1,721,007 research outputs found
Surface impacts of large offshore wind farms
No full textFuture offshore wind farms around the world will be built with wind turbines of size and capacity never seen before (with diameter and hub height exceeding 150 and 100 m, respectively, and rated power exceeding 10 MW). Their potential impacts at the surface have not yet been studied. Here we conduct high-resolution numerical simulations using a mesoscale model with a wind farm parameterization and compare scenarios with and without offshore wind farms equipped with these 'extreme-scale' wind turbines. Wind speed, turbulence, friction velocity, and sensible heat fluxes are slightly reduced at the surface, like with conventional wind turbines. But, while the warming found below the rotor in stable atmospheric conditions extends to the surface with conventional wind turbines, with extreme-scale ones it does not reach the surface, where instead minimal cooling is found. Overall, the surface meteorological impacts of large offshore wind farms equipped with extreme-scale turbines are statistically significant but negligible in magnitude
Lagrangian model with heat-carrying particles
No full text<jats:p>Abstract. The dispersion of pollutants in the atmosphere, whether from industrial emissions, wildfires, or other sources, poses significant challenges to air quality management and environmental protection. Understanding the behavior of plumes is crucial for predicting their dispersion patterns and potential impacts on human health and the environment. In this work, we present a new plume rise scheme based on heat transport. The idea at the basis of the new algorithm is the same as the actual scheme embedded in the Lagrangian Particle Model SPRAY-WEB. The temperature difference between the ambient and the plume and the vertical velocity of the plume are expressed on a fixed Eulerian grid. The particles are assigned with an equivalent momentum, temperature, mass, and density, transported as scalar quantities with the particles following the Lagrangian description of the motion. This allows us to reproduce the entrainment phenomenon as a mixing of two fluids (environmental air and plume) with different temperatures: the resulting temperature is given by Richmann's law. The results obtained with the old plume rise algorithm and the new one are compared with Briggs (1975) analytical curve in the case of an idealized atmosphere with a neutral stratification and a constant horizontal wind and with experimental data. From the comparison in an ideal atmosphere, it emerged that with the new algorithm, the plume reaches a higher height than with the old one and the asymptotic trend obtained with both models follows the Briggs curve. As for the comparison with the measurements, the results obtained with the new algorithm are in better agreement with the experimental data than the old one.
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Characterizing different types of lithium ion cells with an automated measurement system
No full textLithium ion batteries are among the most promising electrochemical storage systems currently available.
However, even though their high values of specific energy and energy density make them suitable for the
development of new research approaches to counteract the global energy consumption, its diffusion is
still limited in several sectors because of the high costs and safety problems. Five different Lithium ion
cells of similar energy size but different chemical composition have been studied here, with the aim of
pinpointing the fundamental characteristics of each battery. A comprehensive knowledge of these
technol fogies can helpinding out the critical parameters indicating dangerous situations. An automated
test system based on the synchronous measurement of battery voltage, current and temperature has
been employed in this comparative study. The system allows for testing the cells with a huge variety of
protocols, from the standard charge cycle to the more complex power control test. Experimental results
highlight that, for example, the LiNiCoO2 and the Lithium Polymer batteries outperform for their energy
density and specific energy while the LiFePO4 show the highest versatility, efficiency and safety
Analysis of the outdoor performance and efficiency of two grid connected photovoltaic systems in northern Italy
No full textThis paper analyzes and compares the actual performance of two grid connected photovoltaic plants, which are of similar size but based on different modules technologies. The facilities are located on the roofs of two buildings of Area Science Park in the site of synchrotron ELETTRA in Basovizza (Trieste). The first system is equipped with modules of mono crystalline silicon wafer surrounded by ultra-thin amorphous silicon layers (hetero-junction with intrinsic thin layer), facing south and tilted at 30°, the second is equipped with mono crystalline silicon modules oriented 35° west and inclined at 10°. The set of data analyzed in this paper has been systematically acquired from October 15th 2011 to October 14th 2012 by means of a dedicated monitoring system.
The aim of this study is to analyze the actual performances of the plants and their yearlong evolution, separating the effects of the variability of environmental conditions from those due to the variability of the performance of panels and electrical components. Particular attention is given to the influence that irradiance and temperature have on the efficiency of the system.
An analysis methodology was applied to appropriately filter, classify and normalize the data in order to identify the modules temperature coefficients as a function of irradiance and to compare their actual efficiency with those declared by the manufacturer. Acquired data and mathematical correlations will allow the development of accurate simulation models, useful for assessing the actual profitability of similar installations. The latter can be obtained through the main performance indices of the systems that are calculated and reported in this paper for the period of observation
Modeling and Performance Analysis of an Integrated System: Variable Speed Operated Internal Combustion Engine Combined Heat and Power Unit–Photovoltaic Array
Full text linkThe paper presents the model of a combined heat and power (CHP) unit, based on a variable speed internal combustion engine (ICE) interfaced with a photovoltaic (PV) system. This model is validated by means of experimental data obtained on an 85 kWe CHP unit fueled with natural gas and a PV system with a rated power of 17.9 kW. Starting from daily load profiles, the model is applied to investigate the primary energy saving (PES) of the integrated CHPþPV system in several operating conditions and for different sizes of PV array. The results demonstrate the dependence of the CHP performance on the operating mode and a limited convenience of the variable speed strategy. The integrated system operation leads to performance improvements, which depend on the size of the PV component
Lagrangian modelling evaluation of the NOx pollution reduction due to electric vehicles introduction
No full textAnalisi delle prestazioni di un gruppo integrato cogeneratore con motore a gas e pannelli fotovoltaici
No full textOggetto dello studio è l'analisi sperimentale e la modellazione di un gruppo elettrogeno a gas naturale in assetto cogenerativo, con possibilità di inseguimento del carico termico od elettrico, abbinato ad un impianto fotovoltaico e ad un sistema di accumulo elettrochimico. Esso rientra in un più ampio progetto riguardante la generazione distribuita, denominato Enerplan, condotto da AREA Science Park in collaborazione con il Dipartimento di Ingegneria Civile e Architettura dell'Università degli Studi di Trieste. L’indagine sperimentale ha riguardato il rilievo di numerosi dati funzionali ed il calcolo dei rendimenti elettrici e termici in diversi assetti operativi. Inoltre è stato realizzato un modello di simulazione utile per valutare le prestazioni tecnico-economiche del sistema integrato e per condurre analisi sul comportamento dinamico del sistema in presenza di diverse strategie di controllo
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