Global warming induced by the emissions of greenhouse gases is one of the most important global environmental issues facing the world today. Using the building simulation techniques, this research investigates the interaction and relationship between global warming and built environment, particularly for the air-conditioned office buildings. The adaptation potential of various building designs is also evaluated. Based on the descriptive statistics method, the Pearson Product Moment Correlation and the regression analysis method, ten years of historical hourly climatic data for Australia are first analyzed. The distribution patterns of key weather parameters between a Test Reference Year (TRY) and multiple years (MYs), and between relatively cold and hot years are also compared. The possible cross-correlation between several different weather variables are then assessed and established. These findings form a useful basis and provide insights for the development of future weather models under "hot" global warming conditions and the explanation of building performance at different locations. Based on a review of the existing weather data generation models and findings from historic climatic data analysis, an effective method to generate approximate future hourly weather data suitable for the study of the impact of global warming is presented. This is achieved by imposing the future temperature projection from the global climate model on top of the historically observed weather data. Depending on the level of information available for the prediction of future weather conditions, this method allows either the method of retaining to current level, constant offset method or diurnal modelling method to be used. Therefore it represents a more comprehensive and holistic approach than previous one that have been used to convert the available weather data and climatic information to a format suitable for building simulation study. An example of the application of this method to the different global warming scenarios in Australia is also presented. The performance of a representative office building is then examined in details under the five weather scenarios (present, 2030 Low, 2030 High, 2070 Low and 2070 High) and over all eight capital cities in Australia. The sample building used for this study is an air conditioned, square shape, ten storey office tower with a basement carpark, which is recommended by the Australian Building Codes Board to represent the typical office building found in the central business district (CBD) of the capital cities or major regional centres in Australia. Through building computer simulations, the increased cooling loads imposed by potential global warming is quantified. The probable indoor temperature increases and overheating problems due to heat load exceeding the capacity of installed air-conditioning systems are also presented. It is shown that in terms of the whole building indoor thermal environment, existing buildings would generally be able to adapt to the increasing warming of the 2030 year Low and High scenarios projections and the 2070 year Low scenario projection. For the 2070 year High scenario, the study indicates that the existing office buildings in all capital cities will suffer from the overheating problem. To improve the building thermal comfort to an acceptable standard (ie, less than 5% of occupied hours having indoor temperature over 25°), a further increase of 4-10% of building cooling load is required. The sensitivity of different office building zoning (i.e. zone at different floors and/or with different window orientation) to the potential global warming is also investigated. It is shown that for most cities, the ground floor, and the South or Core zone would be most sensitive to the external temperature change and has the highest tendency to having the overheating problem. By linking building energy use to CO2 emissions, the possible increase of CO2 emissions due to increased building energy use is also estimated. The adaptation potential of different designs of building physical properties to global warming is then examined and compared. The parametric factors studied include the building insulation levels, window to wall ratio, window glass types, and internal load density. It is found that overall, an office building with a lower insulation level, smaller window to wall ratio and/or a glass type with lower shading coefficient, and lower internal load density will have the effect of lowering building cooling load and total energy use, and therefore have a better potential to adapt to the warming external climate. This phenomenon can be linked to the nature of internal-load dominated office-building characteristics. Based on these findings, a series of design and adaptation strategies have been proposed and evaluated.

Doctor of Philosophy(PhD) / This thesis describes the exploration and the development of computational means to investigate the behaviour of design objects before they are available for investigation in the physical world. The motivation is to inform the design process about the design object’s performance in order to achieve better – more performance-oriented – design outcomes in the sense of energy efficiency and comfort performance than can be achieved by conventional design techniques. The research is structured into five successive parts. - Concept Development – A review of the objective domains comfort assessment and energy efficiency assessment is conducted and the design process, human design activity and the application of simulation in the architectural domain is discussed in order to identify requirements for the development of computational means for design analysis. Requirements regarding model content, model features and model integration are developed. The main requirements are that a highly integrated, three-dimensional and dynamic representation of physical processes is needed and that a universal and integrated representation is required. - Concept Formulation – Based on the identified requirements, the concept for a model is formulated. In order to achieve a universal and integrated representation of physical processes the concept uses the approach of a constructive language. Space is represented with autonomous spatial elements, called congeneric cells. Interaction between the cells is represented by near- and remote-conjunctions. Physical and geometric self-contained formulations of the model reduce the model input requirements, so that geometric information and simple property specification (material, activity) is sufficient to describe the design object in the model. - Model Development – The concept is formulated in mathematical physical terms based on well known physical laws and building physical models (first-principle approach). Heat and moisture conduction, diffusion of various components and a flow model is formulated as near-conjunction processes. Heat radiation, light and sound are modelled with a radiosity approach as remote-conjunctions. The simulation algorithm, which governs the interaction between the cells in order to represent the behaviour of space, is explained. - Computational Implementation – The concept and the model is tested by implementation of a prototype using C++ and OpenGL on a conventional Pentium 4 notebook. The prototype consists of three parts: user-interface, model translator and simulation engine. The user interface functions as model-input and result-output device. The implementation of the concept and of further model parts is described in detail. - Assessment and Testing – The developed concept and the model, as implemented in the prototype, are tested and assessed against the initially developed requirements. The physical model is assessed in regard to plausibility and accuracy of the representation of the physical phenomena. At the end of the thesis the project is summarized, the achievements of the project’s objectives are discussed critically and issues for future research are suggested. Possible applications of the developed model are listed, and the contributions to the application of computational simulation in the architectural domain, developed in this research, are named. At the current stage the required processing time and high memory requirements prevent implementation of a design assessment system, following the suggested concept, at a useful scale. Also the developed physical models require further refinement and testing. Although the general feasibility of the concept and the model was successfully demonstrated, its implementation in a fully applicable design assessment system based on the universal and integrated representation of physical processes was not achieved at this stage. While detailed description and analysis is given in the body of the thesis, detailed formulations of the work and the developed model are given in the appendix. The body and the appendix together provide a complete picture of the research presented.

Στην παρούσα εργασία αναπτύχθηκε ένα θεωρητικό πλαίσιο, το οποίο αναλύει την ενεργειακή αποτελεσματικότητα, τους προσδιοριστικούς παράγοντες που ευθύνονται για το ενεργειακό παράδοξο και επικεντρώνεται ιδιαίτερα στον ρόλο της αβεβαιότητας και των προσδοκιών στην πραγματοποίηση επενδύσεων εξοικονόμησης ενέργειας. Επιπλέον αναπτύχθηκε ένα εμπειρικό μοντέλο που εκτιμήθηκε με τη μέθοδο OLS και το υπόδειγμα Tobit για να προσδιοριστούν οι παράγοντες που επιδρούν στις επενδύσεις εξοικονόμησης ενέργειας. Σα εμπειρικά αποτελέσματα αναδεικνύουν ότι οι επενδύσεις σε ΣΕΕ, στην περίπτωση της Ελληνικής Βιομηχανίας είναι στενά συνδεδεμένες με τον κλάδο που δραστηριοποιείται η επιχείρηση. Ο κλάδος δραστηριοποίησης επιδρά και στην επενδυτική συμπεριφορά της επιχείρησης καθορίζοντας τη στάση που κα ακολουθήσει. Ένα άλλο συμπέρασμα είναι ότι η ύπαρξη εναλλακτικού επενδυτικού σχεδίου είναι σημαντικό εμπόδιο στις επενδύσεις εξοικονόμησης ενέργειας. Από την άλλη πλευρά, η θετική στάση της επιχείρησης απέναντι στην σπουδαιότητα των επενδύσεων εξοικονόμησης ενέργειας επιδρά θετικά στην πραγματοποίηση τους. Ομοίως στην περίπτωση των ελληνικών βιομηχανιών, οι μεγάλες επιχειρήσεις και οι επιχειρήσεις που έχουν μεγάλο χρόνο ζωής προωθούν τις επενδύσεις εξοικονόμησης ενέργειας. Τέλος η αβεβαιότητα και οι προσδοκίες είναι κρίσιμοι παράγοντες για την απόφαση των επιχειρήσεων να επενδύσουν σε τεχνολογίες εξοικονόμησης ενέργειας. Για την εγχώρια βιομηχανία η προσδοκία για αύξηση του εργασιακού κόστους είναι αποτρεπτικός παράγοντας για τις επενδύσεις εξοικονόμησης ενέργειας, ενώ η αβεβαιότητα για τις επιπτώσεις στο περιβάλλον αποδεικνύεται ισχυρό κίνητρο για την πραγματοποίησή τους. / Uncertainty and expectations in energy conservation investments.

Syftet med denna studie är att belysa vilka faktorer som fastighetsbolagen upplever påverkar lönsamheten för och genomförandet av energiinvesteringar inom värme och ventilation. Studien är av kvalitativ karaktär och fallstudier görs på sju företag med semistrukturerade intervjuer som insamlingsmetod. Därefter spelas alla intervjuer in och transkriberas. Flera olika faktorer påverkar lönsamheten för och genomförandet av energiinvesteringar i flerbostadshus. De undersökta faktorerna som påverkar investeringarnas lönsamhet är: typ av investering, kalkylmetod, avkastningskrav, energipriset, intressenter och institutionella faktorer. Studiens resultat tyder på att värmeåtervinning (FX), tilläggsisolering av vind, injusteringar och optimering samt styr och reglering varit de mest företagsekonomiskt lönsamma energiinvesteringarna. Den vanligaste beräkningsgrunden var Livscykelkostnadsanalys (LCC). Uppsatsen bidrar till att öka kunskapen om hur fastighetsbolag ser på energiinvesteringar och dess lönsamhet. Studiens kvalitativa resultat kan inte generaliseras till andra fastighetsbolag eller till framtida investeringar. Vidare forskning rekommenderas nationellt och kvantitativt inom lönsamma energiinvesteringar. Det skulle vara av intresse att fastställa de mest lönsamma investeringarna i Sverige, orsaker till vad som hindrar energiinvesteringar samt hur olika beräkningssätt kan påverka dess lönsamhet och realisering. / The purpose of this study is to highlight the factors that real estate companies is experiencing affects the profitability and the implementation of energy investments in heating and ventilation. The study is qualitative in nature and case studies are conducted at seven companies with semi-structured interviews as the method of collection. Furthermore, all the interviews are recorded and transcribed. Several factors affect the viability and implementation of energy investments in apartment buildings. The investigated factors affecting the profitability of investment are: the type of investment, calculation method, yield, energy price, stakeholders and institutional factors. The study's results suggest that heat recovery (FX), additional insulation of attic, adjustments and optimization, and control and regulation was the most economically viable energy investments. The most common basis of calculation was the Life Cycle Cost Analysis (LCC). The study contributes to the knowledge of real estate companies’ perspectives of energy investments and their profitability. The study's qualitative results cannot be generalized neither to other real estate companies or future investments. Further quantitative and national research is recommended in profitable energy investments. It would be of interest to determine the most profitable investments in Sweden, causes of the barriers preventing energy investments and how different methods of calculation may affect its profitability and implementation.

This thesis uses a case study of the Community Home Energy Retrofit Project (CHERP) and it analyzes the larger statewide effort in California to increase energy efficiency in existing residential buildings to reduce greenhouse gas emissions. CHERP’s primary strategy is to embed itself into a community, educate residents on the multiple benefits of energy efficiency, and inspire them to take energy-saving actions in their own homes. It then builds its own community by connecting like-minded individuals together and provides an opportunity for them to exercise their political agency. This thesis analyzes CHERP’s effort in the context of the political, social, and economic climate of California. It identifies three obstacles for widespread energy efficiency adoption: one, CHERP’s lack of funding to support permanent staff and pay for collateral materials; two, low access to energy efficiency measures for low-income households and renters; and three, a lack of high quality home performance contractors that perform energy efficiency upgrades utilizing a whole-house energy systems approach. The thesis concludes with five recommendations to overcome these issues.

Med energieffektivisering menas att man använder energi på ett effektivt sätt som ska leda till en positiv inverkan på miljö och samhälle. Sisjö Entré är ett köpcentrum som har en årlig energiförbrukning på 1 865 270 kWh och bör enligt Energimyndighetens riktvärde ha en årlig förbrukning på 1 530 000 kWh, alltså en minskning med 18 %. Köpcentret består av 17 butiker och i examensarbetet undersöks fem butiker vilka är Toys Я Us, Rusta, Burger King, Babyproffsen och Webhallen. I dessa utförs mätningar på ventilation och belysning med syftet att studera vilka laster i butikerna som orsakar mest förbrukning. Målet är att komma fram till förslag på åtgärder för att minska energiförbrukning samt kostnader. Vi kom fram till att belysning är den största lasten i handelslokaler vilka är Toys Я Us, Rusta, Babyproffsen och Webhallen medan den största lasten i restauranger (Burger King) är utrustningen i köket som står för 75 % av restaurangens totala förbrukning. I Rusta upptäckte vi att elmätarna visade lägre värden än den verkliga förbrukningen. Efter undersökningen kom vi fram till att felet antingen ligger i elmätarna eller i dess strömtransformator och måste åtgärdas. Vi har gett förslag på att byta ut en del av den befintliga belysningen samt gett förslag på att sektionera vissa delar i några av butikerna. Dessutom har vi gett förslag på att reducera drifttiderna på ventilationsaggregaten. Utifrån dessa förslag och energiberäkningar kom vi fram till att man i de fem butikerna kan minska den årliga energiförbrukningen från 1 865 270 kWh till 1 576 670 kWh, alltså en minskning på 15,5 %. Därmed minskar kostnaderna med ca 228 000 sek/år / Energy efficiency means that energy is used in an efficient way that impacts positively on the environment and society. Sisjö Entré is a shopping center which has an annual energy consumption of 1 865 270 kWh, and according to Energy Authority, the recommended value is 1 530 000 kWh per year. That means that energy consumption at the center should reduce by approximately 18 % to comply with the recommended value. The mall consists of 17 stores and the thesis examines five stores which are Toys Я Us, Rusta, Burger King, Babyproffsen and Webhallen. Measurements are taken on ventilation and lighting installations with the aim of studying the loads in the stores that consume the most energy. The goal is to come up with suggestions of actions to reduce energy consumption and costs. We concluded that lighting consumes the most energy in the warehouses; Toys Я Us, Rusta, Babyproffsen and Webhallen, while the largest load in the restaurants (Burger King) is the kitchen, which accounts for 75 % of the restaurants total consumption. In Rusta, we discovered that the electricity meter showed a lower value than the true consumption. After investigation, we concluded that the fault could be either in the electricity meter or in its current transformer and must be addressed. We have given a proposal to replace parts of the existing lighting installations, and given suggestion for sectioning certain parts in some stores. Further, we have given suggestions for reducing operating times on the ventilation units. Based on the above proposals and energy calculations, we concluded that these five stores has the potential to reduce the annual energy consumption from 1 865 270 kWh to 1 576 670 kWh, leading to a reduction by 15.5 %. This reduces costs by about 228 000 SEK per year

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Energy efficiency, as the effective use of energy, is recognized as one of the simplest ways to improve the sustainable use of resources and by implication involves the end-user. The 2008 power crisis which South Africa experienced, highlighted supply exigencies and prompted a subsequent emphasis on affordable, rapidly scalable solutions, notably energy efficiency. As the establishment of new supply capacity is both costly and time-consuming, the logical alternative has been to focus intervention on the demand side. Residential electrical end-use has been identified as an area where the potential for change exists and strategies to address residential demand have gained momentum. The vulnerability of energy systems affects energy security on technical, economic and social levels. South African consumers are confronted with rising living costs and a substantial increase in electricity prices according to the Integrated Resource Plan for Electricity (2010-2030). Integral to addressing end-use is the ensuing behaviour of the end-user. End-use analysis aims to grasp and model customer usage by considering the electric demand per customer type, end-use category, appliance type and time of use. This project has focussed on the development of an interactive web application as a tool for residential end-users to improve energy efficiency through modified consumption behaviour and the adoption of energy efficient habits. The objectives have been aimed at educating an end-user through exposure to energy efficient guidelines and consumption analysis. Based on a Time Of Use-framework, a consumer’s understanding of appliance usage profiles can help realize the cost benefits associated with appliance scheduling. In order to achieve the desired functionality and with extendibility and ease of maintenance in mind, the application relies on the provision of dynamic content by means of a relational database structured around end-use categories and appliance types. In an effort to convey only relevant information in the simplest way, current web technology was evaluated. The resulting design has favoured an interactive, minimalistic, graphic presentation of content in the form of a Rich Internet Application. The development process has been divided into two phases. The residential energy consumption context has been substantiated with a case study of which the main objective and outcome has been to devise a methodology to generate usage profiles for household appliances. Phase one of the development process has been completed, as well as the case study. The conceptualization and framework for phase two has been established and the recommendation is to incorporate the methodology and usage profile results from the case study for implementation of the second phase. The effectiveness of the tool can only be evaluated once phase two of the application is complete. A beta release version of the final product can then be made available to a focus group for feedback. / AFRIKAANSE OPSOMMING: Energie effektiwiteit, gesien as die effektiewe aanwending van energie, word herken as een van die eenvoudigste maniere om die volhoubare gebruik van hulpbronne te bevorder en betrek by implikasie die verbruiker. Die 2008 kragvoorsieningskrisis wat Suid-Afrika beleef het, het dringende tekorte aan die lig gebring en ’n gevolglike klemverskuiwing na bekostigbare, maklik aanpasbare oplossings, vernaamlik energie effektiwiteit. Aangesien die daarstelling van nuwe voorsieningskapasiteit beide duur is en baie tyd in beslag neem, was die voor die hand liggende alternatief om te fokus op vraag-kant toetrede. Huishoudelike elektriese verbruik is geïdentifiseer as ’n area waar die potensiaal vir verandering bestaan en strategieë om residensiële aanvraag aan te spreek het momentum gekry. Die kwesbaarheid van energiestelsels affekteer energie sekuriteit op tegniese, ekonomiese en sosiale vlakke. Suid-Afrikaanse verbruikers word gekonfronteer met stygende lewenskoste en ’n aansienlike toename in elektrisiteitspryse volgens die Geïntegreerde Hulpbron-Plan vir Elektrisiteit (2010-2030). Eie aan die aanspreek van verbruik is die voortvloeiende gedrag van die verbruiker. Verbruiksanalise poog om verbruik te begryp en te modelleer deur die elektriese aanvraag na gelang van verbruikerstipe, verbruikskategorie, toesteltipe en tyd van verbruik in aanmerking te neem. Hierdie projek het gefokus op die ontwikkeling van ’n interaktiewe web-toepassing as ’n instrument vir residensiële verbruikers om energie effektiwiteit te verbeter deur gewysigde verbruiksgedrag en die ingebruikneming van energie effektiewe gewoontes. Die doelwitte is gerig op die opvoeding van ’n verbruiker deur blootstelling aan riglyne vir energie effektiewe verbruik en verbruiksanalise. Gebaseer op ’n Tyd-Van-Verbruik-raamwerk, kan ’n verbruiker se begrip van toestelle se verbruiksprofiele ’n bydrae lewer om die koste-voordele geassosieer met toestel-skedulering te realiseer. Om sodoende die verlangde funksionaliteit te bewerkstellig en met verlengbaarheid en gemak van onderhoud voor oë, steun die toepassing op die verskaffing van dinamiese inhoud deur middel van ’n relasionele databasis wat gestruktureer is rondom verbruikskategorieë en toesteltipes. In ’n poging om slegs toepaslike informasie in die eenvoudigste vorm weer te gee, is teenswoordige web tegnologie geevalueer. Die vooruitspruitende ontwerp is ’n interaktiewe, minimalistiese, grafiese aanbieding van die inhoud in die vorm van ’n sogenaamde "Rich Internet Application". Die ontwikkelingsproses is ingedeel in twee fases. Die huishoudelike energieverbruikskonteks is bevestig deur middel van ’n gevallestudie waarvan die vernaamste doelwit en uitkoms was om ’n metodologie daar te stel om verbruiksprofiele van huishoudelike toestelle te genereer. Fase een van die ontwikkelingsproses is voltooi asook die gevallestudie. Die konsepsuele onwikkeling en raamwerk vir fase twee is reeds gevestig en die aanbeveling is om die metodologie en verbruiksprofielresultate van die gevallestudie te inkorporeer vir implementering van die tweede fase. Die effektiwiteit van die toepassing kan eers geevalueer word sodra fase twee afgehandel is. ’n Beta-weergawe vrystelling van die finale produk kan dan beskikbaar gestel word aan ’n fokusgroep vir terugvoer.

Em função do crescimento populacional e econômico brasileiro, o sistema elétrico nacional está sempre em modificação a fim de atender às necessidades do país. Na última década, ganhou destaque o aumento da geração termoelétrica na matriz elétrica nacional, primeiro proveniente do gás natural, e mais recentemente de fontes renováveis, como a cogeração termoelétrica proveniente do bagaço de cana. Em virtude desta realidade, é importante que, frente ao volume significativo e crescente de centrais de cogeração no país, seja pensada uma forma de administrar esta parcela da geração de maneira a se aprimorar de forma constante o desempenho destes sistemas. No entanto, verifica-se que os programas de eficiência energética no Brasil e no mundo estão geralmente associados aos usos finais de energia elétrica e praticamente inexiste uma ação estruturada de gestão da eficiência nas transformações energéticas para geração de eletricidade ao longo de sua operação. Portanto, este trabalho tem como objetivo, propor uma metodologia de gestão continuada da eficiência energética de centrais de cogeração a biomassa que operam em ciclo Rankine no Brasil. A metodologia está baseada no ciclo de melhoria contínua da qualidade, conhecido como PDCA. São estabelecidas as etapas para implementação da metodologia: enquadramento, cálculo, medição, verificação e ação. O parâmetro escolhido para cálculo e medição na metodologia é o fator de utilização de energia (FUE). A implementação da metodologia permite passar por cada fase do ciclo PDCA: planejamento, execução, verificação e ação. O ciclo Rankine foi o escolhido para o desenvolvimento do modelo de aplicação por representar a totalidade das centrais de cogeração a biomassa no Brasil. É apresentado um estudo de caso no qual a metodologia foi aplicada a duas centrais de cogeração enquadradas em classes semelhantes. Os resultados demonstram a validade da metodologia para o propósito de implementar um sistema de gestão continuada da eficiência energética global em centrais de cogeração a biomassa. São por fim recomendadas as ações de melhoria decorrentes da aplicação do ciclo nas centrais, e recomendações de desenvolvimento futuro complementares a este trabalho. / Due to the Brazilian population and economic growth, the national grid is in continuous change in order to meet the country needs. During the last decade, the highlights are the thermoelectric generation expansion, first by natural gas plants growth and recently by alternative renewable cogeneration sugarcane bagasse plants. Due to this situation, face to the significant growing number of biomass cogeneration plants in Brazil, it is important to think a way to manage this electric generation portion in order to have a continuous improvement of its performance. However, it is noticed that the energy efficiency policies either in Brazil or worldwide are usually connected to end uses of electricity and actually there is not any structured action towards the energy efficiency management for electricity generation along operation. Thus, this work proposes a methodology for energy efficiency management in Rankine cycle operated biomass cogeneration plants in Brazil. The methodology is based on the so called PDCA continual improvement cycle. The steps for implementation of the methodology: classification, calculation, measurement, verification and action, are established. The energy utilization factor (EUF) was chosen for calculation and measurement in the methodology. The implementation of it permits to pass through each phase of PDCA cycle: plan, do, check and act. The Rankine cycle was chosen for the application model development because it represents 100% of biomass cogeneration commercial plants operating in Brazil. A application of the methodology for two cogeneration plants with the same class is presented in the study case. The results show the validity of the application of the proposed methodology for establishment of an overall energy efficiency management system in biomass cogeneration plants. Improvement actions are recommended as results from the application of the cycle. Further development recommendations for this work are also presented.

Polymer extrusion is an energy intensive process whereby the simultaneous action of viscous shear and thermal conduction are used to convert solid polymer to a melt which can be formed into a shape. To optimise efficiency, a homogeneous melt is required with minimum consumption of process energy. In this work, in-process monitoring techniques have been used to characterise the thermal dynamics of the single screw extrusion process with real-time quantification of energy consumption. Thermocouple grid sensors were used to measure radial melt temperatures across the melt flow at the entrance to the extruder die. Moreover, an infrared sensor flush mounted at the end of the extruder barrel was used to measure non-invasive melt temperature profiles across the width of the screw channel in the metering section of the extruder screw. Both techniques were found to provide useful information concerning the thermal dynamics of the extrusion process; in particular this application of infrared thermometry could prove useful for industrial extrusion process monitoring applications. Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers but in practise this is rarely achieved due the lack of understanding. Here, LDPE, LLDPE, three grades of HDPE, PS, PP and PET were extruded using three geometries of extruder screws at several set temperatures and screw rotation speeds. Extrusion data showed that polymer rheology had a significant effect on the thermal efficiency on the extrusion process. In particular, melt viscosity was found to have a significant effect on specific energy consumption and thermal homogeneity of the melt. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. Single flighted extruder screws exhibited poorer temperature homogeneity and larger fluctuations than a barrier flighted screw with a spiral mixer. These results highlighted the importance of careful selection of processing conditions and extruder screw geometry on melt homogeneity and process efficiency. Extruder scale was found to have a significant influence on thermal characteristics due to changes in surface area of the screw, barrel and heaters which consequently affect the effectiveness of the melting process and extrusion process energy demand. In this thesis, the thermal and energy characteristics of two single screw extruders were compared to examine the effect of extruder scale and processing conditions on measured melt temperature and energy consumption. Extrusion thermal dynamics were shown to be highly dependent upon extruder scale whilst specific energy consumption compared more favourably, enabling prediction of a process window from lab to industrial scale within which energy efficiency can be optimised. Overall, this detailed experimental study has helped to improve understanding of the single screw extrusion process, in terms of thermal stability and energy consumption. It is hoped that the findings will allow those working in this field to make more informed decisions regarding set conditions, screw geometry and extruder scale, in order to improve the efficiency of the extrusion process.

With the development of modern smartphones, mobile devices have become ubiquitous in our daily lives. With high processing capabilities and a vast number of applications, users now need them for both business and personal tasks. Unfortunately, battery technology did not scale with the same speed as computational power. Hence, modern smartphone batteries often last for less than a day before they need to be recharged. One of the most power hungry components is the central processing unit (CPU). Multiple techniques are applied to reduce CPU energy consumption. Among them is dynamic voltage and frequency scaling (DVFS). This technique reduces energy consumption by dynamically changing CPU supply voltage depending on the currently running workload. Reducing voltage, however, also makes it necessary to reduce the clock frequency, which can have a significant impact on task performance. Current DVFS algorithms deliver a good user experience, however, as experiments conducted later in this thesis will show, they do not deliver an optimal energy efficiency for an interactive mobile workload. This thesis presents methods and tools to determine where energy can be saved during mobile workload execution when using DVFS. Furthermore, an improved DVFS technique is developed that achieves a higher energy efficiency than the current standard. One important question when developing a DVFS technique is: How much can you slow down a task to save energy before the negative effect on performance becomes intolerable? The ultimate goal when optimising a mobile system is to provide a high quality of experience (QOE) to the end user. In that context, task slowdowns become intolerable when they have a perceptible effect on QOE. Experiments conducted in this thesis answer this question by identifying workload periods in which performance changes are directly perceptible by the end user and periods where they are imperceptible, namely interaction lags and interaction idle periods. Interaction lags are the time it takes the system to process a user interaction and display a corresponding response. Idle periods are the periods between interactions where the user perceives the system as idle and ready for the next input. By knowing where those periods are and how they are affected by frequency changes, a more energy efficient DVFS governor can be developed. This thesis begins by introducing a methodology that measures the duration of interaction lags as perceived by the user. It uses them as an indicator to benchmark the quality of experience for a workload execution. A representative benchmark workload is generated comprising 190 minutes of interactions collected from real users. In conjunction with this QOE benchmark, a DVFS Oracle study is conducted. It is able to find a frequency profile for an interactive mobile workload which has the maximum energy savings achievable without a perceptible performance impact on the user. The developed Oracle performance profile achieves a QOE which is indistinguishable from always running on the fastest frequency while needing 45% less energy. Furthermore, this Oracle is used as a baseline to evaluate how well current mobile frequency governors are performing. It shows that none of these governors perform particularly well and up to 32% energy savings are possible. Equipped with a benchmark and an optimisation baseline, a user perception aware DVFS technique is developed in the second part of this thesis. Initially, a runtime heuristic is introduced which is able to detect interaction lags as the user would perceive them. Using this heuristic, a reinforcement learning driven governor is developed which is able to learn good frequency settings for interaction lag and idle periods based on sample observations. It consumes up to 22% less energy than current standard governors on mobile devices, and maintains a low impact on QOE.