The building sector is one of the sectors that consume the most energy in Sweden. In order to deal with this problem Swedish government aims to reduce the energy consumption in the building sector 50% by 2050. Another ambitious goal set by the Swedish government is zero greenhouse gas emissions by 2040. Most of the buildings in Sweden were built during 1950-1990 before the first energy regulations were voted in Europe. A high percentage of these buildings date to 1950 and the majority of them are multi family buildings. Apartments built during this period are now requiring major renovation and retrofitting measures in order to comply with the energy and indoor environment regulations. Despite the urgent need for retrofitting expressed above, the retrofitting ratio in Sweden was 0.88% in 2013, so the number of buildings that haven’t gone through any energy retrofitting is still high making it clear that the biggest opportunity for energy savings lies within the existing building stock and that the retrofitting ratio has to enhance in order to achieve the governments energy and emission goals for 2050. In this study a new patented innovative energy retrofitting method is studied within IDAICE simulation program in order to find the heat load and the energy savings after applying this method. The simulated building is a three story multi family building with building characteristics from 1950 and the simulation takes place in two different climate zones (Stockholm and Umeå). Three different insulation thicknesses were tested creating three different variant cases in order to investigate the difference in energy savings an increase of the insulation thickness will bring. This retrofitting method except installation of extra facade insulation includes roof insulation, replacement of the air handling unit with heat recovery ventilation whose pipe system runs through the insulation behind the radiators of each zone and replacement of the old windows with triple glazed low U-value windows. The results show a high reduction in heat supplied after the retrofit, 66.4% room unit heat reduction in Stockholm and 59.6% in Umeå and even higher energy reduction 68.3% in Stockholm and 68.9% in Umeå. The CO2 emission reduction was 58.4% in Stockholm and 60.9% in Umeå. The difference in room unit heat, energy consumption and CO2 emissions among the Variant cases varies between 1-2%. The explanation for such a small difference lies in the fact that the only difference among these cases is the insulation thickness of the facade. The thermal comfort was also investigated and has shown an increase in hours of dissatisfaction after the retrofitting and as the insulation increased due to overheating. However it must be stated here that the reason behind the increase in dissatisfaction is that no window shading or window opening schedules were taken into account in the simulation maximizing the solar heat gains of the building. The study concludes that the studied retrofitting method is very efficient and the studied building achieves higher energy reduction than the goal that the Swedish government has set for 2050. The results of this study bring this retrofitting method ahead of the 2050 energy reduction goals set by the Swedish government with significant reductions in CO2 emissions and heat load.

Tropical forests are amongst the most important ecosystems in the world. It is also the biome estimated to experience the most rapid losses of habitats in the next 50 years, mainly due to anthropogenic exploitation. The Kakamega forest, western Kenya, is important both for conservation and human livelihood and is essential for peoples’ survival. The main threat to the forest’s subsistence is collection of firewood used for cooking. Energy-efficient cookstoves, with almost 50 % lower demand for firewood compared to traditional 3-stone-stoves, have been installed to ease the pressure on the forest. The present study evaluates the effect of utilizing energy-efficient cookstoves, installed during the project Stoves for Life (years 2010-2019), on the forest structure of the Kakamega forest, Kenya. This was done by quantifying forest structural and compositional differences, as well as occurrence of human made damage, within the Kakamega forest. Sampling was made in 59 plot locations, with varying numbers of energy-efficient cookstoves in the surrounding area. Results indicate that the stoves 1) promote recruitment of both pioneer and climax trees and 2) increase survival of fast-growing pioneer trees, 3) ease the pressure on preferred species used as firewood and 4) preserve important structural components such as woody debris found on the forest floor. Additionally, the growth of pioneer trees is potentially creating a climate suitable for later successional species to thrive and establish, potentially leading to forest maturation. However, future comparative studies should be conducted before any statement about the stoves’ effect on forest structure is made.

A Wireless Sensor Network (WSN) is a collection of tiny devices called sensor nodes which are deployed in an area to be monitored. Each node has one or more sensors with which they can measure the characteristics of their surroundings. In a typical WSN, the data gathered by each node is sent wirelessly through the network from one node to the next towards a central base station. Each node typically has a very limited energy supply. Therefore, in order for WSNs to have acceptable lifetimes, energy efficiency is a design goal that is of utmost importance and must be kept in mind at all levels of a WSN system. The main consumer of energy on a node is the wireless transceiver and therefore, the communications that occur between nodes should be carefully controlled so as not to waste energy. The Medium Access Control (MAC) protocol is directly in charge of managing the transceiver of a node. It determines when the transceiver is on/off and synchronizes the data exchanges among neighbouring nodes so as to prevent collisions etc., enabling useful communications to occur. The MAC protocol thus has a big impact on the overall energy efficiency of a node. Many WSN MAC protocols have been proposed in the literature but it was found that most were not optimized for the group of WSNs displaying very low volumes of traffic in the network. In low traffic WSNs, a major problem faced in the communications process is clock drift, which causes nodes to become unsynchronized. The MAC protocol must overcome this and other problems while expending as little energy as possible. Many useful WSN applications show low traffic characteristics and thus a new MAC protocol was developed which is aimed at this category of WSNs. The new protocol, Dynamic Preamble Sampling MAC (DPS-MAC) builds on the family of preamble sampling protocols which were found to be most suitable for low traffic WSNs. In contrast to the most energy efficient existing preamble sampling protocols, DPS-MAC does not cater for the worst case clock drift that can occur between two nodes. Rather, it dynamically learns the actual clock drift experienced between any two nodes and then adjusts its operation accordingly. By simulation it was shown that DPS-MAC requires less protocol overhead during the communication process and thus performs more energy efficiently than its predecessors under various network operating conditions. Furthermore, DPS-MAC is less prone to become overloaded or unstable in conditions of high traffic load and high contention levels respectively. These improvements cause the use of DPS-MAC to lead to longer node and network lifetimes, thus making low traffic WSNs more feasible. / Dissertation (MEng)--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

At present, an important task for Chinese governments at all levels is to save energy and reduce pollutant emissions. The task of buildings energy efficiency accounts for 21% in the 12th Five Year Plan which from 2011 to 2015. With the development of social economy，the energy shortage is serious day by day．The energy-conservation of buildings is a high relevant issue in China．There are a large capacity and a wide range of existing buildings in Qingdao among which the overwhelming majority is the non-energy-efficient buildings and the operate energy consumption are enormous．At Present, according to the related statistic，the energy efficient building area only accounts for 3% to 5% of the total building area newly increased in our country every year, while in such existing buildings in Qingdao ，most of them are highly energy-consuming, the energy consumption in buildings is about 100-350 kWh for each floor area of the whole year，which is 2 to 3 times of the energy consumption of the same area of energy efficient buildings．So we can say that whether could we promote the effective use of resources and energy in buildings is very important，which will finally determine whether could we and take the road to sustainable development． In respect of the application of the complicated systematic scientific conclusions，the thesis carries out the analysis of geographic and climate characteristics in Qingdao area and the research of current energy consumption． Based on the quantitative model analysis of environmental and economic benefits of implementation of energy efficient buildings in Qingdao in scenario k, promotion and implementation of energy efficient buildings can substantially reduce the current high environmental cost associated with energy consumption for heating and cooling in buildings in Qingdao. Emission including carbon dioxides, sulfur oxide, nitrogen oxides and ash can be reduced, it means that under the scenario k energy efficient buildings has an idea performance on reducing pollutant gas. At the same time, companied by the great environmental benefits, there are also substantial economic benefits. Barriers to energy efficiency in buildings in Qingdao, including political, economic, social and technological barriers are discussed in this thesis. According to the investigation and analysis about the present situation and factors affecting the implementation of energy efficient buildings in Qingdao, this thesis put forward recommendations from the aspects of environment, politics, economy, society and technology to improving energy efficient buildings in Qingdao.

The notion of the networked society is more than ever true nowadays. The Internet has a big impact on our daily lives. Network operators provide the underlying infrastructure and continuously deploy services in order to meet customer demands. The amount of data transported through operator networks is also increasing with the introduction of new high band width services and over the network content. That being said, operators, most often deploy or operate networks to meet these demands without any regard to energy-efficiency. As the price of electricity continues to grow,  tends to become a problem with serious implications. To solve this problem a trend towards more energy efficient networks has emerged. In this thesis, we investigate a way to facilitate the introduction of new energy efficiency paradigms for fixed networks. Towards this end, we investigate the energy efficiency schemes proposed up to now and select one that we believe is more realistic to deploy. Furthermore, we specify the inputs required for the selected “green” routing approach. Moreover, we study existing and new protocols that can provide basic network monitoring functionality that enables the acquirement of these inputs. In the end, a Software Defined Networking (SDN) approach is proposed to facilitate the development of energy-efficient aware networks. The details of a basic SDN monitoring application are presented from an abstract architectural point of view and three designs stemming from this basic architecture are discussed. The three designs are namely All_Flow, First_Switch and Port_FlowRemoved. The first two were implemented as steps towards understanding the full capabilities of performing monitoring in SDN enabled networks and provided useful input towards realizing the third one as a proof of concept. Their usage and faults are discussed as they can provide useful insight for possible future implementations. The Port_FlowRemoved is the design and implementation that is suggested as providing the most fitting results for the monitoring purpose at hand. This purpose is to retrieve the identified inputs for the selected “green” networking approach. The differentiation factor among the three designs is how they collect the required inputs from the network. A fast-prototype is created as a proof of concept in order to validate the proposed architecture and thus empower the validity of the idea.

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Aujourd’hui, il y a une demande croissante de fournir les informations d'environnement en temps réel tels que la qualité de l'air, le niveau de bruit, état du trafic, etc. pour les citoyens dans les zones urbaines a des fins diverses. La prolifération des capteurs de smartphones et la mobilité de la population font des Mobile Crowdsensing (MCS) un moyen efficace de détecter et de recueillir des informations a un coût faible de déploiement. En MCS, au lieu de déployer capteurs statiques dans les zones urbaines, les utilisateurs avec des périphériques mobiles jouent le rôle des capteurs de mobiles à capturer les informations de leurs environnements, et le réseau de communication (3G, WiFi, etc.) pour le transfert des données pour MCS applications. En général, l'application MCS (ou tâche) non seulement exige que chaque participant de périphérique mobile de posséder la capacité de réception missions de télédétection, de télédétection et de renvoi détecte résultats vers un serveur central, il exige également de recruter des participants, attribuer de télédétection tâches aux participants, et collecter les résultats obtenues par télédétection ainsi que représente les caractéristiques de la cible zone de détection. Afin de recruter un nombre suffisant de participants, l'organisateur d'une MCS tâche devrait considérer la consommation énergétique causée par MCS applications pour chaque participant et les questions de protection dans la vie privée, l'organisateur doit donner a chaque participant un certain montant des incitations comme un encouragement. En outre, afin de recueillir les résultats obtenues par télédétection et représentant la région cible, l'organisateur doit s'assurer que les données de télédétection qualité des résultats obtenues par télédétection, p. ex., la précision et la spatio-temporelle la couverture des résultats obtenus par télédétection. Avec la consommation d'énergie, la protection de la vie privée, les mesures d'incitation, de télédétection et qualité des données à l'esprit, dans cette thèse nous avons étudié quatre problèmes d'optimisation de mobile crowdsensing et mené après quatre travaux de recherche [...] / Nowadays, there is an increasing demand to provide real-time environment information such as air quality, noise level, traffic condition, etc. to citizens in urban areas for various purposes. The proliferation of sensor-equipped smartphones and the mobility of people are making Mobile Crowdsensing (MCS) an effective way to sense and collect information at a low deployment cost. In MCS, instead of deploying static sensors in urban areas, people with mobile devices play the role of mobile sensors to sense the information of their surroundings and the communication network (3G, WiFi, etc.) is used to transfer data for MCS applications. Typically, an MCS application (or task) not only requires each participant's mobile device to possess the capability of receiving sensing tasks, performing sensing and returning sensed results to a central server, it also requires to recruit participants, assign sensing tasks to participants, and collect sensed results that well represents the characteristics of the target sensing region. In order to recruit sufficient participants, the organizer of the MCS task should consider energy consumption caused by MCS applications for each individual participant and the privacy issues, further the organizer should give each participant a certain amount of incentives as encouragement. Further, in order to collect sensed results well representing the target region, the organizer needs to ensure the sensing data quality of the sensed results, e.g., the accuracy and the spatial-temporal coverage of the sensed results. With the energy consumption, privacy, incentives, and sensing data quality in mind, in this thesis we have studied four optimization problems of mobile crowdsensing and conducted following four research works: • EEMC - In this work, the MCS task is splitted into a sequence of sensing cycles, we assume each participant is given an equal amount of incentive for joining in each sensing cycle; further, given the target region of the MCS task, the MCS task aims at collecting an expected number of sensed results from the target region in each sensing cycle.Thus, in order to minimize the total incentive payments and the total energy consumption of the MCS task while meeting the predefined data collection goal, we propose EEMC which intends to select a minimal number of anonymous participants to join in each sensing cycle of the MCS task while ensuring an minimum number of participants returning sensed results. • EMC3 - In this work, we follow the same sensing cycles and incentives assumptions/settings from EEMC; however, given a target region consisting of a set of subareas, the MCS task in this work aims at collecting sensed results covering each subarea of the target region in each sensing cycle (namely full coverage constraint).Thus, in order to minimize the total incentive payments and the total energy consumption of the MCS task under the full coverage constraint, we propose EMC3 which intends to select a minimal number of anonymous participaNts to join in each sensing cycle of the MCS task while ensuring at least one participant returning sensed results from each subarea. • CrowdRecruiter - In this work, we assume each participant is given an equal amount of incentive for joining in all sensing cycles of the MCS task; further, given a target region consisting of a set of subareas, the MCS task aims at collecting sensed results from a predefined percentage of subareas in each sensing cycle (namely probabilistic coverage constraint).Thus, in order to minimize the total incentive payments the probabilistic coverage constraint, we propose CrowdRecruiter which intends to recruit a minimal number of participants for the whole MCS task while ensuring the selected participants returning sensed results from at least a predefined percentage of subareas in each sensing cycle. • CrowdTasker - In this work, we assume each participant is given a varied amount of incentives according to [...]

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Due to fundamental physical limitations, conventional digital circuits have not been able to scale at the pace expected from Moore’s law. In addition, computationally intensive applications such as neural networks and computer vision demand large amounts of energy from digital circuits. As a result, energy efficient alternatives are needed in order to provide continued performance scaling. Analog circuits have many well known benefits: the ability to store more information onto a single wire and efficiently perform mathematical operations such as addition, subtraction, and differential equation solving. However, analog computing also comes with drawbacks such as its sensitivity to process variation and noise, limited scalability, programming difficulty, and poor compatibility with digital circuits and design tools. We propose to leverage the strengths of analog circuits and avoid its weaknesses by using digital circuits and time-encoded computation. Time-encoded circuits also operate on continuous data but are implemented using digital circuits. We propose a novel scalable general purpose analog processor using time-encoded circuits that is well suited for emerging applications that require high numeric precision. The processor’s datapath, including time-domain register file and function units are described. We evaluate our proposed approach using an implementation that is simulated with a 0.18µm TSMC process and demonstrate that this approach improves the performance of a scientific benchmark by 4x compared against conventional analog implementations and improves energy consumption by 146x compared against digital implementations.