Energy saving, in battery operated wireless sensor networks, for the purpose of increasing the node and network lifetime, has gained substantial importance. This research was conducted with the objective of reducing the power consumption of the MICA2 sensors. The objective was pursued by manipulating the MAC layer, and by introducing a dynamic transmission power control algorithm. A new simulation tool was developed in order to reduce the complexity related to the design and testing of the transmission power control algorithm. The power control algorithm was also developed in the NesC language for the MICA2 sensors. In addition,several modifications were introduced to the original MAC protocol. Data, derived from both simulations and experiments, demonstrated that a significant reduction in energy expenditure was achieved, for the MICA2 sensors. In addition,the data revealed that the network lifetime was extended. This research dramatically illustrated the energy saving potential of the application of transmission power control procedures in wireless sensor networks.

Various macroeconomic effects resulted from the changing economic and societal structure in the second half of the 20th century, which greatly impacted women's economic position in the United States. Using dynamic programming as the main modeling tool, and U.S. data for factual evidence, three papers are developed to test the validity of three related hypotheses focusing on female employment, education, marriage, and divorce trends. The first chapter estimates how much of the post-World War II evolution in employment and average wages by gender can be explained by a model where changing labor demand requirements are the driving force. I argue that a large fraction of the original female employment and wage gaps in mid-century, and the subsequent shrinking of both gaps, can be explained by labor reallocation from brawn-intensive to brain-intensive jobs favoring women's comparative advantage in brain over brawn. Thus, aggregate gender-specific employment and wage gap trends resulting from this labor reallocation are simulated in a general equilibrium model. The material in the second chapter is based on an ongoing joint project with Fatih Guvenen. We argue for a strong link between the rise in the proportion of educated women and the evolution of the divorce rate since mid-century. As women become increasingly educated their bargaining power within marriage rises and their economic situation in singlehood improves making marriage less attractive and divorce more attractive. Similarly, a change in the divorce regime (e.g., U.S. unilateral divorce laws in the 1970s), making marriages less stable, incentivizes women to seek education as insurance against the higher divorce risk. A framework that models the interdependence between education, marriage and divorce is developed, simulated, and contrasted against United States data evidence. The third chapter considers the implications of marital uncertainty on aggregate household savings behavior. To this end, an infinite horizon model withperpetual youth that features uncertainty over marriage quality is developed. Similarly to Cubeddu and Ríos-Rull (1997), I test how much of the savings rate decline from the 1960s to the 1980s can be explained by the changing United States demographic composition, specifically the rise in divorce rates and the fall in marriage rates. / text

Koldioxidnivåerna ökar i takt med en allt högre världslig energianvändning. Detta har lett till reglering och bestämmelser av utsläppsrätter samt energianvändning. För att stoppa den globala uppvärmningen och minska energianvändningen har EU enats om fyra gemensamma mål att uppnå till år 2020, även benämnda 20-20-20 målen. Lika så har Sverige satt upp egna miljömål att sträva efter till år 2020. De omfattar en ökning av andel förnyelsebar energi med minst 50 procent, effektivisera energianvändningen med minst 20 procent samt öka andelen förnyelsebar energi i transportsektorn med minst 10 procent.  Tack vare lagar gällande krav på skärpt energianvändning och utsläpp strävar företag mot användandet av energieffektivare teknik och ett mer energimedvetet beteende. Energikartläggning är ett viktigt samt effektivt verktyg vid kartläggning och illustrering av ett företags energianvändning för underlättande och tydliggörande av framtida åtgärd samt förbättring.  Examensarbetet syftar till att åskådliggöra Kv. Fredens energianvändning samt ta fram ekonomiskt genomförbara energibesparande åtgärder för att sänka energianvändningen både för denna och liknande byggnader. Till hjälp för utförande har sex frågeställningar använts vilka berör och syftar till att ta reda på energifördelningen i byggnaden, brister i drift och uppehållande av inomhusklimat samt ta fram kostnadseffektiva lösningar för val av åtgärd.För tillvägagång av arbetet har fem metoder valts för besvarande av frågeställningar. En litteraturstudie utfördes med hjälp av nyckelord som ”Energy saving”, ”Energy audit” samt ”Behaviour” i online-databaser för vetenskapliga artiklar. Därefter utfördes en empirisk analys av tillhandahållen data för byggnaden, vilket möjliggjorde modellering och simulering av byggnaden i programmet IDA ICE 4.6.1. För styrkande av antaganden samt undersökning av energimedvetet beteende utfördes termografering och en kvalitativ enkätundersökning.  Efter utförande av arbetet med hjälp av nämnda metoder, konstateras bristfällig ventilation. Vid simulerad installation av FTX i byggnaden uppnås en maximal energibesparing på dryga 17 procent, vilket motsvarar en slutlig energianvändning på 97 kWh/m2. Simulerade åtgärder, exklusive FTX, vilka visar sig vara mest lönsamma för byggnaden är tätning av dörrar och fönster för minskad infiltration. Dessa två simulerade åtgärder är de mest kostnadseffektiva simulerade lösningarna för Kv. Freden samt liknande byggnader.   Den simulerade energianvändningen för byggnaden representeras av 29 procent elanvändning samt 71 procent fjärrvärmeanvändning, vilka förhåller sig till en tillförlitlighet motsvarande 97,5 procent respektive 96 procent jämfört med energidata tillhandahållen av Gävle Energi. Simuleringsprogrammet IDA ICE visade sig vara ett effektivt hjälpmedel vid simulering av en byggnads energianvändning samt applicering av möjliga åtgärder. / Carbon dioxide levels are increasing as a consequence of larger energy use worldwide. This has led to regulations and rules of emission and energy consumption. In order to stop global warming and reduce energy consumption, EU has agreed on four common goals to achieve by the year 2020, also known as the 20-20-20 goals. Sweden has also come up with its own environmental goals to achieve by the year 2020. They include increasing the share of renewable energy by at least 50 percent, improve the use of energy by at least 20 percent and increase the share of renewable energy in the transportation sector by at least 10 percent.   Due to the laws and requirements related to stricter energy consumption and carbon emissions companies strive to use more energy efficient technology and more energyconscious behavior. Energy audit is an effective and an important tool in identifying and illustrating a company's energy usage for the clarification of future measures and improvement.  The thesis aims to illustrate Kv. Freden's use of energy and come up with both economically and energy saving measures to reduce its and other similar building's energy consumption. Six questions have been used to determine the energy distribution in the building and find defects in the management and maintenance of the indoor climate and develop cost-effective solutions for the choice of measures.   Five methods were chosen for approaching and answering the questions. A literature review was performed using keywords such as "Energy Saving", "Energy Audit" and "Behaviour" in online databases containing scientific articles. Thereafter an empirical analysis of the data supplied for the building was performed, which enabled modeling and simulation of the building in the program IDA ICE 4.6.1. A thermography and a qualitative survey regarding energy conscious behavior were performed as proof of assumptions.  The ventilation in this thesis is found inadequate after applied methods.  With simulated FTX-systems installed in the building, a maximum energy saving potential about 17 percent is achieved, which corresponds to a energy use of 97 kWh/m2. Excluding FTX, the simulated measures which prove to be the most profitable for the building is the sealing of doors and windows in order to reduce infiltration. These two measures are the most cost effective energy saving solutions regarding Kv. Freden and similar buildings.  The building's simulated energy use is represented by 29 percent electricity and 71 percent of district heating usage, which compared with the energy data provided by Gävle Energi relates to a reliability equivalent to 97.5 percent and 96 percent. The simulation program IDA ICE proved to be an efficient tool for the simulation of a building's energy use and application of possible measures.

Device-to-device communication has been suggested as a complement to traditional cellular networks as a means of offloading cellular traffic. In this thesis we explore a solution for device-to-device communication based on opportunistic content distribution in a content-centric network. Communication opportunities arise as mobile nodes roam around in an area and occasionally enter in direct communication range with one another. We consider a node to be a pedestrian equipped with a mobile device and explore the properties of opportunistic communication in the context of content dissemination in urban areas. The contributions of this thesis lie in three areas. We first study human mobility as one of the main enablers of opportunistic communication. We introduce traces collected from a realistic pedestrian mobility simulator and demonstrate that the performance of opportunistic networks is not very sensitive to the accurate estimation of the probability distributions of mobility parameters. However, capturing the space in which mobility occurs may be of high importance. Secondly, we design and implement a middleware for opportunistic content-centric networking, and we evaluate it via a small-scale testbed, as well as through extensive simulations. We conclude that energy-saving mechanisms should be part of the middleware design, while caching should be considered only as an add-on feature. Thirdly, we present and evaluate three different energy-saving mechanisms in the context of opportunistic networking: a dual-radio architecture, an asynchronous duty-cycling scheme, and an energy-aware algorithm which takes into account node selfishness. We evaluate our proposals analytically and via simulations. We demonstrate that when a critical mass of participants is available, the performance of the opportunistic network is comparable to downloading contents directly via the cellular network in terms of energy consumption while offloading large traffic volumes from the operator. / <p>QC 20151120</p>

Στην εργασία αυτή μελετούνται ζητήματα που αφορούν την εφαρμογή των δικτύων αισθητήρων και του διαδικτύου των αντικειμένων σε κτίρια, με στόχο την εξοικονόμηση ενέργειας. Αρχικά, γίνεται μία επισκόπηση για τα πράσινα και τα έξυπνα κτίρια, τόσο για τα χαρακτηριστικά τους όσο και για τις τεχνικές κατασκευής τους. Η μελέτη επικεντρώνεται όμως στον τομέα της εξοικονόμησης ενέργειας παρουσιάζοντας τις πιο διαδεδομένες εμπορικές λύσεις αλλά και την πρόοδο σε επίπεδο έρευνας, παρουσιάζοντας τα αποτελέσματα από τα πιο πρόσφατα ερευνητικά προγράμματα. Στη συνέχεια, παρουσιάζεται το σύστημα και οι αυτοματισμοί που αναπτύχθηκαν προκειμένου να μπορέσουν να ελεγχθούν τα ηλεκτρομηχανολογικά συστήματα του κτιρίου. Πρώτα, αναλύεται η αρχιτεκτονική του συστήματος και των αυτοματισμών. Έπειτα, περιγράφεται η ασύρματη δικτύωση των αυτοματισμών χρησιμοποιώντας ενσωματωμένες IPv6 τεχνολογίες. Τέλος, παρουσιάζονται οι τρόποι διασύνδεσης του αυτοματισμού με την κάθε συσκευή και ο τρόπος που ελέγχονται μέσα από τις εντολές που δίνει ο χρήστης και τα σενάρια που έχει ορίσει. Τέλος, περιγράφονται οι εφαρμογές του συστήματος, τα σενάρια που εφαρμόστηκαν, οι μετρήσεις και η εξοικονόμηση ενέργειας που επετεύχθη στην κάθε περίπτωση. Η κύρια εφαρμογή που αναλύεται είναι στο εργαστήριο δικτύων αισθητήρων του τμήματος Μηχανικών Ηλεκτρονικών Υπολογιστών και Πληροφορικής στο πανεπιστήμιο της Πάτρας ενώ επίσης γίνεται αναφορά στις εφαρμογές που έγιναν στις αίθουσες ενός Γυμνασίου της Πάτρας, στο σύστημα ποτίσματος ενός θερμοκηπίου φράουλας και στο σύστημα πρόληψης βλαβών σε ηλεκτρολογικούς πίνακες στο εργοστάσιο της Αθηναϊκής Ζυθοποιίας στην Πάτρα. / In this work are studied issues relating to the application of sensor networks and the internet of things in buildings, in order to save energy. Firstly, there is an overview of green and smart buildings, both for their features and techniques for their construction. The study, however, focuses on energy saving, indicating the most common commercial solutions and progress at the research level, presenting the results of the latest research programs. Then, occurs the system and automations that developed to be able to control the electro-mechanical systems of the building. First, is analyzed the system architecture and the structure of automations. Then, is described the wireless networking of the automations using embedded IPv6 technologies. Finally, is shown how the automations are interface with each device and the way they controlled through commands given by the user and the scenarios that are designated. Finally, is described the applications of the system, the scenarios that were applied, the measurements and the energy savings that achieved in each case. The main application that is analyzed took place in the sensor networks laboratory of Computer Engineering and Informatics Department at the University of Patras. There are also references to applications that were made in the classrooms of a high school of Patras, in the irrigation system of a greenhouse with strawberries and in the early notification system to prevent damage in the electrical panels of Heineken's factory in Patras.

This paper presents the energy saving curtains, in order to make the consumers be more aware of the energy efficiency of the energy saving curtains, the paper gave related analysis and conclusions. The work was performed by using the Parasol Program, developed by Lunds University, Sweden. The Program is used for quantifying the influence of window size, glass type, textile type, wall thermal insulation and sun shading on annual energy use and indoor thermal comfort. The results which are obtained from the calculations are applicable to similar climatic and environment conditions. Calculations were performed to investigate the potential for using sunshade devices to reduce annual energy demand for cooling and heating. Different materials and dimensions of the energy saving curtain are used as variables in the analysis. The results indicated that for the current climatic conditions and other related factors, the total reduction rate of the annual energy consumption of office used buildings in Stockholm is estimated generally 20% -30% lower comparing to those buildings without energy saving curtain system. That means at least 20% of energy cost can be saved by the energy saving curtain system.

Bakalauro baigiamajame darbe nagrinėjamos Lietuvos namų ūkio nariui tenkančios vidutinės mėnesio disponuojamos pajamos ir numatomos šių pajamų perspektyvos. Teoriniu aspektu analizuojama pajamų sąvoka, jų gavimo šaltiniai ir klasifikacija. Išskiriamos dvi pagrindinės disponuojamų pajamų funkcijos (vartojimas ir taupymas) ir jų pokyčius sąlygojantys veiksniai. Empirinėje darbo dalyje išanalizuota Lietuvos namų ūkio nariui per mėnesį tenkančių disponuojamų pajamų dinamika ir struktūra. Norint nustatyti veiksnius, lėmusius tokias disponuojamų pajamų kitimo tendencijas, atlikta priklausomybės tarp disponuojamų pajamų ir jų pokyčius galėjusių sąlygoti pagrindinių makroekonominių rodiklių analizė. Nustačius veiksnius, lemiančius Lietuvos namų ūkio nario vidutines mėnesio disponuojamas pajamas, ir atsižvelgus į jų pokyčius, atliktas disponuojamų pajamų perspektyvų numatymas kintančioje Lietuvos ekonominėje situacijoje. / In this bachelor‘s paper are analyzed average monthly disposable income per inhabitant of Lithuania‘s households and estimated perspecitives of this income. In the theoretical part of this bachelor‘s paper is analyzed the concept of income, the sources of income and classification. There are also presented two main functions of disposable income (consumption and saving) and factors influencing the changes of disposable income. In the empirical part of this work paper is analyzed dynamics and structure of Lithuania‘s households average monthly disposable income per inhabitant. To determine the factors that led to such disposable income changes, there is conducted the dependence between household disposable income per inhabitant and economic factors such as the gross domestic product per capita, the unemployment rate and average anually infliation rate. There is performed forecasting of the Lithuanian household member‘s average monthly disposable income, after the factors, which led to the disposable income changes, were determined and basing on their changes.

The demand for electricity in South Africa has grown faster than the increase in generation capacity. However, it is expensive and time consuming to commission new power stations. Another approach is to reduce electricity demand through the implementation of energy efficiency projects. This alternative is usually less expensive. Compressed air on South African mines is a large electricity consumer with a reputation of wastage. This allows significant potential for electrical and financial savings. A typical mine compressed air system consists of multiple compressors at various locations, surface connection networks, underground distribution systems, thousands of users and leaks. The size, complexity and age of these systems provide a major challenge for electricity saving efforts. Simulating such an intricate system is difficult as it is nearly impossible to accurately gather all the required system parameters. Some initiatives focused on subsections of mine compressed air systems. This is not the best approach as changes to one subsection may adversely affect other systems. A new approach to simplify mine compressed air systems was developed to identify saving opportunities and to assess the true impact of saving efforts. This new approach enables easier system analysis than complex simulation models. Techniques to gather critical system information are also provided. A new implementation procedure was also developed to integrate different energy saving strategies for maximum savings. An electrical power saving of 109 MW was achieved through the implementation of the integrated approach on twenty-two mine compressed air systems. The savings is equivalent to a reduction of 0.96 TWh per annum that relates to a saving of 0.4% of South Africa’s total electricity consumption. Average compressor power consumption was reduced by 30%. The power consumption reduction relates to an estimated annual electricity cost saving of R315 million. A saving of 0.96 TWh per annum is equivalent to a carbon dioxide emission reduction of 0.98 million tonne. The implementation of the integrated approach could be applied to other industrial compressed air systems. A reduction in electricity consumption of 30% on all industrial compressed air systems has the potential to reduce global electricity demand by 267 TWh per annum. That is more than the total amount of electricity consumed in South Africa. / Thesis (PhD (Electrical Engineering))--North-West University, Potchefstroom Campus, 2013

South African cement manufacturers are under financial pressure. Sales have declined due to the 2008 recession and electricity costs have tripled from 2005 to 2012. Electricity cost savings are therefore more important than ever. Unfortunately retrofitting highly energyefficient equipment is not ideal. These installations are costly and take a long time to implement. Alternative strategies that can produce quick results in reducing electricity costs are needed. One such alternative is a programme called Demand Market Participation (DMP). The DMP programme was implemented by Eskom, South Africa’s national electricity utility, to reduce electricity demand during supply shortages. This programme offers potential cost savings for clients with excess production capacity. Clients such as cement plants can switch off non-essential production equipment in Eskom’s peak demand periods for a financial incentive. To maximise the benefits for both the clients and Eskom, accurate electricity forecasting is needed, as are systems enabling a quick response to load reduction requests. In this study DMP opportunities on typical cement plants were identified. A DMP strategy to assist cement plants was developed to achieve maximum cost savings without influencing production, quality and safety. An existing energy management system (EnMS) was adapted to incorporate the new DMP participation strategy. The new EnMS and DMP strategy were implemented at a South African cement plant, resulting in savings of R220 000 per month. This translates into an annual cost-saving potential of R2-million for the plant, and an R13- million cost-saving potential for the total South African cement industry. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

The demand for electricity in South Africa has grown faster than the increase in generation capacity. However, it is expensive and time consuming to commission new power stations. Another approach is to reduce electricity demand through the implementation of energy efficiency projects. This alternative is usually less expensive. Compressed air on South African mines is a large electricity consumer with a reputation of wastage. This allows significant potential for electrical and financial savings. A typical mine compressed air system consists of multiple compressors at various locations, surface connection networks, underground distribution systems, thousands of users and leaks. The size, complexity and age of these systems provide a major challenge for electricity saving efforts. Simulating such an intricate system is difficult as it is nearly impossible to accurately gather all the required system parameters. Some initiatives focused on subsections of mine compressed air systems. This is not the best approach as changes to one subsection may adversely affect other systems. A new approach to simplify mine compressed air systems was developed to identify saving opportunities and to assess the true impact of saving efforts. This new approach enables easier system analysis than complex simulation models. Techniques to gather critical system information are also provided. A new implementation procedure was also developed to integrate different energy saving strategies for maximum savings. An electrical power saving of 109 MW was achieved through the implementation of the integrated approach on twenty-two mine compressed air systems. The savings is equivalent to a reduction of 0.96 TWh per annum that relates to a saving of 0.4% of South Africa’s total electricity consumption. Average compressor power consumption was reduced by 30%. The power consumption reduction relates to an estimated annual electricity cost saving of R315 million. A saving of 0.96 TWh per annum is equivalent to a carbon dioxide emission reduction of 0.98 million tonne. The implementation of the integrated approach could be applied to other industrial compressed air systems. A reduction in electricity consumption of 30% on all industrial compressed air systems has the potential to reduce global electricity demand by 267 TWh per annum. That is more than the total amount of electricity consumed in South Africa. / Thesis (PhD (Electrical Engineering))--North-West University, Potchefstroom Campus, 2013