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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Termisk lagring vid Akademiska sjukhuset : Kapning av effekttoppar, ökad redundans och energisäkerhet

Ohlsson, Pontus January 2018 (has links)
The Academic Hospital in Uppsala is a major heat energy consumer with an average consumption of 39 GWh/year in recent years, and the heat is supplied by the district heating system which is owned by Vattenfall. The purpose of this work was to investigate if a thermal storage can reduce the costs of district heating consumption and increase the redundancy at the hospital by cutting the heat demand peaks and provide back-up heat in case of district heating deliverance failures. The type of heat storage used in this study is a pit heat storage which consists of an insulated basin in the ground filled with hot water which is sealed from above with a lid that acts as an insulating layer. Matlab was used for the simulations of different storages sizes and used year 2016:s heat consumption of the hospital building B11 to see how the storage worked. The introduction of a thermal storage will increase the total sum of purchased heat for all storage sizes and the two larger storage sizes manage to cut down the heat demand peak while the two smaller storage sizes increases it slightly. This means increased annual costs for the smaller storage sizes but reduced annual costs for the larger storage sizes. However this doesn’t included the drift or the investment costs. The conclusion is that heat storage is not an economic benefit because the annual cost savings are highly dependent on Vattenfall's price model and the repayment period will be several decades long. A heat storage can be an energy-saving benefit but at a high cost.
32

Road map of the ultimate sustainable bio-fuel production from microalgae

Idris, Lina January 2015 (has links)
No description available.
33

FEASIBILITY STUDY OF BUILDING INTIGRATED HYBRID SOLAR PV AND WIND POWER SYSTEMS: A CASE-STUDY ON THE SWEDISH ISLAND OF GOTLAND

Lee-Jones, David January 2016 (has links)
This Thesis carries out a high level analysis of the financial feasibility of building integrated small scale renewable energy systems. A number of alternative system configurations have been established that include a mixture of grid connected wind turbines and solar photovoltaic (PV) applications to provide electricity to meet the demand of the base load demand of the building, with any occurrence of excess production sold back to the grid. A methodology to account for an analysis of their feasibility has been developed. The methodology is based on a well-known clean energy system analysis tool, namely RETScreen. The local climate data has been extrapolated and calculations carried out using the RETScreen database and software. From this, the maximum initial financial investment of the systems has been estimated, based on a given financial hurdle rate (i.e. the annual financial interest return on initial investment) and the savings and income generated from reduced grid electricity consumption and selling electricity back to the grid. The methodology is applied to an academic building located in the city of Visby on the Swedish island of Gotland, with a hurdle rate set to 7%. Electricity generation scenarios include 4 systems with 3.6 - 15.2 kW of wind, and 21.5 kW of PV located on a flat roof of a building containing office space, lecture rooms and a large student break area. Of the considered systems, it was concluded that the most feasible system was the system with a mixture of 15.2 kW of installed wind capacity and 21.5 kW of installed solar PV capacity. In addition, the results suggested that even with the grant system in place in Sweden for solar PV systems, the solar PV part of the systems would likely not be feasible. Therefore it was suggested that future work in this area should involve an investigation of a purely wind power system be carried out, as well as to investigate the hourly demand of the building and the hourly potential supply of the renewable energy system. The building permit process, installation and energy resources and requirements and installation should also be researched further, including taking actual energy consumption readings from the building and installing climate measuring instruments in the proposed positions on the roof in order to achieve more accurate input data.
34

A Disaggregation Model for Studying Behaviours in Power Consumption

Wik, Ellika January 2017 (has links)
A feature of the Smart Grid is the utilization of flexible load in the power system. The presence of flexible load allows part of the power consumption to be shifted from peak hours to off-peak hours; this change in power consumption is called a load shift. If the usage pattern of appliances is identified, it is possible to estimate the capacity of a potential load shift as well as evaluate if the utilization of flexible load in the power system results in a load shift. This master thesis project aims to create a model which works as an aid when studying usage patterns by identifying when appliances that contribute to the load shift are active. The model should be able to give approximations of the switch-on and switch-off time of the appliances using only information from a single meter that measures the total power consumption of the entire household. Recently, artificial neural networks have been successfully applied to these kinds of problems. The constructed model thus includes neural networks which regress the start time and end time of a target appliance. The networks are trained and evaluated both on simulated data and on real measured data from the Stockholm Royal Seaport project. The model is able to give highly accurate estimates of the start and stop time when trained with simulated data. When using real data the accuracy of the model is relatively low. In order to increase the performance the neural network part of the model has to be trained on a larger dataset. A study of how the sampling time of the input affects the performance of the model is also carried out. The results show no evidence that the sampling time affects the accuracy of the model. However, the architecture of the neural networks trained to recognize data with different sampling frequencies are not identical; if the pooling layers of all networks were removed it might be possible to establish a connection between sampling time and performance.
35

Hållbar energiförsörjning inom Bertegruppen AB : Tekniska och marknadsmässiga förutsättningar för solcellsinvesteringar inom koncernen / Sustainable energy consumption within Bertegruppen

Johansson, Hampus January 2017 (has links)
This thesis was conducted to study Bertegruppens vision of being a business group self-sufficient on electrical energy. The scope was to investigate the potential of the vision being realized in a near future by adding solar energy to the existing energy production mix. Examinations of the energy need and the consumption pattern at the different companies were made by studying hourly data from the electricity supplier. Future energy need was determined during interviews and study visits, where potential areas for solar modules also were identified. Global solar radiation data was collected fromthe STRÅNG model, provided by the Swedish Meteorological and Hydrological Institute. These data were inserted to the micro power simulation tool HOMER ENERGY, along with solar module parameters from a solar energy installer Bertegruppen has initiated discussions with. The simulations resulted in potential solar energy production for a maximized and an adapted case for each company. In the adapted case, the implications from the Swedish solar energy market were considered while in the maximized case they were not. The simulation output data were then processed in the computational tool MATLAB, along with the hourly data over the electrical energy consumption at each company. At last economical calculations were carried out for the maximized and adapted case for each company, based on the Levelized Cost of Energy method. By adapting the maximized solar cell systems at each company, expand the hydropower station according to the plans, add diary-residues from Sia Glass to the biogas plant and account for the electrical energy bought from other hydropower stations in Suseån within the guarantees of origin system, Bertegruppen would produce 50.8 percent of their electrical energy need in 2021. For the adapted solarcell systems, the share would be 46.3 percent. The maximized solar cell systems resulted in a LCOE of 0.522 kr/kWh for Bertegruppen at a present value of 1 934 tkr.The LCOE for the adapted solar cell systems would be 0.529 kr/kWh at a presentvalue of 823 tkr.
36

Utilisation of Excess Heat Towards a Circular Economy : Implications of interorganisational collaborations and strategic planning

Päivärinne, Sofia January 2017 (has links)
In order to significantly lower the environmental impact from human activities, numerous efforts and approaches related to the transformation of human activities have developed during the last decades. Examples of such efforts are policies and strategies at different levels, some with a top-down approach focusing on extensive institutional changes, and some with a bottom-up approach focusing on industrial actors and industry-led activities. One essential aspect of these efforts concerns the energy used producing the products and services provided within our society. This includes, for example, improved efficiency of processes in order to minimise the amount of energy used, or optimisation of efficiency by using energy with the lowest possible exergy value. It can also be about re-use of energy, which is the focus of this thesis. Heat, which is the main by-product of all energy systems, can be utilised for heating purposes to lower the primary energy demand for heating. Increased utilisation of excess heat, however, requires collaboration between normally unrelated actors, those with a supply of and those demanding excess heat. In Sweden, which is a Northern European country with high demand for heat, the tradition of large energy-intensive manufacturing industries generating large amounts of excess heat, in combination with well-established district heating distribution systems, constitute good conditions for excess heat utilisation. Despite the fact that Sweden is among the world leaders in utilising excess heat, there is however, still a large unutilised potential. From this background, the objective of this thesis is to identify challenges behind excess heat utilisation for heating purposes, and to propose practical suggestions to facilitate expanded excess heat utilisation. The overall objective is analysed with a focus on drivers and barriers behind interorganisational collaborations on excess heat utilisation, important components of interorganisational business models and how the technical conditions regarding supply and demand could be facilitated by strategic municipal spatial planning processes. The research is largely based on interviews conducted with societal actors with different perspectives on excess heat utilisation; energy companies, industries generating high-grade excess heat, facilities generating low-grade excess heat, facilities demanding low-grade excess heat, experts of utilisation of low-grade excess heat, branch organisations, municipal spatial planners, energy- and climate advisors, and developers. Document studies have been conducted in order to collect case specific knowledge. The research questions are explored based on literature studies on the principles of industrial symbiosis, business model perspective and strategic planning. Further, they are examined in a Swedish context. It is concluded that the three perspectives complement each other by providing a system perspective on increased utilisation of excess heat as they seek to contribute both environmental and financial benefits at both a company and societal level. In order to facilitate further utilisation of excess heat it is important to focus on the organisational factors of humility, honesty, transparency, trust, fine-grained information transfer, joint problem solving, and shared visions of common goals, which are important conditions behind development of functional and long-term durable collaborations. Business models for collaboration could contribute to the creation of these organisationally important conditions. Such business models could also provide knowledge on how to create and capture joint values. For some collaborations involving actors lacking the technical knowledge related to the capturing and distribution of excess heat, a third-party providing services related to the technical knowledge required could be beneficial. Collaborations in which one of the actors consists of an energy company often entail the technical knowledge required. This implies that different collaborations involving different types of actors and under different prevailing financial, technical and organisational conditions require customised and flexible business solutions. Local authorities could, through their overall function, initiate interorganisational collaborations on excess heat within the framework of municipal spatial planning. The results do however show that the investigated planning processes could develop more extensive stakeholder participation to include further societal actors related to excess heat. More extensive stakeholder participation, have the potential to initiate new development of collaborations on excess heat between normally unrelated actors, both with and without involvements of third-party knowledge brokers. A broader participation is also expected to result in increased knowledge on how to plan to further facilitate the condition of excess heat utilisation.
37

Utredning om hur 4:e generationens fjärrvärmeteknik kan implementeras i Borlänge Energis fjärrvärmenät

Strand, Simon January 2017 (has links)
Genom att samhället utvecklas och bland annat strävar mot effektivare energianvändning, ökning av andelen förnyelsebara energikällor samt sänkta koldioxidutsläpp. Är det ofrånkomligt att energisystemen i samhället inte påverkas. Bland annat så krävs det inte lika mycket energi för att täcka byggnaders energibehov i dag än tidigare. Detta medför att energisystemen i samhället utvecklas och strävar efter att bli mer effektiva. I Sverige är fjärrvärmen den vanligaste uppvärmningsformen där mer än 50 % av alla bostäder och lokaler använder fjärrvärme som värmekälla. Fjärrvärmens grundtanke är mycket enkel och beprövad. Den går ut på att producera värme storskaligt vid ett eller flera värmeverk och distribuera värmen i två stålrör som ligger nedgrävda i marken ut till kunder som har värmebehov. När värmen når kunden genom framledningsröret finns där en fjärrvärmecentral som växlar värmen till fastighetens egna interna värmesystem. Det avkylda fjärrvärmevattnet pumpas då tillbaka i det andra röret (returledningen) till produktionsanläggningen för att återigen värmas upp. Genom åren har fjärrvärmen utvecklas, och ser man från de första fjärrvärmesystemen (generation 1) till dagens system (generation 3) har utvecklingen generellt varit att gå mot lägre temperaturer i systemen. Man menar nu att det är hög tid att gå från generation 3 till 4:e generationens system som generellt strävar efter att sänka temperaturerna ytterligare i systemen. Sänkta temperaturer gällande fjärrvärmesystem har visat sig ge positiva effekter gällande ekonomi, miljö och resursutnyttjande. Dels så ger sänkta temperaturer effektivare produktion eftersom mer el kan genereras i kraftvärmeverken och större andel rökgaskondensering kan användas samt att mer integrering av spill- och restvärme från industrier kan utnyttjas. Det finns olika förslag på hur man ska gå mot lägre temperaturer i systemen. Rapporten ämnar att undersöka om en ny fjärrvärmeteknik som kallas 4GDH- 3P kan vara lönsam att redan idag implementeras i befintliga fjärrvärmenät. Teknikens grundtanke är att förlägga 3 distributionsledningar istället för 2, detta för att kunna få ner temperaturerna samt spara energi och helt enkelt få mer effektiva system. Tekniken är i grunden till för nyanslutningar av lågenergihus och är under utveckling. I denna studie undersöks vilka möjligheter som finns i att ansluta ett exploateringsområde på 63 lägenheter i Borlänge. Kostnader jämförs, beräkningar på hur mycket energi som kan sparas samt vilka möjligheter det finns att sänka temperaturerna i nätet med hjälp av tekniken utreds. Resultaten visar att den nya tekniken är relativt dyr att bygga jämfört med att bygga på konventionellt sätt. I detta sammanhang visar det sig att investeringen av den nya tekniken uppskattas bli ca: 70 % dyrare än vanlig konventionell byggnation. Resultaten visar också att med den nya tekniken kan man teoretisk gå mot lägre returtemperaturer på uppemot 12,5 °C i en bestämd punkt i returledningen. Energibesparingen uppgick till 62,57 MWh under perioden juni, juli och augusti för de 63 lägenheterna som undersöktes. / The society is constantly evolving and strives for, among other things: energy efficiency, increase the proportion of renewable energy sources and reduced CO2 emissions. It is inevitable that the energy systems in the community are not affected. Among other things, it does not require as much energy today to cover the energy needs than in the past. This means that the energy systems in the society evolve and strive to become more efficient. In Sweden the most common form of heating is district heating, where more than 50% of all dwellings and premises using district heating as heating source. District heating concept is very simple and proven. It aims to produce heat on a large scale and distribute the heat in two steel tubes that are buried in the ground out to customers who have a heating requirement. When the heat reaches the customer, there is a substation that switches the heat to the building's own internal heat system. The cold water is pumped back of district heating in the other pipe (return line) to the production site to once again heat up. Over the years, district heating is developed and you can see from the first district heating systems (generation 1) to today's system (generation 3) that it has generally been moving towards lower temperatures in the systems. Now it is high time to move from generation 3 to the 4th generation system that generally strive to lower the temperature even further in the systems. Lower temperatures in district heating systems have been shown to produce positive effects regarding economic, environmental, and resource utilization. On the one hand, it also gives, more efficient production because more electricity can be generated in CHP plants and larger share of RKG can be used as well as more integration of waste and residual heat from industries can be utilized. There are various proposals on how to move towards lower temperatures in the systems. The report intends to investigate whether a new district heating technology called 4GDH-3p may be profitable to already be implemented in existing district heating network. The Technology's basic idea is to place 3 distribution wires instead of 2 in order to bring down the temperatures as well as save energy and simply get more efficient systems. The technique is basically for new accessions of low-energy houses and is under development. This study examines the possibilities of connecting a developable area of 63 apartments in Borlänge. Costs are compared, calculations on how much energy that can be saved and the options available to reduce the temperatures in the net with the help of the technology examines. The results shows that the new technology is relatively expensive to build compered to building conventionally. In this context, it turns out that the investment of the new technology are estimated to be approximately 70% more expensive than standard conventional construction. The results also shows that with the new technology, it can theoretical move towards lower return temperatures of up to 12.5 ° C at a certain point in the return line. Energy savings was amounted to 62,57 MWh in the period of June, July and August for the 63 apartments that were examined.
38

Conceptual design of a piston and piston rod for a new wave energy converter concept

Westeneng, Teus, Tajadura Cubillo, Adrian, De Miguel, Rodrigo January 2017 (has links)
No description available.
39

Digital district heating : Developing the heating value proposition with the help of digitalisation

Rangstedt Canholm, Hanna January 2021 (has links)
The aim of this thesis has been to identify key points in a district heating system where digitalisation can add higher value to the customer, and thereby contribute to a better district heating offer.  The purpose has been to examine how digitalisation of district heating processes could improve a Swedish district heating system and develop the district heating business in Sweden. This was done through simulations of four digitalisations scenarios in a district heating production and by conducting a semi structured interview study.    The scenarios were based on research on load control, for both district heating network and of a hot water tank, regulation of substations and visualizing customers' energy consumption. These digitalisations correspond to actions such as reduced supply- and return temperatures, peak reductions, reduced heat demand and reduced water mass flow.   The simulation result shows that reducing heat demand by visualizing customers' energy consumption increases customer satisfaction the most. The interview study showed, however, that visualizing customers' energy consumption will probably not be enough to make a permanent heat demand reduction. Other digitalisation solutions is to control the substation or district heating network in such a way that reductions in peak power occur. Furthermore, opportunities for data-driven pricing models are also discussed in order to create better price incentives for customers to contribute with system benefits.  All digital solutions described in this thesis are based on qualitative data collection and it is clear that digitalisation in the district heating sector is not only a technical problem. Finally, a risk analysis is done on risks and opportunities associated with digitalisation. The risks are data and personal integrity, availability, confidential risks etc. The opportunities are increased flexibility, increased use of renewable energy and waste heat, and development of the district heating offer.
40

Transmission line protection performance in presence of power electronic-interfaced devices : Impact and needed countermeasures in the Swedish transmission system

Olofsson, Hanna January 2021 (has links)
The penetration level of power electronic-interfaced devices (PEID:s) in power systems isincreasing, including wind- and solar power, HVDC and FACTS devices. Fault current injectedby PEID:s is lower in magnitude, may lack or contain a reduced negative sequence componentand can have a wide range of phase angles, as opposed to fault current supplied bysynchronous generators (SG:s). In this thesis, the impact of these changes on transmission lineprotection in the Swedish 400 kV network is investigated trough a literature review and steadystate short circuit simulations.The literature review shows that residual overcurrent protection and line differential protectionworks well in presence of PEID:s in most cases. Traveling wave based protection and other fasttime-domain protection may be suitable as well. Some type of distance protection on the otherhand, are facing challenges associated with their impedance, directional and fault identificationalgorithms, when PEID:s are the only fault current source. This is partly caused by varying prefault grid conditions, lack of negative sequent current and oscillations in fault current magnitudeand phase angle caused by the PEID controller. The thesis underlines the need for anincreased understanding of specific algorithms included in distance protection in the Swedish400 kV transmission system, as their performance in presence of PEID:s likely varies betweendifferent vendors and year of manufacturing.

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