Dissertationen zum Thema „Engineering, General|Energy“
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1
Ramberg, David J. (David John). „General equilibrium impacts of new energy technologies on sectoral energy usage“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99536.
Annotation:
Thesis: Ph. D., Massachusetts Institute of Technology, Engineering Systems Division, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 185-198).
The dissertation examines conditions under which gas-to-liquids (GTL) technology penetration shifts the crude oil-natural gas price ratio. Empirical research finds long-run relationships between crude oil and natural gas prices. Some studies include time trends that steadily evolve the pricing relationship, while others show a long-run relationship that occasionally shifts significantly. A common hypothesis is that technologies that increase substitutability or complementarity between fuels are the source of the price linkage. However, empirically measuring the effects of a gradually-penetrating technology across narrow time frames is not possible due to intervening economic shocks. This thesis examines the effects of an energy conversion technology penetration on the crude oil-natural gas price ratio through its influence on sectoral energy use in the U.S. GTL must be less expensive and more efficient, and natural gas prices must be lower, than currently forecast for an effect to be measured. In the absence of a technology that explicitly allows for substitution between natural gas and petroleum-based fuels, different rates of demand growth result in a steadily-rising oil-gas price ratio. If a viable GTL technology successfully competes against petroleum-derived refined fuels, it dampens crude oil price increases and brings the oil-gas price ratio below the levels found in cases without a viable GTL technology.
by David John Ramberg.
Ph. D.
2
Wang, Hao. „The effect of primary air distribution on emissions from a natural gas water heater“. Marquette University, 2013.
3
Wills, William Noah. „A General Method for Sizing Battery Energy Storage Systems for Use in Mitigating Photovoltaic Flicker“. Thesis, University of Missouri - Columbia, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13850758.
Annotation:
A method for sizing battery energy storage (BES) systems for use in mitigating voltage flicker caused by solar intermittency in photovoltaic generation was developed. The method creates a “design day” from existing solar data and designs the power and energy requirements for a BES system that can help a photovoltaic facility mitigate flicker caused by solar activity associated with the design day. An economic analysis of lead-acid and lithium-ion options for the BES was also developed. The method was then applied to a proposed photovoltaic project in the Midwestern United States.
4
Ali, Rehan. „Effect of Solar Panel Cooling on Photovoltaic Performance“. Thesis, Southern Illinois University at Edwardsville, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1560782.
Annotation:
One of the main problems in using the photovoltaic system is the low energy conversion efficiency of photovoltaic cells and, furthermore, during the long operational period of solar cells, their energy conversion efficiency decreases even more due to increase in operating cell temperature over a certain limit. One way of improving the efficiency of photovoltaic system is to maintain a low operating temperature by cooling it down during its operation period. This study compares the effects of cooling on the performance of photovoltaic system. Experiments are performed on the solar panel inclined at fixed 45° angle without active cooling initially to have a set of reference performance parameters for comparison. Afterwards, cooling of the solar panel is carried out using air and water, separately, as the cooling fluids. I-V tests and temperature tests, for all the cases, are performed for comparative analysis. The energy balance calculations showed that the experimental results are in conformity with the theoretical results. The results further showed that the cooling of photovoltaic system using water over the front surface enhances the performance even more as compared to air cooling of solar panel.
5
DeLuca, Christopher. „Numerical Modeling and Optimization of Mechanically Active Electrochemical Systems“. Thesis, University of Colorado at Boulder, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3592275.
Annotation:
This work is primarily motivated by the hope that Silicon (Si) can be utilized in Lithium (Li) ion batteries to enable an order of magnitude capacity increase if Li-Si systems can be better understood. In order to create a valuable tool that could be used to study a wide range of problem, pertinent physical models were implemented in an extended finite element method (XFEM) framework written in c++. One of the major contribution of this work goes to the battery modeling community, by generalizing several existing electrochemical-mechanical models which use a small deformation approximations so they can accommodate finite deformation. A general theory which can be used to guide the development of new finite element models is presented in detail. This work also contributes new finite element modeling tools with novel predictive capabilities to the battery modeling community, which will hopefully facilitate the design and optimization of next generation battery micro-structures. Studies within demonstrate that small deformation approximation models can produce incorrect predictions about the behavior of Li-Si systems, supporting the case for using finite deformation models. The developed tools are used to demonstrate that arbitrary geometries can easily be simulated on a the same fixed grid, facilitating automated geometry studies including parameter sweeping and topology optimization.
6
Attalah, Said. „Energy evaluation of the High Velocity Algae Raceway Integrated Design (ARID-HV)“. Thesis, The University of Arizona, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1536266.
Annotation:
The original ARID (Algae Raceway Integrated Design) raceway was an effective method to increase temperature toward the optimal growth range. However, the energy input was high and flow mixing was poor. Thus, the ARID-HV (High Velocity Algae Raceway Integrated Design) raceway was developed to reduce energy input requirements and improve flow mixing. This was accomplished by improving pumping efficiency and using a serpentine flow pattern in which the water flows through channels instead of over barriers. A prototype ARID-HV system was installed in Tucson, Arizona, and the constructability, reliability of components, drainage of channels, and flow and energy requirements of the ARID-HV raceway were evaluated. Each of the electrical energy inputs to the raceway (air sparger, air tube blower, canal lift pump, and channel recirculation pump) was quantified, some by direct measurement and others by simulation. An algae growth model was used to determine the algae production rate vs. flow depth and time of year. Then the electrical energy requirement of the most effective flow depth was calculated. Channel hydraulics was evaluated with Manning's equation and the corner head loss equation. In this way, the maximum length of channels for several raceway slopes and mixing velocities were determined. Algae production in the ARID-HV raceway was simulated with a temperature and light growth model. An energy efficient design for the ARID-HV raceway was developed.
7
Basgall, Lance Edgar. „Thermal energy storage design for emergency cooling“. Thesis, Kansas State University, 2010. http://hdl.handle.net/2097/4637.
Annotation:
Master of ScienceDepartment of Mechanical and Nuclear Engineering
Donald L. Fenton
Emergency cooling systems are applied to any application where the loss of cooling results in damage to the product, loss of data, or equipment failure. Facilities using chilled water for cooling that experience an electrical power outage, even a small one, would cause the chiller to shut down for 20 minutes or more. If emergency cooling is not available, temperatures would continue to increase to dangerous levels, potentially damaging the facility. Examples of facilities that could be protected by having emergency cooling systems are data centers, hospitals, banks, control rooms, laboratories, clean rooms, and emergency shelters among others. This project addresses the current lack of information and methods needed to correctly design emergency cooling systems. Three application uses were investigated for the possible benefits of having emergency cooling systems. The software TRNSYS was used to simulate five typical emergency cooling systems for each of the three applications. The characteristics and differences of the systems developed from the simulations were then analyzed and documented. The five systems simulated include a pressurized chilled water tank (parallel), atmospheric chilled water tank (parallel and series), low temperature chilled water tank (parallel), and ice storage tank (series). Simulations showed that low temperature chilled water tanks were less stratified than regular chilled water tanks by approximately 10%. Simulations also showed that the differences between atmospheric and pressurized tanks were negligible. Each tank discharged energy in the same manner and managed to replenish itself in the same amount of time. Examination of the different system configurations showed that tanks in series with the thermal load have issues with recharging due to its inability to isolate itself from the thermal load. It was also observed that while low temperature chilled water and ice storage tanks had the potential of reducing the storage tank volume, the amount of time ragged cooling will last is decreased by at least a factor of two. The examination of the five systems produced the desired design methodologies needed to address the lack of information on emergency cooling systems. With the reported information designers can effectively engineer systems to meet their needs.
8
Soner, Ilker. „Utilization Of Fluidized Bed Combustion Ashes As Raw Material In The Production Of A Special Cement“. Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610651/index.pdf.
Annotation:
Fluidized bed combustion (FBC) ashes containing significant amount of free CaO and CaSO4 in addition to valuable inorganic acidic oxide ingredients such as SiO2, Fe2O3 and Al2O3 can be utilized as potential raw materials in the production of nonexpansive belite-rich calcium sulfoaluminate cement which is one of the special cement type of sulfoaluminate-belite cements having performance characteristics similar to those of ordinary portland cement besides lower energy requirements and
CO2 emissions during manufacturing. Therefore, in this thesis study, possibility of producing non-expansive belite-rich
calcium sulfoaluminate cement by adding FBC ashes in various proportions to the raw meal was investigated. For this purpose, a raw meal composed a mixture of limestone, bauxite, gypsum together with 10 wt % bottom ash and 15 wt % baghouse filter ash was prepared. It was sintered in a laboratory scale muffle furnace at temperatures of 1200, 1250 and 1300 °C for various holding times. The results of chemical and mineralogical analysis as well as microscopic examination reveal that FBC ashes have the potential to be used in the raw meal due to the presence of characteristic mineral phases of this type of cements, i.e. yeelimite, larnite, ferrite and anhydrite, in the sample obtained at optimum sintering temperature of 1250 °
C for 60 min.
9
Dogruoz, Cihan. „Effect Of Pick Blunting On Cutting Performance For Weak Moderate Rocks“. Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612614/index.pdf.
Annotation:
The laboratory cutting specific energy is widely used to estimate the cuttability of rocks by a roadheader fitted with sharp picks. Sharp picks on the other hand become blunt due to wear in time and require replacement. Although it is known that the pick blunting affects adversely the rock cuttability, no study exists to show the relationships between the degree of pick wear and the cutting specific energy obtained by standard cutting tests. In this study, standard cutting tests were carried out on different rock types, with picks having varying degrees of blunting. The relationships between wear flats and the cutting forces, specific energies and size distribution for various rock properties such as uniaxial compressive strength, tensile strength, cone indenter number, shore hardness, schmidth hammer hardness, density and grain size were established. The mean cutting force and the cutting specific energy have been found to increase 2-3 times and 4-5 times respectively with 4 mm wear flat as compared to sharp picks as the strength and density of rocks increase. No relation exists between mineral grain size and the cutting performance. A definite relation could not be established between the wear land and the size distribution of the product. Charts have been produced to predict critical wear flats for different rock property values considering 25 MJ/m³as the limiting specific energy above which poor cutting performance occurs. Nine prediction models have been developed by statistical analysis to estimate the laboratory cutting specific energy from various rock properties and wear rates.
10
Kusyilmaz, Ahmet. „Finite Element Study On Local Buckling And Energy Dissipation Of Seismic Bracing“. Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609662/index.pdf.
Annotation:
Seismic provisions for steel buildings present limiting width-thickness and slenderness ratios for bracing members. Most of these limits were established based on experimental observations. The number of experimental studies is limited due to the costs associated with them. With the rapid increase in computing powerhowever, it is now possible to conduct finite element simulation of brace components using personal computers. A finite element study has been undertaken to evaluate the aforementioned limits for pin-ended pipe section steel braces. Fifty four tubular pipe brace models possessing different diameter-to-thickness ratios varying from 5 to 30 and slenderness ratios varying from 40 to 200 were analyzed. The effect of cyclic hardening modulus on the response of braces was explored. In all analysis, the models were subjected to reversed cyclic displacements up to ten times the yield displacement. Local buckling was traced during the loading history using a criterion based on local strains. Results are presented in terms of the ductility level attained by the member at the onset of local buckling. It is shown that local buckling of the section is influenced by the diameter-to-thickness and the slenderness ratios of the member. Moreover, the amount of hardening modulus was found to affect the local buckling response significantly. The need to include this material property into seismic provisions is demonstrated. Finally, the hysteretic energy dissipated by the member was quantified for each displacement excursion.
11
Blush, Aaron. „Impact of ASHRAE standard 189.1-2009 on building energy efficiency and performance“. Kansas State University, 2010. http://hdl.handle.net/2097/6909.
Annotation:
Master of ScienceDepartment of Architectural Engineering and Construction Science
Fred L. Hasler
The purpose of this report is to provide an introduction to the new ASHRAE Standard 189.1-2009, Standard for the Design of High-Performance Green Buildings. The report will include an overview of the standard to detail what the purpose, scope and requirements for high-performance buildings will be. The entire standard will be overviewed, but the focus of this paper is in the areas of energy efficiency and building performance. Next, the report will examine further impacts that the standard will have on the building design and construction industry. Chapter 3 includes the impact on other standards, specification writing and coordination of the design and construction teams. A case study of an office building is performed to compare a baseline building meeting ASHRAE Standard 90.1 to a building meeting the minimum standards of ASHRAE Standard 189.1. The case study compares the total annual energy use of the two projects to determine an expected energy savings. Based on this information, recommendations about the new standard will be discussed. Universities and government entities should require ASHRAE Standard 189.1 for new construction projects, to show willingness to provide sustainability in buildings. Finally, conclusions about how the standard will change and impact industry will be addressed. These conclusions will include issues with adopting ASHRAE Standard 189.1 as code as well as discussion on the LEED rating system.
12
Acun, Bora. „Energy Based Seismic Performance Assessment Of Reinforced Concrete Columns“. Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611728/index.pdf.
Annotation:
Severe seismic events in urban regions during the last two decades revealed that the structures constructed before the development of modern seismic codes are the most vulnerable to earthquakes. Sub-standard reinforced concrete buildings constitute an important part of this highly vulnerable urban building stock. There is urgent need for the development and improvement of methods for seismic performance assessment of existing reinforced concrete structures.
As an alternative to current conventional force-based assessment methods, a performance evaluation procedure for structural members, mainly reinforced concrete columns is proposed in this study, by using an energy-based approach combined with the low cycle fatigue concept. An energy-based hysteresis model is further introduced for representing the inelastic response of column members under severe seismic excitations. The shape of the hysteresis loops are controlled by the dissipated cumulative energy whereas the ultimate strength is governed by the low cycle fatigue behavior. These two basic characteristics are obtained experimentally from full scale specimens tested under constant and variable amplitude
displacement cycles.
The first phase of the experimental program presented in the study constitutes of testing sub-standard non-conforming column specimens. The second phase of testing was conducted on standard, code compliant reinforced concrete columns. A
total number of 13 specimens were tested. The behavior of these specimens was observed individually and comparatively according to the performance based objectives. The results obtained from the experiments were employed for developing relations between the energy dissipation capacity of specimens, the specimen properties as well as the imposed displacement history. Moreover, the measured rotation capacities at the plastic regions are evaluated comparatively with the limits proposed by modern displacement-based seismic design and assessment provisions.
13
Ozkaya, Cenan. „Development Of A New Seismic Isolator Named“. Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612712/index.pdf.
Annotation:
The experimental research presented in this dissertation aims to develop a new rubber&ndashbased seismic isolator type on the basis of the idea that the damping of a conventional annular elastomeric bearing (EB) can be increased by filling its central core with small diameter steel balls, which dissipate energy via friction inside the confined hole of the bearing during their movements under horizontal loads. The proposed bearing type is called &ldquo
Ball Rubber Bearing (BRB)&rdquo
. A large set of BRBs with different geometrical and material properties are manufactured and tested under reversed cyclic horizontal loading at different vertical compressive load levels. Effect of supplementary confinement in the central hole of the bearing to performance of BRB is studied by performing some additional tests. Test results are used to develop design equations for BRB. A detailed non-linear finite element model is developed to verify the test results. The proposed analytical model is determined to simulate the structural hysteretic behaviour of the bearings. In design of BRBs, the proposed design guideline can be used in conjunction with the proposed non-linear finite element analysis. Extensive test results indicate that steel balls do not only increase the energy dissipation capacity of the elastomeric bearing (EB) but also increase its horizontal and vertical stiffness. It is also observed that the energy dissipation capacity of a BRB does not degrade as the number of loading cycles increases, which indicates remarkably reliable seismic performance.
14
Peña, Duque Leidy E. „Acid-functionalized nanoparticles for hydrolysis of lignocellulosic feedstocks“. Thesis, Kansas State University, 2009. http://hdl.handle.net/2097/2201.
Annotation:
Master of ScienceDepartment of Biological and Agricultural Engineering
Donghai Wang
Acid catalysts have been successfully used for pretreatment of cellulosic biomass to improve sugar recovery and its later conversion to ethanol. However, use of acid requires a considerable equipment investment as well as disposal of residues. Acid-functionalized nanoparticles were synthesized for pretreatment and hydrolysis of lignocellulosic biomass to increase conversion efficiency at mild conditions. Advantages of using acid-functionalized metal nanoparticles are not only the acidic properties to catalyze hydrolysis and being small enough to penetrate into the lignocellulosic structure, but also being easily separable from hydrolysis residues by using a strong magnetic field. Cobalt spinel ferrite magnetic nanoparticles were synthesized using a microemulsion method and then covered with a layer of silica to protect them from oxidation. The silanol groups of the silica serve as the support of the sulfonic acid groups that were later attached to the surface of the nanoparticles. TEM images and FTIR methods were used to characterize the properties of acid-functionalized nanoparticles in terms of nanoparticle size, presence of sulfonic acid functional groups, and pH as an indicator of acid sites present. Citric acid-functionalized magnetite nanoparticles were also synthesized and evaluated. Wheat straw and wood fiber samples were treated with the acid supported nanoparticles at 80°C for 24 h to hydrolyze their hemicellulose fraction to sugars. Further hydrolysis of the liquid fraction was carried out to account for the amount of total solubilized sugars. HPLC was used to determine the total amount of sugars obtained in the aqueous solution. The perfluroalkyl-sulfonic acid functional groups from the magnetic nanoparticles yielded significantly higher amounts of oligosaccharides from wood and wheat straw samples than the alkyl-sulfonic acid functional groups did. More stable fluorosulfonic acid functionalized nanoparticles can potentially work as an effective heterogeneous catalyst for pretreatment of lignocellulosic materials.
15
Sari, Ibrahim. „Design, Fabrication And Implementation Of A Vibration Based Mems Energy Scavenger For Wireless Microsystems“. Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610096/index.pdf.
Annotation:
This thesis study presents the design, simulation, micro fabrication, and testing steps of microelectromechanical systems (MEMS) based electromagnetic micro power generators. These generators are capable of generating power using already available environmental vibrations, by implementing the electromagnetic induction technique. There are mainly two objectives of the study: (i) to increase the bandwidth of the traditional micro generators and (ii) to improve their efficiency at low frequency environmental vibrations of 1-100 Hz where most vibrations exist.
Four main types of generators have been proposed within the scope of this thesis study. The first type of generator is mainly composed of 20 parylene cantilevers on which coils are fabricated, where the cantilevers are capable of resonating with external vibrations with respect to a stationary magnet. This generator has dimensions of 9.5×8×
6 mm3, and it has been shown that 0.67 mV of voltage and 56 pW of power output can be obtained from a single cantilever of this design at a vibration frequency of 3.45 kHz. The second type generator aims to increase the bandwidth of the traditional designs by implementing cantilevers with varying length. This generator is sized 14×
12.5×
8 mm3, and the mechanical design and energy generation concept is similar to the first design. The test results show that by using 40 cantilevers with a length increment of 3 &
#956
m, the overall bandwidth of the generator can be increased to 1000 Hz. It has also been shown that 9 mV of constant voltage and 1.7 nW of constant power output can be obtained from the overall device in a vibration frequency range of 3.5 to 4.5 kHz. The third type is a standard large mass coil type generator that has been widely used in the literature. In this case, the generator is composed of a stationary base with a coil and a magnet-diaphragm assembly capable of resonating with vibrations. The fabricated device has dimensions of 8.5×
7×
2.5 mm3, and it has been considered in this study for benchmarking purposes only. The test results show that 0.3 mV of voltage and 40 pW of power output can be obtained from the fabricated design at a vibration frequency of 113 Hz. The final design aims to mechanically up-convert low frequency environmental vibrations of 1-100 Hz to a much higher frequency range of 2-3 kHz. This type of generator has been implemented for the first time in the literature. The generator is composed of two parts
a diaphragm-magnet assembly on the top, and 20 cantilevers that have coils connected in series at the base. The diaphragm oscillates by low frequency environmental vibrations, and catches and releases the cantilevers from the tip points where magnetic nickel (Ni) areas are deposited. The released cantilevers then start decaying out oscillations that is at their damped natural frequency of 2-3 kHz. It has been shown with tests that frequency up-conversion is realized in micro scale. The fabricated device has dimensions of 8.5×
7×
2.5 mm3, and a maximum voltage and power output of 0.57 mV and 0.25 nW can be obtained, respectively, from a single cantilever of the fabricated prototype at a vibration frequency of 113 Hz.
16
Yan, Zuanhong. „Control of fluctuating renewable energy sources : energy quality & energy filters“. Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8568/.
Annotation:
This doctoral study discusses how to control fluctuating renewable energy sources at converter, unit, and system layers to deliver smoothed power output to the grid. This is particularly relevant to renewable power generation since the output power of many kinds of renewable energy sources have huge fluctuations (e.g. solar, wind and wave) that needs to be properly treated for grid integration. In this research, the energy quality is developed to describe the friendliness and compatibility of power flows/waveforms to the grid, by contrast with the well-known concept of power quality which is used to assess the voltage and current waveforms. In Chapter 1 & 2, a background introduction and a literature review of studied subjects are presented, respectively. In Chapter 3, the problem of determining the PI parameters in dq decoupling control of voltage source converter (VSC) is studied based on a state-space model. The problems of the conventional method when there is insufficient interface resistance are addressed. New methods are proposed to overcome these drawbacks. In Chapter 4 & 5, energy quality and the energy filters (EFs) are proposed as tools to assess and manage power fluctuations of renewable energy sources. The proposed EFs are energy storage control systems that could be implemented on a variety of energy storage hardware. EFs behave like low-pass filters to the power flows. Finally, in Chapter 6, as an application example of renewable power plant with energy filter control and smoothed power output, a master-slave wave farm system is proposed. The wave farm system uses enlarged rotor inertia of electric machines as self-energy storage devices.
17
Yang, Xiangxin. „Sol-gel synthesized nanomaterials for environmental applications“. Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/884.
18
Palmer, James Dirk. „Vibrational energy flow in structures“. Thesis, University of Nottingham, 1994. http://eprints.nottingham.ac.uk/28481/.
Annotation:
This investigation explores the use of an approximate energy flow approach to provide a global modelling tool capable of predicting the pattern and level of vibrational energy flow in complex structures. The modelling approach is based on a differential control volume formulation which, by virtue of its simplified nature, describes the flow of mechanical energy within a structural component in a manner analogous to the flow of thermal energy in heat conduction problems. For complex structures the approach can be implemented using existing finite element software through an analogy between the thermal and vibrational systems. Energy flow predictions along simple beam structures, obtained using the energy flow approach, are compared to "exact" analytical solutions and experimental structural intensity measurements on real structures. This provides useful insight into the capabilities and requirements of the approach, such as the quality of model predictions at lower frequencies and the accuracy requirement for modelling parameters. The task of modelling the transmission of vibrational energy in practical engineering structures is complicated by the partial reflection of incident wave energy at structural discontinuities. Methods to account for this effect are discussed and an approach is developed which can be incorporated into the finite element global modelling scheme. This is used to model a complex multiple transmission path structure which illustrates the ability of the approach to form an effective transmission path ranking tool. Finally, the approach is used to build a representative energy flow model of a ribbed bulkhead structure typical of marine applications. A wavenumber measurement technique is used to assess the wave transmission characteristics of this structure which exhibit strong directional dependence. Predictions provided by the energy flow model are in good general agreement with energy flow measurements obtained from the real structure. Throughout these modelling exercises particular attention is paid to the provision of suitable estimates of the parameters (damping, group velocity, power input and transmission efficiency) on which the accuracy of the model predictions rely. This investigation represents a significant contribution to current knowledge regarding the use of the energy flow approach and its ability to provide representative models of real structures. Although further research is still required, considerable progress has been made and the work documented here provides the framework for a global modelling tool using existing finite element software.
19
Papafragrou, Anastasios. „Urban carbon and energy analysis : calculation of energy flows and emissions from residential housing clusters and assessment of sustainable energy options“. Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/210375/.
Annotation:
In the UK, the domestic sector accounts for around 30% of fuel-use and energy related carbon emissions, and therefore has the potential to deliver significant reductions in carbon dioxide emissions. The purpose of this work is to form and examine various heat and electricity supply scenarios at the street-level and identify which of these scenarios offer the most potential to reduce consumption of resources and carbon dioxide emissions. The path to realisation of a reduction in carbon emissions from the domestic sector incorporates three consecutive steps: (1) saving energy, (2) use of renewables and (3) use energy as efficiently as possible, including fossil fuels. In reality, there is a strong interaction between all three steps and often they take place simultaneously. The first two steps tend to minimise the use of fossil fuels, but not to eliminate them. In this work it is recognised that in mature urban regions fossil fuels cannot be readily displaced completely, but can be used in a more efficient way. This research considers what can be achieved by applying at or near to market technologies at the street level microgrid scale, such as Combined Heat and Power (CHP). The renewable energy technologies considered were photovoltaics (PV) for electricity generation, solar thermal for domestic hot water heating and ground source heat pumps (GSHP) for space heating. For the development of the models, the transient simulation package TRNSYS was used and a residential area in Southampton that represents a typical UK area, was chosen as a case study. The notion of combining a number of houses to form a local microgrid proved to be beneficial for all the technologies examined in this research. It was shown that renewable energy microtechnologies can improve their carbon performance up to 10% when operating as a microgrid, whilst estimated benefits were even greater for CHP systems. Parallel operation strategies were also investigated and it was shown that they have the potential to deliver further savings from microgrid schemes. Microgrids, although their high capital costs, were estimated to have better financial performance compared with the single house level for many of the cases examined. Increased generation and lower heating demand were the key outcomes due to the impact of change in climate
20
Ma, Yingnan. „Intelligent energy management system : techniques and methods“. Thesis, City University London, 2011. http://openaccess.city.ac.uk/1212/.
Annotation:
ABSTRACT Our environment is an asset to be managed carefully and is not an expendable resource to be taken for granted. The main original contribution of this thesis is in formulating intelligent techniques and simulating case studies to demonstrate the significance of the present approach for achieving a low carbon economy. Energy boosts crop production, drives industry and increases employment. Wise energy use is the first step to ensuring sustainable energy for present and future generations. Energy services are essential for meeting internationally agreed development goals. Energy management system lies at the heart of all infrastructures from communications, economy, and society’s transportation to the society. This has made the system more complex and more interdependent. The increasing number of disturbances occurring in the system has raised the priority of energy management system infrastructure which has been improved with the aid of technology and investment; suitable methods have been presented to optimize the system in this thesis. Since the current system is facing various problems from increasing disturbances, the system is operating on the limit, aging equipments, load change etc, therefore an improvement is essential to minimize these problems. To enhance the current system and resolve the issues that it is facing, smart grid has been proposed as a solution to resolve power problems and to prevent future failures. This thesis argues that smart grid consists of computational intelligence and smart meters to improve the reliability, stability and security of power. In comparison with the current system, it is more intelligent, reliable, stable and secure, and will reduce the number of blackouts and other failures that occur on the power grid system. Also, the thesis has reported that smart metering is technically feasible to improve energy efficiency. In the thesis, a new technique using wavelet transforms, floating point genetic algorithm and artificial neural network based hybrid model for gaining accurate prediction of short-term load forecast has been developed. Adopting the new model is more accuracy than radial basis function network. Actual data has been used to test the proposed new method and it has been demonstrated that this integrated intelligent technique is very effective for the load forecast. Choosing the appropriate algorithm is important to implement the optimization during the daily task in the power system. The potential for application of swarm intelligence to Optimal Reactive Power Dispatch (ORPD) has been shown in this thesis. After making the comparison of the results derived from swarm intelligence, improved genetic algorithm and a conventional gradient-based optimization method, it was concluded that swam intelligence is better in terms of performance and precision in solving optimal reactive power dispatch problems.
21
Mackay, Edward B. L. „Wave energy resource assessment“. Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/79448/.
Annotation:
The use of satellite altimeter data for spatial mapping of the wave resource is examined. A new algorithm for estimating wave period from altimeter data is developed and validated, which enables estimates of wave energy converter (WEC) power to be derived. Maps of the long-term mean WEC power from altimeter data are of a higher spatial resolution than is available from global wave model data. They can be used for identifying promising wave energy locations along particular stretches of coastline, before a detailed study using nearshore models is undertaken. The accuracy of estimates of WEC power from wave model data is considered. Without calibration estimates of the mean WEC power from model data can be biased of the order of 10-20%. The calibration of wave model data is complicated by non-linear dependence of model parameters on multiple factors, and seasonal and interannual changes in biases. After calibration the accuracy in the estimate of the historic power production at a site is of the order of 5%, but the changing biases make it difficult to specify the accuracy more precisely. The accuracy of predictions of the future energy yield from a WEC is limited by the accuracy of the historic data and the variability in the resource. The variability in 5, 10 and 20 year mean power levels is studied for an area in the north of Scotland, and shown to be greater than if annual power anomalies were uncorrelated noise. The sensitivity of WEC power production to climate change is also examined, and it is shown that the change in wave climate over the life time of a wave farm is likely to be small in comparison to the natural level of variability. It is shown that despite the uncertainty related to variability in the wave climate, improvements in the accuracy of historic data will improve the accuracy of predictions of future WEC yield. The topic of extreme wave analysis is also considered. A comparison of estimators for the generalised Pareto distribution (GPD) is presented. It is recommended that the Likelihood-Moment estimator should be used in preference to other estimators for the GPD. The use of seasonal models for extremes is also considered. In contrast to assertions made in previous studies, it is demonstrated that non-seasonal models have a lower bias and variance than models which analyse the data in separate seasons.
22
Monir, Habib Saeed. „A new energy absorber for earthquake resistant buildings“. Thesis, City University London, 2001. http://openaccess.city.ac.uk/8283/.
Annotation:
The research work which has been reported in this thesis is associated with the design of an energy absorbing device. The device as well as being capable to absorb high amount of energy, possess all the necessary properties of a structural member. Most energy absorbing devices have not the necessary conditions to be used as a structural members. Their problems have been demonstrated in chapter 1 and chapter 3 of the this thesis. In order to overcome these problems an alternative kind of energy absorbing device, has been proposed. The inversion of tubes has been proposed as the basic of the work. This is a wellknown energy-absorbing principle and has been widely used in industry and many mechanical engineering cases as the basic of design. However, the device has some disadvantages and these required improvement. The following steps have been taken to improve the energy absorbing characteristics: 1- Normally the energy absorbing capacity of the device is limited due to buckling. This problem has been improved by including an adhesive within the device. 2- The second problem in this energy-absorbing device is that its elastic stiffness is very low and this is unacceptable for a structural member. The elastic stiffness has been improved by forming a stiff shell at the top of the tube. 3- The device undergoes a significant change in length during the energy absorbing process and if it is not compensated in some way, the device will be useless in the subsequent cycles of vibration. A special mechanism has been installed in the device to solve this problem. This enables the deformation to be compensated after the absorption process. Two major applications for the device have been considered to be studied in the thesis: First because of its special response at high speed loading, it has been installed in a simply supported framework. The middle member of this framework has been replaced by the energy absorbing device and the behaviour of the framework has been analysed under an explosive load. In order to determine the advantages of the installation of this device in a framework, this framework has also been analysed without the inclusion of the device. The comparison of these results showed that when the framework is equipped with the absorber, a great reduction in the forces and strains of the members of the framework have been achieved. The framework has become 2.5 times stronger, when just one device was used in the frame. In the second application of the device, its behaviour has been studied as an absorber of a first soft story method. The first soft story is one of the ideas which has been presented for the isolation of buildings from earthquake effects, however, no proper absorber has been suggested to be used in this method. This device has an excellent performance in this regard, because of its shortening ability and its compact form along with its high energy absorbing capacity. Two energy absorbing devices were inserted in the braces of a single degree freedom structure and subjected to a high rate base acceleration. For a comparison, the behaviour of the frame, when it was not equipped with the devices, was also analysed. The results indicated that by the inclusion of the absorber, the acceleration has been decreased more than three times. The forces in the members were also three times less than the frame without the device. Finally, the behaviour of a multi story building has been examined when it was equipped with two energy absorbing device in the braces of the first floor. The results showed that a great reduction in the accelerations, velocities and also the forces and moments has been achieved, as was the case in the previous example. By using this absorber in the braces, the accelerations and velocities were four times less than the case which the frame did not include any absorber. In simple words, this energy absorber is similar to the dampers, which are used in the vehicles to reduce vibrations, but with this difference that the dampers in the car are active all the time while this damper is activated only when a high rate loading is applied.
23
Ribeaux, Michael. „Energy absorbtion capability of damage affected composite structures“. Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/13040/.
Annotation:
The aim of this project is to consider the effect of damage on the energy absorption potential of continuous filament random mat (CoFRM) E-glass / polyester composite tubes. Composite materials have been shown to absorb significantly higher specific energy levels than metals under axial crushing conditions. This property can be exploited in automotive crashworthiness applications. Replacing steel crash structures with composites can lead to significant weight reductions. However, damage in composite structures can be difficult to assess and may not be visible by casual inspection. There is a concern that damage may accumulate in the crash structures, as a result of in-service wear and tear or due to operator negligence. It is important to understand how much accidental damage the crash structures can sustain before they are no longer able to fulfil their requirements. Two wall thicknesses of circular and square tube geometries were tested, with over 650 samples crushed either quasi-statically at 5mm/min or dynamically at 5m/s. Damage was induced in three ways: drilled holes, delamination in the form of Melinex® inserts moulded into the samples, and out-of-plane impact damage of various energy levels. Cylindrical samples made from this low cost composite are able to absorb up to 87 kJ/kg when tested quasi-statically. Dynamic testing was carried out as it provides a better representation of the loading conditions the parts will see in operation. Dynamically tested samples absorbed less energy than the quasi-statically tested samples (up to 18%). This was due to the viscoelastic nature of the matrix causing a greater degree of fragmentation at the higher test speed, leaving the load bearing fibres less well constrained and therefore reducing their load bearing capability. Square section tubes absorb less energy (up to 31 %) than a circular section of the same cross sectional area and fibre volume fraction. This is due to geometric stress raisers at the comers causing intralaminar failure. This splitting at the comers leaves the fronds less constrained and allows them to splay at a lower load. A threshold level was found for each type of damage. Below the threshold level the damage zone had no effect on the progressive failure mode or the specific energy absorption (SEA). Above the threshold level unstable compressive failure occurs in the form of a crack initiating at the damage zone and then propagating around the tube. In this situation a portion of the tube breaks off uncrushed and therefore reduces the energy absorption capability of the structure. For this material tested, relatively small hole sizes (5mm) and relatively low impact energy levels (l.5J - 3J) can cause unstable failure to occur at quasi-static test speeds. However, it has been shown that the damage tolerance of the material increases (to 10mm and 3J - 9J) at higher test rates (5m/s). Having observed the failure modes and damage tolerance of the tubes under various testing parameters it was important to look at ways of improving the damage tolerance of the samples. Moulding a thermoplastic interleaf into the sample to increase the interlaminar fracture toughness increases the damage tolerance of the tubes. Increasing the wall thickness and adding an interleaf increases the damage tolerance by up to a factor of 9. However, the increased damage tolerance of samples with interleaf was offset by a reduction in SEA by up to 48% due to a reduction in coefficient of friction in the crush zone from 0.36 to 0.22. The ultimate compressive stress (UCS) increases at dynamic test speeds and the mean crush load observed decreases. Therefore the crushing stress of the dynamically tested samples is a far lower percentage of the UCS of the material than under quasi-static loading. A greater stress concentration is therefore required to cause unstable failure at higher rates. Improved damage tolerance is also seen by increasing the wall thickness of the sample, testing square rather than circular section samples, and moulding interleaves into the samples. In all of these cases the changes that lead to improved damage tolerance lead to a reduction in the crush load of samples as a percentage of the ultimate crush load. Understanding the work in this thesis will enable the design of damage tolerant composite crash structures for the automotive industry. Such a part will, even with the inclusion of accidental damage, be able to absorb the energy required in the event of a collision.
24
Akena, p'Ojok Robert. „Improving road transport energy efficiency through driver training“. Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5275/.
Annotation:
Fuel consumption by road vehicles is the most significant component of total road transport energy use and is significantly affected by driving style. This research was aimed at improving the effectiveness and efficiency of driver training for fuel economy for drivers involved in the management and operations of a road network in England. A unique approach to driver training was designed and tested with 94 drivers of heavy, medium and light vehicles. The improvement in fuel economy (in terms of MPG) for the first month after the training was observed to improve by up to 7%. The improvements reduced at varying rates after the training suggesting the need for regular refresher training. The behaviours of the drivers were also observed to change as a result of the training, towards styles more suited to achieving a better fuel economy. The results suggest that both linear and logarithmic models could be suited to predicting the drivers' performances and could be integrated in models of the type of HDM-4 which currently lack such capability. The driver training methodology was found to be more cost effective than the Safe And Fuel Efficient Driving (SAFED) training method recommended by the Department for Transport (DfT).
25
Barrett, Emily Lord. „The Investigation and Optimization of a Two-Heat-Pump System Incorporating Thermal Storage for Shaping Residential Heating Load“. PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3025.
Annotation:
Portland General Electric has proposed coupling one or more water tanks with two heat pumps in order to perform load-shifting in residential customer heating and cooling applications. By using the water tanks as a thermal storage unit, this project attempts to partially decouple energy consumption from generation to provide peak demand reduction and to better facilitate the integration of variable renewable energy resources. A scoping study was performed to evaluate the potential impact of this project if implemented in single family homes in Portland, Oregon. This study revealed that the system could provide meaningful savings in the cost of electricity to both the customer and utility. Additionally, an optimization algorithm was developed to dictate system operation and to maximize gains to the utility. Evolutionary algorithms were explored in an attempt to increase the effectiveness of the algorithm's search in limited computation time. Ultimately, an evolution strategy was selected as the most suitable based on tests run in winter and spring months. A genetic algorithm was then developed to handle fixed-speed heat pump operation for compatibility with an alpha-system prototype that has been developed by the research team.
26
Ooi, Chia Ai. „Balancing control for grid-scale battery energy storage systems“. Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/93020/.
Annotation:
Grid-scale battery energy storage systems (BESSs) are becoming increasingly attractive as the connection of a BESS has been shown to improve the dynamic behaviours of the power grid. A key problem with BESSs is the potential for poor utilisation of mismatched cells and reliability issues resulting from the use of a large number of cells in series. This thesis proposes a technique for state-of-charge balancing of many thousands of cells individually (i.e. not in packs) using a tightly integrated power electronic circuit coupled with a new control system design. Cells are organised in a hierarchical structure consisting of modules, sub-banks, banks and phases. The control strategy includes five levels of balancing: balancing of cells within a module, balancing of modules within a sub-bank, sub-banks within a bank, banks in a phase and balancing between phases. The system seeks to maximise the accessible state-of-charge range of each individual cell, thereby enhancing the overall capacity of the system. The system is validated in simulation for a 380 kWh BESS using 2835 lithium-ion cells where charge balancing is demonstrated for mismatched cells. A ‘peak sharing’ concept is implemented to manage voltage constraints so that alternative modules assume a portion of the load when certain modules are not capable of meeting the demand. An experimental validation has been performed to demonstrate the effectiveness of the balancing control. This work is intended to address the challenges of eventual scaling towards a 100 MWh+ BESS, which may be composed of hundreds of thousands of individual cells.
27
Farshad, Mehr A. „Determination of design of optimal actuator location based on control energy“. Thesis, City, University of London, 2018. http://openaccess.city.ac.uk/19115/.
Annotation:
The thesis deals with the selection of the sets of inputs and outputs using the energy properties of the controllability and observability of a system and aims to define input and output structures which require minimization of the energy for control and state reconstruction. Such a study explores the energy dimension of the properties of controllability and observability, develops computations for the controllability and observability Gramians for stable and unstable systems and examines measures of the degree of controllability and observability properties using SVD (Singular Value Decomposition) of Gramians to compute the maximal and minimal energy requirements. These characterize the relative degree of controllability and observability under conditions where the available energy is constrained. The notion of energy surfaces in the state space is introduced and this enables the characterization of restricted notions of controllability and observability when the available energy is bounded. The maximal and minimal energy requirements for different input vectors is demonstrated and this provides the basis for the development of strategies and methodologies for selection of systems of inputs and outputs to minimize the energy required for control, respectively state reconstruction. These results enable the development of input, output structure selection methodology using a novel optimization method. This thesis contributes in the further development of the area of systems, or global instrumentation, developed so far based on the assignment of structural characteristics by incorporating the role of energy requirements. The research provides energy based tools for the selection of input and outputs schemes with a main criterion the minimization of the energy required for control and observation and thus provide an alternative approach based on quantitative system properties in characterizing control and state observation as functions of given sets of inputs and output sets. The methodologies developed may be used as design tools where apart from energy requirements other design criteria may be also incorporated for the selection of inputs and outputs. The methodology that is used is based on linear systems theory and tools from numerical linear algebra. The solution to the problems considered here is an integral part of the effort to develop an integrated approach to control and global process instrumentation.
28
Johnson, Benjamin Michael Carver. „Computational Fluid Dynamics (CFD) modelling of renewable energy turbine wake interactions“. Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/12120/.
Annotation:
This thesis presents Computational Fluid Dynamics (CFD) simulations of renewable turbines akin to those used for wind, hydro, and tidal applications. The models developed took the form of actuator discs with the solution of incompressible Reynolds-Averaged Navier-Stokes equations with the k-ω SST turbulence models. Simulations were initially conducted of a single turbine in water and air and then two axially aligned turbines to study the flow field interactions. These models were compared with previous theoretical, experimental and numerical data evident in the literature. Generally, good agreement was found between these models and other analogous data sources in terms of velocity profiles in the far wake. The actuator disc method was underpinned using the transient actuator line method, which showed good agreement from a quantitative and qualitative viewpoint. However, it required significant additional computational time when compared to the actuator disc method. Each of the models were developed and solved using complimentary commercially available CFD codes, ANSYS-CFX and ANSYS-Fluent. For this type of study, a critical evaluation of these codes was in all probability performed for the first time, where it is shown that for the studies investigated in this thesis ANSYS-CFX performed better than ANSYS-Fluent with respect to the computational effort (i.e. time and lines of code).
29
Saleh, Ahmed. „Enhancement of the IEEE 802.15.4 standard by energy efficient cluster scheduling“. Thesis, University of Huddersfield, 2015. http://eprints.hud.ac.uk/id/eprint/28530/.
Annotation:
The IEEE 802.15.4 network is gaining popularity due to its wide range of application in Industries and day to day life. Energy Conservation in IEEE 802.15.4 nodes is always a concern for the designers as the life time of a network depends mainly on minimizing the energy consumption in the nodes. In ZigBee cluster-tree network, the existing literature does not provide combined solution for co-channel interference and power efficient scheduling. In addition, the technique that prevents network collision has not been provided. Delay and reliability issues are not addressed in the QoS-aware routing. Congestion is one of the major challenges in IEEE 802.15.4 Network. This network also has issues in admitting real time flows. The aim of the present research is to overcome the issues mentioned above by designing Energy Efficient Cluster Scheduling and Interference Mitigation, QoS Aware Inter-Cluster Routing Protocol and Adaptive Data Rate Control for Clustered Architecture for IEEE 802.15.4 Networks. To overcome the issue of Energy efficiency and network collision energy efficient cluster scheduling and interference mitigation for IEEE 802.15.4 Network is proposed. It uses a time division cluster scheduling technique that offers energy efficiency in the cluster-tree network. In addition, an interference mitigation technique is demonstrated which detects and mitigates the channel interference based on packet-error detection and repeated channel-handoff command transmission. For the issues of delay and reliability in cluster network, QoS aware intercluster routing protocol for IEEE 802.15.4 Networks is proposed. It consists of some modules like reliability module, packet classifier, hello protocol module, routing service module. Using the Packet classifier, the packets are classified into the data and hello packets. The data packets are classified based on the priority. Neighbour table is constructed to maintain the information of neighbour nodes reliabilities by Hello protocol module. Moreover, routing table is built using the routing service module. The delay in the route is controlled by delay metrics, which is a sum of queuing delay and transmission delay. For the issues of congestion and admit real-time flows an Adaptive data rate control for clustered architecture in IEEE 802.15.4 Networks is proposed. A network device is designed to regulate its data rate adaptively using the feedback message i.e. Congestion Notification Field (CNF) in beacon frame received from the receiver side. The network device controls or changes its data rate based on CNF value. Along with this scalability is considered by modifying encoding parameters using Particle Swarm Optimization (PSO) to balance the target output rate for supporting high data rate. Simulation results show that the proposed techniques significantly reduce the energy consumption by 17% and the network collision, enhance the performance, mitigate the effect of congestion, and admit real-time flows.
30
Roberts, Joseph. „Synthesis and characterisation of nanoscale oxides for energy applications“. Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2005979/.
Annotation:
The motivation for this research is the synthesis and characterisation of nanostructured oxide materials for potential applications in renewable energy generation or storage. In particular, the research in this thesis addresses the development of nanostructured oxide materials which could be exploited as photovoltaics and transparent conductive oxides. The exploitation of anodised aluminium oxide (AAO) to fabricate nanostructured semiconductor pn-junctions as the basis photovoltaic devices is investigated. Various microstructures are modelled with the aim of identifying ones with high interface area and consequently high energy conversion efficiencies. Experiments reveal that AAO prepared using an oxalic acid electrolyte could be achieved with a growth rate of 5.7μm/h. The uniformity and size of the hexagonal cross-section pores is influenced by the first-step anodisation time. Atomic layer deposition (ALD) was used to coat commercially available AAO, to synthesise conformal nanotubes or wires. It was observed that the uniformity of the nanostructures breaks down towards the bulk of the AAO, without high exposures, due to the lack of precursor penetration. However, the proposed geometric mass-gain model to understand the process is supported by experimental mass gain measurements and how deposition occurs within the templates. A second materials system based on copper / copper oxide is also explored as a method of synthesising and controlling the formation of nanostructured oxide materials. The surface preparation of the starting copper sheet material was investigated and it was found to be pivotal in the nanoscale morphology achievable with subsequent heat treatment to grow nanowires and porous layers. Thermal growth of CuO and Cu2O on pre- treated copper foils at 500°C exhibited growth of high aspect ratio CuO nanowires. Further studies on the growth process disproved the vapour-liquid-solid and vapour-solid growth mechanisms for the nanowires and showed that tensile strain within the Cu substrate was the driving force behind the nanowire growth. The use of nanometre-scale ALD alumina barrier layers was employed to suppress spallation and preserve the nanowire surfaces. It was found that for samples with alumina layers between ~3 and 15nm the oxide spallation was significantly reduced and that for samples with ~20nm of alumina the diffusion of Cu atoms to the surface was hindered. Photovoltaic measurements were made on electrolytically synthesised Cu2O surfaces coated with ALD TiO2, ZnO and Ga-doped ZnO to form pn-junctions. The samples showed only weakly rectifying behaviour which was attributed to short-circuits between the n-type layers and the back contact. Several of the samples did show some difference in electrical response when under illumination indicating that, at least in some parts of the device, the pn-junction had formed. Lastly the growth and characterisation of ALD Ga-doped ZnO was investigated to determine the optimal doping levels for the growth of highly conductive and transparent oxides, to be used as a front contact for photovoltaic devices. It was found that Ga doping at around 1at% in ZnO produced film with the lowest resistivity. CdTe films were then grown onto substrates coated in 1at% Ga-doped ZnO and subjected to AM1.5 photovoltaic IV testing, yielding photovoltaic cells with conversion efficiencies ~10.8% and fill-factors of ~65%.
31
Rowe, Geoffrey Michael. „Application of the dissipated energy concept to fatigue cracking in asphalt pavements“. Thesis, University of Nottingham, 1996. http://eprints.nottingham.ac.uk/11888/.
Annotation:
Following a description of the general properties of asphaltic materials, a review is presented on fatigue damage. Fatigue element tests have been carried out using two types of procedures; uniaxial tension-compression and a trapezoidal cantilever beam. The data from the Trapezoidal test has been used to develop relationships between dissipated energy and the number of load cycles to crack initiation. A method has been developed which enables the stiffness loss during a fatigue test to be quantified in terms of the initial mixture rheology. In addition, an improved method for defining the crack initiation point, N1, has been developed along with the definition of an energy ratio to enable determination of fatigue life for intermediate modes of loading. An assessment of two tests involving indirect tension has been made. A series of tests were conducted in the Slab Test Facility to determine the performance of various asphaltic mixtures with respect to fatigue. These have been used to validate the results from the element tests and assess the suitability of different shift factors. A 2-dimensional Finite Element visco-elastic analysis method has been used to calculate dissipated energy in pavement structures. This method has been compared to an elastic analysis method. It was observed that the F.E. method is less sensitive to pavement thickness. The F.E. method has some potential for prediction of surface cracking and fatigue life but further work is needed to implement a 3 dimensional model. Finally, based upon an assessment of the results obtained, recommendations have been made for additional work involving materials testing, model development and pavement design.
32
Bailey, D. A. „The effect of damage on the energy absorption potential of composite structures“. Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/13560/.
Annotation:
This thesis describes work undertaken to investigate the effects of damage on the energy absorption potential of composite tubes. Tubes of various geometries and manufactured from either continuous filament random mat (CoFRM) or glass braid and polyester resin were subjected to various types of damage before testing. Damage types consisted of drilled holes, to simulate the use of drilling components for the need of assembly, impacts, to simulate damage that may occur through tool drops or items being kicked up during use and PET inserts to simulate delamination. Large glass CoFRM/polyester tubes with an outer diameter of 89.1mm and varying wall thicknesses were crushed quasi-statically at a speed of 5mmlmin. Small CoFRM and braided glass/polyester tubes with an outer diameter of 38.1mm and a 2mm wall thickness were tested quasi statically and dynamically at a speed of 5m1s. Tubes were tested undamaged and containing various sizes of holes, simulated delamination and impacts. Specific energy absorptions (SEA) and failure modes were compared. Threshold values of damage size have been found for each tube and test type, above which unstable failures and subsequent unpredictable reductions in energy absorptions occur. The small CoFRM tubes showed a decrease in SEA as the test rate increased and this was attributed to the rate dependency of the resin, causing greater fragmentation allowing fibres to bend more easily and without fracturing. The braided small tubes showed an increase in SEA as the test rate increased due to a change in the mode of failure attributed to a higher compressive strength at the increased rate. Relatively small hole sizes and impacts, of 5mm and 1.5J-3J, were seen to reduce the energy absorption of the materials tested at quasi-static test speeds. However, an increase in damage tolerance was identified as test rate increased and this was attributed to an increase in compressive strength and fracture toughness, and reduction in crush load, as the speed of test increased.
33
Hashim, Hasan. „Full-spectrum solar energy harvesting using nanotechnology-enabled photovoltaic/thermoelectric hybrid system“. Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/87143/.
Annotation:
Carbon emissions, climate change and the finite resource of fossil fuels are driving an increasing need for renewable energy, and in particular, an interest in photovoltaic (PV) cells. Most PV cells operate in temperatures above 25 oC, and the performance of PV cells reduces with increased operation temperature. This research aims to resolve some engineering issues by integrating PV cells with a thermoelectric generator (TEG). Integrating TEG with PV cells helps to transfer heat from the PV through the TEG to an actively or passively cooled heat sink. The temperature difference established across the TEG can generates additional electrical power by the Seebeck effect. The main objective of this research is to investigate the feasibility of developing a PV/TEG hybrid system that can offer better performance than that can be obtained from each individual system. The key parameters, which are crucial to the development of efficient hybrid system, were investigated. These include the temperature coefficient of PV cells, geometry of TEGs and thermal coupling between the PV and TEG. It was found that the dye sensitised solar cells (DSC) has a preferred temperature coefficient that are the most suitable for use in a PV/TEG system. In this work, a theoretical model was also developed for determination of the optimal geometry of the TEG for PV/TEG hybrid systems. A special type of DSCs was designed and fabricated which employ titanium as the counter electrode (other than conventional FTO-glass) to improve the thermal coupling between the PV and TEG. A unique DSC/TEG hybrid system was constructed using this special type of DSC and its generating performance was studied in comparison with a similar system that uses conventional FTO-glass counter electrode. The experimental results show that the power output and efficiency of the hybrid PV/TEG system with Ti counter electrode is significantly higher than the similar system with a conventional FTO-glass electrode due to an improved thermal coupling between the DSC and TEG. It is concluded that a hybrid PV/TEG system can provide improved performance beyond that of each individual system. However, the improvement can only be achieved with appropriate type of PV cells, optimised TEGs and advanced structures for integration, such as Ti counter electrode.
34
Vincent, Timothy A. „Development of a handheld breath analyser for the monitoring of energy expenditure“. Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/93856/.
Annotation:
Metabolic rate is not routinely assessed in healthcare for the general population, nor is it a measure commonly recorded for in-patients (incorrect feeding can slow post-operation recovery rate). For the general community, this lack of knowledge prevents the accurate determination of calorific need and is a factor contributing towards the onset of an overweight and an increasingly obese population. In the UK alone, obesity costs the National Health Service a staggering £5 billion annually. In this thesis a novel low-cost hand-held breath analyser is presented in order to measure human energy expenditure (EE). A unique optical CO2 sensor was developed, capable of sampling exhaled breath with a fast response time ~1 s and resilience to a humidity range of ~30 % to near saturated. The device was tested in a laboratory gas testing rig and a detection limit of ~25 ppm CO2 was measured. A low power metal oxide sensor (~100 mW) was developed to detect volatile organic compounds (VOCs) in the breath, for disease detection and investigation of the variation of inter-individual metabolism processes. The device was sensitive to acetone (100 to 300 ppm, which is a biomarker for type-I diabetes). Other VOCs, such as NO2 were tested (10 to 250 ppb). Further work includes investigating the inter-individual variance of metabolism processes, for which the metal oxide sensor would be well-suited. Software was developed to operate the gas testing rig and acquire sensor output data in real-time. An application was written for smartphones to enable EE measurements with the breath analyser, outside of a laboratory environment. Three hand-held analysers were constructed and tested with a trial of 10 subjects. A counterpart (benchmark) unit with medical grade commercial sensors (cost of ~£2500) and hospital respiratory rooms (reference) were included in the trial. The newly developed analysers improved upon the performance of the benchmark system (average EE measurement error +2.4 % compared to +7.9 %). The affordable device offered far greater accuracy than the traditional method often used by practitioners (predictive equations, error +41.4%). It is proposed a set of periodic (hourly) breath measurements could be used to determine daily EE. The EE analyser and associated low-cost sensors developed in this work offer a potential solution to halt the growing cost of an obese population and provide point-of-care health management.
35
Bao, Minxi. „Structural and functional integrity of energy-efficiency glazing units“. Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5289/.
Annotation:
Windows are the least insulated components in the modern buildings envelopes. The energy-efficiency glazing units have been developed and used to reduce the heat loss from windows. As a type of most common glass product, insulating glass units (IGUs) have been widely adopted in the residential and commercial buildings. A type of new design of glazing units, vacuum glazing units (VGUs), has also been developed to further enhance the insulation performance. Research on the structural/durability behaviours of such new insulating glazing units is relatively limited, although the structural behaviours and safety of monolithic or laminated glass panels have been abundantly studied. This thesis intends to fill in this gap by performing thorough assessments on the structural performance of IGUs and VGUs under various environmental actions.
36
Cemesova, Alexandra. „Enhancing BIM-based data transfer to support the design of low energy buildings“. Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/57565/.
Annotation:
Sustainable building rating systems and energy efficiency standards promote the design of low energy buildings. The certification process is supported by Building Performance Simulation (BPS), as it can calculate the energy consumption of buildings. However, there is a tendency for BPS not to be used until late in the design process. Building Information Modelling (BIM) allows data related to a buildings design, construction and operation to be created and accessed by all of the project stakeholders. This data can also be retrieved by analysis tools, such as BPS. The interoperability between BIM and BPS tools however is not seamless. The aim of this thesis is to improve the building design and energy analysis process by focusing on interoperability between tools, and to facilitate the design of low energy buildings. The research process involved the following: undertaking a literature review to identify a problematic area in interoperability, extending an existing neutral data transfer schema, designing and implementing a prototype which is based on the extension, and validating it. The schema chosen was the Industry Foundation Classes. This can describe a building throughout its lifecycle, but it lacks many concepts needed to describe an energy analysis and its results. It was therefore extended with concepts taken from a BPS tool, Passive House Planning Package, which was chosen for its low interoperability with BIM tools. The prototype can transfer data between BIM and BPS tools, calculate the annual heat demand of a building, and inform design decision-making. The validation of the prototype was twofold; case studies and a usability test were conducted to quantitatively and qualitatively analyse the prototype. The usability testing involved a mock-up presentation and online surveys. The outcome was that the tool could save time and reduce error, enhance informed decision making and support the design of low energy buildings.
37
Bottome, Kristofer John. „The energy absorption of damaged braided and non-crimp fibre composite material structures“. Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10173/.
Annotation:
The effects of pre-existing damage on the mode of failure and energy absorption characteristics of Non-Crimp Fabric (NCF) and biaxially braided tubular sections under axial loading were considered. Loading rate effects were incorporated by testing at quasi-static rates and impact rates up to 7ms-1 and the pre-existing damage was simulated through stress concentrations and out-of-plane impact damage. Circular and square geometries were tested, and a range of NCF and braided fibre architectures were investigated. A number of failure modes were exhibited. NCF tubes were seen to splay at static and impact rates; at impact rates a reduction in Specific Energy Absorption (SEA) was recorded. Braided tubes failed in a combination of buckling and splaying at static rates. Under dynamic conditions all braided samples splayed and where a change in failure mode was seen, SEA was increased. Both NCF and biaxially braided tubes have been shown to offer a much lower SEA than Continuous Filament Random Mat (CoFRM) samples. A threshold size of damage was observed, where, typically, below that threshold the SEA was unaffected by the damage, and above that size the tube would fail globally. The NCF tubes exhibited an improved damage tolerance over CoFRM and braided samples. The braided tubes showed a poor damage tolerance at quasi-static rates although results suggest that the architectures with high axial fibre content will have a higher damage tolerance. It has been shown that modelling damaged areas of tubes as a cut-out is a conservative approach to finding failure levels. Peak stress was seen to be the dominant factor in determining loading at global failure as samples could fail even though the crushing stress is less than the failure stress. Previous work upon Interlaminar Shear Strength (ILSS) and SEA has been investigated and shown to overestimate energy absorption for tubular specimens and found to apply only to samples that fail by progressive crush or fragmentation; for those that do fail in this mode a link between ILSS and SEA has been stated. A technique for determining SEA and for predicting the effect of a SCF on failure mode of composite tubes has been proposed using UCS (Ultimate Compressive Strength) data and SCF (Stress Concentration Factor) data.
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De, Almeida Katia Campos. „A general parametric optimal power flow“. Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28660.
Annotation:
The objective of an Optimal Power Flow (OPF) algorithm is to find the steady-state operation point of a generation-transmission system which minimizes a pre-specified cost function and meets a set of operational and/or security constraints. OPF algorithms are among the tools present in many Energy Management Systems and their usefulness is increasingly being recognized by power utilities.This thesis presents an algorithm which uses the parameters existing in the OPF problem to find its solution. These parameters can be in the objective function or the equality or inequality constraints. This algorithm is applied to a parameterized OPF model built according to the following criteria: (i) when all parameters present in the model are relaxed from their given levels, a solution can be trivially found for this parameterized problem and (ii) when all parameters are returned to their original values, the parameterized model is equal to the original OPF. As the initially relaxed parameters are returned to their original values, they define a sequence of OPF problems which converge to the original one. The algorithm is designed to track the optimal solutions of these intermediate problems until the optimum of the original OPF. This tracking is made in a systematic manner. By using a binary search or a linear prediction method, the algorithm finds the maximum increment of the parameters which allow only one inequality to be fixed at its limit or to be released. The parameters are then adjusted to their new values, defining a new OPF problem with known optimal active feasible set. As a consequence, the optimal solution of this new problem can be easily found by solving the first order optimality conditions by Newton's method. In this way, the optimum is tracked from one active feasible set to the next until the parameters reach their original values.
The parameterization permits the solution of the OPF problem for a fixed and variable load using the same mechanism described in the previous paragraph. As a result of this systematic tracking, the method is robust and able to provide a very good insight about the behaviour of the OPF solutions. In addition, the main difficulties encountered in solving the OPF problem are easily visualized and, in particular, the approach permits the differentiation of the potential causes for the failure of the tracking process, including the identification of unsolvable cases. The sensitivities of the optimal solution as a function of the parameters are also by-products of the method; including the Bus Incremental Costs and the System Incremental Cost as functions of the loads. The approach is also flexible enough to permit the simulation of line contingencies and of Flexible AC Transmission Systems (FACTS devices). The algorithm developed was tested in numerous networks with different objective functions and initializations and the results demonstrated the potential of this technique.
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Aziz, Alia Ruzanna. „The energy-absorbing characteristics of novel tube-reinforced sandwich structures“. Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2037907/.
Annotation:
This thesis presents the findings of a research study investigating the energy-absorbing characteristics of the foam sandwich cores reinforced with aluminium, steel and carbon fibre-reinforced polymer (CFRP) cylindrical tubes under quasi-static and dynamic loading conditions. Initial testing focused on establishing the influence of the length and inner diameter to thickness ratio (D/t) of the tubes on their specific energy absorption (SEA) characteristics. Following this, individual aluminium, steel and CFRP tubes were embedded in a range of foams with varying densities and the SEA was determined. The effect of increasing the number of tubes on the energy-absorbing response was also studied. In addition, preliminary blast tests were conducted on a limited number of sandwich panels. It has been shown that the stiffness of the foam does not significantly enhance the energy-absorbing behaviour of the metal tubes, suggesting that the density of the foam should be as low as possible, whilst maintaining the structural integrity of the part. Tests on the CFRP tube-reinforced foams have shown that the tubes absorb greater levels of energy with increasing foam density, due to increased levels of fragmentation. Values of SEA as high as 86 kJ/kg can be achieved using a low density foam in conjunction with dense packing of tubes. The SEA values of these structures compare very favourably with data from tests on a wide range of honeycombs, foams and foldcore structures. The crushing responses of the structures were predicted using the finite element method Abaqus and the predictions of the load–displacement responses and the associated failure modes are compared to experimental results. It is proposed that these models can be used for further parametric studies to assist in designing and optimising the structural behaviour of tube-reinforced sandwich structures.
40
Abobghala, Abdelmenem. „Assessing the energy efficiency of railway vehicles with wheelset active control“. Thesis, University of Huddersfield, 2018. http://eprints.hud.ac.uk/id/eprint/34756/.
Annotation:
Energy consumption in electric locomotives is principally the power consumed in traction motors. In order to reduce this energy consumption, the motion resistances of the train need to be reduced. These resistances include aerodynamics; inertial and grade forces; curving resistance; and bearing and wheel/rail friction. Though many factors such as gradient resistance cannot be modified, if a control system is included, curving resistance can be minimised by reducing the energy losses in the contact patches between wheel and rail. Therefore, operational practices could be modified in order to obtain the most appropriate wheelset attack angle between wheel and rail, and appropriate train speed. One solution is to implement a steering control system. The function of this control system is to monitor and control the wheelset lateral displacement or the attack angle of the wheelset. This could reduce the energy dissipated at the contact points between wheel and rail, consequently reducing the energy consumed by traction motors in railway vehicles. Therefore, the work presented in this thesis aims to design and develop a control method for combined vehicle traction and wheelset active steering control systems and to assess the energy efficiency of a rail vehicle under typical operational conditions. In order to achieve these aims, two dynamic models of a typical railway vehicle have been developed in MATLAB and Simulink. The first model comprises the electrical traction and mechanical system passive system). The second model includes the passive and the wheelset active steering control system (active system). These models are used to determine the relationship between traction energy consumption and the energy dissipated in the contact points between wheel and rail, and to compare the passive steering system to the wheelset active steering control system, determining the possibilities for energy saving. In order to assess the influence of the wheelset active steering control on the relationship between wheel and rail contact forces and traction power a series of deterministic track features are set comprising curve radii with different cant deficiencies and wheel conicities. Also a typical track profile from Leeds to Hull is used. From these simulations, the traction energy consumption, energy dissipated at the contact patches, and energy consumed by the steering actuators are calculated. Statistical analyses are used to understand the relationship between the traction power and wheelset motion dynamics (lateral displacement and attack angle). The active vehicle model scheme is used to investigate the improvement of the energy efficiency of a railway vehicle using active steering. The wheelset active steering control system analysis shows whether different combinations of vehicle speed, wheelset conicity and track curve radius lead to a reduction, no reduction, or an increase intraction power consumption. The probability of high power consumption under different conditions is assessed to ensure that it is reduced wherever possible. The ability of a forecasting model to predict the traction power consumption behaviour of railway vehicles from the wheelset motion dynamic is assessed. Findings show that the overall prediction accuracy is fairly similar to the power measured from the passive vehicle running on a track from Leeds to Hull. However, the algorithm does not perform effectively for the deterministic track features. Finally, the benefits of implementing wheelset active steering control systems in terms of the mitigation of contact forces between wheels and rails and how this mitigation influences traction energy consumption are evaluated to determine under what conditions energy can be saved.
41
Fok, Alan Tat-Kuen. „A contribution to the analysis of energy losses in transient pipe flow“. Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5421.
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Emeakaroha, Anthony. „Energy conservation through product integrated persuasive feedback using smart sensors in a university campus“. Thesis, University of Kent, 2014. https://kar.kent.ac.uk/48985/.
Annotation:
The world’s energy consumption is increasing. This has been attributed to global warming and increase in CO2 emission. Experts in this area are emphasising on the need to conserve energy both in industry and residential areas. This is especially true in University campuses where students do not have any direct insight or feedback on their energy consumption. Currently, there are few approaches aiming to reduce electricity usages in higher education institutions by providing students with feedback on their electricity consumption rates. These approaches suffer from the lack of motivations by the students to change their energy usage behaviours. To address this issue, they mainly provide students with incentives (gift rewards). However, their feedback systems present data only in near real time using data loggers and Modbus data collector, which are characterised with a slow and unstable data transfer rate. Furthermore, they are not designed for long-term deployment in a wider campus energy management environment. Thus, the challenges for reducing energy consumption and carbon emissions in the higher education sector still remain. To adequately address these challenges, a novel initiative was developed and implemented in this thesis. It includes a dedicated interface design, hardware and software configurations to form a robust methodology known as: Integrated Persuasive Technology and Energy Delegate (IPTED). Energy delegates were appointed to facilitate energy conservation and carbon emission reduction. This thesis presents the complete architecture of the IPTED, its system interface and the real-time measurement feedback and output strategies. To demonstrate its applicability and to assess its effectiveness, the student halls of residence at the University of Kent were used as a use case scenario to test the system with psychology tailored initiatives. The deployment of IPTED in the student residential halls shows that, instantaneous real-time energy feedback with a visual interface when combined with a human factor (energy delegate) can provide significant energy savings. Overall, the intervention revealed that, the use of real-time feedback system reduces energy consumption significantly when compared to baseline readings. Interestingly, it was found that applying the combination of real-time feedback system with energy delegate in the 8 experimental halls resulted in high energy consumption reduction of 37% when compared to the baseline. This amounts to the savings of 1526.73 kWh of energy and 800.92 kg of CO2. On the contrary, the 8 non-experimental halls, which were exposed to the real-time feedback and weekly email alert, resulted in 3.5% energy consumption reduction when compared to the baseline. This amounts to the savings of only 165.00 kWh of energy and 86.56 kg of CO2. These results show the novelty and significance of our contributions towards energy consumption and CO2 emission reduction. 3.5% energy consumption reduction when compared to the baseline. This amounts to the savings of only 165.00 kWh of energy and 86.56 kg of CO2.
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Aldossary, Naief. „Domestic sustainable and low energy design in hot climatic regions“. Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/70748/.
Annotation:
Low energy building methods, and the corresponding economic and environmental aspects, are an important area of consideration in many developed countries. Saudi Arabia characterized by its hot climates and geographical location in a global region renowned for its high energy consumption and carbon emission rates. Consequently, this research aims to foster the development of low energy housing in Saudi Arabia and establish a low carbon domestic design framework for Saudi Arabia that takes into account the local climatic conditions, context and socio-cultural challenges. In order to fulfil the above stated aims, this research establishes a definition system for low energy consumption in kWh/m² for the Saudi Arabian climate. To achieve the aims stated above, a comprehensive, four stage study has been performed. This investigation has attempted to: (a) identify factors resulting in high energy consumption in domestic buildings in Saudi Arabia; (b) identify the weaknesses of housing design in terms of architectural layouts and mass, house envelope design and construction materials used, and on-site renewable energy strategies; (c) establish and develop a low carbon domestic design framework that supports architects, civil engineers and building professionals in the design of sustainable homes for the Saudi Arabian climate, context and cultural requirements; and (d) propose three different, viable housing prototypes employing the established framework, thereby validating that framework through the identification of their energy consumption levels. Each stage of this research utilizes a specific methodology: public survey analysis; site visits and modeling analysis; expert consultation, using the Delphi technique approach; and the validation analysis approach. This study contributes to the body of knowledge within this field by offering a low carbon domestic framework for the design of low energy homes in Saudi Arabia. These findings are broadly applicable to other regions with similar climatic conditions and cultural requirements, such as those in the Middle East and GCC countries. The findings suggest that an energy reduction of up to 71.6 % is possible. Therefore, the system for low energy consumption level standards is suggested as a range between 77 kWh/m² and 98 kWh/m². The comprehensive economic and environmental benefits of these reductions have been analysed and benchmarked against the current situation in selected developed countries.
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Jayan, Bejay. „Real-time Multi-scale Smart Energy Management and Optimisation (REMO) for buildings and their district“. Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/99480/.
Annotation:
Energy management systems in buildings and their district today use automation systems and artificial intelligence (AI) solutions for smart energy management, but they fail to achieve the desired results due to the lack of holistic and optimised decision-making. A reason for this is the silo-oriented approach to the decision-making failing to consider cross-domain data. Ontologies, as a new way of processing domain knowledge, have been increasingly applied to different domains using formal and explicit knowledge representation to conduct smart decision-making. In this PhD research, Real-time Multiscale Smart Energy Management and Optimisation (REMO) ontology was developed, as a cross-domain knowledge-base, which consequently can be used to support holistic real-time energy management in districts considering both demand and supply side optimisation. The ontology here, is also presented as the core of a proposed framework which facilitates the running of AI solutions and automation systems, aiming to minimise energy use, emissions, and costs, while maintaining comfort for users. The state of the art AI solutions for prediction and optimisation were concluded through authors involvement in European Union research projects. The AI techniques were independently validated through action research and achieved about 30 - 40 % reduction in energy demand of the buildings, and 36% reduction in carbon emissions through optimisation of the generation mix in the district. The research here also concludes a smart way to capture the generic knowledge behind AI models in ontologies through rule axiom features, which also meant this knowledge can be used to replicate these AI models in future sites. Both semantic and syntactic validation were performed on the ontology before demonstrating how the ontology supports the various use cases of the framework for holistic energy management. Further development of the framework is recommended for the future which is needed for it to facilitate real-time energy management and optimisation in buildings and their district.
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Elsayed, Hatim Ibrahim. „Utility applications of smart online energy systems : a case for investing in online power electronics“. Thesis, City University London, 2014. http://openaccess.city.ac.uk/12238/.
Annotation:
The backbone of any power grid, the transmission and sub-transmission networks, should be flexible, robust, resilient and self-healing to cope with wide types of network adverse conditions and operations. Power electronic applications are making a major impact on the present and future state of power systems generation, transmission and distribution. These applications include FACTS (Flexible Alternating Current Transmission), HVDC (High Voltage Direct Current) in transmission and Custom Power devices in distribution. FACTS devices are some of the advanced assets that network planners can use to make the transmission grid become more flexible and robust. Many established research ideas to advance operations of these devices have been published in the open literature over the last ten years. The most recent publications in this field are reviewed in this thesis. A critical analysis of literature and existing conditions reveals a range of potentials that are ideal for development in Qatar’s increasingly strained electricity network. As a result of demand surge in Qatar in recent years and the forecast to grow in the same rate, the need for improvement in Qatar Power Transmission System (QPTS) is great and significant. Conventional planning and operational solutions such as conductor up-rating, and fixed series capacitors (FSC) are considered. However there are growing challenges on getting new rights of ways for new overhead lines and even corridors for new cables. Advanced FACTS devices are considered for dynamic control of power flows and voltages, such as TCSC (Thyristor Controlled Series Capacitor) and GUPFC (Generalized, Unified Power Flow Controller). The research in this thesis examines the potential for QPTS to improve and develop, with emphasis on increased output through integrated online energy systems, online FACTS and HVDC controllers based on synchrophasor measurements. The devices are modelled in Siemens PTI’s PSS®E software, through steady-state mode case study to investigate power flow control and voltage support. Comparison between similar FACTS technologies, such as SVC and STATCOM, is also presented. The improvement in power flow imbalance between transmission lines with different ratings and lengths is studied. The FACTS devices are tested for voltage support to enhance the network voltage profile and hence increase security and reliability to important industrial customers. Optimization techniques of the FACTS devices allocation and rating are generally discussed considering the voltage improvement and optimal power flow control. The results achieved showing the network improvement with using the FACTS are presented in the case studies. In a separate case study, applying medium voltage custom power devices to convert DC battery storage and photovoltaic energy into AC energy using a power conversion system is discussed. The dynamic mode of the STATCOM is modelled in QPTS in the succeeding case study using the same software and compared with the capacitor banks. This is followed by another case of HVDC analysis modelled with and without STATCOM present. The thesis discussed the real time operation and control of power system physical parameters in QPTS using capacitors, FACTS and HVDC. The key contribution of this thesis is the application and resting of all sorts of FACTS and HVDC in QPTS. The system wide area, coordinated control of FACTS (Online Power Electronics-OPE) is a new concept. Another major contribution is being able to look at a system wide approach for a transmission smart grid application. The results of thesis are presented in international conferences in USA, Hong Kong, France, Portugal, and locally in the Arabian Gulf (Dubai, Oman and Qatar). The thesis’s papers are listed in the ‘References’ section and in Appendix-F.
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Marian, Laurentiu. „The tuned mass damper inerter for passive vibration control and energy harvesting in dynamically excited structural systems“. Thesis, City University London, 2016. http://openaccess.city.ac.uk/14884/.
Annotation:
A novel passive vibration control configuration, namely the Tuned-Mass-Damper-Inerter (TMDI) is proposed in this work. The TMDI combines the “inerter”, a mechanical two-terminal flywheel device developing resisting forces proportional to the relative acceleration of its terminals, with the well-known and widely used in various passive vibration control applications Tuned-Mass-damper (TMD). Introduced as a generalization of the TMD, the TMDI takes advantage of the “mass amplification effect” of the inerter to achieve enhanced performance compared to the classical TMD. For linear harmonically excited primary systems, analytical closed-form expressions are derived for optimal TMDI design/tuning parameters using the well-established and widely applied for the case of the classical TMD semi-empirical fixed-point theory. It is shown that for the same attached mass the TMDI system is more effective than the classical TMD to suppress vibrations close to the natural frequency of the uncontrolled primary system, while it is more robust to de-tuning effects. Moreover, it is analytically shown that optimally designed TMDI outperforms the classical TMD in minimizing the displacement variance of undamped linear single-degree-of-freedom (SDOF) white-noise excited primary systems. For this particular case, optimal TMDI parameters are derived in closed-form as functions of the additional oscillating mass and the inerter constant. Furthermore, pertinent numerical data are furnished, derived by means of a numerical optimization procedure, for classically damped mechanical cascaded chain-like primary systems base excited by stationary colored noise. This exemplifies the effectiveness of the TMDI over the classical TMD to suppress the fundamental mode of vibration for linear MDOF structures. It is concluded that the incorporation of the inerter in the proposed TMDI configuration can either replace part of the TMD vibrating mass to achieve lightweight passive vibration control solutions, or improve the performance of the classical TMD for a given TMD mass. The TMDI is further applied for passive vibration control of seismically excited building structures. An input non-stationary stochastic process compatible with the elastic design spectrum of the European aseismic code provisions (EC8) is assumed. The effectiveness of the proposed TMDI configuration over the classical TMD is assessed by performing response history analyses for an ensemble of EC8 spectrum compatible field recorded strong ground motions. The optimally tuned TMDI solution achieves considerable reduction of the peak average top floor displacement and peak average top floor accelerations of the considered primary structures compared to the one achieved by the optimally designed classical TMD, assuming the same additional mass in both cases. Furthermore, the TMDI configuration achieves significant reduction in the maximum displacement of the additional oscillating mass. In this study, the primary structures are assumed to behave linearly in alignment with current trends in performance based requirements for minimally damaged structures protected by passive control devices. Furthermore, optimally designed TMDI is applied for vibration suppression and energy harvesting via an electromagnetic device which transforms the mechanical kinetic energy into electrical energy. Unlike the case of traditional energy harvesting enabled TMD systems, the amount of available energy to be harvested by the herein proposed TMDI-based harvester is leveraged by changing the intensity of the mass amplification effect of the inerter, through mechanical gearing, without changing the weight of the TMDI system. Therefore, the inclusion of the inerter adds a “degree of freedom” or a design parameter to the classical TMD-based harvesters allowing to control the trade-off between vibration suppression and energy harvesting in a more flexible manner. Overall, the herein reported numerical data and analytical work provide evidence that the TMDI offers a novel promising solution for passive vibration control and energy harvesting. Most importantly, it opens several new research paths involving numerical/parametric work, as well as, prototyping, experimental testing and field deployment.
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Ramlan, Roszaidi. „Effects of non-linear stiffness on performance of an energy harvesting device“. Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/69588/.
Annotation:
Vibration-based energy harvesting devices have received much attention over the past few years due to the need to power wireless devices in remote or hostile environments. To date, resonant linear generators have been the most common type of generators used in harvesting energy for such devices. Simple tuning and modelling methods make it a more favourable solution theoretically if not practically. This thesis considers the limitations of resonant linear devices and investigates two non-linear generators to see if they can outperform the linear devices in certain situations. So far, in most of the literature, the energy harvester is assumed to be very small dynamically compared to the source so the source is not aected by the presence of the device. This thesis considers how the dynamics of the source is aected by the device if its impedance is signicant compared to the source. A tuning condition for maximum power transfer from the source to the device is derived. This tuning condition converges to the one presented in most of the literature when the impedance of the device is assumed to be very small compared to that of the source i.e. tuned so that the natural frequency of the device equals the excitation frequency. For the case when the impedance of the device has a negligible eect on the source, the performance of the device is only limited to a narrow frequency band and drops o rapidly if mistuned. To accommodate the mistuning limitations, new types of generators are proposed mainly by using a non-linear mechanism. These mechanisms are made up of a non-linear spring connected together with a mass and a linear viscous damper i.e. the energy harvesting component. The analysis of the fundamental performance limit of any non-linear device compared to that of a tuned linear device is carried out using the principal of conservation of energy. The analysis reveals that the performance of a non-linear device in terms of the power harvested is at most 4= greater than that of a tuned linear system and is strongly dependent upon the type of the non-linearity used. Two types of non-linear mechanisms are studied in this thesis. The rst one is a non-linear bi-stable mechanism termed a snap-through mechanism which rapidly moves the mass between two stable states. The aim is to steepen the displacement response curve as a function of time which results in the increase of velocity for a given excitation, thus increasing the amount of power harvested. This study reveals that the performance of the mechanism is better than a linear system when the natural frequency of the system is much higher than the excitation frequency. The study also shows that the power harvested by this mechanism rolls o at a slower rate compared to that of the linear system. Another non-linear mechanism described in this thesis uses a hardening-type spring. The aim of this mechanism is to provide a wider bandwidth over which the power can be harvested. This thesis presents numerical solutions and approximate analytical solutions for the bandwidth and eective viscous damping of a non-linear device employing a hardening-type stiness. Unlike the linear system, in which the bandwidth is only dependent on the damping ratio, it is found that the bandwidth of the nonlinear device depends on both the strength of the nonlinearity and the damping ratio. Experimental results are presented to validate the theoretical results. This thesis also investigates the benets of the non-linear device for a low frequency and high amplitude application using the measured vibration inputs from human motion such as walking and running. The eect of harmonics on the power harvested is also studied. Numerical simulations are carried out using measured input vibrations from human motion to study the best placement of the natural frequency of the device across the range of harmonics.
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Pitié, Frédéric. „High temperature thermal energy storage : encapsulated phase change material particles : determination of thermal and mechanical properties“. Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/57108/.
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Shan, Jian. „Application of the sub-region mixed energy principle to numerical modelling of prestressed clad cable nets“. Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/107966/.
Annotation:
The sub-region mixed energy principle is applied to the analysis of pre-stressed clad cable net structures, with the emphasis on the interaction between the cable net and the cladding panels. The sub-region mixed energy principle is reformulated with special consideration of the conditions under which the principle is applicable to geometrically non-linear problems. The established governing equations are solved using the dynamic relaxation technique. Comparison of the results from the proposed numerical approach and from an experimental model shows good agreement. Two numerical models, a five-force model and a four-force model, arc developed to represent the behaviour of flat or warped quadrilateral panels. The flexibility matrices of these models are calculated using the finite element method. The influence of curvature of the panels on flexibility, and the influence of different finite element meshes on the results of flexibility analysis are investigated. The five-force model is proved to be capable of expressing any self-balanced nodal forces applied to a panel. Several computer programs for the analysis of clad network structures are introduced. These programs are the result of optimisation of dynamic relaxation, involving viscous and kinetic dampings respectively, and different selections of parameters that control the speed of convergence of the method, mainly the fictitious masses. Numerical examples are calculated and the effects of using these programs on the rate of convergence of the solution are discussed.
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Doerffel, Dennis. „Testing and characterisation of large high-energy lithium-ion batteries for electric and hybrid electric vehicles“. Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/47951/.
Annotation:
This thesis considers the drivetrain and battery system requirements of Hybrid Electric Vehicles. The data herein proves that a series hybrid electric drivetrain with Lithium-ion batteries and plug-in recharge promises to be viable and sustainable. However, for mass production of series HEVs comprehensive performance characteristics and prediction of ageing behaviour of Lithium-ion batteries is essential but currently not available. The main part of the thesis, following a graphical comparison of different energy storage solutions, is a detailed treatise on large Li-ion batteries. Construction and Li-ion working principles are summarised, together with several effects such as Peukert and memory effects, ageing of Li-ion cells, their temperature dependence and safety, and limits of charging/discharging. Preliminary performance tests on 50 and 100 Ah Li-ion cells showed the necessity for a careful investigation of suitable reference conditions in order to achieve reproducibly precise results from repeated discharge/charge cycles. Then the main tests result in detailed graphs and tables of the discharge and charge characteristics. These main tests include effects of rate of discharge, energy-efficiency, temperature, resting time between test-cycles, hysteresis, ageing, and degradation. A new testing method that is based on the step response technique is suggested and investigated to whether it gives a meaningful but rapid measure of open circuit voltage and equivalent circuit models of the battery. Statistically significant theoretical models, equations and graphs are included. The Appendix gives summaries of the author's seven main publications and presentations dealing with Systems Approach and five publications on Large Li-ion batteries, followed by most of these in full.