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Abstract: Development of safe and effective hydrogen storage systems becomes a critical factor for further implementation of fuel cell and hydrogen technologies. Among new approaches aimed at improving the performance of such systems, the concept of porous materials-based adsorptive hydrogen storage is now considered as a long-term solution due to the reversibility, good kinetics and absence of thermal management issues. However, the low packing densities associated with the porous materials such as carbon structure materials, zeolites, metal-organic frameworks lead to the compromised volumetric capacity, potential pipe contaminations and difficulties in handling, when introducing the powdered adsorbents into hydrogen storage systems. Some efforts have been devoted to solve this problem by shaping the porous materials into beads, pellets or monoliths and achieve higher storage densities at more moderate temperatures and pressures. This review will firstly state the essential properties of shaped structures for hydrogen adsorption, and then highlight the recent attributes that potentially can be utilized to shape porous materials into specific configurations for hydrogen storage applications. Later, several testing techniques on structured porous material will be also discussed. Keywords: Porous materials,hydrogen storage systems, shaping process, application-specific configuration, packing density. Download Full Article |
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Abstract: The improvement of renewable energy sources exploitation is a central topic of the present studies in the energetic field. One of the main obstacles to the renewable energy increase in the global energetic mix is represented by the fluctuating nature of renewable power sources. The power fluctuations are cause of stress for the electric grid to which the individual nodes are connected. A wider exploitation of renewable power is possible through the implementation of a “smart grid”, constituted by an interconnection of several smart nodes consisting in a user and a renewable source. To reduce the stochastic effects of the renewable energy source it is possible to introduce in the nodes composing the smart grid an energy storage, finalized to smooth the power peaks, rending the node itself less disturbing for the electric grid. This paper presents a simulation model of a smart node, consisting in a user power profile, a photovoltaic panel, an electric vehicle and a battery. Through the simulation model it is possible to evaluate the node effect on the electric grid, with a quantitative approach. Tests were worked out in different node configurations: basic (the only user power profile), basic with photovoltaic panel, basic with storage, basic with panel and storage and finally the complete configuration including also the electric vehicle. The tests were repeated for a domestic and an industrial user to evaluate the size influence over the parameters of interest. Keywords: Smart grid, electrochemical storage, renewable energy, dynamic simulation, Matlab-Simulink.Download Full Article |
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Abstract: Considering complexity in process of the liquor’s evaporation-freezing and irregularity on the liquor surface, generating and developing model of ice on liquor surface was proposed by humidity difference based on fractal theory and diffusion limited aggregation model (DLA). The effect of gas flow velocity and humidity difference between gas and liquor surface on generating and developing of ice above liquor surface were analyzed by numerical simulation. The results showed that the fractal method could simulate the process generating and developing model of ice above liquor surface. It provided the new idea and method for the study of the liquor evaporation-freezing and ice growth. Keywords: Evaporation-freezing, fractal simulation, ice.Download Full Article |
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Abstract: Comparison between simulation results and measured performances is usually an open scientific problem, crucial to achieving the goal of NZEB performance. This paper addresses this issue in relation to residential buildings, using as a case study “RhOME for denCity”, the housing prototype developed by Roma TRE University and winner of Solar Decathlon Europe 2014. In a Mediterranean climate, the use of the mass combined with natural cross ventilation to control the indoor microclimate can be very effective in reducing HVAC use. Therefore, a “massive layer” was introduced in the inner surface of the envelope to not only contribute to the envelope transmittance value and the shifting phase of the thermal waves, but also as a thermal shock absorber to adjust the internal temperature, in both summer and winter. This experimental envelope was tested over two weeks during the competition in Versailles. Although prototype thermal behaviour was monitored only during the competition, and not over an extended period, initial results provide information on how to size the thermal mass contribution for indoor comfort. In-depth simulation through TRNSYS was run prior to the construction phase. This paper presents the comparison between monitored performance and simulations in order to measure the amount of mass needed to obtain a numerical improvement in indoor comfort performance. Keywords: Thermal mass contribution, Energy performance in Mediterranean Climate, Dynamic thermal simulation, Thermal mass in lightweight envelope, building performance comparison. |
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Abstract: Pure electric mobility is still struggling to emerge in the present road vehicles scenario. This is mostly due to costs, nowadays still very high, and to battery range, which is intrinsically very limited with respect to the fuel tank of a traditional vehicle. To be effectively competitive, e-mobility should not be thought as the mere substitution of the thermal powertrain with the electric one on the same vehicle; instead, a holistic approach comprehensive of the integration of a charging network within the territory should be adopted. The vehicles should be tailored on the missions to be accomplished promoting the lightness, simplicity and low cost, and should be integrated within a charging infrastructure and a car-sharing system implemented in the reference territory. In this paper the authors aim at exposing their idea of e-mobility, justifying it by simulations carried out on three different vehicles (a Diesel-fuelled Renault Kangoo, an electric driven Renault Kangoo and an electric micro-vehicle Renault Twizy) and experimental data. The simulations were carried out with the help of a validated road vehicle model in different real road missions, namely a urban, an extra-urban and a mountain mission. Keywords: Electric mobility, simulation model, comparative assessment, Matlab-Simulink, carbon dioxide Reduction, car sharing.Download Full Article |
