• Energy Research
• 7. Clean energy close
• 1. No poverty close
• 9. Industry and infrastructure close
• IT close

Aeroengine manufacturers must continuously develop new high-performance engines, in terms of both specific fuel consumption and pollutant emissions. During the combustion of kerosene, CO 2 and lower amounts of SO 2 , CO, NO x and hydrocarbons are produced; those gases are directly or indirectly responsible for greenhouse effect. Large emission of NO x is produced by engines during the aircraft operation in airport. In the near future, the target in Europe for the aviation sector provides a reduction of SO% of NO x and 50% of CO 2 . For this reason, the hybrid-electric propulsion systems (HEPS) are becoming a viable alternative propulsion technology in the field of aviation, useful to guarantee a massive reduction of pollution. In the paper, the authors analyze and simulate a hybrid turbine/electric engine for a passengers regional aircraft, comparing the results in terms of pollutant and fuel consumption with the conventional thermal engine ones.

Abstract This literature review was built upon recently published articles on Life Cycle Assessments (LCAs) of agricultural biogas plants, to: enhance understanding of the relevant literature in the field and the related question by readers worldwide. It was designed to highlight methodological issues and impact indicators, which best represent this research field; consequently, they should be considered in performing environmental assessments of agro-biogas derived energy systems. The literature review highlighted the wide variability of environmental results due to the ways the feedstock mixtures were produced, managed, and supplied; and due to the regions in which the anaerobic digesters were located and operated. Differences were found to be related to the aim and function of the study and to the methodological approach used, especially for the development of the environmental impact assessments. Other differences resulted from the ways the energy produced was utilised, whether it was used as an input to the natural gas national grid, and/or if it was used within the production system. The authors of this review concluded that, although much progress has been made, many unsolved challenges and methodological choices must be addressed to further improve the robustness of LCA in relation to AD and to related approaches.

En este documento, proponemos una solución de eficiencia energética para implementar la codificación de red (NC) en redes inalámbricas basada en el estándar IEEE 802.11. El mecanismo propuesto, llamado GreenCode, permite a los nodos realizar el ciclo de trabajo cambiando a un estado de baja potencia (suspensión) cuando escuchan transmisiones de paquetes codificados que no proporcionarán ninguna información nueva para ellos. Para facilitar la operación de suspensión, las transmisiones bidireccionales que involucran paquetes codificados y no codificados entre pares de nodos remitente-receptor se integran en la operación de GreenCode. Tanto los resultados analíticos como de simulación presentados en este documento muestran la alta eficiencia energética de GreenCode con ganancias de hasta el 360% en comparación con los mecanismos existentes basados en el Estándar IEEE 802.11. Dans cet article, nous proposons une solution écoénergétique pour la mise en œuvre du codage de réseau (NC) dans les réseaux sans fil basée sur la norme IEEE 802.11. Le mécanisme proposé, appelé GreenCode, permet aux nœuds de fonctionner en passant à un état de faible puissance (veille) lorsqu'ils entendent des transmissions de paquets codés qui ne leur fourniront aucune nouvelle information. Pour faciliter le fonctionnement en veille, des transmissions bidirectionnelles impliquant à la fois des paquets codés et non codés entre des paires de nœuds expéditeurs-récepteurs sont intégrées dans le fonctionnement de GreenCode. Les résultats d'analyse et de simulation présentés dans cet article montrent l'efficacité énergétique élevée de GreenCode avec des gains allant jusqu'à 360% par rapport aux mécanismes existants basés sur la norme IEEE 802.11. In this paper, we propose an energy-efficient solution for implementing Network Coding (NC) in wireless networks based on the IEEE 802.11 Standard. The proposed mechanism, called GreenCode, allows nodes to duty cycle by switching to a low-power (sleep) state when they overhear coded packet transmissions that will not provide any new information for them. To facilitate the sleep operation, bidirectional transmissions involving both coded and non-coded packets between pairs of sender-receiver nodes are integrated into the operation of GreenCode. Both analytical and simulation results presented in this paper show the high energy efficiency of GreenCode with gains of up to 360% when compared to the existing mechanisms based on the IEEE 802.11 Standard. في هذه الورقة، نقترح حلاً موفرًا للطاقة لتنفيذ ترميز الشبكة (NC) في الشبكات اللاسلكية بناءً على معيار IEEE 802.11. تسمح الآلية المقترحة، المسماة GreenCode، للعقد بدورة العمل عن طريق التبديل إلى حالة منخفضة الطاقة (السكون) عندما تسمع عمليات إرسال الحزم المشفرة التي لن توفر أي معلومات جديدة لها. لتسهيل عملية السكون، يتم دمج عمليات الإرسال ثنائية الاتجاه التي تنطوي على كل من الحزم المشفرة وغير المشفرة بين أزواج من عقد المرسل والمستقبل في تشغيل GreenCode. تُظهر كل من النتائج التحليلية والمحاكاة المقدمة في هذه الورقة كفاءة الطاقة العالية للـ GreenCode مع مكاسب تصل إلى 360 ٪ بالمقارنة مع الآليات الحالية القائمة على معيار IEEE 802.11.

It is shown that due to power take-off losses, optimal control provides maximum energy absorption, but not maximum energy production. A new reactive control criterion in the frequency-domain is deduced assuming constant power take-off efficiency, respectively, in the power feeding and power absorption parts of the wave cycle. If applied in the time-domain, this criterion requires the incident wave to be predicted some time into the future. Whilst the OWC type of Wave Energy Converters (WEC) is presented in the paper, the extension to WECs of the floating body type is also considered. Illustrative numerical results for a two-dimensional OWC of simple geometry are presented, which include the performance of this device in three wave spectra with increasing demands of active control for improved energy production. Linear hydrodynamic theory is considered throughout the paper.

Abstract European and Italian standards establish high levels of energy performance of buildings that have to be designed considering their energy balance near zero. To achieve this goal, the reduction of energy demand, attainable by improving energy efficiency of the construction, and the use of renewable energy available both on site and off site are effective solutions to be applied. In particular, in buildings that use energy produced from renewable sources, due to their unstable and unpredictable nature, having the right strategy to compensate the variations is essential. A technical solution reevaluated as a consequence of passive design principles, is to provide an adequate thermal inertia in order to store energy when it is offered and to use it when the source is not available. In these cases, the ability of construction elements to retain heat becomes fundamental as they contribute to maintain internal comfort conditions. This paper aims to investigate how various types of heating and cooling systems, based on different modes of heat transfer, are able to interact differently with the thermal mass of the building, producing a different level of its activation. The investigation considers a case study used to carry out dynamic simulation by means of DesignBuilder which is a user interface of EnergyPlus. The model consists of a building with elementary geometry and a single thermal zone, delimited by walls with outside thermal insulation and a heat accumulation layer inside. The variation of the internal temperature by using different types of conditioning system is analyzed in order to individuate the technology that takes the greatest advantages from the thermal mass.

Abstract The OECD/NEA Sandia Fuel Project provided unique thermal-hydraulic experimental data associated with Spent Fuel Pool (SFP) complete drain down. The study conducted at Sandia National Laboratories (SNL) was successfully completed (July 2009 to February 2013). The accident conditions of interest for the SFP were simulated in a full scale prototypic fashion (electrically heated, prototypic assemblies in a prototypic SFP rack) so that the experimental results closely represent actual fuel assembly responses. A major impetus for this work was to facilitate severe accident code validation and to reduce modeling uncertainties within the codes. Phase I focused on axial heating and burn propagation in a single PWR 17 × 17 assembly (i.e. “hot neighbors” configuration). Phase II addressed axial and radial heating and zirconium fire propagation including effects of fuel rod ballooning in a 1 × 4 assembly configuration (i.e. single, hot center assembly and four, “cooler neighbors”). This paper summarizes the comparative analysis regarding the final destructive ignition test of the phase I of the project. The objective of the benchmark is to evaluate and compare the predictive capabilities of computer codes concerning the ignition testing of PWR fuel assemblies. Nine institutions from eight different countries were involved in the benchmark calculations. The time to ignition and the maximum temperature are adequately captured by the calculations. It is believed that the benchmark constitutes an enlargement of the validation range for the codes to the conditions tested, thus enhancing the code applicability to other fuel assembly designs and configurations. The comparison of lumped parameter and CFD computer codes represents a further valuable achievement.

AbstractIn this paper, a dataset of 92,906 dwellings was analysed adopting data mining techniques for the classification of heating and domestic hot water primary energy demand and for the evaluation of the most influencing factors. The sample was classified in three energy demand categorical variables (Low, Medium, High) considering different geometrical and physical attributes. The output of the model made it possible to set reference threshold values among the physical variables. Moreover, high energy demand dwellings were analysed in depth using a k-means algorithm in order to evaluate the design variables which need to be considered in a refurbishment process.