In this thesis, the spectrum and energy efficiency of cooperative spectrum prediction (CSP) in cognitive radio networks are investigated. In addition, the performance of CSP is evaluated using a hidden Markov model (HMM) and a multilayer perceptron (MLP) neural network. The cooperation between secondary users in predicting the next channel status employs AND, OR and majority rule fusion schemes. These schemes are compared for HMM and MLP predictors as a function of channel occupancy in terms of prediction error, spectrum efficiency and energy efficiency. The impact of busy and idle state prediction errors on the spectrum efficiency is determined. Further, the spectrum efficiency is compared for different numbers of primary users (PUs). Simulation results are presented which show a significant improvement in the spectrum efficiency using CSP with the majority rule at the cost of a small degradation in energy efficiency compared to single spectrum prediction (SSP) and traditional spectrum sensing (TSS). The HMM predictor provides better performance than the MLP predictor. Moreover, the total probability of prediction error with the majority rule provides the best performance compared to SSP and the other fusion rules. On the other hand, the AND and OR rules have the worst performance in the high and low traffic cases, respectively. The majority rule provides a good tradeoff between busy and idle state prediction errors compared with the AND and OR rules and SSP. Further, a reduction in the busy state prediction error increases the SE more compared to a reduction in the idle state prediction error. / Graduate

While more efficient use of energy is increasingly vital to the development of the modern industrialized world, emerging visualization tools and approaches of telling data stories provide an opportunity for the exploration of a wide range of topics related to energy consumption and conservation (Olsen, 2017). Telling energy stories using data visualization has generated great interest among journalists, designers and scientific researchers; over time it has been proven to be effective to provide knowledge and insights (Holmes, 2007). This thesis proposes a new angle of tackling the challenge of designing visualization experience for building energy data, which aims to invite the users to think besides the established data narratives, augment the knowledge and insight of energy-related issues, and potentially trigger ecological responsible behaviors, by investigating and evaluating the efficacy of the existing interactive energy data visualization projects, and experimenting with user-centric interactive interface and unusual visual expressions though the development of a data visualization prototype.

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Rapporten redovisar resultatet från energikartläggningen samt utredningen om kylsystemet som genomförts på glassgrossisten i Umeå. En övergripande studie av hela verksamheten med samtliga tekniska system har utförts. Grossisten ämnar minska sin klimatpåverkan som orsakas av energianvändning i fastigheten samt läckage av köldmedium från kylanläggning och fordonskylaggregat. Grossisten förbrukar frånsett bränsle till lastbilarna endast elenergi. Följande energiaspekter har framkommit som betydande för verksamheten:   Total energianvändning                            394 MWh Kylanläggning                                          258 MWh      (65% av total energianvändning) Kylaggregat lastbilar                                75   MWh      (19% av total energianvändning) Kylanläggningen utgör en stor del av grossistens totala energianvändning och måste efter beslut från EU:s f-gasförordning åtgärdas innan år 2020 då ett service- och underhållsförbud träder i kraft för det befintliga köldmediet.   Utredningen avser besvara hur man bäst tillmötesgår detta förbud, konvertera och ersätta köldmediet för fortsatt drift av den befintliga anläggningen eller investera i en ny klimatneutral kylanläggningstyp. Efter inspektion av kylsystemet samt genomförd studie om kylanläggningar och köldmedier rekommenderas att investera i en ny klimatneutral transkritisk koldioxidkylanläggning. En prisuppskattning är gjord och har uppskattats kosta mellan 1,3 – 1,5 mkr.   Transmission (värmeförluster genom klimatskal) och infiltration (ofrivillig ventilation) står för 50 % av den totalt avgivna energin. Avgiven värmeenergi via kylanläggningens kondensorfläktar på taket står för 18 % och lastbilarnas kylaggregat 19 %. Förslag på effektiviseringsåtgärder som framtagits efter energikartläggningen är följande: Installera en luftridå för att minska infiltrationsflöden i portöppning mellan frys- och varmlager. Installera timerstyrda motorvärmare på gårdsplanen. Tillsätta ett nytt ventilationsaggregat med roterande värmeväxlare Täta kring nödutgången på fryslagret Utförs alla effektiviseringsåtgärder beräknas en minskning av energianvändningen med 42 MWh, detta utgör 11% av grossistens totala energitillförsel.   I samband med en installation av en transkritisk koldioxidkylanläggning finns stora möjligheter att installera systemet så att den högtempererade kondensorvärmen kan tillvaratas för värmeåtervinning. Den heta gasvärmen kan förvärma tilluften i ventilationsaggregaten samt värma tappvarmvatten. Detta skulle bidra till att sänka det totala energibehovet ytterligare. / The report presents the results of the energy mapping and the investigation of the cooling system performed at the ice cream wholesaler GB Glass in Umeå. An overall study of the entire operation with all technical systems has been performed. GB glass aims to reduce its climate impact caused by energy consumption in the property as well as leakage of refrigerant from the cooling system and vehicle refrigeration equipment. Except fuel for trucks the wholesaler only consumes electricity. The following energy aspects have been identified as significant for the business:   Total energy use                                       394 MWh Cooling system plant                                258 MWh      (65% of total total energy use) Refrigeration trucks                                 75   MWh      (19% of total total energy use) The cooling system plant constitutes a major part of the wholesaler's total energy use and must be rectified due to a decision by the EU's F-Gas Regulation by 2020 when a service and maintenance prohibition carries out for the existing refrigerant. The investigation concerns how to best accommodate this prohibition, convert and replace the refrigerant for continued operation of the existing plant or invest in a new climate-neutral type. After inspection of the cooling system and completed study of cooling systems and refrigerants, it is recommended to invest in a new climate-neutral transcritical carbon dioxide plant. A price estimate has been made and has been estimated to cost between 1.3 - 1.5 million.  Transmission (thermal loss through climate scale) and infiltration (involuntary ventilation) accounts for 50% of the total energy delivered. Ceded heat energy by the cooling plants condenser fans on the roof accounts for 18% and the truck's cooling units 19%. Proposals for efficiency enhancements developed after the energy survey are as follows:  Install an air curtain to reduce infiltration flows in the doorway between freezing and storage Install timer-controlled engine heaters on the yard Add a new ventilation unit with rotary heat exchanger Seal around the emergency exit on the freezer Performing all efficiency measures is estimated to reduce energy consumption by 42 MWh, which represents 11% of the wholesaler's total energy supply. In connection with the installation of a transcritical carbon dioxide cooling system, there is a great opportunity to install the system so that the high temperature condenser heat can be used for heat recovery. The hot gas heater can preheat the supply air in the ventilation units as well as heating the tap water. This would help to further reduce the overall energy demand.

Elanvändningen till ventilation har ökat med 40 % sedan 1990 i Sverige. Ventilationen är en miljöbov enligt undersökningar som visar att elanvändningen till ventilationssystemens fläktar kan reduceras. Minskning av elförbrukningen kan t.ex. uppnås genom utbyte av fläktmotor till en EC-motor eller till en fläkt med bakåtböjda skovlar och direktdrift. Effektivieringsåtgärder kan ge en lägre elförbrukning på upptill 50 % i vissa applikationer. Ventilationsfläktarna i Sverige förbrukar 12,3 TWh per år. Idag har 175 000 ventilationsaggregat en för hög elanvändning och saknar värmeåtervinning. Enligt Energimyndigheten har området ventilation en stor besparingspotential eftersom energianvändningen till ventilation kan minska med 30 % (3,5 TWh), vilket ungefär motsvarar vindkraftsproduktionen i Sverige under ett år. Det analysverktyg som utvecklats i detta examensarbete är användarvänligt utformat och är tänkt som ett hjälpmedel vid utvärdering av funktion och effektivitet i luftbehandlingssystem. Verktyget analyserar mätdata från luftbehandlingssystemet och producerar nyckeltal som sedan jämförs mot givna nyckeltal och riktvärden, samt myndigheters gällande krav. Analysverktyget har provats på ett referensobjekt och fungerade som tänkt men får, i nuvarande utformning, anses vara en prototyp som kan vidareutvecklas. Viss utbildning krävs innan användning av analysverktyget sker, med hänsyn till elsäkerhet och mätnoggrannhet. Detta examensarbete avser vidare att kartlägga hur stor besparingspotential det finns för energieffektivisering av byggnaders ventilation samt att utveckla ett beräkningsverktyg för att kunna möta efterfrågan som troligtvis kommer att uppstå från fastighetsägare som vill spara energi. / Electricity consumption for ventilation has increased by 40% since 1990 in Sweden. Ventilation is an environmental villain since inquiries indicates that the electricity consumption for ventilation system fans can be much reduced. Reduction of electricity consumption for ventilation purposes can be achieved through e.g. the exchange of fan motors to EC motors or to fans with backward curved blades and direct drive. Such measures can provide reduced power consumption by up to 50 % in some applications. The ventilation fans in Sweden consume 12.3 TWh each year. Today Sweden has 175 000 ventilation systems with too high consumption of electricity and no heat recycling. According to the Swedish Energy Agency the ventilation sector has a large potential for savings and the energy consumption for ventilation could be lowered by 30 % (3,5 TWh), which roughly corresponds to the total annual wind power production in Sweden. The Analytical tool developed in this thesis work is designed to be user friendly and is thought to be an aid when evaluating functionality and efficiency in air treatment system. The tool analyzes data from measurements and produces key ratios which are then compared with given key ratios and standard guidelines. The Analysis tool was tested on one reference object and functioned as intended, but may at this stage be considered as a prototype that can be further developed. Specific training will be required before using the analysis tool with consideration to electrical safety and accuracy of measurement. This thesis work aims at evaluating the potential savings within air treatment systems in energy efficient buildings, and to develop a calculation tool to meet the demand that is likely to arise from property owners who want to save energy.

Data traffic demand has been increasing exponentially and this trend will continue over theforeseeable future. This has forced operators to upgrade and densify their mobile networks toenhance their capacity. Future networks will be characterized by a dense deployment of different kinds of base stations (BSs) in a hierarchical cellular structure. However network densification requires extensive capital and operational investment which limits operator revenues and raises ecological concerns over greenhouse gas emissions. Although networks are planned to support peak traffic, traffic demand is actually highly variable in both space and time which makes it necessary to adapt network energy consumption to inevitable variations in traffic demand. In this thesis, stochastic geometry tools are used to perform simple and tractable analysis of thecoverage, rate and energy performance of homogeneous networks and heterogeneous networks(HetNets). BSs in each tier are located according to independent Poisson Point Processes(PPPs) to generate irregular topologies that fairly resemble practical deployment topologies. The homogeneous network is optimized to determine the optimal BS density and transmit power configuration that minimizes its area power consumption (APC) subject to both coverage and average rate constraints. Results show that optimal transmit power only depends on the BSpower consumption parameters and can be predetermined. Furthermore, various sleep modemechanisms are applied to the homogeneous network to adapt its APC to changes in userdensity. A centralized strategic scheme which prioritize BSs with the least number of usersenhances energy efficiency (EE) of the network. Due to the complexity of such a centralizedscheme, a distributed scheme which implements the strategic algorithm within clusters of BSsis proposed and its performance closely matches that of its centralized counterpart. It is more challenging to model the optimal deployment configuration per tier in a multi-tier HetNet. Appropriate assumptions are used to determine tight approximations of these deployment configurations that minimize the APC of biased and unbiased HetNets subject tocoverage and rate constraints. The optimization is performed for three different user associationschemes. Similar to the homogeneous network, optimal transmit power per tier also depends onBS power consumption parameters only and can also be predetermined. Analysis of the effect of biasing on HetNet performance shows appropriate biasing can further reduce the deploymentconfiguration (and consequently the APC) compared to an unbiased HetNet. In addition, biasing can be used to offload traffic from congesting and high-power macro BSs to low-power small BSs. If idle BSs are put into sleep mode, more energy is saved and HetNet EE improves. Moreover, appropriate biasing also enhances the EE of the HetNet.

In the current global climate of declining fossil fuel reserves and due to the impact of industry on the natural environment, industrial sustainability is becoming ever more important. However, sustainability is quite a vague concept for many, and there are a range of interpretations of the word. If the resource efficiency of a factory is taken as a measure of its sustainability, then the concept becomes better defined and quantifiable. In order to analyse the resource efficiency of a factory and suggest improvements, all flows through the manufacturing system need to be modelled. However the factory is a complex environment, there is a wide variation in the quality levels of energy as well as the composition of material flows in the system. The research presented in this thesis shows how the thermodynamics-based concept of ‘exergy’ can be used to quantify the resource efficiency of a factory. The factory is considered an ‘integrated system’, meaning it is composed of the building and the production processes, both interacting with each other. This is supported by three case studies in different industries that demonstrate the practical application of the approach. A review of literature identified that it was appropriate to develop a novel approach that combined exergy analysis with the integrated view of the factory. Such an approach would allow a ‘holistic’ assessment of resource efficiency for different technology options possibly employable. The development of the approach and its illustration through practical case studies is the main contribution of the work presented. Three case studies, when viewed together, illustrate all aspects of the novel exergy based resource accounting approach. The first case study is that of an engine production line, in which the resource efficiency of this part of the factory is analysed for different energy system options relating to heating ventilation and air conditioning. Firstly, the baseline is compared with the use of a solar photovoltaic array to generate electricity, and then a heat recovery unit is considered. Finally, both of these options were used together, and here it is found that the non-renewable exergy supply and exergy destruction are reduced by 51.6% and 49.2% respectively. The second case study is that of a jaggery (a sugar substitute) production line. The exergy efficiency of the process is calculated based on varying the operating temperature of the jaggery furnace. The case study describes the modelling of al flows through the jaggery process in terms of exergy. Since this is the first example of an exergy analysis of a jaggery process, it can be considered a minor contribution of the work. An imaginary secondary process that could utilize the waste heat from the jaggery process is considered in order to illustrate the application of the approach to industrial symbiosis. The non-renewable exergy supply and exergy destruction are determined for the baseline and the alternative option. The goal of this case study is not to present a thermally optimized design; rather it illustrates how the exergy concept can be used to assess the impact of changes to individual process operations on the overall efficiency in industrial symbiosis. When considering natural resource consumption in manufacturing, accounting for clean water consumption is increasingly important. Therefore, a holistic methodology for resource accounting in factories must be able to account for water efficiency as well. The third case study is that of a food production facility where the water supply and effluent are modelled in terms of exergy. A review of relevant literature shows that previously, the exergy content of only natural water bodies and urban wastewater had been quantified. To the author’s knowledge, this is the first example of applying this methodology of modelling water flows in a manufacturing context. The results show that due to a high amount of organic content in food process effluent, there is significant recoverable exergy in it. Therefore, a hypothetical water treatment process was assumed to estimate the possible savings in exergy consumption. The results show that at least a net 4.1% savings in terms of exergy could be possible if anaerobic digestion water treatment was employed. This result can be significant for the UK since the food sector forms a significant portion of the industry in the country. Towards the end of the thesis, a qualitative study is also presented that aims to evaluate the practical utility of the approach for the industry. A mixed method approach was used to acquire data from experts in the field and analyse their responses. The exergy based resource accounting method developed in this thesis was first presented to them before acquiring the responses. A unanimous view emerged that the developed exergy based factory resource accounting methodology has good potential to benefit industrial sustainability. However, they also agreed that exergy was too complex a concept to be currently widely applied in practice. To this effect, measures that could help overcome this barrier to its practical application were presented which form part of future work.

Mobile devices have evolved rapidly in recent years and increased usage and performance are pushing contemporary battery technology to its limits. The constrained battery resources mean that the importance of energy-efficient application design is growing and in this regard wireless network accesses are a major contributor to a mobile device's overall energy consumption. Additionally, the energy consumption characteristics of modern cellular technologies make small volumes of poorly scheduled traffic account for a substantial share of a device's total energy consumption. However, quantifying the communication energy footprint is cumbersome, making it difficult for developers to profile applications from an energy consumption perspective and optimize traffic patterns. This thesis examines the traffic patterns of the Android client of the popular multimedia streaming service Spotify with the intention to reduce its energy footprint, in terms of 3G energy consumption. The application's automated test environment is extended to capture network traffic, which is used to estimate energy consumption. Automated system tests are designed and executed on a physical Android device connected to a 3G network, shedding light on the traffic patterns of different application features. All traffic between the Spotify client application and the backend servers is encrypted. To extract information about the traffic, the application code is instrumented to output supplementary information to the Android system log. The system log is then used as a source of information to attribute data traffic to different application modules and specific lines of code. Two simple traffic shaping techniques, traffic aggregation and piggybacking, are implemented in the application to provide more energy-efficient traffic patterns. As a result, 3G energy consumption during normal music playback is reduced by 22-54%, and a more contrived scenario achieves a 60% reduction. The reductions are attained by rescheduling a small class of messages, most notably data tracking application usage. These messages were found to account for a small fraction of total traffic volume, but a large portion of the application's overall 3G energy consumption.

In this paper an ARM big.LITTLE system with Global Task Scheduling is evaluated in terms of its energy efficiency and performance measured in execution time. The big.LITTLE system is evaluated against the same system but with only the big or LITTLE processor active. The evaluation is done by performing experiments that target three different levels of load: full load, varying load and low load. The benchmarking software PARSEC Blackscholes and BBench are used to put the system under a synthetic workload in the tests. The results show that overall big.LITTLE achieves an improvement in execution time for all test scenarios, although very slim for varying load, and is more energy efficient than the big processor with the possible exception of a low load scenario. However, the LITTLE processor by itself is found to be the most energy efficient system even though it showed the slowest execution time.

Energy efficiency optimization of electric machines is an important research field and is part of the objectives of several international projects such as the European Commission Climate and Energy package which has set itself a 20% energy savings target by 2020, and was extended for 2030 with higher targets. Therefore, this thesis proposes an efficiency optimization method of the Induction Machine (IM) through the variation of the control parameters. To achieve this goal, the flux in the airgap is modified according to an optimal flux table computed off-line for all possible operating points. The flux table is calculated with the best possible accuracy through an improved dynamic model of the IM, developed in these works. The latter avoids the main drawback of the classic dynamic model, by considering the effect of core losses. The core loss model established by Bertotti is used. It depends on the frequency and the amplitude of the magnetic field. The losses are then represented by a variable resistor, continuously evaluated according to the operating point. The established optimal flux table is a function of the operating conditions in terms of torque and speed. Indeed, the results show that the flux can be optimized for torque values less than about half the rated torque, and that this threshold is influenced by the speed. The proposed optimization method is simulated, then tested for the scalar control and the field-oriented control, in order to show the genericity of the proposed approach. The validation is carried on an experimental test bench for two 5.5 kW induction motors of different efficiency standards (IE2 and IE3). The results obtained show the reduction of the losses in the motor, thus an improvement of the overall efficiency while preserving a satisfactory dynamic behavior. Consequently, the optimization of the energy efficiency is validated for the two control structures and for the two studied motors. In addition to the validation of the simulation results, the proposed approach is compared to existing methods to assess its effectiveness