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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
411

Energieffektiva maskinval : Hjälpmedel för projektering av pumpar och blåsmaskiner till avloppsreningsverk / Selecting Energy Efficient Pumps and Blowers

Sundqvist, Bo January 2013 (has links)
Idag fokuserar företag mer och mer på att energieffektivisera sina verksamheter då det finns både ekonomiska och miljömässiga vinster i detta. För att minska energiförbrukningen i samhället är det bra att börja med dess infrastruktur. För att funktionen hos ett avloppsreningsverk ska vara god samtidigt som energikostnaderna hålls nere är bland annat valet av rätt pumpar och blåsmaskiner för den aktuella driftsituationen av största vikt. Att hitta balansen mellan funktion och energieffektivitet hos en kombination av maskiner är dock ett tidskrävande arbete. Genom två fallstudier och matematisk modellering var syftet med detta examensarbete att bestämma huruvida det är möjligt att grovt uppskatta livscykelkostnaden hos olika kombinationer av pumpar och blåsmaskiner i varierande driftsituationer. En sådan modell skulle hjälpa projektören att uteslutande undersöka de kombinationer av maskiner som är mest troliga att ha den lägsta livscykelkostnaden. Det har visats att det krävs en förmåga att mycket noggrant kunna förutsäga verkningsgraden hos de individuella maskinerna för att det ska vara möjligt att bestämma livscykelkostnaden så pass väl att resultatet är användbart. Sannolikt är det dock inte möjligt att finna en modell som är tillräckligt noggrann. Detta beror huvudsakligen på att mycket små förändringar av verkningsgraden ger en kraftig påverkan av livscykelkostnaden samt att verkningsgraden beror av många faktorer som är svåra att generalisera. Däribland att verkningsgraden inte förändras proportionellt till en varierande belastning på maskinen samtidigt som påverkan inte heller är densamma mellan olika maskinmodeller. Projektet har däremot mynnat ut i en ekvation för det flöde en blåsmaskin behöver generera i en given driftsituation samt ett beräkningsverktyg som underlättar undersökandet av de ingående parametrarnas inverkan på detta flödesbehov och därmed i förlängningen på livscykelkostnaden. Utöver detta slår rapporten fast att det i många fall är möjligt att sänka livscykelkostnaden med hjälp av icke frekvensstyrda maskiner. / Today companies tend to focus more and more on energy efficiency as there are both economical and environmental benefits to be gained. From a society’s point of view a good start to save energy is in its infrastructure. When designing wastewater treatment plants and their pumps and blowers choosing the right machines for the right operational circumstances is crucial to make it all work together and lower the energy cost at the same time. But to weigh the function against the energy efficiency of a combination of machines is a time consuming effort. Through two case studies and mathematical modeling this thesis project aimed to determine whether it is possible to roughly predetermine the life cycle cost of different combinations of pumps and blowers in variable operational circumstances. This would help the process engineers to focus their time and effort on the combinations of machines that are the most probable to have the lowest life cycle cost. The results show that the ability to accurately predetermine the efficiency of the individual machine is crucial to determine the life cycle cost to a usable degree. Unfortunately it doesn't seem feasible to find a model that will be accurate enough to be of practical use. This is due to the fact that slight changes to the efficiency cause great changes to the life cycle cost and that the efficiency depends on several factors that are hard to predict including the fact that it does not change proportionally to a variable load.
412

DVFS power management in HPC systems

Etinski, Maja 01 June 2012 (has links)
Recent increase in performance of High Performance Computing (HPC) systems has been followed by even higher increase in power consumption. Power draw of modern supercomputers leads to very high operating costs and reliability concerns. Furthermore, it has negative consequences on the environment. Accordingly, over the last decade there have been many works dealing with power/energy management in HPC systems. Since CPUs accounts for a high portion of the total system power consumption, our work aims at CPU power reduction. Dynamic Voltage Frequency Scaling (DVFS) is a widely used technique for CPU power management. Running an application at lower frequency/voltage reduces its power consumption. However, frequency scaling should be used carefully since it has negative effects on the application performance. We argue that the job scheduler level presents a good place for power management in an HPC center having in mind that a parallel job scheduler has a global overview of the entire system. In this thesis we propose power-aware parallel job scheduling policies where the scheduler determines the job CPU frequency, besides the job execution order. Based on the goal, the proposed policies can be classified into two groups: energy saving and power budgeting policies. The energy saving policies aim to reduce CPU energy consumption with a minimal job performance penalty. The first of the energy saving policies assigns the job frequency based on system utilization while the other makes job performance predictions. While for less loaded workloads these policies achieve energy savings, highly loaded workloads suffer from a substantial performance degradation because of higher job wait times due to an increase in load caused by longer job run times. Our results show higher potential of the DVFS technique when applied for power budgeting. The second group of policies are policies for power constrained systems. In contrast to the systems without a power limitation, in the case of a given power budget the DVFS technique even improves overall job performance reducing the average job wait time. This comes from a lower job power consumption that allows more jobs to run simultaneously. The first proposed policy from this group assigns CPU frequency using the job predicted performance and current power draw of already running jobs. The other power budgeting policy is based on an optimization problem which solution determines the job execution order, as well as power distribution among jobs selected for execution. This policy fully exploits available power and leads to further performance improvements. The last contribution of the thesis is an analysis of the DVFS technique potential for energyperformance trade-off in current and future HPC systems. Ongoing changes in technology decrease the DVFS applicability for energy savings but the technique still reduces power consumption making it useful for power constrained systems. In order to analyze DVFS potential, a model of frequency scaling impact on MPI application execution time has been proposed and validated against measurements on a large-scale system. This parametric analysis showed for which application/platform characteristic, frequency scaling leads to energy savings. / El aumento de rendimiento que han experimentado los sistemas de altas prestaciones ha venido acompañado de un aumento aún mayor en el consumo de energía. El consumo de los supercomputadores actuales implica unos costes muy altos de funcionamiento. Estos costes no tienen simplemente implicaciones a nivel económico sino también implicaciones en el medio ambiente. Dado la importancia del problema, en los últimos tiempos se han realizado importantes esfuerzos de investigación para atacar el problema de la gestión eficiente de la energía que consumen los sistemas de supercomputación. Dado que la CPU supone un alto porcentaje del consumo total de un sistema, nuestro trabajo se centra en la reducción y gestión eficiente de la energía consumida por la CPU. En concreto, esta tesis se centra en la viabilidad de realizar esta gestión mediante la técnica de Dynamic Voltage Frequency Scalingi (DVFS), una técnica ampliamente utilizada con el objetivo de reducir el consumo energético de la CPU. Sin embargo, esta técnica puede implicar una reducción en el rendimiento de las aplicaciones que se ejecutan, ya que implica una reducción de la frecuencia. Si tenemos en cuenta que el contexto de esta tesis son sistemas de alta prestaciones, minimizar el impacto en la pérdida de rendimiento será uno de nuestros objetivos. Sin embargo, en nuestro contexto, el rendimiento de un trabajo viene determinado por dos factores, tiempo de ejecución y tiempo de espera, por lo que habrá que considerar los dos componentes. Los sistemas de supercomputación suelen estar gestionados por sistemas de colas. Los trabajos, dependiendo de la política que se aplique y el estado del sistema, deberán esperar más o menos tiempo antes de ser ejecutado. Dado las características del sistema objetivo de esta tesis, nosotros consideramos que el Planificador de trabajo (o Job Scheduler), es el mejor componente del sistema para incluir la gestión de la energía ya que es el único punto donde se tiene una visión global de todo el sistema. En este trabajo de tesis proponemos un conjunto de políticas de planificación que considerarán el consumo energético como un recurso más. Estas políticas decidirán que trabajo ejecutar, el número de cpus asignadas y la lista de cpus (y nodos) sino también la frecuencia a la que estas cpus se ejecutarán. Estas políticas estarán orientadas a dos objetivos: reducir la energía total consumida por un conjunto de trabajos y controlar en consumo puntual de un conjunto puntual para evitar saturaciones del sistema en aquellos centros que puedan tener una capacidad limitada (permanente o puntual). El primer grupo de políticas intentará reducir el consumo total minimizando el impacto en el rendimiento. En este grupo encontramos una primera política que asigna la frecuencia de las cpus en función de la utilización del sistema y una segunda que calcula una estimación de la penalización que sufrirá el trabajo que va a empezar para decidir si reducir o no la frecuencia. Estas políticas han mostrado unos resultados aceptables con sistemas poco cargados, pero han mostrado unas pérdidas de rendimiento significativas cuando el sistema está muy cargado. Estas pérdidas de rendimiento no han sido a nivel de incremento significativo del tiempo de ejecución de los trabajos, pero sí de las métricas de rendimiento que incluyen el tiempo de espera de los trabajos (habituales en este contexto). El segundo grupo de políticas, orientadas a sistemas con limitaciones en cuanto a la potencia que pueden consumir, han mostrado un gran potencial utilizando DVFS como mecanismo de gestión. En este caso, comparado con un sistema que no incluya esta gestión, han demostrado mejoras en el rendimiento ya que permiten ejecutar más trabajos de forma simultánea, reduciendo significativamente el tiempo de espera de los trabajos. En este segundo grupo proponemos una política basada en el rendimiento del trabajo que se va a ejecutar y una segunda que considera la asignación de todos los recursos como un problema de optimización lineal. Esta última política es la contribución más importante de la tesis ya que demuestra un buen comportamiento en todos los casos evaluados. La última contribución de la tesis es un estudio del potencial de DVFS como técnica de gestión de la energía en un futuro próximo, en función de un estudio de las características de las aplicaciones, de la reducción de DVFS en el consumo de la CPU y del peso de la CPU dentro de todo el sistema. Este estudio indica que la capacidad de DVFS de ahorrar energía será limitado pero sigue mostrando un gran potencial de cara al control del consumo energético.
413

MIND - Modelling in Industry for Increased Energy Efficiency and Reduced Greenhouse Gas Emissions

Sasu-Boakye, Yaw January 2010 (has links)
In industry, energy efficiency reduces system cost and emissions to the environment. Energy audits are carried out in industry to identify measures that would increase energy efficiency. However, the usual case is that low-cost measures are implemented while capital intensive measures receive less attention possibly due to, example, inadequate information available to study risks involved. Decisions support tools have been identified as a means of supporting complex production related investment decision. The aim of this paper is to investigate profitability and potential global CO2 emission reduction of energy conversion investments in a small energy intensive industry by using an optimisation method as a decision support tool. The investments are evaluated using consistent future energy market scenarios with interdependent parameters. An optimisation model is developed with reMIND optimisation tool which is used to optimise the system cost of each scenario. The reduction in system cost and global CO2 emissions of the new investments and results from sensitivity analysis are evaluated to determine the optimal investment solution. In the report, it is established that optimisation methods provide a structured means of studying the risk involved in capital intensive investments. The optimisation results show that investment in a small-scale steam turbine combined heat and power production is a profitable and robust investment. The net reduction of global CO2 emission is substantial compared with the reference system. Furthermore, it is shown that biofuel policies alone may not make cost intensive biofuel investments attractive, further reduction in investment cost is required. The energy savings and global CO2 emission reductions achieved in this study can play an important role in achieving the aims of the European Union to reduce greenhouse gas emissions by 20% and save 20 % of energy by the year 2020.
414

Energieffektiv projektering : Projektering för ett träffsäkert och energieffektivt slutresultat

Jonsson, Viktor, Lundberg, Mattias January 2010 (has links)
Byggnadssektorn uppskattas idag stå för närmare 40 % av vår totala energiförbrukning, varav nästan 60 % utgörs av uppvärmning och varmvatten. Från myndigheter såväl som allmänheten börjar högre krav ställas på energihushållning i vårt byggnadsbestånd. I media duggar informationen tätt om nya metoder för energieffektivisering, ändå visar statistiken att mycket finns kvar att göra. Frågan som bör ställas är var problemet ligger. Detta examensarbete behandlar projekteringens roll för slutresultatet med avseende på energianvändningen i flerbostadshus. Syftet är att identifiera förbättringsfaktorer för hur projekteringen kan påverka byggprocessen mot ett mer energieffektivt slutresultat. Arbetet grundar sig på tidigare studier och utnyttjar dels en fallstudie av ett 3 st. flerbostadshus i Västerås från 2000-talets början, dels en intervjustudie med fokus på upplevda svårigheter i arbetet med energifrågor bland byggbranschens aktörer. I den inledande litteraturstudien identifierades tekniska och processberoende faktorer som avgör en byggnads energianvändning. Den knyter också an till liknande studier för att tillvarata tidigare erfarenheter. Fallstudien resulterade i att uppmärksamma hur stora konsekvenserna blir av att inte beakta energianvändningen i tillräcklig omfattning. Intervjustudien resulterade i att identifiera likheter och skillnader i de olika aktörernas syn på projekteringen med avseende på byggnaders energianvändning. Bland de förbättringsfaktorer som identifierats bör framför allt en mer framträdande roll hos byggherren nämnas. En tydlig ambitionsnivå för projektet tillsammans med kravformuleringar är också en nödvändighet. Ett samarbete mellan aktörer där all tillgänglig kompetens utnyttjas redan i tidiga skeden krävs också för att kunna beakta energifrågan på allvar. Tekniska konsulter måste ges tillfälle att påverka projektet innan det låsts i alltför stor utsträckning. Fokus genom hela projekteringen bör ligga på ett betraktningssätt där hela byggnaden ses som ett sammanhängande system. Under arbetets gång har också uppmärksammats ett behov av att underlätta uppföljning av utförda byggprojekt. Uppföljning är nödvändigt för att utveckla branschen och frångå ryktet om en byggbransch oförmögen att lära av tidigare misstag. Slutligen kan nämnas att en ökad efterfrågan från samhället måste ske som incitament för byggherren att bygga mer energieffektivt. Samtidigt handlar det för byggherren om att marknadsföra fördelarna med energieffektiva alternativ till konventionella bostäder för att skapa efterfrågan.
415

The potential of energy efficiency measures in micro and small scale businesses in Kumasi-Ghana

Kuranchie, Francis Atta January 2011 (has links)
In industry, energy efficiency reduces operating cost and emissions to the environment whiles enhancing energy security. In order to ensure the sustainability of micro and small scale businesses in a developing country such as Ghana, measures that can ensure energy efficiency are therefore essential for these businesses to have a productive and economical operation that will ensure their sustainability. In this study, the potential of energy efficiency measures for micro and small scale businesses have been examined by performing industrial energy systems analysis on some selected micro and small scale businesses in Kumasi-Ghana through a practical study and administering of questionnaire about their energy consumption. Legislative instruments that are linked with energy use in Ghana were looked into. Some possible energy efficiency measures that could be adopted by these businesses have been analyzed. In this study it is established that energy supply to these businesses is not reliable and it is continuously becoming expensive. In addition, other findings were that value could be added to the processes of these businesses if they incorporate energy efficiency measures in their operations. The main driving force that will encourage these businesses to incorporate energy efficiency measures in their operation is the energy prices increase; therefore, their interest is the measures that could reduce their energy cost rather than the positive impacts that will come to the environment. In doing this renewable energy has the greatest potential in ensuring energy efficiency to these businesses. Finally, it is established that there are no specific legislations on energy use that will bring negative effects to these businesses and this could create enabling environment for private investors of energy efficiency.
416

Evaluation of Building Integrated Heating System in Terms of Thermal Comfort & Energy Efficiency : A Case Study of Multistory Apartment Buildings in Kumla

Farooq Qureshi, Harris, Alvi, Aber January 2011 (has links)
This work comprises of a detail study of the impact of building integrated heating (BIH) systems on energy efficiency and thermal comfort. The work has been sponsored by a company called Thermotech AB which supplied the BIH system for twin apartment buildings in Kumla owned by Kumla Bostäder. Comprehensive energy analysis was done using IDA simulation software for the building with normal radiator heating and BIH heating systems. The analysis showed 7.5 % annual savings in favor of the BIH system but since the ground and first floor thermostatic set point was not achieved we are a bit skeptical about the actual savings. Detailed literature study in this regard showed that there was no significant difference in the energy consumption for both of the systems. In the case of thermal comfort there are many citations preferring the integrated heating with features like better comfort, air quality, less noisy system ,flexible room layout and ability to use a sustainable source such as solar power. Simulations for thermal comfort were unable to determine any significant betterment of one system over the other as both were theoretically able to deliver the same comfort. Actual measurements however showed extremely good PPD % values during a hot summer day. Unfortunately a winter measurement could not be taken due to time constraint but is a strong recommendation for further work. A detailed survey was also conducted to gauge the people’s reaction on the system during the past winter. While most of the people were satisfied average PMV of around 0.5, people from lower floors did complain about it being too cold during the winter. Some complained about it being too warm during summer time which is understandable as there no external shades and the ventilation system runs at constant speed. Some people had complains about the air quality and lack of ventilation as well. In conclusion the system’s superior thermal comfort over the conventional radiator circuit cannot be denied but its energy efficiency features may be up for debate. We recommend the system in spite of the additional cost due to the comfort for the occupants and the fact that it utilizes a low temperature source which is much more sustainable and environment friendly then the conventional high temperature sources.
417

Energieffektivisering genom förvärmning av flis till kokare med sekundärvärme / Energy efficiency improvement by pre heating of woodchips to kraft digester with secondary heat

Ivarsson, Magnus January 2012 (has links)
The Swedish pulp and paper industry meets higher demand for energy efficiencyi mprovements with increasing energy prices and changes in the Swedish renewable energy certificate system. One action of energy efficiency improvement is by using secondary heat, that otherwise would have been treated as waste heat, for use in a system with lower temperature demands. The aim of this Master´s thesis is to identify possible secondary heat sources in a typical Swedish pulp and paper mill and to investigate what economic benefits the secondary heat will provide when being used for pre heating of wood chips to a kraft digester. The Master´s thesis focuses on three secondary heat sources; dry warm air, warm water and moisture saturated warm air located inside the pulp or paper mill. Two types of kraft digesters are simulated within this study, a typical Scandinavian digester and a modern twin vessel steam phase digester. Due to quality aspects and low temperature level drying is the drying technology with dry warm air rejected. Using warm water in direct contact with wood chips increases the quantity of water to the evaporation plant and thus reduced pulp or paper production and is therefore also rejected. The thesis nevertheless indicates a goodopportunity for further investigation of using moisture saturated warm air for preheating of wood chips. The humid air, from a drying machine or produced from secondary heat warm water, is used in a theoretical modified belt drier. Conservative assumptions regarding heat transfer and investment cost calculations yield a yearly net saving for a typical Swedish pulp mill at over 5 MSEK with a return on investment at 7years.
418

The Specificities of Market Entry Strategies into a Developing Country : A research study on the entry strategies ofenergy efficiency light industry

Raihan, Rubaiyat, Azeem, Shah January 2011 (has links)
Date May 31, 2011 Course Name: Masters Thesis in Marketing, 4FE02E, 15 hp, Spring 2011 LinnaeusUniversity,Växjö,Sweden Program Masters in Marketing Authors: Rubaiyat Raihan 840812 Shah Azeem 761210 Tutor: Engelbert Weiss Examiner: Sarah Philipson Title of the Paper: The specificities of market entry strategies into a developing country Problem Statement: “What are the specificities of market entry strategies into a developing country?” Purpose: To understand the market entry strategy of high tech product like energy efficiency light for the developing country taking into consideration the aspects discussed under problem discussion. Delimitation: In our thesis paper, we are only discussed about the energy saving industry and more specific the light manufactures. Also, our paper is discussed only about the market entry strategies and entry barrier, not to measure the effect of it. Methodology: The project is based on primary data retrieved in connection with the theoretical framework. A qualitative approach of research and questionnaire has been considered to reach the desirable result. Conclusion: After investigating the factors of energy efficiency light industry, we can conclude that it will be a good idea for a company to expand their business in developing country as the industry and the countries have a lot of potential to offer. An Investment entry mode (Joint Venture) has been suggested. Suggestion for Further Research: This research was focused on market entry strategy and entry barriers of energy efficiency light manufacturer, not the effect of entry barriers. Therefore, the next step should be to make in order to examine the effect of the barriers discussed in this research. Key Words: International market entry strategies, energy efficiency light industry, entry modes and entry barriers.
419

Energy Efficient Protocols for Delay Tolerant Networks

Choi, Bong Jun January 2011 (has links)
The delay tolerant networks (DTNs) is characterized by frequent disconnections and long delays of links among devices due to mobility, sparse deployment of devices, attacks, and noise, etc. Considerable research efforts have been devoted recently to DTNs enabling communications between network entities with intermittent connectivity. Unfortunately, mobile devices have limited energy capacity, and the fundamental problem is that traditional power-saving mechanisms are designed assuming well connected networks. Due to much larger inter-contact durations than contact durations, devices spend most of their life time in the neighbor discovery, and centralized power-saving strategies are difficult. Consequently, mobile devices consume a significant amount of energy in the neighbor discovery, rather than in infrequent data transfers. Therefore, distributed energy efficient neighbor discovery protocols for DTNs are essential to minimize the degradation of network connectivity and maximize the benefits from mobility. In this thesis, we develop sleep scheduling protocols in the medium access control (MAC) layer that are adaptive and distributed under different clock synchronization conditions: synchronous, asynchronous, and semi-asynchronous. In addition, we propose a distributed clock synchronization protocol to mitigate the clock synchronization problem in DTNs. Our research accomplishments are briefly outlined as follows: Firstly, we design an adaptive exponential beacon (AEB) protocol. By exploiting the trend of contact availability, beacon periods are independently adjusted by each device and optimized using the distribution of contact durations. The AEB protocol significantly reduces energy consumption while maintaining comparable packet delivery delay and delivery ratio. Secondly, we design two asynchronous clock based sleep scheduling (ACDS) protocols. Based on the fact that global clock synchronization is difficult to achieve in general, predetermined patterns of sleep schedules are constructed using hierarchical arrangements of cyclic difference sets such that devices independently selecting different duty cycle lengths are still guaranteed to have overlapping awake intervals with other devices within the communication range. Thirdly, we design a distributed semi-asynchronous sleep scheduling (DSA) protocol. Although the synchronization error is unavoidable, some level of clock accuracy may be possible for many practical scenarios. The sleep schedules are constructed to guarantee contacts among devices having loosely synchronized clocks, and parameters are optimized using the distribution of synchronization error. We also define conditions for which the proposed semi-asynchronous protocol outperforms existing asynchronous sleep scheduling protocols. Lastly, we design a distributed clock synchronization (DCS) protocol. The proposed protocol considers asynchronous and long delayed connections when exchanging relative clock information among nodes. As a result, smaller synchronization error achieved by the proposed protocol allows more accurate timing information and renders neighbor discovery more energy efficient. The designed protocols improve the lifetime of mobile devices in DTNs by means of energy efficient neighbor discoveries that reduce the energy waste caused by idle listening problems.
420

Energy-Efficient RF Transmitter and Receiver Using Injection-Locked Oscillators

Chen, Chi-Tsan 30 July 2012 (has links)
Future wireless communication systems will have higher data transmission rates and energy efficiencies than those used today. This fact raises serious challenges to the design of conventional transceiver architectures. This doctoral research develops energy-efficient RF transmitters and receivers for next-generation wireless communications. It begins with a theoretical analysis of the injection locking of oscillators and a modified Class-E power amplifier (PA) for use in developing the proposed transmitter and receiver. Based on the presented theory, a novel envelope elimination and restoration (EER)/polar transmitter using injection-locked oscillators (ILOs) and a novel cognitive polar receiver using two ILO stages are proposed. The EER/polar transmitter combines the approaches of EER/polar modulation and injection locking to achieve linear amplification with a high gain and high efficiency. Experimental results demonstrate its effectiveness for delivering WCDMA and EDGE signals. Additionally, the cognitive polar receiver utilizes two ILO stages to extract the modulation envelope and phase components of a received nonconstant envelope modulation signal without using a phase-locked loop (PLL)-based carrier recovery circuit. Experiments are conducted to verify the feasibility of the novel architecture by performing £k/4 DQPSK and QPSK demodulation. Rigorous theoretical analysis and experimental verification prove that both the proposed transmitter and the receiver are effective for energy-efficient wireless communications.

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