uu.seUppsala universitets publikasjoner
Endre søk
Begrens søket
10111213 601 - 611 of 611
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 601.
    Åberg, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Widén, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Development, validation and application of a fixed district heating model structure that requires small amounts of input data2013Inngår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 75, s. 74-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reducing the energy use of buildings is an important part in reaching the European energy efficiency targets. Consequently, local energy systems need to adapt to a lower demand for heating. A 90% of Swedish multi-family residential buildings use district heating (DH) produced in Sweden’s over 400 DH systems, which use different heat production technologies and fuels. DH system modelling results obtained until now are mostly for particular DH systems and cannot be easily generalised. Here, a fixed model structure (FMS) based on linear programming for cost-optimisaton studies of DH systems is developed requiring only general DH system information. A method for approximating heat demands based on local outdoor temperature data is also developed. A scenario is studied where the FMS is applied to six Swedish DH systems and heat demands are reduced due to energy efficiency improvements in buildings. The results show that the FMS is a useful tool for DH system optimisation studies and that building energy efficiency improvements lead to reduced use of fossil fuels and biomass in DH systems. Also, the share of CHP in the production mix is increased in five of the six DH systems when the heat demand is reduced.

  • 602.
    Åberg, Magnus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Widén, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Henning, Dag
    Large-scale introduction of new residential district-heating loads to increase renewable electricity generation in CHP plants2012Inngår i: Proceedings of the World Renewable Energy Forum 2012, Denver, Colorado, USA, May 13-17, 2012, 2012, s. 2407-2414Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Combined heat and power (CHP) plants enable an efficient use of low-grade energy carriers, such as domestic waste and biomass, for co-generation of district heating (DH) and electricity. Expected future building energy-efficiency improvements reduce the demand for space heating and may limit the possibilities to cogenerate electricity. The use of DH for new applications, such as household appliances, can improve conditions for co-generation of electricity. This paper investigates the future potential to increase DH demand and co-generation of electricity due to large-scale implementation of household appliances that use DH instead of electricity. The analysis is applied to the DH system in Uppsala, Sweden. Results show that co-generation of electricity and total fuel use increase with implementation of household appliances connected to a building hot water circuit (HWC). The impact on CO2 emissions depends on DH fuel mix and electricity assessment approach.

  • 603.
    Ågren, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Energieffektivisering av industribelysning: Planering av belysningsanläggning i mekanisk verkstad2012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In Uppsala, Sweden, Vattenfall has a combined heat and power plant. On the premises there is an engineering workshop with old fluorescent and mercury lamps that need to be replaced. This provides a great opportunity to save energy and money by installing more efficient lighting. The main purpose of this study was to present two functional and energy efficient lighting systems including control system. The lighting systems were designed by investigating the working environment, measuring illuminance and by simulations in the software DIALux. Additionally Life Cycle Cost (LCC) was used as an instrument of comparison. One alternative was designed using mainly modern T5 fluorescent lighting. For the other alternative powerful LED-lamps were chosen as the primary light source. The simulations showed the two alternatives to be equally good in regard to performance and energy saving potential. With sustained illuminance level the installed power of both systems was around 34 kW ascompared to 54 kW, the estimated value of the existing lighting system. The LCC, however, differed significantly with the fluorescent alternative having a total cost of 1.1 million SEK over a 20 year period while the same number for the LED alternative being 2.2 million SEK. The difference in LCC makes fluorescent lighting the preferable alternative. The present consumption is estimated to 142 MWh. The fluorescent lighting alternative would have an approximated energy consumption of 78.6 MWh including a control system, giving an energy saving potential of 45 %.

  • 604.
    Åkerlund, Hanna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Scenarion och potential för energieffektivisering i Uppsala kommuns bostäder fram till år 2050: Ett arbete inom Färdplan 2050 för ett klimatpositivt Uppsala2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Syftet med detta examensarbete är att kartlägga potentialen för energieffektiviseringar i småhus och flerbostadshus i Uppsala kommun fram till 2050. Studien inkluderar både befintliga och framtida byggnader. Uppsala kommun arbetar tillsammans med flera olika organisationer i kommunen med att ta fram en ”Färdplan för ett klimatpositivt Uppsala år 2050” (kallad Färdplan 2050), detta med uppdrag av Naturvårdsverket. Målet med Färdplan 2050 är att ta fram en långsiktsprognos för hur Uppsala kommun kan minska utsläppen av växthusgaser med 45 % per invånare till år 2020 jämfört med år 1990. Detta för att sedan nå det långsiktiga målet, ett maximalt koldioxidutsläpp på 0,5 ton per invånare senast 2050. Resultaten från examensarbetet kommer ingå i Färdplan 2050 och på så sätt ligga till grund för kommunens framtida energipolitik.

     

    I examensarbetet bestämdes tre olika framtidsscenarion: referens-, aktörs- samt ett potentialscenario. Referensscenariot beskriver en trolig utveckling av energianvändningen där en ”spontan” energieffektiviseringstakt på 0,4 % per år för småhus och 0,6 % per år för flerbostadshus antas. Aktörscenariot ska inkludera effekter av åtgärder som lokala aktörer genomför eller planerar att genomföra. För flerbostadshus innebär detta en energibesparing på 5,5 % och för småhus saknas ett riktat initiativ att göra mer än snittet i Sverige. Potentialscenariot var ämnat att baseras på energideklarationer gjorda i Uppsala kommun. Åtgärdsförslagen i energideklarationerna var tänk att ligga till grund för energieffektiviseringspotentialen. Det visade sig att åtgärdsförslagen inte var tillräckliga för att kartlägga den energieffektiviseringspotential som fanns i kommunen.

     

    För att kartlägga potentialen för energieffektiviseringar i befintliga byggnader simulerades olika energieffektiviseringsåtgärder på ett antal typhus. Simuleringsprogrammet som användes var VIP-Energy. Simuleringarna resulterade i en potential att minska energiförbrukningen i småhus med 64 % och 45 % för flerbostadshus. Potentialen för framtida byggnader beräknades till ungefär 23 % för bostäder som byggs fram till 2030 och 22 % till år 2050.

     

    Slutsatserna av arbetet är bland annat att BBR:s krav på energiförbrukning i byggnader är för låga för att nå klimatmålen. Simuleringarna av scenarion i LEAP visar att det finns en stor potential för energieffektiviseringar i Uppsala kommun. För att nå potentialen krävs dock mer energieffektiviseringsarbete, både i befintliga byggnader och för nybyggnationer.

  • 605.
    Åström, Christer
    Uppsala universitet, The Svedberg-laboratoriet.
    Neutron Irradiation of Concrete at TSL: a Comparison of Nuclide Specific Measurmentswith FLUKA Simulations.2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis studies the possibility of using the Monte Carlo simulation program FLUKA to determine the neutron induced radioactivity of concrete walls at the The Svedberg Laboratory (TSL) in Uppsala. If a simulation of the activation would produce reliable results, it would be a useful complement to measurements for the decommissioning and clearance of the buildings of the facility. An experiment was performed in which a concrete core was taken from one of the non-activated walls in the facility. The core was cut into samples and irradiated with a neutron beam. The samples were then measured in a gamma-ray spectroscopy setup, by which the produced radioactive nuclides were identified and their activities determined. The same setup was then simulated in FLUKA. A comparison of the simulations and the measurements shows that the average activity for all nuclides obtained with FLUKA is similar to the measured one, however with large differences for some nuclides. The average ratio of the simulated and measured activities or all nuclides is 1.07 with a standard deviation of 0.55. The obtained results may be useful for future radiological clearance work at TSL.

  • 606.
    Öhrlund, Isak
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för samhällsbyggnad och industriell teknik, Industriell teknik.
    Stikvoort, Britt
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Schultzberg, Mårten
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Bartusch, Cajsa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för samhällsbyggnad och industriell teknik, Industriell teknik.
    Rising with the sun? Encouraging solar electricity self-consumption amongapartment owners in Sweden2020Inngår i: Energy Research & Social Science, ISSN 2214-6296, E-ISSN 2214-6326, Vol. 64, artikkel-id 101424Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies suggest that householders who turn prosumers become more energy aware, change their pattern ofelectricity use and may even start to engage in other pro-environmental activities. However, few of these studieswere equipped to investigate such causal relationships—mainly because most prosumers are inherently selfselected.However, as real estate companies and building owners have begun installing photovoltaics on theircustomers’ behalf, a new breed of non-self-selected prosumers is emerging, which presents new opportunities toaddress questions of causality and thus improve our understanding of the possible implications of a more prosumer-dense future. Using a sample of 54 apartment households with a shared rooftop PV installation, thisarticle presents the first causal analysis on non-self-selected prosumers’ response to information about havingbecome prosumers, what that means for themselves and the collective they are part of, how to self-consume solarelectricity and why they should do so. Using a stepped wedge design and stratified randomization procedure wewere able to design an experimental study with sufficient power. A panel regression model and various statisticalanalyses on pre and post treatment survey- and electricity use data were used to evaluate the intervention. In linewith studies of self-selected prosumers, the self-reported measures suggest that householders have shifted the useof major appliances to increase their self-consumption. However, based on the electricity use data, we find noevidence of a such a shift and no indications of spillovers to other pro-environmental behaviours—highlightingthe need to use multiple measures to assess behavioural change.

  • 607.
    Örarbäck, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Självkörande fordon: En analys av energianvändning och kapacitet2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Self-driving cars are soon to become a reality to the commercial market. A self-driving car does not have a human operator, which enables some interesting characteristics. The main benefits are considered to be:

    • The number of accidents and traffic jams should be reduced.
    • Enhanced comfort.
    • Energy usage could be decreased while capacity could be increased.

    This study concerns the causes for improved energy efficiency. The reason for improved energy efficiency is mainly because of the variation in terms of acceleration, braking and distance holding are reduced. The vehicles are more intelligent and can work together as a unity. There are reasons to believe that self-driving cars will first operate in highway conditions. The study has therefore tried to estimate what the potential benefits could be in terms of energy usage and capacity when comparing two sets of traffic flows in such an environment. One set of traffic flow was symbolized by self-driving cars, and one set was composed by conventional vehicles. With the settings and conditions defining the simulations in this study one can expect positive effects in both in energy usage and capacity with a traffic flow symbolized by self-driving cars. When comparing the two sets, with an increasing traffic flow from non-congestion up to congestion, the results showed energy savings around 10 percent with self-driving cars. 

  • 608.
    Östangård, Louise
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Reactivity Analysis of Nuclear Fuel Storages: The Effect of 238U Nuclear Data Uncertainties2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this master thesis work was to investigate how the uncertainties in nuclear data for 238U affects the uncertainty of keff in criticality simulations for nuclear fuel storages. This was performed by using the Total Monte Carlo (TMC) method which allows propagation of nuclear data uncertainties from basic nuclear physics to reactor parameters, such as keff. The TMC approach relies on simulations with hundreds of calculations of keff with different random nuclear data libraries for 238U for each calculation. The result is a probability distribution for keff where the standard deviation for the distribution represents a spread in keff due to statistical and nuclear data uncertainties.

    Simulations were performed with MCNP for a nuclear fuel storage representing two different cases:  Normal Case and Worst Case. Normal Case represents a scenario during normal conditions and Worst Case represents accident conditions where optimal moderation occurs. In order to validate the MCNP calculations and the libraries produced with TMC, criticality benchmarks were used.

    The calculated mean value of keff for the criticality benchmark simulations with random libraries produced with TMC obtained a good agreement with the experimental keff for the benchmarks. This indicates that the libraries used in this this work were of good quality.

    The TMC method´s drawback is the long calculation time, therefore the new method, fast TMC, was tested.  Both fast TMC and original TMC were applied to the Normal Case. The two methods obtained similar results, indicating that fast TMC is a good option in order to reduce the computational time. The computer time using fast TMC was found to be significantly faster compared with original TMC in this work.

    The 238U nuclear data uncertainty was obtained to be 209 pcm for the Normal Case, both for original and fast TMC. For the Worst Case simulation the 238U nuclear data uncertainty was obtained to be 672 pcm with fast TMC. These results show the importance of handling uncertainties in nuclear data in order to improve the knowledge about the uncertainties for criticality calculations of keff

  • 609.
    Öztürk, Esma
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    WAKE INDUCED POWER DEFICIT ANALYSIS ON WIND TURBINES IN FORESTED MODERATELY COMPLEX TERRAIN USING SCADA DATA2018Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Over the last few decades, wind power has shown a continuous and significant developmentin the energy market globally. Having reached a certain level in both technologyand in dimensions, the role of optimizing wind turbines as well as wind farms hasbecome an additional aspect to future development and research. Since turbine wakescan cause significant power deficits within a farm, research in this area has the potentialfor large improvements in wind farm design.

    A wake is described as the downstream flow behind the rotor of an operating windturbine. The two main characteristics of wakes are a velocity (momentum) deficit and anincreased turbulence level. The velocity deficit behind the upwind turbine results in apower loss of the downstream turbines, whereas the higher turbulence causes additionalloads on the downstream turbines’ structures resulting in fatigue problems.

    The study of wakes is a complex topic, they are influenced by an interconnection of anumber of parameters like ambient wind speed and turbulence, atmospheric stabilityconditions (stable, unstable, and neutral), the turbines’ operational characteristics, andthe terrain properties.

    In order to assess the power deficits affected by wake interaction between turbines,an analysis can be realized by processing SCADA data of turbines in a wind farm. The collected data is treated by a comprehensive filtration process, excluding events of icing, curtailment, faults, etc. and by grouping into different atmospheric conditions, windspeed intervals and wind speed sectors. Finally, power deficit values, as a function ofwind direction, are calculated and quantified, and thereafter analyzed to assess the wakebehavior at different conditions for different cases.In this thesis, the wake-induced power deficit has been investigated in a specificstudy case for three pairs of two neighboring turbines in a forested moderately complexterrain using SCADA data. The production losses amounted between the range of 32% to 67% for the specific site with turbine spacing around 4D. The obtained results werepartially unsatisfactory, caused by the reasons of inaccurate wind direction values due toyaw misalignment issues and challenging separation into different stability conditions. Moreover, the power deficits showed a clear reduction of losses with increasing windspeed. A conclusion regarding the differences between stable and near neutral conditionscould not be determined from the data.

  • 610.
    Ülker, Muhammed Akif
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Balancing of Wind Power: Optimization of power systems which include wind power systems2011Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    In the future, renewable energy share, especially wind power share, in electricity generation is expected to increase. Due to nature of the wind, wind power generation pattern includes uncertainties which affects the energy prices in the electricity markets.

    New simulations are needed for efficient planning process for the resources in the power systems to address the uncertainties in demand, generation, legal, economical and technical limitations.

    In this study, the aspects of planning process for wind power generation is described and some example scenarios are implemented with the help of MATLAB software.

  • 611. Şahin, C.D.
    et al.
    Mengüç, M.P.
    3D spatial reconstruction and non-destructive energy diagnostics of building interiors with smart devices2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 145-153Konferansepaper (Fagfellevurdert)
10111213 601 - 611 of 611
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf