simplifications, and includes the concentration-dependency of parameters that have been studied in previous literature. Furthermore, we propose a highly efficient implementation of the CDFN model that leads to a considerable decrease in computation time, and is developed into a freely downloadable toolbox. This toolbox allows the user to easily toggle between the studied simplifications to make the desired trade-off between model accuracy and computation time. We compare several simplified DFN models to the single-particle-model and the CDFN model. Here, we show that with the proposed implementation, and by selectively making the proposed simplifications, as well as selectively choosing the grid parameters, a model can be obtained that has a minor impact on model accuracy, achieving a simulation time of over 5000 times faster than real-time

Optimal Control of Active Cell Balancing: Extending the Range and Useful Lifetime of a Battery Pack

The range of electric vehicles (EV), especially those powered by aged battery packs, is partly limited by cell-to-cell imbalance, i.e., the weakest cell determines the performance of the entire battery pack. Active cell balancing can mitigate these differences, but balancing ad hoc discrepancies in voltage or state-of-charge (SoC) does not necessarily result in the best performance in terms of range. This brief employs a distributed feasibility approach to retrieve the maximum range and corresponding balancing currents for a specific scenario. Moreover, using aging data from literature and a real-time applicable model-predictive-controller, a lifetime projection is made on the benefits of active cell balancing, which shows that a significant extension of End-of-Life (EoL) is achieved, i.e., 10% for the considered example. Finally, we show when and why the applied balancing controller, which can effectively balance a battery pack using balancing currents with a maximum C-rate of only 1/50C, performs better than others in terms of maximizing the range

Ageing-aware charging of lithium-ion batteries using an electrochemistry-based model with capacity-loss side reactions

In this paper, we utilize a Doyle-Fuller-Newman (DFN) model including capacity-loss side reactions to present a model-based design method for multi-stage charging protocols. This design method allows making a trade-off between charging time and battery ageing in a more systematic way. The results are leveraged by a highly efficient implementation of the DFN model, that has a short computation time. We show that by obtaining the Pareto front that describes the optimal trade-off between charging time and battery ageing for a single cycle, the results can be extended to the lifetime of the battery. Finally we show that the negative electrode over-potential is not always a good indicator for ageing, and that ageing will occur even when the battery operates in over-potential regions that are considered to not lead to ageing

Ageing-Aware Charging of Lithium-ion Batteries Using a Surrogate Model

In this paper, we present an optimal-control-based method for ageing-aware charging. A surrogate modeling approach is used to approximate ageing-related Doyle-Fuller-Newman (DFN) model states, where the surrogate model is a combination of a black-box finite-dimensional linear-time-invariant model and a static nonlinear model that is a function of state-of-charge. We formulate the optimal-control problem as minimizing the side reactions for a given charging time and subject to several ageing-related constraints that are commonly used in literature. We will show that the ageing-related DFN model states can be well approximated by the proposed surrogate model. Furthermore, we will show that with the surrogate modeling approach, even in an open-loop execution of the optimal-control-based method, the considered constraints are only marginally violated when applied to the DFN model. Finally, we will compare the Pareto front achieved with the proposed optimal-control-based method with the Pareto fronts achieved with various multi-stage charging protocols. Here, we will show that the proposed optimal-control-based method achieves a significantly improved Pareto front over the multi-stage charging protocols