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A. Freddi, G. Olmi
EXPERIMENTAL STRESS ANALYSIS SYLLABUS AND COURSE DESIGN

According to tradition, an Experimental Analysis Course has the task of presenting the main methods of experimental analysis in the awareness that stress and strain are responsible for a variety of phenomena of structural failures of modern artefacts, which are due to several causes such as load estimates, insufficient stress analysis and lack of data on materials. The discipline was created as a selection of tools for finding results when analytical solutions did not formerly exist, but today it has the new task of clarifying the limitations of analytical theories, of validating numerical results, of building the fundaments of phenomenological theories and simulations and of allowing reliability and life extension estimations especially in case of incomplete data and badly posed problems.

Stefan M. Sarge, Sergey P. Verefkin, Dzimitry H. Zaitsau, Vladimir N. Emelyanenko
METROLOGY FOR THE THERMODYNAMIC CHARACTERIZATION OF BIOFUELS

The most important physical parameter of any fuel is its energy content which is usually described by its specific inferior calorific value. The inferior calorific values of two biodiesels, rape seed methyl ester (RME) and soy bean methyl ester (SME) have been determined by precision bomb calorimetry to 37088.9 ± 11.0 J g-1 and 36998.7 ± 8.2 J g-1, resp.

H. Wolf, S. Heinsch
DENSITY MEASUREMENTS OF FOSSIL FUELS BLENDED WITH BIOFUELS TO DETERMINE TEMPERATURE CONVERSION FACTORS FOR LEGAL METROLOGY

In a national project preceding the European project EMRP ENG09 Metrology for biofuels, several fuel blends were investigated at the Physikalisch-Technische Bundesanstalt (PTB). Density data were measured for mixtures of fossil petrol with ethanol and for fossil diesel with biodiesel.
The volume concentration of the biofuels component varied between 0% and 100% to have data available for all possible mixtures. The data were measured in a temperature range between -10 °C and +50 °C. The measurement data were obtained by using a modified Anton Paar DMA 5000.

T. Hager, A. Bentaleb, E.-A. Wehrmann, H.-P. Beck
IDENTIFICATION OF THE PARAMETERS "PRESSSURE, FLOW AND CALORIFIC VALUE" IN UNDER-INSTRUMENTED GAS DISTRIBUTION GRIDS BY USING MODERN RECONSTRUCTION METHODS

The simulation of natural gas networks is only feasible with available simulation tools, if all inlets and rather all offtakes of the grids are measured. At regional gas distribution grids these premises are often not fulfilled. In detail this means, that not enough offtakes are measured and because of that it is not possible to use the common simulation tools. For this reason a method was developed at Clausthal University of Technology which emulates the unmeasured offtakes with a Nodal Point Load Observer. With this emulated offtakes it is possible to simulate the pressures and the pipe flows in gas distribution grids and with them to reconstruct the calorific values. The results of simulations at different gas distribution grids are shown in the article.
A simulation system for gas distribution grids with an incomplete measurement infrastructure would bring a new quality to the controlling and monitoring of gas distribution grids and to the billing. If different gas qualities are in the grid, for example if biogas plants feed in their biogas, it will be necessary to trace the calorific values for billing.

F. Haloua, S. M. Sarge, T. E. Fernandez, C. García Izquierdo, J. J. Segovia, C. Chamorro, M. Bozoianu
CALORIC QUANTITIES AND DENSITY MEASUREMENT OF NON-CONVENTIONAL GASES

This article presents a general description of the technical program of a work package related to the EMRP joint research project (JRP) ENG01 GAS supported by EURAMET and the European Commission as part of the targeted programme Energy (2009). The JRP “Characterisation of Energy Gases” proposes to put in place the necessary metrology infrastructure to enable the “interchangeability” of energy gases so that gaseous fuels from non-conventional sources can access gas grids across the EU. Four-funded European JRP partners participate to the work package dedicated to direct measurement of the energy content of non-conventional gases as biogas or coal bed methane by calorimetry. Energy content measurements with calorimetry ensure validation of the indirect method (gas chromatography) generally adopted by operators for on-site gas control. A reference gas calorimeter and different field calorimeters will be used to measure the energy content of real samples of non-conventional gases. Results will then be compared with indirect measurements. The work package will also focus on development of novel methods for density (needed for Wobbe index calculation) and thermophysical property as heat capacity of these gases.

I. Gasparac, M. Vrazic, I. Petrovic
EXPECTED AND MEASURED VALUES OF LUMINANCE SENSORS IN DUALAXIS PHOTOVOLTAIC POSITIONING SYSTEM

A dual-axis photovoltaic positioning system has a primary task of directing a PV module towards the optimal light source when placed on electric vehicle. The idea of a positioning loop requires proper information on the PV module direction in order to get more irradiance, i.e. more energy. The assumption of a proper luminance sensor distribution is described in this paper. With this kind of distribution every angle position is described by a unique combination of luminance sensor readings. This paper compares expected readings and measured readings of a real model.

V. Šunde, M. Vražic, M. Šverko
OUTDOOR SIMULATION MODEL OF PHOTOVOLTAIC THERMAL (PV/T) WATER BASED SOLAR COLLECTOR

Photovoltaic modules and solar collectors are used together in hybrid photovoltaic-thermal solar collectors (PV/T) for simultaneous provision of electrical and thermal energy. This paper proposes design of a simulation model for testing of efficiency of photovoltaic-thermal solar collectors. The model is used for testing of dependence of thermal and electrical efficiency of the systems on a series of factors; material of the photovoltaic module, type of cooling medium, flow of cooling medium, collector design, exposure to sunlight, speed of wind and environment temperature. Values measured within the system were recorded and the measuring equipment and methods for the measuring system were proposed.

A. J. Roscoe, G. M. Burt
COMPARISONS OF THE EXECUTION TIMES AND MEMORY REQUIREMENTS FOR HIGH-SPEED DISCRETE FOURIER TRANSFORMS AND FAST FOURIER TRANSFORMS, FOR THE MEASUREMENT OF AC POWER HARMONICS

Conventional wisdom dictates that a Fast Fourier Transform (FFT) will be a more computationally effective method for measuring multiple harmonics than a Discrete Fourier Transform (DFT) approach. However, in this paper it is shown that carefully coded discrete transforms which distribute their computational load over many frames can be made to produce results in shorter execution times than the FFT approach, even for large number of harmonic measurement frequencies. This is because the execution time of the presented DFT actually rises with N and not the classical N2 value, while the execution time of the FFT rises with Nlog2N.

R. Laronde, A. Charki, D. Bigaud
LIFETIME ESTIMATION OF A PHOTOVOLTAIC MODULE BASED ON TEMPERETAURE MEASUREMENT

In the building domain, components or equipment are often subjected to severe environmental conditions. In order to predict the reliability and the lifetime of such equipment, accelerated life testing can be carried out. Severe conditions are applied to accelerate the ageing of the components and the reliability at nominal conditions is then deduced considering that these nominal conditions are not constant but stochastic. In this paper, the accelerated life testing of photovoltaic modules is carried out at severe module temperature levels. The module power losses are monitored and the limit state is determined when a threshold power is reached. The stochastic data and the reliability are simulated during a period of fifty years. Finally, the lifetime of the component is evaluated.

A. Bergman
METROLOGY FOR HIGH VOLTAGE DIRECT CURRENT STATE-OF-ART AND CURRENT DEVELOPMENT

Energy transmission by high voltage direct current – HVDC - is steadily increasing in the world, both at the highest power levels, but also at medium power, for example in connections of remote wind-parks to the main a.c. grid. Although principles for d.c. side measurements are known since long, support from metrology is not on par with the needs. An overview of available technologies and the challenges for metrology shows that advances are needed in determination of power losses in convertors, traceability for transmission line voltage measurement, power quality and d.c. side metering. Response to these challenges is given by seven national metrology institutes, one university and one industrial partner, in a project funded by the European Union under Article 169. The research will provide traceable calibrations and measurements in the assigned areas, and capability of measurement will extend to transmission line levels including 1000 kV d.c.

Page 646 of 977 Results 6451 - 6460 of 9762