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Evaluation of (plasma-assisted) decomposition of transition metals doped CaCO3 for CO2 capture and conversion
No full textSolution-processed tin oxide-PEDOT-PSS interconnecting layers for efficient inverted and conventional tandem polymer solar cells
No full textImpedance Spectra and Surface Coverages Simulated Directly from the Electrochemical Reaction Mechanism: A Nonlinear State Space Approach
Get PDFCurrent voltage curves and electrochemical impedance spectra (EIS) are crucial for investigating the performance and the electrochemical limitations of electrochemical cells. Therefore, we developed an approach which allows the direct simulation of such data based on microkinetic modeling. This approach allows us to assess the influence of various input parameters on the EIS and on the current–voltage curves and, hence, the overall performance of electrochemical cells. We develop our approach for the oxygen evolution reaction (OER) taking place at the semiconductor–electrolyte interface. At this interface, the microkinetic equations, that is, electrochemical reactions, for the multiple steps in OER are formulated and the resulting set of equations are modeled in a state-space form. As an input to the state-space model, we use the theoretical reaction rates calculated using density functional theory and Gerischer theory for semiconductors. Then, the electrochemical data are simulated as a function of applied potential. Next to the theory and the model development, a case study on the hematite–electrolyte interface which is a typical interface in photoelectrochemical cells is presented. Current voltage curves and EIS data for the hematite interface are simulated from the electrochemical model. The data are compared to experimental measurements. Apart from the current density and the EIS, the model can simulate the coverage of intermediate species as a function of applied potential which is highly demanded for identifying the limiting processes at the interface, but not available from experimental studies. This approach is generic and can be used for other electrochemical interfaces, such as present in fuel cells, electrolysers, or batteries.</p
Real-time plasma state monitoring and supervisory control on TCV
No full textIn ITER and DEMO, various control objectives related to plasma control must be simultaneously achieved by the plasma control system (PCS), in both normal operation as well as off-normal conditions. The PCS must act on off-normal events and deviations from the target scenario, since certain sequences (chains) of events can precede disruptions. It is important that these decisions are made while maintaining a coherent prioritization between the real-time control tasks to ensure high-performance operation. In this paper, a generic architecture for task-based integrated plasma control is proposed. The architecture is characterized by the separation of state estimation, event detection, decisions and task execution among different algorithms, with standardized signal interfaces. Central to the architecture are a plasma state monitor and supervisory controller. In the plasma state monitor, discrete events in the continuous-valued plasma state are modeled using finite state machines. This provides a high-level representation of the plasma state. The supervisory controller coordinates the execution of multiple plasma control tasks by assigning task priorities, based on the finite states of the plasma and the pulse schedule. These algorithms were implemented on the TCV digital control system and integrated with actuator resource management and existing state estimation algorithms and controllers. The plasma state monitor on TCV can track a multitude of plasma events, related to plasma current, rotating and locked neoclassical tearing modes, and position displacements. In TCV experiments on simultaneous control of plasma pressure, safety factor profile and NTMs using electron cyclotron heating (ECH) and current drive (ECCD), the supervisory controller assigns priorities to the relevant control tasks. The tasks are then executed by feedback controllers and actuator allocation management. This work forms a significant step forward in the ongoing integration of control capabilities in experiments on TCV, in support of tokamak reactor operation
The European roadmap towards fusion electricity
No full textThe European roadmap to the realization of fusion electricity breaks the quest into eight missions. For each mission, it reviews the current status of research, identifies open issues, and proposes a research and development programme. ITER is the key facility on the roadmap as it is expected to achieve most of the important milestones on the path to fusion power. The Fusion Roadmap is tightly connected to the ITER schedule and the vast majority of resources in fusion research are presently dedicated to ITER and its accompanying experiments. Parallel to the ITER exploitation in the 2030s, the construction of the demonstration power plant DEMO needs to be prepared. DEMO will for the first time supply fusion electricity to the grid and it will have a self-sufficient fuel cycle. The design, construction and operation of DEMO require full involvement of industry to ensure that, after a successful DEMO operation, industry can take responsibility for commercial fusion power. The European fusion roadmap provides a coherent path towards the fusion power plant, and it proposes in an integrated way to find solutions for all challenges that still need to be addressed.
This article is part of a discussion meeting issue ‘Fusion energy using tokamaks: can development be accelerated?
Model-based estimation and control of the particle distribution and discharge supervision in nuclear fusion reactors
No full textHydrogen storage properties of Li-decorated B2S monolayers: A DFT study
Get PDFHydrogen storage properties of Li functionalized B2S honeycomb monolayers are studied using density functional theory calculations. The binding of H2 molecules to the clean B2S sheet proceeds through physisorption. Dispersed Li atoms on the monolayer surface increase both the hydrogen binding energies and the hydrogen storage capacities significantly. Additionally, ab initio molecular dynamics calculations show that there is no kinetic barrier during H2 desorption from lithiated B2S. Among the studied B8S4Lix (x = 1, 2, 4, and 12) compounds, the B8S4Li4 is found to be the most promising candidate for hydrogen storage purposes; with a 9.1 wt% H2 content and 0.14 eV/H2 average hydrogen binding energy. Furthermore, a detailed analysis of the electronic properties of the B8S4Li4 compound before and after H2 molecule adsorption confirms that the interactions between Li and H2 molecules are of electrostatic nature.</p
Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade
No full textWithin the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (n e,sep / nG about 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.</p
Control of the hydrogen:deuterium isotope mixture using pellets in JET
No full textDeuterium pellets are injected into an initially pure hydrogen H-mode plasma in order to control the hydrogen:deuterium (H:D) isotope mixture. The pellets are deposited in the outer 20% of the minor radius, similar to that expected in ITER, creating transiently hollow electron density profiles. A H:D isotope mixture of approximately 45%:55% is obtained in the core with a pellet fuelling throughput of @pel = 0.045 P aux / T e.ped similar to previous pellet fuelling experiments in pure deuterium. Evolution of the H:D mix in the core is reproduced using a simple model, although deuterium transport could be higher at the beginning of the pellet train compared with the flat-top phase