4,740 research outputs found
Comparison of 4-ball and 5-ball rolling contact fatigue tests on lubricated Si3N4/steel contact
No full textAccelerated four-ball and five-ball rolling tests were performed on HIPed Si3N4 ball samples (rough lapped with surface
roughness value Ra0.08 μm and Rq0.118 μm) in fully lubricated condition. The contact load and the stress cycles per minute
for four-ball rolling and five-ball rolling tests were maintained the same. The rolling track appearances of five-ball tests reveal
severe sliding occurred. In one case, the opposite arc cracks were generated all over the two sides of the rolling track, and this
could not be explained by simplified kinematics model. The failure mechanisms were discussed, which suggest the sliding on the
two sides of the track was in the opposite direction
The linear polarization constant of R^n
No full textThe present work contributes to the determination of
the n-th linear polarization constant cn(H) of an n-dimensional
real Hilbert space H. We provide some new lower bounds on the
value of supkyk=1 | hx1, yi · · · hxn, yi |, where x1, . . . , xn are unit vectors
in H. In particular, the results improve an earlier estimate of
Marcus. However, the intriguing conjecture cn(H) = nn/2 remains
open
Aggregated Impact of EV Charger Type and EV Penetration level in Improving PV Integration in Distribution Grids
No full textMass deployment of Electric Vehicles (EVs) can improve the loading characteristics of low voltage distribution grids with high Photovoltaic (PV) penetration. This impact is investigated in the paper from two point of views, namely, the EV charger type and the EV penetration level. Based on the measured usage data for home, public and semi-public EV chargers, it is highlighted that the ratio of the number of these charger types can influence the grid level impact of PV penetration. Using Monte-Carlo method with aggregated power balance model, it is suggested that the increase in percentage of public and semi-public chargers relative to home chargers can improve self-consumption of PV energy in the grid, thereby reducing the power mismatch due to excess local generation. A PowerFactory based simulation with real measurement based data on real German distribution grids reveals that the grids have no risk of congestion at all with 80% EV penetration, allowing for a possibility even higher EV penetration in the future. Furthermore, with the considered uncontrolled EV charging, it is observed that the grids experience reverse power flows due to excess PV generation. This excess PV energy reduces by about 5% with high EV penetration, indicating a future potential for targeted smart charging application for improving these benchmarked results.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Differentially expressed genes selected on spline (EV) or VSN transformed data
No full text<p><b>Copyright information:</b></p><p>Taken from "An adaptation of the LMS method to determine expression variations in profiling data"</p><p></p><p>Nucleic Acids Research 2007;35(9):e71-e71.</p><p>Published online 25 Apr 2007</p><p>PMCID:PMC1888829.</p><p>© 2007 The Author(s)</p> The same dataset represented in was used to select differentially expressed genes on spline (EV) or VSN-transformed data. MA plots of scaled log-transformed signals for probe sets from two experimental conditions of the B6.1 cells. Color codes are as in . Up-regulated genes are shown as green bold dots, down-regulated as red bold dots. () Distribution of 555 genes (-value = 0.05) selected upon a spline fit. () Distribution of 555 genes (FC = 1.63) on VSN-transformed data. () Distribution of genes selected by both approaches. () Distribution of genes selected by EV (spline fit) alone. () genes selected by VSN (arcsinh transformation) alone
Frequency Regulation Reserves Provision in EV Smart-Charging
No full textSmart-Charging of Electric Vehicles (EVs) is able to provide frequency regulation capacity services to the System Operator (SO) upon an automation generation control (AGC) signal. While the amount of available regulation capacity is of-fered in the Day-Ahead Market (DAM), there is high uncertainty on the actual amount of reserves that will be called in the Real-Time Market (RTM). This work focuses on aiding EV smart-charging to offer a consistent and reasonable amount of regulation capacity, taking into account the impact of potential future instantaneous called regulation reserves while also maintaining simplicity. The work also analyzes the results of different charger types with different characteristics and shows that they play an important role on the regulation provision. Finally, it has been shown that even though the regulation income is inevitably reduced (up to 66%), the Energy Management System (EMS) can still successfully charge the EV s and simultaneously provide regulation reserves with remuneration.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Optimal System Design for a Solar Powered EV Charging Station
No full textCharging electric vehicles (EV) from photovoltaic (PV) panels provides a sustainable mode of transportation. In order to reduce the net costs of charging EV from PV and the grid, the PV generation and/or the EV charging can be controlled based on the energy prices in the grid. The traditional approach to designing the solar system for EV charging is to maximize the energy yield. In this paper, an alternate approach to PV system design is proposed by which the PV panels are orientated so as to maximize the PV revenue. This technique is compared with that of reducing the net costs by smart charging of the EV based on energy prices. Two case studies for Netherlands and Texas are done to compare the PV energy generated and the net cost of EV charging from PV based on the two techniques.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
End-of-Life Comparison of Full-Bridge and Half-Bridge DC/DC Converter Switches Used for EV Charging
No full textEV fast chargers are essential in addressing the concern of limited driving range for E-mobility applications. However, the load profile of a converter for fast charging involves a high-current pulse that can last for a few minutes to efficiently replenish the EV battery, which is followed by a cooldown period after the charging process is finished. This results in thermal cycles that can lead to thermo-mechanical fatigue and degradation of power electronic components, thereby impacting device lifetime. This paper presents a comparative study on the reliability of power devices in isolated half-bridge and full-bridge DC-DC converters in EV fast chargers. The study focuses on the differences in thermal stresses that Si switches experience in each converter during charging cycles and how it impacts the end-of-life of each device. This study provides valuable insights for selecting reliable power converters for EV fast charging applications.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
High temperature optical absorption investigation into the electronic transitions in sol–gel derived C12A7 thin films
No full textOptical absorption into 6 mm thick sol–gel derived films, annealed at 1300 °C of 12CaO·7Al2O3 calcium aluminate binary compound on MgO〈100〉 single crystal substrates was studied at temperatures ranging from room temperature to 300 °C. Experimental data were analysed in both Tauc and Urbach regions. The optical band gap decreased from 4.088 eV at 25 °C to 4.051 eV at 300 °C, while Urbach energy increased from 0.191 eV at 25 °C to 0.257 eV at 300 °C. The relationship between the optical band gap and the Urbach energy at different temperatures showed an almost linear relationship from which the theoretical values of 4.156 and 0.065 eV were evaluated for the band gap energy and Urbach energy of a 12CaO·7Al2O3 crystal with zero structural disorder at 0 K
Using dedicated EV charging areas to resolve grid violations caused by renewable energy generation
No full textEV Charging is expected to be a significant load on the grid in the future. But they can also be a part of the solution to grid violations. As the amount of renewable energy generation increases, there is a large amount of power flowing in the reverse direction in the distribution network, which is undesirable. To reduce this, EVs can charge at strategically located “Grid Management Parking Lots”. Here the EV charging power level varies in accordance with the amount of capacity available in the grid. This is a win-win situation for both parties, the grid operator and the EV owner, as the grid operator reduces the amount of violations in the grid and the EV owner has his/her vehicle charged sooner.Accepted Author ManuscriptDC systems, Energy conversion & Storag
Submodeling Method-Based Thermal Investigation of the Battery Energy Storage System Integrated in a 450 kW EV Charger
No full textThe electric vehicle (EV) market is expanding rapidly. However, the main barriers to EV adoption are high vehicle costs, range issues, and charging infrastructure. Meanwhile, energy storage systems (ESS) appear as a promising solution to preventing grid overload during charging and reducing infrastructure costs. In this paper, the integration of the battery energy storage system (BESS) in a 450 kW EV charger is designed and investigated via modeling and simulation mainly from the perspective of thermal management. To explore the heat dissipation and the temperature distribution across the pack, the thermal model based on the sub-modeling technique is developed via COMSOL, and a preliminary layout and cooling strategy are determined.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
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