• Energy Research
• 2021-2025close
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The web services discovery process in mobile adhoc networks is considered as a very difficult challenge due to the continuous change in the topology of the network and also the lack of a fixed central directory for publishing web services. Several approaches have been proposed which are based on either keywords or identifiers representing the service to be searched or by using a specific scenario of discovery. All of those proposed solutions try to respect the constraints of ad hoc networks such as energy, bandwidth, throughput ... etc. In this paper we present our new proposed model for measuring the cost of the overall energy consumption in ad hoc networks depending on the web services discovery protocols. We also present a new optimized web services discovery protocol in MANET based on cross_layer routing techniques with the dissemination in the routing process at the same time the semantic web services information and a Discovery_Diameter parameter that we have proposed to limit the area of discovery in the network. Finally, we present simulation results of our defined approach showing a significant optimization of the energy consumption level and the average throughput.

Most of wireless sensors are dynamically changing and execute two types of tasks: hard deadline periodic ones and aperiodic ones with no deadline. The emergence of energy harvesting technologies makes it possible to design self-powered sensors through environmental energy. Nevertheless, classical scheduling techniques need to be reconceived so as to take into account the fluctuating energy source and energy consumptions of tasks. Hence, we firstly describe the called TB-H and TB*-H aperiodic task servers which are extensions of the famous Total Bandwidth server. We show how TB-H and TB*-H permit to provide short response times for the aperiodic tasks by computing adequate virtual deadlines taking into account both time and energy constraints. Our second contribution lies in extensive simulations to bring to light the effectiveness of these two novel Bandwidth based servers in comparison to basic background approaches.

This paper presents a control scheme of a power generation system based on a dual star squirrel-cage induction machine operating as an induction generator. The operating mode based on an excitation control scheme is chosen to ensure a controlled magnitude and frequency of the generator output voltage. Some preliminary simulation and experimental test results, carried out on a prototype of dual star induction machine operating as generator and supplying various loads under different conditions, are presented and discussed.

The Acoustic Black Hole (ABH) effect refers to a special vibration damping technique adapted to thin-walled structures such as beams or plates. It usually consists of a local decrease of the structure thickness profile, associated to a thin viscoelastic coating placed in the area of minimum thickness. It has been shown that such structural design acts as an efficient vibration damper in the high frequency range, but not at low frequencies. This paper investigates how different types of vibration absorbers, linear and nonlinear, added to the primary system can improve the low frequency performance of a beam ABH termination. In particular, the conjugated effects of the Acoustic Black Hole effect and a Tuned Mass Damper (TMD), a Nonlinear Energy Sink (NES), a bi-stable NES (BNES), and a vibro-impact ABH (VI-ABH) are investigated. Forced response to random excitation are computed in the time domain using a modal approach combined with an energy conserving numerical scheme. Frequency indicators are defined to characterize and compare the performance of all solutions. The simulation results clearly show that all the proposed methods are able to damp efficiently the flexural vibrations in a broadband manner. The optimal tuning of each proposed solution is then investigated through a thorough parametric study, showing how to optimize the efficiency of each solution. In particular, TMD and VI-ABH show a slight dependence on vibration amplitude, while the performance of NES and BNES have a peak of efficiency for moderate amplitudes.

Abstract An effective encapsulation solution for flexible CIGS is urgently needed to ensure a competitive market entry of the technology. In this work, we demonstrate the feasibility to effectively encapsulate module-level (10 × 10 cm2) CIGS/glass solar cells by employing a thin Al2O3 barrier layer grown by atomic layer deposition (ALD). As determined by a direct methodology, 10 nm ALD-Al2O3 is proved to be sufficient in preventing electrical degradation of the Al:ZnO (AZO) window layer upon exposure to damp heat test (DHT) and equally effective to encapsulate 10 × 10 cm2 CIGS/glass mini-modules by efficient blockage of moisture ingress. CIGS mini-modules encapsulated by ALD-Al2O3 barrier layer retain an average of 80% and 72% of initial efficiency after 1000 and 2000 h of DHT, respectively. Whereas unencapsulated modules drop to an average of 67% (1000 h DHT) and 22% (2000 h DHT) of initial efficiency. Thanks to the presence of ALD-Al2O3 barrier layer, less electrical degradation occurred in AZO window layer and P3 interconnection; also less shunting paths appeared – both led to a lower FF drop in encapsulated CIGS mini-modules. However, an issue of Na migration out of the CIGS layer is observed, which negatively impacts the module stability during DHT.

AbstractIntegrated assessment models (IAMs) have emerged as key tools for building and assessing long term climate mitigation scenarios. Due to their central role in the recent IPCC assessments, and international climate policy analyses more generally, and the high uncertainties related to future projections, IAMs have been critically assessed by scholars from different fields receiving various critiques ranging from adequacy of their methods to how their results are used and communicated. Although IAMs are conceptually diverse and evolved in very different directions, they tend to be criticised under the umbrella of ‘IAMs’. Here we first briefly summarise the IAM landscape and how models differ from each other. We then proceed to discuss six prominent critiques emerging from the recent literature, reflect and respond to them in the light of IAM diversity and ongoing work and suggest ways forward. The six critiques relate to (a) representation of heterogeneous actors in the models, (b) modelling of technology diffusion and dynamics, (c) representation of capital markets, (d) energy-economy feedbacks, (e) policy scenarios, and (f) interpretation and use of model results.

Le générateur asynchrone est de plus en plus utilisé dans les systèmes de production éoliens. Le générateur asynchrone à double alimentation est le mieux adapté pour les systèmes éoliens comparativement au générateur autonome qui sert à alimenter des endroits isolés. Dans notre étude, nous avons présenté le modèle du générateur en tenant compte de l’effet de saturation dans le système d’axes d-q. Nous avons appliqué ce modèle dans le cas d’une coupure du réseau électrique afin d’analyser la répercussion sur la dynamique des courants dans le générateur et ce pour les deux types de générateurs autonome et à double alimentation. Dans le cas du générateur autonome, des résultats expérimentaux sont présentés et comparés à ceux issus de la simulation.