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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

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.
42

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.
43

Scenarier för framtida effektbalans i elområde tre

Catarina, Sparre January 2019 (has links)
No description available.
44

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.
45

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.
46

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.
47

Energy Balance and Quantification of Rest Energies at SSAB Oxelosund AB

Datta, Rajarshee January 2015 (has links)
The iron and steel industry is an energy intensive energy that consumes vast quantities of fossil fuels as the primary source of energy due to the dependence on coal for steel making. Although the SSAB integrated iron and steel plant at Oxelosund generates electricity and district heat from the process gases, the overall efficiency of the system is a mere 58%. In order to meet future climate targets and energy prices, the iron and steel industry has to improve its energy and resource efficiency. Furthermore, an extensive energy balance for SSAB Oxelosund has not been conducted till date. This served as the main motivation for this project. This report forms the basis of such a study and also provides a near accurate picture of the energy balances at SSAB Oxelosund, encouraging future work in this domain. This report shows that there is lot of waste heat at present that can be utilized by SSAB if such a demand exists. A few improvements have been suggested to improve the overall efficiency, however major changes may not be profitable due to the fact that the steel industry is in a decline today and major process changes will not be a viable solution.
48

Energikartläggning av förskolor - en fallstudie

Holmén, Malin, Härdelin, Sofia January 2015 (has links)
This study was performed in order to evaluate the difference in energy performance between two buildings, Temmelburken 1 and Temmelburken 2, by comparing the measured and the expected values calculated during the planning process. The two buildings were built after almost the same blueprints with the exception that the floor plan was mirrored from one another. In this study, energy measurements have been done and with these measurements as foundation, the energy demand was calculated. After this, a sensitivity analysis of the input parameters has been carried out. The result of the energy calculations were that the specific energy usage of the buildings were; 129,2 kWh/m2 and year for Temmelburken 1 and 111,0 kWh/m2 and year for Temmelburken 2. The expected energy performance of Temmelburken 1 and Temmelburken 2 were 94,36 kWh/m2 and year and 89,69 kWh/m2 and year, respectively. The major difference between the expected energy usage and the measured was for the domestic hot water, where the real value was over 300 percent more. The heating demand for the ventilation system showed the lowest difference compared to the values assumed during the planning, and were 17 percent higher for Temmelburken 1 and 21 percent higher for Temmelburken 2. Whereas the energy demand for the radiator systems were calculated to values 100 and 46 percent higher for Temmelburken 1 and Temmelburken 2, respectively. The study also showed that the radiator system’s energy demand was where the two building significantly differed. The sensitivity analysis of the simulation model concluded that the indoor dry bulb temperature and the climate file made the greatest difference in the result. When increasing or lowering the indoor dry bulb temperature with one degree, the total energy demand increased or lowered by 5.3 percent respectively. When another climate file was used, the total energy demand increased with 6.8 percent. / Denna studie har sökt svar på varför två byggnader, Temmelburken 1 och Temmelburken 2, byggda efter spegelvända riktning har påvisat olika energianvändning. Studien har även undersökt varför byggnaderna ifråga har påvisat sämre energiprestanda än vad som projekterades. För att göra detta har energimätningar i byggnaderna gjorts samt energiberäkningar med mätningarna som grund. En undersökning av valda indataparametrars känslighet har även gjorts. Resultatet av beräkningarna av byggnadernas specifika energianvändning visade att Temmelburken 1 använder 129,2 kWh/m2 och år och Temmelburken 2 använder 111,0 kWh/m2 och år. Detta ska jämföras med de projekterade värden som var 94,36 kWh/m2 och år respektive 89,69 kWh/m2 och år. Den största skillnaden mellan de projekterade och beräknade värdena var för varmvattenanvändningen som var mer än 300 procent högre. Elanvändningen i de två byggnaderna visade sig vara lägre än de projekterade värdena, 13 respektive 14 procent lägre. Ventilationens värmebehov var det fjärrvärmebehov som var närmast de projekterade värdena - 17 respektive 21 procent högre. Radiatorsystemets värmebehov beräknades till 100 och 46 procent högre gör Temmelburken 1 respektive Temmelburken 2. Anledningen till det den stora skillnaden för radiatorsystemet har inte kunnat kartläggas, då studien genomfördes under månader då byggnaderna saknade värmebehov. Känslighetsanalysen visade att de indataparametrar som påverkade den totala energianvändningen mest var inomhustemperaturen samt den klimatfil som användes. En höjning eller sänkning av inomhustemperaturen med en grad resulterade i en ökning respektive minskning av det totala energibehovet med 5,3 procent. Att använda en annan klimatfil gav utslag med 6,8 procent på den totala energianvändningen.
49

Feasibility Study of Vertical Axis wind turbines in Urban areas of Sweden

Awan, Muhammad Rizwan January 2013 (has links)
No description available.
50

Framtida energiförsörjning till off-grid basstationer

Bramberg, Gustav January 2013 (has links)
Telekombranschen har de senaste decennierna upplevt en stark tillväxt, framförallt i urbana områden och västvärlden. Nu när denna tillväxt även sker i utvecklingsländer och dess landsbygd, söks det efter nya sätt att försörja basstationer som ej är kopplade till elnätet med energi. Syftet med detta examensarbete är att studera och analysera framtida hållbara energilösningar för basstationer inom telekombranschen. Detta görs genom att kartlägga alternativ, analysera vilka hinder och möjligheter som finns samt undersöka vilka kompetenser som krävs för en vidare utveckling. Arbetet har framförallt baserats på intervjuer av aktörer i telekombranschen samt litteraturstudier. Studien visar att de tekniker som i framtiden har störst potential att ersätta dieselgeneratorerna idag är solceller samt småskalig vindkraft. För att denna utveckling skall ske krävs det innovationer och nya sätt att implementera energisystem med basstationer. I framtiden kommer det även finnas ett stort behov av projektering och modeller för att dimensionera samt optimera basstationers energisystem. / In recent decades, the telecom industry has experienced a rapid growth in urban areas and the western world. This growth is now spreading towards developing countries and their rural areas, where proper energy grids may be lacking. In order to cope with insufficient energy infrastructure and improve their services in rural areas, the telecom industry is now looking to develop better off-grid telecom base stations. The purpose of this thesis is to study and analyse future sustainable energy solutions for off grid base stations in the telecom industry. This is purpose will be met by mapping possible alternatives and analysing what advantages and disadvantages these alternatives have, as well as investigating what competencies the industry needs. The work is foremost based on literature studies and interviews of stakeholders in the telecom industry. The study concludes that photovoltaic solar cells and small scale wind power are the two energy generating technologies that has the greatest potential of replacing the diesel generators that are now commonly used on off grid base stations. In order for this to happen, two important areas that the industry needs to focus on is innovation and new ways of implementing the energy systems with base stations. The demand of planning, dimensioning and designing the energy systems will increase in the near future as the renewable energies increases their market share.

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