Modern data centers host hundreds of thousands of servers to achieve economies of scale. Such a huge number of servers create challenges for the data center network (DCN) to provide proportionally large bandwidth. In addition, the deployment of virtual machines (VMs) in data centers raises the requirements for efficient resource allocation and find-grained resource sharing. Further, the large number of servers and switches in the data center consume significant amounts of energy. Even though servers become more energy efficient with various energy saving techniques, DCN still accounts for 20% to 50% of the energy consumed by the entire data center. The objective of this dissertation is to enhance DCN performance as well as its energy efficiency by conducting optimizations on both host and network sides. First, as the DCN demands huge bisection bandwidth to interconnect all the servers, we propose a parallel packet switch (PPS) architecture that directly processes variable length packets without segmentation-and-reassembly (SAR). The proposed PPS achieves large bandwidth by combining switching capacities of multiple fabrics, and it further improves the switch throughput by avoiding padding bits in SAR. Second, since certain resource demands of the VM are bursty and demonstrate stochastic nature, to satisfy both deterministic and stochastic demands in VM placement, we propose the Max-Min Multidimensional Stochastic Bin Packing (M3SBP) algorithm. M3SBP calculates an equivalent deterministic value for the stochastic demands, and maximizes the minimum resource utilization ratio of each server. Third, to provide necessary traffic isolation for VMs that share the same physical network adapter, we propose the Flow-level Bandwidth Provisioning (FBP) algorithm. By reducing the flow scheduling problem to multiple stages of packet queuing problems, FBP guarantees the provisioned bandwidth and delay performance for each flow. Finally, while DCNs are typically provisioned with full bisection bandwidth, DCN traffic demonstrates fluctuating patterns, we propose a joint host-network optimization scheme to enhance the energy efficiency of DCNs during off-peak traffic hours. The proposed scheme utilizes a unified representation method that converts the VM placement problem to a routing problem and employs depth-first and best-fit search to find efficient paths for flows.

Orientador: Luiz Felipe Mendes de Moura / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-28T12:01:47Z (GMT). No. of bitstreams: 1 Nobrega_ClaudiaRosadoEspiritoSanto_M.pdf: 49731796 bytes, checksum: 231227e66649d1f3e29b15b3a64c3913 (MD5) Previous issue date: 2015 / Resumo: O presente trabalho refere-se a uma investigação experimental do comportamento de um sistema de refrigeração utilizando um compressor de rotação variável. Diante da necessidade do uso racional de energia elétrica, estudos entorno da eficiência energética são desenvolvidos como alternativas de redução do desperdiço em equipamentos, como desenvolvimento de dispositivos que necessite de menos consumo de energia sem comprometimento de sua eficiência, e possibilitando a acessibilidade destas alternativas para comunidade em geral. O uso do compressor de rotação variável tem sido estudado como alternativa de redução no consumo de energia por ser responsável por 80% do consumo total de energia consumida pelo sistema de refrigeração, que está cada vez mais presente nas indústrias e residências. Foi implementada uma bancada de teste composta por um subsistema de refrigeração por compressão a vapor e um subsistema secundário de resfriamento. Este estudo visa investigar experimentalmente a potência consumida, potência de compressão, coeficiente de performance (COP) e eficiência do sistema de refrigeração variando-se a carga térmica solicitada utilizando um compressor de rotação variável e o compressor em rotação fixa máxima fornecida pelo fabricante. Os resultados encontrados experimentalmente com a utilização do compressor em rotação variável apresentaram valores satisfatórios para os parâmetros avaliados e um melhor desempenho do sistema se comparado aos valores obtidos com o compressor em rotação fixa variando-se a carga térmica solicitada / Abstract: The present work relates to an experimental investigation of the behavior of a refrigeration system using a variable speed compressor. Faced with the need for rational use of energy, environment studies of energy efficiency are developed as wasting reduction alternatives in equipment such as developing devices that need less power consumption without compromising its efficiency and allowing the accessibility of these alternatives community. The use of variable speed compressor has been studied as alternative reduction in energy consumption to be responsible for 80 % of total energy consumption consumed by the cooling system, which is increasingly present in industry and households. A test bench comprising a subsystem vapor compression refrigeration and secondary cooling subsystem has been implemented. This study aims to experimentally investigate the consumed power, compression power, coefficient of performance (COP) and the refrigeration system efficiency by varying the thermal load applied using a variable speed compressor and the compressor at maximum fixed speed provided by the manufacturer. The results experimentally using the variable speed compressor showed satisfactory values for the parameters evaluated and improved system performance compared to the values obtained with fixed speed compressor in varying the required heat load / Mestrado / Termica e Fluidos / Mestra em Engenharia Mecânica

abstract: Due to extreme summer temperatures that regularly reach 122°F (50°C), cooling energy requirements have been responsible for 70% of peak demand and 45% of total electricity consumption in Kuwait. It is estimated that 50%-60% of electric power is consumed by the residential sector, mostly in detached villas. This study analyzes the potential impact of energy efficiency measures (EEM) and renewable energy (RE) measures on the electric energy requirements of an existing villa built in 2004. Using architectural plans, interview data, and the eQUEST building energy simulation tool, a building energy model (BEM) was developed for a villa calibrated with hourly energy use data for the year 2014. Although the modeled villa consumed less energy than an average Kuwaiti villa of the same size, 26% energy reductions were still possible under compliance with 2018 building codes. Compliance with 2010 and 2014 building codes, however, would have increased energy use by 19% and 3% respectively. Furthermore, survey data of 150 villas was used to generate statistics on rooftop solar area availability. Accordingly, it was found that 78% of the survey sample’s average total rooftop area was not suitable for rooftop solar systems due to shading and other obstacles. The integration of a solar canopy circumvents this issue and also functions as a shading device for outdoor activities and as a protective cover for AC units and water tanks. Combining the highest modeled EEMs and RE measures on the villa, the energy use intensity (EUI) would be reduced to 15 kWh/m2/year from a baseline value of 127 kWh/m2/year, close to net zero. Finally, it was determined that EEMs were able to reduce the entire demand profile whereas RE measures were most effective at reducing demand around mid-day hours. In future studies, more effort should be spent on collecting hourly data from multiple villas to assist in the development of a detailed hourly bottom-up residential energy modeling methodology. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2020

To broaden the application scenario and reduce energy consumption, we propose an energy-efficient fixed-gain (FG) amplify-and-forward (AF) relay assisted orthog- onal frequency-division multiplexing with index modulation (OFDM-IM) scheme in this thesis. The proposed system needs neither instantaneous channel state informa- tion (CSI) nor performing complicated processing at the relay node. It operates based on a new design of power allocation that minimizes the sum of transmit power at both source and relay node, given an outage probability constraint. Considering the actual situation and combining with the characteristics of normalization research, the pro- posed scheme can be discussed in two scenarios regarding to whether the subcarriers are interfered with by fading and noise independently. Based on the consistency of statistical CSI for each subcarrier, through a series of problem transformation and simplification, this thesis converts the original power allocation problem to a relaxed version and solve the relaxed problem using the convex optimization techniques. To reveal the computing efficiency of the proposed power allocation scheme, we analyze its computational complexity. Numerical simulations substantiate that the proposed optimization scheme has a neglectable loss compared with the brute force search, while the computational complexity could be considerably reduced. As for the sce- nario about the independence of statistical CSI for each subcarrier, an approach of artificial neural network (ANN) based on deep learning is incorporated into the sys- tem, enabling the proposed scheme to achieve a high accuracy comparing perfect optimization scheme. In the processing of power minimization, this study utilizes the adaptive moment estimation (Adam) method to implement back-propagation learn- ing and achieve the power allocation needed.

The increasing bandwidth demands in access networks motivates network operators, networking devices manufacturers, and standardization institutions to search for new approaches for access networks. These approaches should support higher bandwidth, longer distance between end user and network operator, and less energy consumption. Ethernet Passive Optical Network (EPON) is a favorable choice for broadband access networks. EPONs support transmission rates up to 10 Gbps. EPONs also support distance between end users and central office up to 20 Km. Moreover, optical networks have the least energy consumption among all types of networks. In this dissertation, we focus on reducing delay and saving energy in EPONs. Reducing delay is essential for delay-sensitive traffic, while minimizing energy consumption is an environmental necessity and also reduces the network operating costs. We identify five challenges, namely excess bandwidth allocation, frame delineation, congestion resolution, large round trip time delay in long-reach EPONs (LR-EPONs), and energy saving. We provide a Dynamic Bandwidth Allocation (DBA) approach for each challenge. We also propose a novel scheme that combines the features of the proposed approaches in one highly performing scheme. Our approach is to design novel DBA protocols that can further reduce the delay and be simultaneously simple and fair. We also present a dynamic bandwidth allocation scheme for Green EPONs taking into consideration maximizing energy saving under target delay constraints. Regarding excess bandwidth allocation, we develop an effective DBA scheme called Delayed Excess Scheduling (DES). DES achieves significant delay and jitter reduction and is more suitable for industrial deployment due to its simplicity. Utilizing DES in hybrid TDM/WDM EPONs (TWDM-EPONs) is also investigated. We also study eliminating the wasted bandwidth due to frame delineation. We develop an interactive DBA scheme, Efficient Grant Sizing Interleaved Polling (EGSIP), to compensate the unutilized bandwidth due to frame delineation. Our solution achieves delay reduction ratio up to 90% at high load. We also develop a Congestion Aware Limited Time (CALT) DBA scheme to detect and resolve temporary congestion in EPONs. CALT smartly adapts the optical networking unit (ONU) maximum transmission window according to the detected congestion level. Numerical results show that CALT is more robust at high load compared to other related published schemes. Regarding LR-EPONs, the main concern is large round trip delay mitigation. We address two problems, namely bandwidth over-granting in Multi-Thread Polling (MTP) and on-the-fly void filling. We combine, with some modifications, EGSIP and DES to resolve bandwidth over-granting in MTP. We also manage to adaptively tune MTP active running threads along with the offered load. Regarding on-the-fly void filling, Our approach, Parallel Void Thread (PVT), achieves large delay reduction for delay-sensitive traffic. PVT is designed as a plus function to DBA and can be combined with almost all DBA schemes proposed before. The powerful feature of our proposed solutions is integrability. We integrate our solutions together and form a multi-feature, robust, fairly simple, and well performing DBA scheme over LR-TWDM-EPONs. Our final contribution is about energy saving under target delay constraints. We tackle the problem of downstream based sleep time sizing and scheduling under required delay constraints. Simulation results show that our approach adheres to delay constraints and achieves almost ideal energy saving ratio at the same time.

With the growing concerns about energy shortage and demand supply imbalance, demand side management (DSM) activities has found its way into the mining industry. This study analyzes the potential to save energy and energy-costs in underground mine ventilation networks, by application of DSM techniques. Energy saving is achieved by optimally adjusting the speed of the main fan to match the time-varying flow demand in the network, which is known as ventilation on demand (VOD). Further cost saving is achieved by shifting load to off-peak or standard times according to a time of use (TOU) tariff, i.e. finding the optimal mining schedule. The network is modelled using graph theory and Kirchhoff’s laws; which is used to form a non-linear, constrained, optimization problem. The objective of this problem is formulated to minimize the energy cost; and hence it is directly given as a function of the fan speed, which is the control variable. As such, the operating point is found for every change in the fan speed, by incorporating the fan laws and the system curve. The problem is solved using the fmincon solver in Matlab’s optimization toolbox. The model is analyzed for different scenarios, including varying the flow rate requirements and tariff structure. Although the results are preliminary and very case specific, the study suggests that significant energy and energy-cost saving can be achieved in a financially viable manner. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

Recently, wireless sensor networks (WSNs), consisted of battery-powered sensor nodes, are widely adopted by various civilian/military applications for implementing real-time monitoring or long-term surveillance tasks. One of the critical issues of WSNs is energy efficiency. Due to the limited battery capacity, the network lifetime and performance of WSNs are constrained. Also, once the sensor is deployed into a risky/remote environment, the replacement of its battery is hard. Therefore, how to improve the energy efficiency of the WSN is a critical issue and has gained tremendous attention from researchers around the world. To address this problem, by taking advantage of the emerging high-mobility devices (e.g., unmanned aerial vehicle (UAV)), we propose energy-efficient mobile device-assisted schemes in different-scale WSNs. Thanks to the rapid development of wireless techniques, two emerging approaches, i.e., data gathering technique and wireless charging technique, are beneficial to balance the workloads among all sensors or replenish energy to achieve the semi-permanent WSN. First, we design data gathering schemes using the mobile data collector. In order to meet the performance requirements of systems with different scales, our algorithms have two working modes: single- and multiple-data-collector scenarios. For the small-scale system, a single data collector is adopted to access and collect data from the deployed node, and we propose single mobile data collector-assisted (SDCA) data collection schemes for small-scale WSNs. For the large-scale system, multiple data collectors are utilized to gather sensed data from deployed nodes, and two-mode multiple mobile data collector-assisted (MDCA) data collection scheme is designed for balancing between the system energy consumption and the data forwarding latency. Second, the joint data collection and energy charging scheme is developed by adopting mobile chargers (MCs) as mobile devices that are responsible for energy charging and data collection simultaneously. For facing the different performance requirements of systems, a two-mode MC scheduling algorithm is presented. To evaluate our works, extensive simulation experiments are conducted on the OMNeT++ simulator. The results demonstrate that the proposed algorithms achieve better performance than the control group regarding system-wide energy efficiency, network lifetime and average end-to-end delay.

L’Union européenne et les États membres doivent progresser de manière continue vers une société durable, intelligente, inclusive et à faible intensité de carbone. Vue sous le prisme de l’Union de l’énergie, l’efficacité énergétique serait à la base de la refonte socio-économique de l’Europe et poserait les jalons des nouveaux paradigmes socio-économiques, nécessairement transversaux. Encore faut-il que le domaine plurisectoriel de l’efficacité énergétique soit mis en œuvre dans un cadre réglementaire et normatif harmonisé, transparent et évolutif. Nous avons donc effectué une analyse sur la mise en œuvre de l’efficacité énergétique au niveau du droit européen et niveau du droit national français. Dans une première partie, nous avons constaté la singularité juridique de la notion d’efficacité énergétique qui réside dans sa genèse et ses rapports multiformes. Dans une seconde partie, nous avons démontré le caractère pluridisciplinaire de l’efficacité énergétique. En effet, nous avons pu constater que l’efficacité énergétique est intégrée en droit public et en droit privée. En somme, le concept d’efficacité énergétique matérialise l’apparition d’une nouvelle grille de lecture en droit, résidant dans une approche transversale afin de mieux tenir compte des interactions et des synergies entre les différents phénomènes socio-économiques contemporains allant de pair avec les progrès technologiques et l’innovation. / The European Union and its Member States shall continue to evolve towards a sustainable, intelligent, inclusive and low-carbon society. Energy efficiency would be the basis for the socio-economic redesign of Europe and would lay the groundwork for new, necessarily transverse socio-economic paradigms. The multi-sector domain of energy efficiency need to be fully implemented in a harmonized, transparent and evolving regulatory and normative framework. We therefore carried out an analysis of the implementation of energy efficiency at two levels: regional level (European law) and nation level (French law). Firstly, we have noted the legal singularity of energy efficiency, which lies in its genesis and its multiform relationships. Secondly, we have demonstrated the multidisciplinary nature of energy efficiency. Indeed, we have seen that energy efficiency is recognized in both public and private law. In sum, the concept of energy efficiency materializes the emergence of a new legal reading grid. The approach is transverse to account more accurately for the interactions and synergies between the various contemporary socio-economic phenomena, which go hand in hand with technological progress and innovation.

Legal instruments of energy efficiency Abstract and key words The diploma thesis deals with energy efficiency as a unique source of energy. The subject of this thesis is to specify key legal instruments of energy efficiency, i.e. conceptual, administrative and economical instruments. The diploma thesis is divided into five chapters. In the introductory chapter, being called Energy Policy, there is a brief outline of the background of energy politics on both the international and EU level, including environmental protection. This introductory chapter also ranks the Czech Republic among countries with high energy performance. Energy efficiency is the opportunity to lower its energy performance. The second chapter, Legal Instruments of Energy Efficiency, defines legal instruments of energy efficiency as a part of environmental protection. This chapter is a general one; the instruments are concretized in the following chapters. In addition, this chapter focuses on the principle of sustainable development, as well as issues related to human factor, climate conditions and rebound effect. The third chapter, called Conceptual Instruments, provides further information relating to conceptual strategies of energy efficiency. For the EU conceptions, key directives are mentioned to regulate energy efficiency, namely the...

<div>With the United States being the world’s second largest consumer of primary energy, research into areas of significant consumption can provide large impacts in terms of the global energy consumption. Buildings account for 41% of U.S. total energy consumption with the residential sector making up a majority. Household appliances account for the second largest site energy consumption at 27%, after the HVAC system for the U.S. residential sector. Federal appliance standards have been instrumental in improving efficiencies but have been increasing aggressively to where it is unknown what suitable technologies can support this rate of increase. Thermally integrating residential appliances by leveraging waste heat recovery goes outside standards and has not been adequately explored by connecting all residential appliances. Limited studies exist focused only on single appliances connected to waste heat recovery or being thermally integrated. Preliminary modeling on waste heat availability from five major appliances, namely refrigerator-freezer, clothes dryer, clothes washer, dishwasher, and cooking oven was conducted. Conservative estimates predict the total amount of heat recovery to be around 2,000 kWh/year; clothes dryer - 137 kWh/year, clothes washer - 60 kWh/year, 1,500 kWh/year- refrigerator-freezer, 27 kWh/year – dishwasher, and 178 kWh/year – cooking oven. The cooking oven presents technical challenges coupled with safety concerns. The clothes dryer and refrigerator-freezer can deliver useful water temperatures and reduce compressor power consumption, up to 20%. The dishwasher has better opportunity as a heat sink to offset the internal heater, 0.17 kWh of electricity/cycle for heating wash water. The clothes washer drains large volumes of water available for heat recovery and can offset the impact of using high temperature washes with improved wash performance. </div><div>Modelica appliance models have been developed for four of these five appliances. The Modelica models capture individual use and the predictions of the RF and DW were compared against available experimental data. The individual models have been connected to a simple storage tank model to simulate the integrated appliance system. An integrated appliance prototype was designed and fabricated for the collection of experimental data. Comparisons made between the experimental data and the integrated appliance simulation results adjusted the modeling approach and improved agreement with collected data. After tuning, ideal modifications to each appliance are made and reflected in a new integrated model. A parametric study is conducted on ideal improved, thermally capable appliances under a 1-week schedule for two different tank sizes. For 300L and 150 L tank sizes, the appliance total energy for the week is roughly 30.5 kWh compared to a baseline appliance system with no thermal resource sharing at 33.8 kWh. At an electricity cost of $0.15/kWh, the cost savings for the integrated system is a little over $0.40/week. Furthermore, the savings is completely diminished when considering the required auxiliary power to support the exchange of heat between each appliance and storage tank. The impact of tank size should be explored further to identify a critical tank size where the system savings is no longer available. Accounting for all the domestic hot water needs of the home would generate an improved picture where integrated appliances have technical feasibility. </div><div><br></div>