Power Measurement Data Research Articles

A Comparative study on the aeromechanic performances of upwind and downwind horizontal-axis wind turbines

Traditional horizontal-axis wind turbines are mainly designed as upwind configuration. In order to avoid blade strikes, the rotor blades have to be positioned far enough away from the turbine tower and have to be designed as inflexible as possible. In addition, a complicated yaw control system is required to keep the turbine rotor facing the incoming wind. Due to these drawbacks, the turbine in downwind configuration is proposed to overcome these disadvantages because, first of all, rotor blades can be designed more flexible since there is no danger of blade strikes, and secondly, yaw control system could be eliminated if nacelle is designed appropriately to follow the incoming wind direction passively. In the present study, a comparative experimental investigation was conducted to quantify the aeromechanic performance of a downwind turbine (DWT), in comparison to that of a traditional upwind turbine (UWT). The thrust coefficient of the DWT model was found to be increased slightly in the time-averaged quantity, but have a significant augment in the fluctuations. Due to the shadow effect, the power outputs of the DWT model was found to be decreased by 3.2% when they were operated in a same atmospheric boundary layer (ABL) wind. In addition, a high-resolution particle image velocimetry (PIV) system was employed to characterize the ensemble-averaged and phase-locked wake flow structures to quantify the turbulent flow characteristics in the turbine wakes. The velocity deficit in the lower half turbine wake for the UWT case was found to be greater than that of the DWT case at the location of X/D < 1.0. The higher wind load fluctuations for the DWT system were found to be correlated well with the higher TKE distributions in the turbine wakes. The phase-locked PIV measurements illustrated that the wake regions can be divided into four zones, which are dominated by the vortices shedding from different turbine components. The detailed flow field measurements were correlated with the dynamic force and power measurement data to elucidate the underlying physics.

Fisher Information as a Measure of Privacy: Preserving Privacy of Households With Smart Meters Using Batteries

In this paper, batteries are used to preserve the privacy of households with smart meters. It is commonly understood that data from smart meters can be used by adversaries to infringe on the privacy of the households, e.g., figuring out the individual appliances that are being used or the level of the occupancy of the house. The Cramer-Rao bound is used to relate the variance of the estimation error of any unbiased estimator of the household consumption from the aggregate consumption (i.e., the household plus the battery) to the Fisher information. Subsequently, optimal policies for charging and utilizing batteries are devised to minimize the Fisher information (in the scalar case and the trace of the Fisher information matrix in the multi-variable case) as a proxy for maximizing the variance of the estimation error of the electricity consumption by adversaries (irrespective of their estimation policies). The policies are chosen to respect the physical constraints of the battery regarding capacity, initial charge, and rate constraints. The results are demonstrated on real power measurement data with non-intrusive load monitoring algorithms.

An evaluation of electrochemical performance of a solid oxide electrolyzer cell as a function of co-sintered YSZ-SDC bilayer electrolyte thickness

Using porous Ni-YSZ (Yttria Stabilized Zirconia, ZrO2-Y2O3) as a fuel electrode, dense YSZ-SDC (Samaria Doped Ceria, Sm0.2Ce0.8O1.9) as an electrolyte, and porous 20wt%SDC-80wt% BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3−δ) as an air electrode, with the three distinguishable layers well adhered to each other, a Ni-YSZ/YSZ-SDC/BSCF-SDC solid oxide electrolyzer cell (SOEC) was constructed in order to satisfy the aim of this research which is studying the effect of YSZ blocking layer on its electrochemical performance over the temperature range of 650–800°C. Coating of SDC with a very thin layer of YSZ to form a YSZ-SDC bilayer electrolyte was performed using the spin coating technique in order to prevent the open circuit voltage (OCV) loss and enhance the chemical stability of doped ceria electrolyte in reducing atmospheres. For further examination to find out which microstructure is crack-free in order to provide electrical current leakage prevention in the SDC layer and at the same time to have an optimum thickness, impedance measurement under 0.1V bias with different hydrogen humidity level as well as cell polarization study were conducted at 800°C. Detailed investigations on the microstructural, electrochemical, and power measurement data confirmed that abilayer electrolyte structure with 3.5µm YSZ thickness can provide chemical, mechanical, and structural stability of the YSZ-SDC bilayer electrolyte in the Ni-YSZ/YSZ-SDC/BSCF-SDC single cell.

A Data-Driven, Cooperative Approach for Wind Farm Control: A Wind Tunnel Experimentation

This paper discusses a data-driven, cooperative control strategy to maximize wind farm power production. Conventionally, every wind turbine in a wind farm is operated to maximize its own power production without taking into account the interactions between the wind turbines in a wind farm. Because of wake interference, such greedy control strategy can significantly lower the power production of the downstream wind turbines and, thus, reduce the overall wind farm power production. As an alternative to the greedy control strategy, we study a cooperative wind farm control strategy that determines and executes the optimum coordinated control actions for maximizing the total wind farm power production. To determine the optimum coordinated control actions of the wind turbines, we employ a data-driven optimization method that seeks to find the optimum control actions using only the power measurement data collected from the wind turbines in a wind farm. In particular, we employ the Bayesian Ascent (BA) algorithm, a probabilistic optimization method constructed based on Gaussian Process regression and the trust region concept. Wind tunnel experiments using 6 scaled wind turbine models are conducted to assess (1) the effectiveness of the cooperative control strategy in improving the power production; and (2) the efficiency of the BA algorithm in determining the optimum control actions of the wind turbines using only the input control actions and the output power measurement data.

PSCAD/EMTDC를 이용한 측정기반의 부하모델링 연구

To supply electrical power with high quality, the power system must be optimized in many ways such as planning, control and management. In order to optimize the power system, the analysis of the power system is necessary. The elements of the power system require an accurate model to analysis of the power system. The components of the power systems such as generators, transformers and transmission lines have been studied and researched a lot in their modeling and very sophisticated models have been proposed. However, in case of load in-depth studies on the exact model are required. In this paper, measurement-based load modeling method using real-time measured data is proposed in various methods to reflect the characteristics of the load. To prove the validity of the proposed method, PSCAD/EMTDC program is used to configure the power system and measurement data according to the various failures are used to study on load modeling.

Modelling of escalator energy consumption

The energy consumed by an escalator can be logically subdivided into two main components. The first component depends on the vertical rise of the escalator and its mechanical and electrical design. This component has been denoted as the fixed power losses. It is the power that is drawn from the supply when the escalator is running unloaded (regardless of the direction of travel). The second component depends on the vertical rise of the escalator and the number of passengers using the escalator per day as well as their walking behaviour. This component has been denoted as the variable power losses for an upward moving escalator (or variable power gains for a downward moving escalator).The formulae used to calculate both components are derived based on power measurements on a large group of escalators in addition to a number of passenger count surveys on a selection of escalators (synchronised to the power measurement data). Further analysis is carried out into the phenomenon of passengers walking on escalators and its effect on the overall energy consumption.

Noncontact common-path Fourier domain optical coherence tomography method for in vitro intraocular lens power measurement

We propose a novel common-path Fourier domain optical coherence tomography (CP-FD-OCT) method for noncontact, accurate, and objective in vitro measurement of the dioptric power of intraocular lenses (IOLs) implants. The CP-FD-OCT method principle of operation is based on simple two-dimensional scanning common-path Fourier domain optical coherence tomography. By reconstructing the anterior and posterior IOL surfaces, the radii of the two surfaces, and thus the IOL dioptric power are determined. The CP-FD-OCT design provides high accuracy of IOL surface reconstruction. The axial position detection accuracy is calibrated at 1.22 μm in balanced saline solution used for simulation of in situ conditions. The lateral sampling rate is controlled by the step size of linear scanning systems. IOL samples with labeled dioptric power in the low-power (5D), mid-power (20D and 22D), and high-power (36D) ranges under in situ conditions are tested. We obtained a mean power of 4.95/20.11/22.09/36.25 D with high levels of repeatability estimated by a standard deviation of 0.10/0.18/0.2/0.58 D and a relative error of 2/0.9/0.9/1.6%, based on five measurements for each IOL respectively. The new CP-FD-OCT method provides an independent source of IOL power measurement data as well as information for evaluating other optical properties of IOLs such as refractive index, central thickness, and aberrations.

Electrical properties of polyaniline and substituted polyaniline derivatives

Polyaniline and substituted polyaniline derivatives which the ortho position hydrogen is substituted with CH 3, OCH 3 and Cl are studied. Both protonic acid doping (i.e. the addition of protons to the polymer chain without changing the number of electrons in the chain) and the acceptor doping (i.e., the number of electrons in the polymer chain is decreased by the acceptor which is iodine in this case) results on these samples show metallic conductivity. On the other hand, the signs of thermoelectric power are different. The sign of protonic acid doped polyaniline becomes negative upon doping, but the sign of the acceptor doped sample remains positive. The effect of the substitution of ortho hydrogen is more significant in the protonic acid doping than in the iodine doping. Electron affinity of the substituted molecules could affect the electronic structure of the polyaniline. The electrical conductivity and thermoelectric power measurement data as functions of doping concentration and temperature for these samples are presented.

The relative variance in sound power measurements using reverberation rooms

The relative variance observed in power measurement data when using reverberation rooms is analyzed, based on modal wave theory. It is well known that a biased error due to room variance is contained in power measurement data from the power output of a source in a free field. It is demonstrated numerically and theoretically that the biased error can be reduced by increasing the modal overlap in the room. Thus, the reverberation time should be shorter than approximately 3·0 s at a center frequency of 125 Hz, in order to make power measurements which meet the ISO specifications of a reverberation room whose volume is 200 m 3.