30 research outputs found
Droplet Collision for Target Shaping
No full textThis dataset consists of simulation input files and analysis scripts concerning the use of droplet collisions at nonzero impact parameters for target shaping in a Laser-Produced-Plasma EUV source
Extreme regimes of femtosecond photoemission from a copper cathode in a dc electron gun
Get PDFThe femtosecond photoemission yield from a copper cathode and the emittance of the created electron beams has been studied in a 12 MeV/m, 100 keV dc electron gun over a wide range of laser fluence, from the linear photoemission regime until the onset of image charge limitations and cathode damaging. The measured photoemission curves can be described well with available theory which includes the Schottky effect, second-order photoemission, and image charge limitation. The second-order photoemission can be explained by thermally assisted one-photon photoemission (1PPE) and by above-threshold two-photon photoemission (2PPE). Measurements with a fresh cathode suggest that the 2PPE process is dominant. The beam emittance has been measured for the entire range of initial surface charge densities as well. The emittance measurements of space-charge dominated beams can be described well by an envelope equation with generalized perveance. The dc gun produces 0.1 pC bunches with 25 nm rms normalized emittance, corresponding to a normalized brightness usually associated with rf photoguns. In this experimental study the limits of femtosecond photoemission from a copper cathode have been explored and analyzed in great detail, resulting in improved understanding of the underlying mechanisms
Energy Management: Techno-economic assessment of a power manager - towards a business case for integrating electric vehicles within a building’s electrical system
No full textDue to the intermittent character of renewable electricity sources and increasing decentralized electricity production, grid operators are facing challenges in balancing electricity- demand and supply within grid operations. These characteristics make it challenging for operators to forecast in- and outflowing electricity in the grid. This often leads to disadvantageous frequency-, voltage-, and electricity fluctuations in the grid. The implementation of smart grid technologies allows the easier integration of sustainable electricity sources and to increase the grid’s reliability. Additionally, more components can be integrated in the grid system that can provide grid regulating services. In the context of sustainability, it’s interesting to stress the potential of grid services delivered by parked electric vehicles. The principle of a Car as Power Plant (CaPP), where vehicles can provide electricity back to the grid via Vehicle-To-Grid (V2G) technology, can potentially solve challenges that grid operators are currently facing. This can be designed in such a way that the operation becomes beneficial for all parties involved. This research implies a techno-economic assessment of a power manager device; which is a multifunctional device that includes an energy management system (EMS), allows for vehicles to charge and discharge and functions as a converter (from direct current to alternating current). The power manager enables electric vehicles to deliver ancillary services when operating in V2G mode. This research stresses the economic- and environmental benefits of a power manager; once it’s integrated in grid-connected commercial- and residential buildings. Emphasis is put on buildings in future energy systems, which are equipped with DC loads and contain features that make the building operate in a more sustainable manner than today. For this purpose, several cases have been modeled to address the cost benefits of a power manager within a buildings’ electrical system. The cost optimization is conducted by means of the HOMER optimization software. Environmental- and financial benefits could be achieved in a behind-the-meter operation, in case electricity flows are managed smartly and ancillary services are delivered to the grid. Price arbitrage and peak shaving were among the most emphasized ancillary services. By integrating electric vehicles by means of a power manager, the batteries of parked electric vehicles could get an extra function, besides being primarily used for driving purposes. Several cases have been optimized by applying a dispatch strategy, considering different components in the microgrid (solar panels, DC electrical loads, battery electric vehicles). These dispatch algorithms were embedded in the power manager’s energy management system.This research has shown that, once the vehicles’ battery capacity was aggregated for grid facilitating purposes in a behind-the-meter operation, parties could achieve financial- and environmental benefits. This could be realized by integrating permanently parked vehicles within commercial- and residential buildings’ electrical systems by means of a power manager. When a power manager was added to a building’s system without integrated solar panels, annual cost savings of € 35 and € 60 could be achieved respectively for residential- and commercial buildings by accounting for price arbitrage services. Once a power manager device was added to a building’s electrical system with integrated solar panels, the renewable energy fraction of the system increased from 53.9 to 57.4 for a residential building and from 68.0 to 70.8 in a commercial building. Altogether, price arbitrage practices primarily caused financial benefits, while peak shaving services resulted in an increase in the system’s renewability. It’s presumed that a power manager’s economic- and environmental benefits could increase once a larger battery capacity is obtained by aggregating BEVs in a ‘before-the-meter’ operation. Favorable regulations and privacy matters need to be established and discussed to make a power manager device run at its full potential. Additionally, it’s important to determine what party will be fulfilling the aggregating role, and therewith, takes the responsibility for demand response operations. For this, a potential business case is established for the implementation of a power manager in the Dutch market.Car as Power Plant (CaPP) | the Green VillageElectrical Engineering | Sustainable Energy Technolog
Electrical, Magnetic, Thermal Modeling and Analysis of a 5000A Solid-State Switch Module and Its Application as a DC Circuit Breaker
No full textThis dissertation presents a systematic design and demonstration of a novel solid-state DC circuit breaker.
The mechanical circuit breaker is widely used in power systems to protect industrial equipment during fault or abnormal conditions. Compared with the slow and high-maintenance mechanical circuit breaker, the solid-state circuit breaker is capable of high-speed interruption of high currents without generating an arc, hence it is maintenance-free. Both the switch and the tripping unit are solid-state, which meet the requirements of precise protection and high reliability. The major challenge in developing and adopting a solid-state circuit breaker has been the lack of power semiconductor switches that have adequate current-carrying capability and interruption capability.
The high-speed, high-current solid-state DC circuit breaker proposed and demonstrated here uses a newly-emerging power semiconductor switch, the emitter turn-off (ETO) thyristor as the main interruption switch. In order to meet the requirement of being a high-current circuit breaker, ETO parallel operation is needed. Therefore the major effort of this dissertation is dedicated to the development of a high-current (5000A) DC switch module that utilizes multiple ETOs in parallel. This work can also be used to develop an AC switch module by changing the asymmetrical ETOs used to symmetrical ETOs.
An accurate device model of the ETO is needed for the development of the high-current DC switch module. In this dissertation a novel physics-base lumped charge model is developed for the ETO thyristor for the first time. This model is verified experimentally and used for the research and development of the emitter turn-off (ETO) thyristor as well as the DC switch module discussed in this dissertation.
With the aid of the developed device model, the device current sharing between paralleled multiple ETO thyristors is investigated. Current sharing is difficult to achieve for a thyristor-type device due to the large device parameter variations and strong positive feedback mechanism in a latched thyristor. The author proposes the "DirectETO" concept that directly benefits from the high-speed capability of the ETO and strong thermal couplings among ETOs. A high-current DC switch module based on the DirectETO can be realized by directly connecting ETOs in parallel without the bulky current sharing inductors used in other current-sharing solutions.
In order to achieve voltage stress suppression under high current conditions, the parasitic parameters, especially parasitic inductance in a high-current ETO switch module are studied. The Partial Element Equivalent Circuit (PEEC) method is used to extract the parasitics. Combined with the developed device model, the electrical interactions among multiple ETOs are investigated which results in structural modification for the solid-state DC switch module.
The electro-thermal model of the DC switch module and the heatsink subsystem is used to identify the "thermal runaway" phenomenon in the module that is caused by the negative temperature coefficient of the ETO's conduction drop. The comparative study of the electro-thermal coupling identifies a strongly-coupled thermal network that increases the stability of the thermal subsystem. The electro-thermal model is also used to calculate the DC and transient thermal limit of the DC switch module.
The high-current (5000A) DC switch module coupled with a solid state tripping unit is successfully applied as a high-speed, high-current solid-state DC circuit breaker. The experimental demonstration of a 5000A current interruption shows an interruption time of about 5 microseconds. This high-speed, high-current DC switch module can therefore be used in DC circuit breaker applications as well as other types of application, such as AC circuit breakers, transfer switches and fault current limiters.
Since the novel solid-state DC circuit breaker is able to extinguish the fault current even before it reaches an uncontrollable level, this feature provides a fast-acting, current-limiting protection scheme for power systems that is not possible with traditional circuit breakers. The potential impact on the power system is also discussed in this dissertation.Ph. D
Test particles dynamics in the JOREK 3D non-linear MHD code and application to electron transport in a disruption simulation
Get PDFIn order to contribute to the understanding of runaway electron generation mechanisms during tokamak disruptions, a test particle tracker is introduced in the JOREK 3D non-linear MHD code, able to compute both full and guiding center relativistic orbits. Tests of the module show good conservation of the invariants of motion and consistency between full orbit and guiding center solutions. A first application is presented where test electron confinement properties are investigated in a massive gas injection-triggered disruption simulation in JET-like geometry. It is found that electron populations initialised before the thermal quench (TQ) are typically not fully deconfined in spite of the global stochasticity of the magnetic field during the TQ. The fraction of 'survivors' decreases from a few tens down to a few tenths of percent as the electron energy varies from 1 keV to 10 MeV. The underlying mechanism for electron 'survival' is the prompt reformation of closed magnetic surfaces at the plasma core and, to a smaller extent, the subsequent reappearance of a magnetic surface at the edge. It is also found that electrons are less deconfined at 10 MeV than at 1 MeV, which appears consistent with a phase averaging effect due to orbit shifts at high energy
A Meta-Analysis of Genome-Wide Association Scans Identifies IL18RAP, PTPN2, TAGAP, and PUS10 As Shared Risk Loci for Crohn's Disease and Celiac Disease
Get PDFThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Investigation of MHD activity caused by shattered pellet injection via JOREK 3D non-linear MHD simulations
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