<p>This thesis presents a solution enabling lower losses in hydraulic actuator systems. A mobile fluid power system often contains several different actuators supplied with a single load sensing pump. One of the main advantages is the need of only one system pump. This makes the fluid power system compact and cost-effective.</p><p>A hydraulic load often consists of two ports, e.g. motors and cylinders. Such loads have traditionally been controlled by a valve that controls these ports by one single control signal, namely the position of the spool in a control valve. In this kind of valve, the inlet (meter-in) and outlet (meter-out) orifices are mechanically connected. The mechanical connection makes the system robust and easy to control, at the same time as the system lacks flexibility. Some of the main drawbacks are</p><p><strong> </strong></p><p><strong>The fixed relation </strong>between the inlet and outlet orifices in most applications produce too much throttling at the outlet orifice under most operating conditions. This makes the system inefficient.</p><p><strong> </strong></p><p><strong>The flow directions </strong>are fixed for a given spool position; therefore, no energy recuperation and/or regeneration ability is available.</p><p>In this thesis a novel system idea enabling, for example, recuperation and regeneration is presented. Recuperation is when flow is taken from a tank, pressurized by external loads, and then fed back into the pump line. Regeneration is when either cylinder chambers (or motor ports) are connected to the pump line. Only one system pump is needed. Pressure compensated (load independent), bidirectional, poppet valves are proposed and utilized.</p><p>The novel system presented in this thesis needs only a position sensor on each compensator spool. This simple sensor is also suitable for identification of mode switches, e.g. between normal, differential and regenerative modes. Patent pending.</p><p>The balance of where to put the functionality (hardware and/or software) makes it possible to manoeuvre the system with maintained speed control in the case of sensor failure. The main reason is that the novel system does not need pressure transducers for flow determination. Some features of the novel system:</p><p><strong>Mode switches </strong>The mode switches are accomplished without knowledge about the pressures in the system</p><p><strong>Throttle losses </strong>With the new system approach, choice of control and measure signals, the throttle losses at the control valves are reduced</p><p><strong>Smooth mode switches </strong>The system will switch to regenerative mode automatically in a smooth manner when possible</p><p><strong>Use energy stored in the loads </strong>The load, e.g. a cylinder, is able to be used as a motor when possible, enabling the system to recuperate overrun loads</p><p>The system and its components are described together with the control algorithms that enable energy efficient operation. Measurements from a real application are also presented in the thesis.</p>

Electricity generation for Information and Communications Technology (ICT) contributes over 2% of the human-generated CO2 to the atmosphere. Energy costs are rapidly becoming the major operational expense for ICT and may soon dwarf capital expenses as software and hardware continue to drop in price. In this dissertation, three new approaches to achieving energy-proportional operation of network links and data servers are explored. Ethernet is the dominant wireline communications technology for Internet connectivity. IEEE 802.3az Energy Efficient Ethernet (EEE) describes a Low Power Idle (LPI) mechanism for allowing Ethernet links to sleep. A method of coalescing packets to consolidate link idle periods is investigated. It is shown that packet coalescing can result in almost fully energy-proportional behavior of an Ethernet link. Simulation is done at both the queuing and protocol levels for a range of traffic models and system configurations. Analytical modeling is used to gain a deeper general insight into packet coalescing. The architecture of a hybrid web server based on two platforms - a low-power (ARM based) and a high-power (Pentium based) - can be used to achieve step-wise energy-proportional operation and maintain headroom for peak loads. A new method based on Gratuitous ARP for switching between two mirrored platforms is developed, prototyped, and evaluated. Experimental results show that for up to 50 requests per minute, a hybrid server where the Master platform is a 2012 server-grade desktop PC can sleep for 50% of time with no increase in response time. HTTP can be used for redirection in space - a new method for precise redirection in time is proposed and used to schedule requests to a high-power server in a hybrid server. The scheduling method is modeled as a single server queue with vacations where the vacation duration is fixed and the service distribution is directly a function of the request load. This approach is well suited for delay tolerant applications such as application updates and file back-up. Energy-proportional operation is shown to be achievable in a prototype system. A first-order estimation with conservative assumptions on the adoption rate of the methods proposed and studied here shows that these methods can collectively enable energy savings in the order of hundreds of million dollars in the US annually.

The ongoing search for energy conservation in built structures and during the construction process prompted this thesis work to explore the use of sustainable technologies for floor heating systems. The thesis work explores the use of thermoplastic material as a sustainable substitute material for future floor heating systems. Concrete materials are presently used extensively for floor heating systems. Thermoplastic materials are seldom used for floor heating and the primary focus of this thesis is to explore the suitability & adaptability of thermoplastics as an innovative energy saving floor heating material. A thorough study of energy demands and the impact on environment due to greenhouse gas emissions has been done. Thermoplastic materials are environmental friendly and light weight. They exhibit high thermal conductivity which is favourable for the floor heating systems. A design technique has been developed for the use of thermoplastic materials as an energy efficient floor heating material. The present technique creates a new modular floor heating system. The design technique uses thermoplastic material of size 2.4m x1.2m with embedded electric heaters. Thermoplastic foam panels act as a single building block. A numerical simulation has been carried out to study the heat transfer characteristics of the proposed material. Limited experiments were conducted to verify the validity of the simulation results. The results from the experiments indicate good agreement with simulation results. The energy savings from the thermoplastic floor heating systems have been compared with that of electrical floor heating systems. The adaptability of the new floor heating system in terms of energy savings and cost benefit analysis is also discussed. / sustainable floor heating system

Reducing the energy consumption of available resources is still a problem to be solved in Wireless Sensor Networks (WSNs). Many types of existing routing protocols are developed to save power consumption. In these protocols, cluster-based routing protocols are found to be more energy efficient. A cluster head is selected to aggregate the data received from root nodes and forwards these data to the base station in cluster-based routing. The selection of cluster heads should be efficient to save energy. In our proposed protocol, we use static clustering for the efficient selection of cluster heads. The proposed routing protocol works efficiently in large as well as small areas. For an optimal number of cluster head selection we divide a large sensor field into rectangular clusters. Then these rectangular clusters are further grouped into zones for efficient communication between cluster heads and a base station. We perform MATLAB simulations to observe the network stability, throughput, energy consumption, network lifetime and the number of cluster heads. Our proposed routing protocol outperforms in large areas in comparison with the LEACH, MH-LEACH, and SEP routing protocols.

South Africa is currently facing a major electricity crisis due to the continuous growth in electricity demand. Eskom, the largest electricity supplier in South Africa, have enabled numerous methods to support energy reduction in both the residential and industrial sectors. Programs developed by Eskom to help the different major electricity consuming industries with the development of energy efficient and load shift strategies, have already been put into practice. These programs solely focus on the potential savings in megawatts each production sector might consist of. The key features of the Eskom electricity reduction initiative are driven by the energy efficiency concept and the peak demand load shift capability. Both the load shift and energy efficient initiatives are mostly active in the mining industry, because of the high electricity consumption levels of a standard mining operation. One of the most inefficient systems currently active within a mining operation is the ventilation control system. This dissertation describes the energy efficient and load shift research on the current underground ventilation system by means of certain design methodologies that might improve the inefficient operational features on both the standard underground auxiliary fans and the main surface fans. The operational features of a standard 2-pole 45 kW issued auxiliary fan were tested, by using a fan-testing column to compare the performance criteria to that of an improved auxiliary fan design. An energy saving potential on a single 45 kW unit of 11 kW was evident during the testing analysis. This amounted to an estimated annual energy saving potential of R 370,000.00 with a total saving of 561 kW on all the installed 45 kW units at Kopanang goldmine, by means of an investment in the replacement of the current installed units with that of the improved units. A secondary study was to gather information on the main surface fan operational features at Kopanang and Mponeng goldmines. The gathered information showed an estimated possibility for load shift and efficiency initiatives, which will result in fan operating life expansion and electricity savings capabilities. Annual electricity savings of up to R I ,500,000.00 were calculated on efficiency and load shift strategies and gave an indication on how costly inefficient operations are. The calculated I 0% increase in main fan efficiency resulted in an annual saving of nearly R 1,100,000.00 with a reduction of 1,05 MW at Mponeng goldmine and an annual saving of nearly R 721,000.00 with a reduction of 675 kW at Kopanang goldmine. The load shift potential at Mponeng and Kopanang goldmines were nearly 3,5 MW and 2,25 MW respectively. Capital investments from either Eskom or alternative investors will definitely play a crucial part in the realization of energy efficiency and load shift measures. It may include, improved fan installations, variable speed drives for the main fans and real time management systems. If the mine should decide to invest in these efficient strategies, the proposed Eskom DSM program might result in a net energy savings potential for any mining operation. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.

South Africa is currently facing a major electricity crisis due to the continuous growth in electricity demand. Eskom, the largest electricity supplier in South Africa, have enabled numerous methods to support energy reduction in both the residential and industrial sectors. Programs developed by Eskom to help the different major electricity consuming industries with the development of energy efficient and load shift strategies, have already been put into practice. These programs solely focus on the potential savings in megawatts each production sector might consist of. The key features of the Eskom electricity reduction initiative are driven by the energy efficiency concept and the peak demand load shift capability. Both the load shift and energy efficient initiatives are mostly active in the mining industry, because of the high electricity consumption levels of a standard mining operation. One of the most inefficient systems currently active within a mining operation is the ventilation control system. This dissertation describes the energy efficient and load shift research on the current underground ventilation system by means of certain design methodologies that might improve the inefficient operational features on both the standard underground auxiliary fans and the main surface fans. The operational features of a standard 2-pole 45 kW issued auxiliary fan were tested, by using a fan-testing column to compare the performance criteria to that of an improved auxiliary fan design. An energy saving potential on a single 45 kW unit of 11 kW was evident during the testing analysis. This amounted to an estimated annual energy saving potential of R 370,000.00 with a total saving of 561 kW on all the installed 45 kW units at Kopanang goldmine, by means of an investment in the replacement of the current installed units with that of the improved units. A secondary study was to gather information on the main surface fan operational features at Kopanang and Mponeng goldmines. The gathered information showed an estimated possibility for load shift and efficiency initiatives, which will result in fan operating life expansion and electricity savings capabilities. Annual electricity savings of up to R I ,500,000.00 were calculated on efficiency and load shift strategies and gave an indication on how costly inefficient operations are. The calculated I 0% increase in main fan efficiency resulted in an annual saving of nearly R 1,100,000.00 with a reduction of 1,05 MW at Mponeng goldmine and an annual saving of nearly R 721,000.00 with a reduction of 675 kW at Kopanang goldmine. The load shift potential at Mponeng and Kopanang goldmines were nearly 3,5 MW and 2,25 MW respectively. Capital investments from either Eskom or alternative investors will definitely play a crucial part in the realization of energy efficiency and load shift measures. It may include, improved fan installations, variable speed drives for the main fans and real time management systems. If the mine should decide to invest in these efficient strategies, the proposed Eskom DSM program might result in a net energy savings potential for any mining operation. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.

Providing efficient data transport is one of the uppermost objectives in the design of wireless sensor networks (WSNs) since the primary role for each sensor is to report the sensed data to the data sink(s). This thesis focuses on designing efficient data transport schemes for WSNs in the dimensions of energy consumption and time respectively. The developed schemes can be directly applied in a number of applications such as intrusion detection, target tracking, environment monitoring, etc., and can be further extended to underwater acoustic sensor networks and unmanned aerial vehicles (UAVs) networks. With the development of WSN technologies, new challenging research problems such as real-time streaming data gathering and intelligent data communication are emerging. This thesis provides useful foundation for designing next-generation data transport schemes for WSNs. Energy is the most important resource in WSNs because sensor nodes are commonly powered by small batteries, and energy is directly related to the lifetime of nodes and the network. In this thesis, energy-efficient data transport schemes are designed for two major types of WSNs: event-driven sensor networks and time-driven sensor networks. A novel on-line routing scheme called EBGR (Energy-efficient Beaconless Geographic Routing) is designed for event-driven sensor networks characterized by dynamic network topology. The main advantage of EBGR is that it can provide energy-efficient sensor-to-sink routing without any prior neighborhood knowledge. Moreover, the total energy consumption for sensor-to-sink data delivery under EBGR has an upper bound. Time-driven sensor networks, in which all sensors periodically report the sensed data to the sink(s), have been widely used for environment monitoring applications. Unbalanced energy consumption is an inherent problem in time-driven sensor networks. An efficient data gathering scheme, called EBDG (Energy-Balanced Data Gathering), is designed to balance energy consumption for the goal of maximizing network lifetime. Combing all advantages of corona-based network division,mixed-routing and data aggregation, EBDG can prolong network lifetime by an order of magnitude compared with conventional schemes. Time-efficient data transport is another critical issue in WSNs since the data generated by the sensor nodes may become outdated after a certain time interval. This thesis focuses on the problem of providing real-time data gathering in time-driven sensor networks. A novel data gathering scheme based on random access is proposed with the objective to minimize the average duration for completing one round of data gathering. Fully localized solutions have been designed for both linear networks and tree networks. A simple data gathering protocol called RADG (Random Access Data Gathering) is designed. Simulation results show that RADG outperforms CSMA based schemes when the size of the data packets is small. / Thesis (Ph.D.) -- University of Adelaide, School of Computer Science, 2009

En France, le secteur du bâtiment est le principal consommateur d'énergie. En outre, le secteur de la maison individuelle représente environ 60% des constructions annuelles de logements. La construction des bâtiments à haute efficacité énergétique représente un grand pas vers l'économie d'énergie. Cependant, même si divers efforts sont déployés dans ce domaine, des outils et des méthodes manquent pour évaluer la performance énergétique de ces bâtiments. Cette évaluation doit permettre non seulement de comprendre les facteurs qui contribuent à cette performance mais également d'identifier les causes de la surconsommation, d’inconfort pour les occupants.Cette thèse vise à contribuer à cet objectif en proposant une approche d'évaluation de la performance énergétique d'un bâtiment. Pour cela on compare la performance réelle et la performance attendue en utilisant le monitoring et la simulation thermique dynamique. Cette approche s’appuie sur différents cas d’études dont principalement une maison individuelle, situé en un climat méditerranéen.Dans un premier temps, en phase de conception, nous utilisons des simulations thermiques dynamiques pour étudier l’impact du comportement sur les besoins énergétiques. L'objectif est d'analyser l'influence du scénario d'occupation sur le comportement du bâtiment et d'établir une plage de valeurs pour les besoins en énergie, basée sur des statistiques nationales. Le comportement du bâtiment est étudié en fonction de différents types de scénarii d'occupation, de consignes de température, de l'utilisation d’appareils domestiques et l'éclairage.Dans un second temps, l'accent est mis sur l'évaluation globale de la performance de l'enveloppe. Un test dynamique in situ innovant a été développé pour en évaluer la performance réelle. Ce test est applicable sur une période courte (de l’ordre de la journée) tout en maitrisant les débits d’infiltrations. La comparaison des résultats théoriques en régime stationnaire avec les résultats expérimentaux montre une bonne précision inférieure à 10%.Enfin, le suivi énergétique en continu des maisons performantes est étudié. Tout d’abord, des travaux sont réalisés dans l’optique de réduire le nombre de capteurs nécessaires au suivi, tout en minimisant la perte d’informations. Ensuite, une méthodologie d’instrumentation est développée et appliquée à une maison individuelle. Le suivi de cette maison a pu être étudié sur les six premiers mois de monitoring et a permis d’expliquer le comportement du bâtiment et ses consommations au regard de son usage et de faire le lien avec les prévisions faites en phase de conception. / In France, the building sector is the main energy consumer. Moreover single-family houses represent about 60% of annual dwelling construction. The construction of energy efficient buildings represents a big step into energy saving. However, even though various efforts are made within this field, there is still a lack of methodologies about how to evaluate the energy performance of these buildings. The performance evaluation of an energy efficient building should allow understanding factors that contribute to its energy performance and as well as identifying the causes of overconsumption, poor indoor conditions.This thesis seeks to contribute to this field, by proposing an approach towards evaluating the energy performance of a house. This is done by comparing the real performance and the expected performance, using monitoring and building performance simulation, from design to operational phases. The energy performance evaluation approach is carried out on different cases of studies, mainly on a single-family house, situated in a Mediterranean climate.First, in the design phase, we use building performance simulation models to study the dispersions in energy use related to occupant’s behavior. The goal is to analyze the influence of the occupancy scenario on the behavior of the building and to establish a range of values for energy demand, based on national statistics. This step study the building’s behavior based on different types of occupancy scenarios, appliances and lighting use and temperature set point.Then, the focus is on the global evaluation of the envelope’s performance. Within the present thesis an innovative in-situ dynamic test is developed to assess the real envelope’s performance. This test is adapted to occupied houses (as it only takes 2 days) while controlling the infiltration air flow. The comparison between theoretical results of steady state calculation and experimental results show a good precision of less than 10%.Finally, continuous monitoring of energy efficient houses is studied. First, a work is done to reduce the number of sensors required for monitoring, while minimizing the loss of information. Then, an instrumentation methodology is developed and applied to a single-family house. The follow-up of this house could be studied during the first six months of monitoring and allowed to explain the behavior of the building and its consumption with regard to its use and to make the link with the previsions made during the design phase.

Context: Cloud computing is providing services and resources to customers based on pay-per-use. As the services increasing, Cloud computing using a vast number of data centers like thousands of data centers which consumes high energy. The power consumption for cooling the data centers is very high. So, recent research going on to implement the best model to reduce the energy consumption by the data centers. This process of minimizing the energy consumption can be done using dynamic Virtual Machine Consolidation (VM Consolidation) in which there will be a migration of VMs from one host to another host so that energy can be saved. 70% of energy consumption will be reduced/ saved when the host idle mode is switched to sleep mode, and this is done by migration of VM from one host to another host. There are many energy adaptive heuristics algorithms for the VM Consolidation. Host overload detection, host underload detection and VM selection using VM placement are the heuristics algorithms of VM Consolidation which results in less consumption of the energy in the data centers while meeting Quality of Service (QoS). In this thesis, we proposed new heuristic algorithms to reduce energy consumption. Objectives: The objective of this research is to provide an energy efficient model to reduce energy consumption. And proposing a new heuristics algorithms of VM Consolidationtechnique in such a way that it consumes less energy. Presenting the advantages and disadvantages of the proposed heuristics algorithms is also considered as objectives of our experiment. Methods: Literature review was performed to gain knowledge about the working and performances of existing algorithms using VM Consolidation technique. Later, we have proposed a new host overload detection, host underload detection, VM selection, and VM placement heuristic algorithms. In our work, we got 32 combinations from the host overload detection and VM selection, and two VM placement heuristic algorithms. We proposed dynamic host underload detection algorithm which is used for all the 32 combinations. The other research method chosen is experimentation, to analyze the performances of both proposed and existing algorithms using workload traces of PlanetLab. This simulation is done usingCloudSim. Results: To compare and get the results, the following parameters had been considered: Energy consumption, No. of migrations, Performance Degradation due to VM Migrations (PDM),Service Level Agreement violation Time per Active Host (SLATAH), SLA Violation (SLAV),i.e. from a combination of the PDM, SLATAH, Energy consumption and SLA Violation (ESV).We have conducted T-test and Cohen’s d effect size to measure the significant difference and effect size between algorithms respectively. For analyzing the performance, the results obtained from proposed algorithms and existing algorithm were compared. From the 32 combinations of the host overload detection and VM Selection heuristic algorithms, MADmedian_MaxR (Mean Absolute Deviation around median (MADmedian) and Maximum Requested RAM (MaxR))using Modified Worst Fit Decreasing (MWFD) VM Placement algorithm, andMADmean_MaxR (Mean Absolute Deviation around mean (MADmean), and MaximumRequested RAM (MaxR)) using Modified Second Worst Fit Decreasing (MSWFD) VM placement algorithm respectively gives the best results which consume less energy and with minimum SLA Violation. Conclusion: By analyzing the comparisons, it is concluded that proposed algorithms perform better than the existing algorithm. As our aim is to propose the better energy- efficient model using the VM Consolidation techniques to minimize the power consumption while meeting the SLAs. Hence, we proposed the energy- efficient algorithms for VM Consolidation technique and compared with the existing algorithm and proved that our proposed algorithm performs better than the other algorithm. We proposed 32 combinations of heuristics algorithms (host overload detection and VM selection) with two adaptive heuristic VM placement algorithms. We have proposed a dynamic host underload detection algorithm, and it is used for all 32 combinations. When the proposed algorithms are compared with the existing algorithm, we got 22 combinations of host overload detection and VM Selection heuristic algorithms with MWFD(Modified Worst Fit Decreasing) VM placement and 20 combinations of host overload detection and VM Selection heuristic algorithms with MSWFD (Modified Second Worst FitDecreasing) VM placement algorithm which shows the better performance than existing algorithm. Thus, our proposed heuristic algorithms give better results with minimum energy consumption with less SLA violation.

Cooperative diversity exploits the broadcast nature of wireless channels and uses relays to improve link reliability. Most cooperative communication protocols are assumed to be synchronous in nature, which is not always possible in wireless communication. Also the relay nodes are assumed to be half duplex which in turn reduces the spectral efficiency. In this thesis, we first present a novel asynchronous cooperative communication protocol exploiting polarization diversity, which does not require synchronization at the relay node. Dual polarized antennas are employed at the relay node to achieve full duplex amplify-and-forward (ANF) communication. Hence the transmission duration is reduced which results into an increased throughput rate. Capacity analysis of the proposed scheme ascertains the high data rate as compared to conventional ANF. Bit error rate (BER) simulation also shows that the proposed scheme significantly outperforms both the non-cooperative single-input single-output and the conventional ANF schemes. Considering channel path loss, the proposed scheme consume less total transmission energy as compared to ANF and non-cooperative scheme in more practical distance range. Thus the proposed scheme is suitable for high rate and energy efficient relay-enabled communication. In addition to that, we also present a novel power allocation scheme for multiple relay nodes that results in efficient cooperative multiple-input multiple-output (MIMO) communication. Considering channel path loss, the total transmission energy is distributed between the source and the relay nodes. The energy distribution ratio between the relay and direct link is optimized such that the quality of received signal is maintained with minimum total transmission energy consumption. We calculate the energy distribution ratio analytically and verified it through computer simulation. With the new power allocation scheme, the system also obtains an increased channel capacity as compared to cooperative scheme with conventional equal power allocation and non-cooperative scheme. Optimal relay positioning with proposed energy allocation scheme is also explored to maximize the capacity.