Characterization of Flywheel Energy Storage System for Hybrid Vehicles

Flywheels are excellent secondary energy storage devices and several applications in road vehicles are under development. They can be used in hybrid vehicles with an internal combustion engine (ICE) as the prime mover or can be used in hybrid energy storage (HES) to complement the battery. When used in HES, they are utilized to load level the battery so as to protect it from peak loads and enhance its capacity and life. This paper deals with defining the main characteristics of the flywheel for an application as a secondary energy storage device for an electric vehicle. Various strategies for defining flywheels are explained. A real world customer usage data is also presented. This data is analyzed and its results are used to support the selection of the flywheel characteristics. The results show that the chosen flywheel is sufficiently sized to perform its intended tasks for a c-segment passenger car electric vehicle

Analysis of Dual Mode Continuously Variable Transmission for Flywheel Energy Storage Systems

There are different types of energy storage devices which are used in today’s hybrid and electric vehicles. Batteries, ultra capacitors and high speed flywheels are the most commonly used ones. While batteries and supercapacitors store energy in the form of electric energy, the flywheel (FW) is the only device that keeps the energy stored in the original form of mechanical energy the same as the moving vehicle. The flywheel needs to be coupled to the driveshaft of the vehicle in a manner which allows it to vary its speed independently of the moving vehicle in order to vary its energy content. In other words a continuously variable transmission (CVT) is needed. The common mechanical variators used in automotive applications, namely the rolling traction drives and the belt drives, have the disadvantage that their speed ratio range defined as the maximum to minimum speed ratio is generally not sufficient for flywheel energy storage system (FESS). One of the ways to improve the ratio range is by using a dual mode transmission, where the ratio coverage of the variator is exploited twice. This paper presents the fundamental kinematics of such a transmission including its variants. The equations of speed ratio, power flow and efficiency are derived for a variator only transmission and a power split CVT (PSCVT) used in dual mode and the results compared

Simulation based study of battery electric vehicle performance in real world cycles

The development of battery electric vehicles (BEV) must continue since this offers the leading route towards a zero emission transport system. The fuel flexibility of the BEV offers the greatest potential to utilize power from renewable or low emission sources to be used in the transport system. However the limited range and high cost of the BEV remain important issues to be addressed. The battery is the element which strongly affects the cost and range of the BEV. The batteries offer either high specific power or high specific energy, but not both. This paper presents the modelling of a BEV which is used to study the potential for improvement in its energy efficiency. The battery model types have been discussed. The vehicle and other component models have been described. The choice of model parameters and the control strategy has been explained. The simulations have been performed on homologation and real world cycles for different scenarios. Results show significant potential for improvement in the energy efficiency of the BEV in real world usage by the utilization of a secondary energy storage device

Advanced techniques for determining long term compatibility of materials with propellants

A method for the prediction of propellant-material compatibility for periods of time up to ten years is presented. Advanced sensitive measurement techniques used in the prediction method are described. These include: neutron activation analysis, radioactive tracer technique, and atomic absorption spectroscopy with a graphite tube furnace sampler. The results of laboratory tests performed to verify the prediction method are presented

Variational collocation for systems of coupled anharmonic oscillators

We have applied a collocation approach to obtain the numerical solution to the stationary Schr\"odinger equation for systems of coupled oscillators. The dependence of the discretized Hamiltonian on scale and angle parameters is exploited to obtain optimal convergence to the exact results. A careful comparison with results taken from the literature is performed, showing the advantages of the present approach.Comment: 14 pages, 10 table

Accuracy of the Semi--Classical Approximation: the Pullen Edmonds Hamiltonian

A test on the numerical accuracy of the semiclassical approximation as a function of the principal quantum number has been performed for the Pullen--Edmonds model, a two--dimensional, non--integrable, scaling invariant perturbation of the resonant harmonic oscillator. A perturbative interpretation is obtained of the recently observed phenomenon of the accuracy decrease on the approximation of individual energy levels at the increase of the principal quantum number. Moreover, the accuracy provided by the semiclassical approximation formula is on the average the same as that provided by quantum perturbation theory.Comment: 12 pages, 5 figures (available upon request to the authors), LaTex, DFPD/93/TH/47, to be published in Nuovo Cimento

Searching for Faint Comoving Companions to the α Centauri system in the VVV Survey Infrared Images

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2017 Crown Copyright. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.The VVV survey has observed the southern disk of the Milky Way in the near infrared, covering 240 deg$^{2}$ in the $ZYJHK_S$ filters. We search the VVV Survey images in a $\sim$19 deg$^{2}$ field around $\alpha$ Centauri, the nearest stellar system to the Sun, to look for possible overlooked companions that the baseline in time of VVV would be able to uncover. The photometric depth of our search reaches $Y\sim$19.3 mag, $J\sim$19 mag, and $K_S\sim$17 mag. This search has yielded no new companions in $\alpha$ Centauri system, setting an upper mass limit for any unseen companion well into the brown dwarf/planetary mass regime. The apparent magnitude limits were turned into effective temperature limits, and the presence of companion objects with effective temperatures warmer than 325K can be ruled out using different state-of-the-art atmospheric models. These limits were transformed into mass limits using evolutionary models, companions with masses above 11 M$_{Jup}$ were discarded, extending the constraints recently provided in the literature up to projected distances of dPeer reviewedFinal Published versio

Non-Abelian Excitations of the Quark-Gluon Plasma

We present new, non-abelian, solutions to the equations of motion which describe the collective excitations of a quark-gluon plasma at high temperature. These solutions correspond to spatially uniform color oscillations.Comment: 8 pages LaTex, 1 figure (not included; available upon request), Saclay preprint T94/0