Kinetic Details of Absorption of Hydrogen Gas into Hydrogen Storage Alloys

A frequency response (FR) method was applied to a hydrogen/hydrogen-storage alloy system. The FR data were analyzed on the basis of two models consisting of two or three rate processes: (i) X?A?C and (ii) X?A?B?C, where X denotes a hydrogen molecule in the gas phase, A is a hydrogen molecule (or atom) adsorbed on the surface, B is atomic hydrogen adsorbed on the surface, and C is atomic hydrogen absorbed in the lattice. Rate coefficients at every rate process in the model were evaluated by computer simulation. It was concluded that this FR method is useful for characterizing valid hydrogen storage alloys, because both the rate coefficients concerned with adsorption-desorption and also diffusion occurring in series can be determined

Vehicle-to-grid plug-in forecasting for participation in ancillary services markets

Electric vehicle (EV) charge points (CPs) can be used by aggregators to provide frequency response (FR) services. Aggregators must have day-ahead half-hourly forecasts of minimum aggregate vehicle-to-grid (V2G) plug-in to produce meaningful bids for the day-ahead ancillary services market. However, there is a lack of understanding on what features should be considered and how complex the forecasting model should be. This paper explores the dependency of aggregate V2G plug-in on historic plug-in levels, calendar variables, and weather conditions. These investigations are used to develop three day-ahead forecasts of minimum aggregate V2G plug-in during 30-minute window. A neural network that considers previous V2G plug-in values the day before, three days before, and seven days before, in addition to day of the week, month, and hour, is found to be the most accurate

Investigation on sound propagation for the measurement of diffusion in microporous solids.

The basic definitions of micropore diffusivities and the experimental techniques applied for their measurement are reviewed. Through a historical perspective, the techniques are briefly described, with an emphasis on the measured property, the theoretical and practical limitations. As a result the need for a novel experimental technique has been identified. The extension of the frequency response (FR) method to frequencies in the audible sound range is proposed. A detailed mathematical model is presented to describe the propagation of sound between two parallel adsorbing plates. The main body of the thesis is the description and derivation of a model that relates an acoustic quantity (i.e. propagation constant) to adsorption parameters (i.e. diffusivity and equilibrium constant) in microporous solids. The theoretical analysis describes the ranges of physical parameters where the complete model reduces to simplified versions: classical absorption isothermal limit equilibrium control temperature control. Based on the theoretical study a prototype apparatus has been designed and constructed. The system allows for flexibility in the loading of adsorbent material, geometrical properties and gas used. Preliminary experimental results are reported and interpreted based upon the theory of acoustics described above

Frequency response from aggregated V2G chargers with uncertain EV connections

Fast frequency response (FR) is highly effective at securing frequency dynamics after a generator outage in low inertia systems. Electric vehicles (EVs) equipped with vehicle to grid (V2G) chargers could offer an abundant source of FR in future. However, the uncertainty associated with V2G aggregation, driven by the uncertain number of connected EVs at the time of an outage, has not been fully understood and prevents its participation in the existing service provision framework. To tackle this limitation, this paper, for the first time, incorporates such uncertainty into system frequency dynamics, from which probabilistic nadir and steady state frequency requirements are enforced via a derived moment-based distributionally-robust chance constraint. Field data from over 25,000 chargers is analysed to provide realistic parameters and connection forecasts to examine the value of FR from V2G chargers in annual operation of the GB 2030 system. The case study demonstrates that uncertainty of EV connections can be effectively managed through the proposed scheduling framework, which results in annual savings of Misplaced &6,300 or 37.4 tCO2 per charger. The sensitivity of this value to renewable capacity and FR delays is explored, with V2G capacity shown to be a third as valuable as the same grid battery capacity

Tunable multiband microstrip antenna for 5GHz WLAN

Copyright @ 2013. Ali Ejaz, R. Nilavalan & Hattan Abutarboush. This is a research/review paper, distributed under the terms of the Creative Commons Attribution-Noncommercial 3.0 Unported License http://creativecommons.org/licenses/by-nc/3.0/), permitting all non commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.In this paper, a tunable Multiband Micro strip Antenna is designed, capable of tuning its operating frequency in 5GHz band independently. Two slots of E & U shape are etched to achieve multiband resonance. Two capacitors of fixed value and a varactor diode are used to achieve tuning. Proposed antenna targets the 5GHz WLAN bands; UNII-1 and UNII-2. Simulated and measured results are in good agreement

Fluctuation-Dissipation-Theorem violation during the formation of a colloidal-glass

The relationship between the conductivity and the polarization noise is measured in a gel as a function of frequency in the range $1Hz - 40Hz$. It is found that at the beginning of the transition from a fluid like sol to a solid like gel the fluctuation dissipation theorem is strongly violated. The amplitude and the persistence time of this violation are decreasing functions of frequency. At the lowest frequencies of the measuring range it persists for times which are about 5% of the time needed to form the gel. This phenomenology is quite close to the recent theoretical predictions done for the violation of the fluctuation dissipation theorem in glassy systems.Comment: 6 pages + 4 figure

Optimum design of electrodynamic shaker’s support spring to improve low frequency performance

The purpose of the present study is to improve the conventional electrodynamic shaker’s performance at low frequency through the optimization of its support spring. It is acknowledged that to improve its low frequency performance, a shaker’s support spring has to be lightweight and simultaneously of high lateral but low axial rigidity. Meanwhile it should have few resonance points in the useable frequency range. But both experimental modal analysis (EMA) and finite element analysis (FEA) in this study indicated that of the support spring of conventional shaker presents undesirable humps in its frequency response (FR) in low frequency area. The first order resonance frequency of the shaker (whose value decides the minimum of the shaker’s useable frequency range) also turned out big. Hence a new support spring plate of laminated composite structure embedded with viscoelastic damping material is proposed in this study whose parameter values are further optimized. The optimization adopts damping thickness, angle and thickness of composite layer as the design variables. It targets at achieving minimum weight while satisfying the shaker’s first order elastic natural frequency and the plate’s intensity. The optimized support spring plate is then put to frequency response analyses. The findings indicate that it not only can suppress the humps in low frequency area, but also widens the shaker’s useable low frequency range. Meanwhile it reduces the shaker’s additional rigidity on the test object. Hence it can ensure the shaker’s performance at low frequency

Measurement of damping of graphite epoxy materials

Work on a damping measurement test apparatus is discussed. The device is designed to excite tube specimens in a vacuum chamber. Also some experiments were conducted on a tube specimen to confirm previously reported results. A table of data showing the results of forced vibration tests using a half ring and a free-free boundary is given. The main purpose was to study the effect of the frequency resolution on the damping ratio measurements

Pricing inertia and Frequency Response with diverse dynamics in a Mixed-Integer Second-Order Cone Programming formulation

Low levels of system inertia in power grids with significant penetration of non-synchronous Renewable Energy Sources (RES) have increased the risk of frequency instability. The provision of a certain type of ancillary services such as inertia and Frequency Response (FR) is needed at all times, to maintain system frequency within secure limits if the loss of a large power infeed were to occur. In this paper we propose a frequency-secured optimisation framework for the procurement of inertia and FR with diverse dynamics, which enables to apply a marginal-pricing scheme for these services. This pricing scheme, deduced from a Mixed-Integer Second-Order Cone Program (MISOCP) formulation that represents frequency-security constraints, allows for the first time to appropriately value multi-speed FR