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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.
41

Energieffektivisering av en byggnad med kulturvärden : En studie av avvägningen mellan kulturhistoriska värden och energieffektivisering / Improving the energy performance of an historic building : A study of the tradeoff between cultural heritage and energy performance

Martelius, Simon, Robertsson, Richard January 2021 (has links)
In order to reduce the energy consumption of buildings some degree of alteration usually needs to be done to its shell and construction, which can change the appearance of the building. At the same time buildings often carry materials, details, construction methods, and other historically significant artifacts, that are important to perserve. This often leads to compromises having to be made between improvements to energy performance, and the perservation of the cultural heritage of the building. In this project, a building from the late 1800s in Söderhamn, Sweden, was analyzed to find appropriate energy saving measures while also taking its cultural history into consideration. The simulation software VIP Energy was used to build a model of the house where simulations of different energy saving measures as well as different cases of occupant behaviour could be tested. From these tests, measures were selected and sorted into three packages depending on their level of energy reduction, invasiveness of cultural heritage, and overall complexity. Package A had the lowest energy reduction, but also the lowest invasiveness and complexity of the three. Package C had the highest energy reduction, but with next to no regard for the cultural heritage of the building, nor the complexity of implementing the measures in it. Package B was chosen to contain the measures that according to the authors sucessfully strike a balance between energy effectiveness and the perservation the building’s cultural heritage. The model of the building without measures implemented had a primary energy value of 181kW h/m2, an energy usage of 117 kW h/m2, and a thermal conductivity of 0.504 W/m2K. With package B implemented, the primary energy value was reduced to 54.3 kW h/m2, the energy usage to 32.4 kW h/m2, and the thermal conductivity to 0.247 W/m2K, which makes the building live up to the current standards set by the National Board of Housing, Building and Planning. With proper occupant behaviour, the primary energy value and the energy usage could be further reduced to 24.5 kW h/m2 and 32.4 kW h/m2 respectively. Our results suggest that large energy improvements can be made to buildings similar to this one, and that occupant behaviour is a big uncertainty when energy simulations on buildings are performed.
42

The social power grid : The role of institutions for decentralizing the electricity grid

Warneryd, Martin January 2020 (has links)
The world’s existing electricity grids face several challenges if they are to continue to provide a stable supply in the future. Aging electricity grids and the massive implementation of renewable sources require a different flexibility and robustness of future grids. Large amounts of renewable sources are implemented locally and on a small scale, increasing pressure on distribution grids to manage variable generation and bi-directional power flows. A decentralized electricity system includes both new technological designs as well as social re-organizations where prosumers become more prominent in the development and responsibilities of the electricity system. The existing centralized electricity system is fundamentally different from the decentralized, and the transformation requires an institutional framework which support the logics of decentralized technologies and organizations. Some technologies which are relevant for a decentralized electricity system include solar PV and MGs. The aim of the thesis is to investigate how the transformation toward a decentralized electricity system affects and is affected by informal institutions among relevant actors, specifically prosumers, and formal institutions related to the existing electricity system. To guide the aim this research uses a conceptual framework stemming from the theoretical field of sustainability transitions with a special emphasis on institutions. The results show that a wide variety of experienced values enhances the positive experiences with solar PV technology and thus prosumers increase their engagement and responsibilities in their own electricity system. Moreover, the values are used to enhance the positive narrative of the niche and thereby increase the attractiveness for external actors. In the formative developing field of community MGs, institutions play an important role. Informal institutions shape the formal institutional development, which also influences the informal institutions in return, by enhancing opportunities for certain groups, such as the energy democracy movement, to reach out with their message. Thus, it is concluded that informal institutions play a significant role in the development of a decentralized electricity system, affecting several niche development parameters and influencing the initial trajectories to further develop. Moreover, it is concluded that institutional developments are crucial for the development of community MGs and that informal institutional developments within communities are shaping the formal institutional developments in the sector.
43

COMPARISON OF THE WIND POWER PRODUCTION MODELS IN THE BALTIC SEA, A CASE STUDY IN THE LILLGRUND OFFSHORE WIND FARM

Liu, Zhenyu January 2021 (has links)
Wind energy, which is no emission of greenhouse gases, is attracting increasing attention world widely. Compared to onshore wind farms, offshore wind farms can yield greater power production since the wind speeds over the sea are higher and steadier than those over the land. An increasing number of offshore wind farms are being planned and deployed all over the global near-sea areas. Thus, accurate evaluation of wind power production is essential for offshore wind farm development. This study compares two popular models, the minimalistic prediction (MP) model and the linear WAsP model, in the modeling power production of the Lillgrund offshore wind farm in the Baltic Sea. The wind condition data from New European Wind Atlas (NEWA) is used to analyze the wind resources and as input data of the models to calculate wind power production. The calculated results are compared in different years and wind direction sections. The sensitivity of the calculated power production to different influencing factors, including the size of the wind farm and hub heights, are examined. The results show that the WAsP model generally yields higher energy production than the Minimalistic Prediction (MP) model. The requirement for wind condition data and wind farm layout parameters in those two models is different. Compared to the WAsP model, the MP model does not require detailed wind farm layout parameters and wind direction data, which leads to different power production results. From the results of sensitivity experiments, both the size of the wind farm and hub heights have an impact on power production. When the wind farm size increases by 5 times the original size, the wind power production increases by around 50 %. However, when the distances between wind turbines are large, the wake effect would disappear gradually. Therefore, the growth rate decreases with the increase in the size of the wind farm. The wind speed is higher with the increase in hub height. However, due to the smaller turbulence flux, the increase in wind power production with higher hub height is not obvious. When the hub height increased by 2.6 times, the wind speed just increased by around 13 %. It is not hard to conclude that designing a wind farm is a process full of trade-offs. Balancing the rich wind resources and the financial benefits from offshore wind farms are equally essential. Our study can contribute to the application of the models and the designing of offshore wind farm layouts in the Baltic Sea.
44

Virtuella Kraftverk : Anpassning av primärreglering för småskaliga vattenkraftverk

Svensson, Rasmus, Gustafsson, Alexander January 2020 (has links)
No description available.
45

Efficiency of heat and work in a regional energy system

Rosén, Tommy January 2019 (has links)
One of the largest flows of energy in Swedish municipalities is the fuel-energy flow through the regional combined heat and power (CHP) plant. The customer products from this flow are mainly electricity to the electricity grid and heat to the building sector. There are many ways to describe and examine this fuel-energy flow, and there are many perspectives. This thesis presents one perspective. It is a top-down, analytical and numerical perspective on the efficiency of heat and work in a regional energy system. The analysis focus on the present situation in Linköping municipality and aims at describing the energy efficiency improvement potential. Three subsystems are considered, the regional production of electricity, the regional production of heat, and the regional public transport by bus. These three systems are physically all heat engines i.e. engines that derive work and/or heat from fuel combustion processes. It is important to notice that the analysis in this thesis does not describe the theoretical improvement potential, that potential is considerably higher than the implementable potential, but of no practical use. Instead the analysis is as far as possible based on real world measured efficiencies and efficiency values of best practice (Best available technology). The analysis shows that hardware investments at the CHP plant can improve the electricity generation efficiency and thereby reduce CO2 emissions. The investments are in high pressure turbines, medium pressure turbines and preheaters. The size of the improvement is hard to quantify because it depends partly on unknown factors in the surrounding electricity market. In the studied system CO2 reduction could be as high as 40 - 60 %. The regionally produced biogas would be used more efficiently if it were used in the local combined cycle gas turbine instead of being used in internal combustion engines in buses. The buses would instead be electrically driven. This use of biogas would create a better integrated fuel-energy flow and reduce heat losses. Another improvement is to reduce the system temperatures in the district heating system. The study shows that the efficiency gains, because of lower system temperatures, would increase electricity production by about 1 – 3%, and that greenhouse gas emissions would be reduced by 4 – 20%. However, these improvements are dependent on demand side investments in the district heating system and are therefore slow to implement. / Ett av de största energiflödena i svenska kommuner är bränsle/energi-flödet genom det regionala kraftvärmeverket. De konsumentprodukter som detta energiflöde producerar är främst uppvärmning av bostäder och elkraft. Det finns många sätt att beskriva och utvärdera detta bränsle/energi-flöde och det finns många olika perspektiv. Det här arbetet analyserar energiflödet med en analytisk ”top-down” metod. Analysen utgår ifrån den nuvarande situationen i Linköpings kommun och avser att belysa den förbättringspotential som finns med avseende på systemets verkningsgrad. Tre delsystem har studerats, det regionala systemet för värmeproduktion, det regionala systemet för elproduktion och det regionala kollektivtrafiksystemet för innerstadstrafik med buss. Dessa tre system är fysikaliskt värmemotorer d.v.s. de är system som nyttjar termisk energi från förbränningsprocesser för att utföra ett arbete och/eller generera värme. Det är viktigt att notera att analyserna i detta arbete inte avser att beskriva en teoretisk förbättringspotential. Analyserna avser istället att belysa den praktiska, implementerbara, förbättringspotentialen. Därför har arbetet så långt som möjligt utgått ifrån uppmätta data och numeriska värden på verkningsgrader ifrån redan existerande anläggningar eller tekniska komponenter. Analyserna visar att hårdvaruinvesteringar i det lokala kraftvärmeverket skulle öka elproduktionen och därigenom sänka koldioxidutsläppen. De investeringar som skulle behöva göras är investeringar i högtrycksturbiner, mellantrycksturbiner och förvärmare. De sänkta koldioxidutsläppen är svåra att kvantifiera eftersom de delvis beror på okända faktorer på den omgivande elmarknaden. Reduktionen av koldioxidutsläppen skulle kunna vara så stor som 40 - 60 %. Den lokalt producerade biogasen skulle användas mer effektivt om den användes i den lokala gaskombi-anläggningen istället för att användas som bussbränsle som är det nuvarande användningsområdet för detta bränsle. Bussarna skulle istället kunna ersättas med elbussar. En sådan förändring av biogas-användningen skulle innebära ett bättre integrerat energisystem med lägre värmeförluster. En annan möjlig förbättring av kraftvärmesystemet är att sänka returtemperaturerna i fjärrvärmesystemet. Analyserna visar att elverkningsgraden skulle förbättras 1 – 3 % och att koldioxidutsläppen skulle kunna minska med 4 – 20 %. Dessa förbättringar skulle däremot kräva investeringar på kraftvärmesystemets kundsida och bedöms därför vara långsamma att implementera.
46

Comparison of different reactor configurations for ex‐situ biological biogas upgrading

Porté Laborde, Hugo January 2016 (has links)
Climate change is one of the major challenges of the 21st century. The energy sector represents the main contributor to global greenhouse gas emissions, due to its reliance on fossil fuels. Renewable energies arise as current solutions. Nevertheless, they are still facing two central difficulties: the lack of large-scale energy storage technologies to deal with their intermittent nature (e.g. wind and solar power), and the absence of energetically dense fuel alternatives for the transportation sector. Additionally, biogas technologies are indispensable for achieving sustainable societies. They result in energy and nutrients recovery from waste, mitigating greenhouse gas emissions and other kinds of pollutions. These technologies are required in circular economies, characterised by the nonproduction of disposable wastes. However, biogas needs to be upgraded to optimise its properties as energy carrier. Indeed, biogas upgrading results in a broader use for the gas, besides combined heat and power generation; enabling its efficient transport, large-scale storage, and use as vehicle fuel. This project shows how electricity and gas systems can be integrated through an innovative Power-to-Gas technology which is able to partially solve these problems. The technology is based on the synergy of coupling biogas plants to hydrogen generation systems powered by off-peak electricity surpluses from intermittent renewable energies (e.g. solar and wind power), and subsequent biological methanation of the CO2 from the biogas and the produced H2 in an ex-situ anaerobic reactor. At first, this thesis presents a detailed definition of the overall innovative system and its different components. Subsequently, focus is put on the search for the most suitable biological methanation technology for industrial purposes. Through experimental work, this thesis examines and compares four different anaerobic reactor configurations, aiming to determine the most effective technology among the ones studied. Expressly, the experiment investigated different diffusion techniques for injection of the gases in the liquid media, together with diverse pore-sizes for the mentioned diffusers. The leading reactor configuration transformed 98.4% of the injected H2 at the highest loading rate tested (3.6 LH2/LR.d), upgrading biogas from a CH4 concentration of 60% to 96% in volume. The performance of the different setups is examined, and origins for the biological efficiency variations are elucidated, in order to help with the selection of subsequent experimental prototypes. Given its early stage of development, this biomethanation unit process forms the pivotal technology of the overall system. As soon as this technique is developed, a fully commercial system will be available to initiate major environmental and socio-economic benefits.
47

Scenarier för framtida effektbalans i elområde tre

Catarina, Sparre January 2019 (has links)
No description available.
48

Heat Pump Data Performance Analysis of Large Scale Ground Source Heat Pump Systems

Norrman, Marcus, Monthan, Felix January 2020 (has links)
This study aimed at refining and improving current methodology concerning large-scale heat pump performance. This study was performed on two large-scale ground source heat pumps located in Solna (Stockholm). These were connected to an aquifer thermal energy storage system which provided heating and cooling for two office buildings. The heat pumps had been equipped with preliminary sensors from the BMS (Building management system) and been in operation since 2016. In 2019, additional detailed measurement equipment from ClimaCheck was installed to collect comprehensive data from the heat pumps to allow a more comprehensive performance evaluation. This study was primarily performed by data pre-processing of the BMS-data and the ClimaCheck-data. Once this was done, the ClimaCheck parameters were backtracked and recalculated. Subsequently new models for system evaluation was implemented. The most desired parameter to replace in the ClimaCheck model was the mass flow rate, which they obtain though an energy balance over the compressors. The latter part of the study was to see whether the BMS had sufficient data to provide the same information as ClimaCheck. This was done by implementing a regression of the BMS-data, where the heating and cooling capacities from ClimaCheck were used as targets. The results from the study showed that implementing a mass flow rate based upon compressor efficiency instead of an assumed heat loss was difficult and only reliable for higher loads. When evaluating the ClimaCheck parameters, interesting results were found concerning their calculations for the heating capacity, which might not be calculated the way they express in their formulas. The regression from the BMS-data was proven difficult because of the insufficient and lacking data for some instances. Five different models were produced and compared, some models showed accuracy up to 95% depending on the desired metric. It can be concluded that it is possible to estimate the key performance indicators using the BMS-data. It yields good results for the COP’s and very accurate results for the SPF’s over a year. This makes it possible to evaluate the heat pump performance for years prior to the installation of the ClimaCheck system. / I den här studien analyseras metodiken för att bestämma prestandan hos industriella värmepumpar. Studien utfördes i Solna utanför Stockholm på ett värmepumpsystem som är kopplat till en grundvattenkälla. Systemet tillförde uppvärmning och kylning till tv˚a kontorsbyggnader. Systemet har varit i drift sedan 2016 och i samband med installation s˚a sattes sensorer upp f¨or att kontrollera systemet. Dessa sensorer ¨ar kopplade till bygnadernas BMS, som är utvecklat av Siemens. I början av 2019 anlitades företaget ClimaCheck för att installera ytterligare ett mätsystem, så att värmepumparnas prestanda kunde analyseras. Denna studie utfördes endast på värmepumparna som bara utgjorde en liten del av hela systemet. Till en början fokuserade studien på analys och databehandling av all data, både på datan från Siemens och ClimaCheck. Med hjålp av den uppmätta ClimaCheck-datan verifierades sedan ClimaChecks metod, genom att implementera ClimaChecks beräkningar i python. Detta gjordes primärt för att både kunna verifiera och sedan kunna implementera en möjlig förbättring i massflödet som ClimaCheck använder i sin modell. Sedan gjordes flera regressionsmodeller med BMS variabler, där targetvariablen sattes till antingen ClimaChecks beräknade värmeeffekt eller kyleffekt, beroende på vilken av dem som analyserades. Anledningen till detta var att BMS-datan inte innehåller de mätpunkter som krävs för att teoretiskt bestämma kapaciteterna. När det nya mass flödet introducerades blev resultatet inte önskvärt och den nya modellen var bara tillämpbar då värmepumparna gick på max effekt. När ClimaChecks beräkningar och parametrar återskapades hittades intressanta resultat angående värmekapaciteten. Den gick inte att återskapa med deras enthalpiberäkningar, utan den hittades istället med en annan metod. Regressionen som gjordes gav goda resultat om man bortser från vissa antaganden som gjorts. Regressionen kunde beroende på vilken parameter som efterfrågades ha en noggrannhet på upp till 95%. Studien visar att ClimaCheck har en bra och fungerande modell men den kan förbättras. Den tar även upp hur viktigt det är med data för att ordentligt och effektivt kunna utvärdera system. Slutligen kommer studien åskådliggöra en god metodik för hur data kan hanteras och tillämpas. Systemutvärdering är av yttersta vikt för att reducera energikostnader och många system skulle behöva utvärderas.
49

Energy and climatescenarios within the doughnut? : Treatment of planetary boundaries, social foundations for human prosperity and economic growth in energy and climate scenarios / Hantering av planetära gränser, sociala grunder för mänsklig välfärd och ekonomisk tillväxt i energi- och klimatscenarier

Musabasic, Adi January 2015 (has links)
No description available.
50

Comprehensive Analysis of Organic Rankine Cycles for Waste heat recovery applications in Gas Turbines and IC Engines

Tristan, Alejandro January 2014 (has links)
Executive Summary This investigation aimed to assess the true technical and environmental potential, plus economic feasibility of the ORC technology as bottoming cycles for Gas turbines and IC Engines power applications. The assessment started by creating a modeling tool using the software EES in order to model several bottoming cycle configurations and match them with the mentioned power generation technologies. This model used as inputs the operational data of small range (5.5V 50 MW) Siemens Gas Turbines and power plant recommended Wärtsila IC Engines. Thus, adding practical reliability to the model. The simulation also defined 5 control parameters: organic working fluid, operative high pressure of the cycle, minimum temperature difference in the heat exchange, degree of superheating and amount of regeneration. These 5 factors were selected because their role in defining not only the power output, but also the economical cost of an eventual application. Six different organic fluids ranging from Alkanes, Aromates and Siloxanes were analyzed in particular ranges for each of the other 4 mentioned control parameters. After the simulation a preliminary analysis was performed through comparative matrixes. This contrast intended to outstand the configuration with the highest power output and the smallest capital investment cost. Although no costs were inserted in the model, this last factor was analyzed through the cycle’s components size. Three different configurations were selected from this analytic process. The two better preforming cycles and a third option that ideally balanced the two examined factors. Further study quantified the fuel and emission reductions per unit of power when the selected ORCs were implemented and the mild environmental impacts that this additions would have were also quantified. Finally a Cost Benefit Analysis was implemented in which it was reached that although feasible, economically ORC implementation is not more attractive that Business as Usual scenario, implementation of the mentioned equipment without bottoming cycle. This investigation concluded that although ORC implementation could be a major technical improvement for IC Engine and Gas Turbine based power plants, increasing the power output up to 20% and 44% respectively, it suffers from high capital prices due to the novelty of the commercial applications and a lack of balance between output, size and reduction of its production costs. It finalizes by recommending that in order to achieve a more positive situation, a strategy towards a higher economy of scale and increased researched in component cost reduction should be performed.

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