hig.sePublikasjoner
Endre søk
Begrens søket
12345 151 - 200 of 219
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • 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.
  • 151.
    Liu, Linn
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Rohdin, Patrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    LCC assessments and environmental impacts on the energy renovation of a multi-family building from the 1890s2016Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 133, s. 823-833Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 2020 and 2050 energy targets increase requirements on energy performance in the building stock, thus affecting both listed and non-listed buildings. It is important to select appropriate and cost-optimal energy efficiency measures, using e.g. Life Cycle Cost (LCC) optimization. The aim of this paper is to find cost-optimal packages of energy efficiency measures (EEMs) as well as to explore the effects of specific predesigned energy target values for a listed Swedish multi-family building from the 1890s. The purpose is also to show the effects on energy use, LCC, primary energy use and CO2 emissions of different energy targets, discount rates, electricity prices and geographic locations. The results show that separate energy targets could be an effective way to simplify the implementation for listed buildings. Furthermore, a cost-optimal package of EEMs is more sensitive to changes in discount rate than in electricity price. The energy renovation has impact on the primary energy use and CO2 emissions. The lower the discount rate is, the more EEMs will be implemented and the easier the national energy targets may be achieved. A higher electricity price also leads to more EEMs being implemented but at the same time higher running costs. 

  • 152.
    Liu, Shichao
    et al.
    Center for the Built Environment, University of California, Berkeley, CA, USA.
    Schiavon, Stefano
    Center for the Built Environment, University of California, Berkeley, CA, USA.
    Kabanshi, Alan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Nazaroff, William W
    Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
    Predicted Percentage Dissatisfied with Ankle Draft2017Inngår i: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 27, nr 4, s. 852-862Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Draft is unwanted local convective cooling. The draft risk model of Fanger et al. (Energy and Buildings 12, 21-39, 1988) estimates the percentage of people dissatisfied with air movement due to overcooling at the neck. There is no model for predicting draft at ankles, which is more relevant to stratified air distribution systems such as underfloor air distribution (UFAD) and displacement ventilation (DV). We developed a model for predicted percentage dissatisfied with ankle draft (PPDAD ) based on laboratory experiments with 110 college students. We assessed the effect on ankle draft of various combinations of air speed (nominal range: 0.1-0.6 m/s), temperature (nominal range: 16.5-22.5 °C), turbulence intensity (at ankles), sex, and clothing insulation (< 0.7 clo; lower legs uncovered and covered). The results show that whole body thermal sensation and air speed at ankles are the dominant parameters affecting draft. The seated subjects accepted a vertical temperature difference of up to 8 °C between ankles (0.1 m) and head (1.1 m) at neutral whole body thermal sensation, 5 °C more than the maximum difference recommended in existing standards. The developed ankle draft model can be implemented in thermal comfort and air diffuser testing standards.

  • 153.
    Lopez Ramirez, Izar
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Operating correction factor of PV system: Effects of temperature, angle of incidence and invertor in PV system performance2017Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    In this project, the correction factor of different solar panels of the laboratory of the University of Gävle, located in Sweden, is going to evaluated. The solar modules’working conditions are different from the ones used to test them in the laboratory. In the laboratory. the output energy of the modules is less than in working conditions,and therefore a correction factor is going to be calculated from the data collected, inorder to describe the factors that affect the performance of the solar modules.Also, the obtained correction factor validity for different PV systems it is going to be examined, determining which system has a better correction factor and the energy losses due to temperature, angle of incidence and micro invertor.

  • 154.
    Louro, Alejo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Studying the feasibility of installing a temperature independent snowmaking system with heat recovery: Case study for the ski resort of Astún2018Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    A research on analysing the feasibility and the benefits obtained from the utilisation of the heat surplus from temperature independent snowmaking systems is proposed. The interest of this research relies on the fact that it is a way of making it viable both economically and environmentally, to use these systems, which are the solution for snow scarcity due to global warming.This will be done by studying the performance of three different alternatives for the installation of a TIS, considering it with and without heat recovery in order to show the importance of the latter. The study will be performed for the ski resort of Astún, in the Spanish Pyrenees, considering the desire to guarantee a ski slope of 3 km from November till end of April. The three cases studied are:

    • Case I: Temperature Independent Snowmaking system without heat recovery

    • Case II: Temperature Independent Snowmaking system with direct heat recovery

    • Case III: Temperature Independent Snowmaking system with direct heat recovery and snow storage

    The feasibility of each of the cases will be studied based on costs and energy savings and consumptions, while ecological impact, maintenance costs or the interest rates will not be included in order to simplify the results. The heat recovery will be performed thanks to a CO2 heat pump that will deliver over 6 GWh through water at 70 ºC to the residential and commercial buildings of the ski resort. The heat recovery has only been studied in detail for direct recovery, but the possibility of indirect heat recovery would be interesting in other situations, therefore, it has also been briefly described.As a way of introducing and justifying the project, a literature review has been performed, on the impact of climate change and the need for snowmaking, and also on the different snowmaking technologies and their limitations, leading finally to the need for temperature independent snowmaking. Moreover, calculations and simulations including heat transfer, fluid dynamics and theory of refrigeration technology are conducted. Finally, putting that together with estimated investment costs and prices gathered either from available public sources or personal communication with suppliers, the final comparison of the cases is performed.Based on the obtained results, the most suitable solution for the ski resort of Astún, considering the current heat demand of its buildings, is the case II, installation of a TIS with direct heat recovery. This case has a total investment cost of 1.957.464 €, and due to the savings generated from the reused heat, it comes with yearly savings of -249.872 €, which implies a payback time lower than 8 years, making it the most viable alternative.

  • 155.
    Lumbier Fernandez, Mikel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Alternative energy supply study for a cottage in Vifors2018Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    The present master thesis was done during the spring of 2018. A cottage located in Vifors is studied with regard to its heating requirements. At the time of the study, the house could not be inhabited the whole year because there was no tap hot water available and the space heating demand was covered by electricity. Thus, an alternative heating supply is required to be developed. As a strategic prerequisite, the solution should be achieved considering both solar thermal collectors and a heat pump.First, the characteristics of the building were collected/determined in order to obtain the total heating demand per month and hence annually. Parameters such as the U-values, roof orientation, room dimensions, ventilation rates and internal gains were required to configure the building model in the software IDA ICE 4.8. In addition, the amount of tap hot water required per year was determined as 17 m3 per year. Cold water at 5 °C had to be heated until 55 °C to obtain the tap hot water.Once the heating requirements were known, the most suitable solution was to use a combi system (solar thermal collectors and a heat pump). Solar energy could fulfil the demand in the summer and the heat pump provided energy in the winter. For a commercial model of the flat solar thermal collector (Vitosol 100-F) the solar system was sized according to the heating demand in the summer time. The maximum energy that could be obtained from the solar collectors in summer was calculated, the rest of the demand had to be fulfilled by a heat pump, model WPL-18 E.The achieved solution is compounded by the heat pump and 3 solar thermal collectors with a surface of 2.33 m2 each. The solar energy obtained is 1 843 kWh per year, which covers 9 % of the total annual heating demand (20 098 kWh). However, the 98 % of the heating demand during the summertime comes from the solar collectors. The investment cost is 113 900 SEK and the payback period is estimated in 8 years.

  • 156.
    Luo, Z.
    et al.
    School of Construction Management and Engineering, University of Reading, United Kingdom .
    Li, B.
    School of Construction Management and Engineering, University of Reading, United Kingdom; School of Municipal and Environmental Engineering, Harbin Institute of Technology, China .
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Liu, J.
    School of Municipal and Environmental Engineering, Harbin Institute of Technology, China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, China.
    Ventilation performance in a passage between two nonparallel buildings2014Inngår i: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, s. 815-820Konferansepaper (Fagfellevurdert)
  • 157.
    Ma, Ding
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Jiang, Bin
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    A Socio-Geographic Perspective on Human Activities in Social Media2017Inngår i: Geographical Analysis, ISSN 0016-7363, E-ISSN 1538-4632, Vol. 49, nr 3, s. 328-342Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Location-based social media make it possible to understand social and geographic aspects of human activities. However, previous studies have mostly examined these two aspects separately without looking at how they are linked. The study aims to connect two aspects by investigating whether there is any correlation between social connections and users' check-in locations from a socio-geographic perspective. We constructed three types of networks: a people–people network, a location–location network, and a city–city network from former location-based social media Brightkite and Gowalla in the U.S., based on users' check-in locations and their friendships. We adopted some complexity science methods such as power-law detection and head/tail breaks classification method for analysis and visualization. Head/tail breaks recursively partitions data into a few large things in the head and many small things in the tail. By analyzing check-in locations, we found that users' check-in patterns are heterogeneous at both the individual and collective levels. We also discovered that users' first or most frequent check-in locations can be the representatives of users' spatial information. The constructed networks based on these locations are very heterogeneous, as indicated by the high ht-index. Most importantly, the node degree of the networks correlates highly with the population at locations (mostly with R2 being 0.7) or cities (above 0.9). This correlation indicates that the geographic distributions of the social media users relate highly to their online social connections.

  • 158.
    Ma, Ding
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Jiang, Bin
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    Characterizing the Heterogeneity of the OpenStreetMap Data and Community2015Inngår i: ISPRS International Journal of Geo-Information, ISSN 2220-9964, Vol. 4, nr 2, s. 535-550Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OpenStreetMap (OSM) constitutes an unprecedented, free, geographical information source contributed by millions of individuals, resulting in a database of great volume and heterogeneity. In this study, we characterize the heterogeneity of the entire OSM database and historical archive in the context of big data. We consider all users, geographic elements and user contributions from an eight-year data archive, at a size of 692 GB. We rely on some nonlinear methods such as power law statistics and head/tail breaks to uncover and illustrate the underlying scaling properties. All three aspects (users, elements, and contributions) demonstrate striking power laws or heavy-tailed distributions. The heavy-tailed distributions imply that there are far more small elements than large ones, far more inactive users than active ones, and far more lightly edited elements than heavy-edited ones. Furthermore, about 500 users in the core group of the OSM are highly networked in terms of collaboration.

  • 159.
    Malysheva, Alexandra
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Rutiner för insamling av indata för energisimuleringsmodeller av skolbyggnader i Norra Sverige (Gävle): En studie baserad på litteraturundersökning och analys av simuleringsmodellen av Stigslundsskolan i Gävle2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Energianvändning i befintlig byggnadsstock utgör en stor del av den totala energianvändningen i Sverige. I dagens läge är minskning av energianvändning av hög prioritet. Moderna simuleringsteknologier ger möjlighet till uppskattning av energianvändning i befintliga hus och utveckling av effektiviseringsåtgärder samt till beräkning av energiprestanda av byggnader i projekteringsfas. Korrekta indata och indatakällor avgör osäkerhetsnivå hos modellen. I detta sammanhang är det viktigt att utveckla rutiner för insamling av indata och specificera osäkerhetskällor. Arbetet fokuseras på utveckling av förslag till rutiner för insamling av indata för energisimuleringsmodeller av skolbyggnader i Norra Sverige, identifiering av termograferings roll vid renovering och ombyggnation samt känslighetsanalys vid byggnadssimulering och framställning av källhierarki. Projektet baserades på litteraturanalys och intervjuning av beträdande konstruktörer. Dessutom utreddes mätdata samlade i samband med renovering av Stigslundsskolan i Gävle och utarbetade simuleringsmodellen av den här skolan. Resultatet av denna studie beskriver rutiner för insamling av indata som omfattar byggnadens lokalisering och klimatdata; specifik konstruktionsdata för simulerad byggnad/del av byggnad; inomhustemperatur, luftflöde vid ventilation och infiltration samt interna värmekällor och data om innevånare och HVAC-system. Dessutom identifierades möjliga osäkerhetskällor och åtgärder för att höja noggrannhet hos modell. Källhierarki för indatakällor bestämdes vilket är angeläget vid modellkalibrering.  Termografin av Stiglundsskolan visade att det finns ett antal bristfälliga delar i klimatskallet som ger upphov till värmeförluster, framför allt fönstren, entrépartierna och sockeln. Fönstren och dörrarna behöver bytas och bristande delar av stommen isoleras. Slutsatserna som kan göras utifrån detta projekt är att det bör väljas indata från källor som står överst i källhierarki för att få fram en modell med låg osäkerhetsnivå. I verkigheten vid simulering av skolbyggnader är hög precision sällan ett krav. I regel prioriteras det tid och bekostnad så länge osäkerheten ligger inom bestämda gränser.

  • 160.
    Mantei, Franz
    et al.
    Technische Universität, Berlin, Germany.
    Henriques, Mafalda
    University of Castelo Branco, Portugal.
    Gomes, João
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Olsson, Olle
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Solarus Sunpower Sweden AB, Gävle, Sweden.
    Karlsson, Björn
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    The night cooling effect on a C-PVT solar collector2015Inngår i: ISES Solar World Congress 2015, Conference Proceedings, International Solar Energy Society, 2015, s. 1167-1175Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Night cooling consists in running a fluid through a solar panel during the night in order to reduce the fluid temperature which can be used for cooling applications. Radiative heat losses can allow the fluid to reach temperatures below ambient while conduction and convection works to equalize the collector with the ambient temperature. This paper analyzes the possibility of using an asymmetric concentrating photovoltaic thermal solar collector (C-PVT) for cooling applications during the night by losing heat through convection, conduction and irradiation. The cooling performance of the C-PVT collector has been measured during the night at different inlet temperatures in the interval of 13 to 38°C which corresponded to a AT (between the collector average and the ambient) from 6 to 28°C. The performance of the tested C-PVT collector has been measured at different inlet temperatures in an interval of 13 to 38°C. During all performed measurements, the radiation losses did not drive the collector temperature below ambient temperature. With high AT (between the inlet and the ambient) of 30°C, a 1,85°C temperature decrease in the fluid was obtained. For AT of 14°C, the temperature decrease was only 0,88°C. The measurements showed a night U-value for the Solarus C-PVT of 4,2 W/m2K This correlates well with previous papers showing measurements taken during the day. Heat losses seem to be dominated by convection and conduction due to the existence of the glass in the collector. Despite this, a measurable relation between heat losses and cloudiness factor exists. This shows that the irradiance losses are not negligible. Only very specific applications can be suited for night cooling with this collector design, since it is not so common to have applications that require low grade cooling during the night time or justify storing this energy. However, if the C-PVT design was made without a glass cover, the results could potentially be very different for locations with many clear nights.

  • 161.
    Martin, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    The impact of building orientation on energy usage: Using simulation software IDA ICE 4.7.12017Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    The building sector consumes 32% of global energy used, and it is responsible for 20% of total greenhouse gases emissions. In Europe, more than one third of the buildings are 50 years or older, thus, it is critical that new dwellings are designed in the most efficient way from an energy perspective, since the consequences of the decisions taken today will remain during decades.

    The use of Building Information Modeling (BIM) software is promising for the design of a wide range of constructions; from small dwellings to big apartment buildings. These programs allow the architect, designer or civil consultant to perform several simulations of the energy behavior of a building in a timely manner, even before a single brick is put in place. Among them, IDA ICE software utilized in this thesis is a top rated program, situated by some authors within the four main building energy simulation tools. This is an outstanding fact considering that it is estimated in more than 400 the number of available BIM programs.

    With the help of IDA ICE it will be demonstrated that for a dwelling object of study, located in Madrid (Spain), it is possible to save up to 4 250€ through the entire life of the building if the proper orientation is chosen. The discussed literature and results will also show that orientation is, by far, the most critical passive design parameter related to a building, from which the efficacy of other related measures depends on.  

    It will be also proven that the optimal orientation depends on the weather where the dwelling is located, even though a general trend consisting in orienting the houses located in the northern hemisphere to the south, and vice versa, is observed.

    Building orientation, BIM programs, building energy consumption, passive design parameters, IDA-ICE simulation tool.

  • 162.
    Mattsson, Magnus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Testing local exhaust ventilation at controlled turbulence generation by using tracer gas and a 3-D anemometer2014Rapport (Annet vitenskapelig)
    Abstract [en]

    Local exhaust (LE) ventilation is a ventilation technique where contaminated air is locally extracted close to the contaminant source, usually with the purpose to reduce the exposure of a person doing work which involves the contaminant. There is a need for well-defined and appropriate methods to test the performance of LE constructions. The present study aims at contributing to the establishment of such tests. The study entails full scale experimental measurements that include 3-D air velocity measurements, tracer gas tests and controlled generation of air turbulence through physical movements of a vertical, human-sized plate. The tested exhaust hood (EH) was of circular, flat plate flanged type.

    One part of the study concerned the task of determining the 0.4 m/s distance, x0.4, at the EH; i.e. the distance from the EH opening to a point where the air velocity has declined to 0.4 m/s. This is a currently used measure of “safe zone” at an EH. It was found that practicable measurements of good accuracy seem to be attained by using the following fairly simple correction equation:

    x0.4=xm*rot(Vm/0.4)

    where Vm is a provisionally measured air velocity, preferably within the zone where Vis within 0.35-0.45 m/s in front of the EH, and xm is the measured distance from the EH opening to the measuring point of Vm.

    The tracer gas tests implied injection of a neutrally buoyant tracer gas through a perforated sphere placed in front of the EH. The amount of tracer gas that escaped from the suction flow was measured in the room air, thus yielding a sensitive method for measuring the capture efficiency (CE) of the EH. The CE is the percentage of injected tracer gas that is directly captured by the EH. Measurements of CE was performed at several test cases, were exhaust flow rate, gas release distance, turbulence level and EH arrangement were varied. The recorded CE values varied between 75 to 100% and the response to the different test cases appeared trustworthy.

    The use of a 3-D sonic anemometer, that yielded both magnitude and direction of the air movement, proved very useful in analyzing the generated air turbulence. Its measurement data was also used to construct another measure of the local exhaust performance: Percentage Negative Velocities, PNV. This measure represents the percentage of the time when the air flow at the measuring point in front of the EH is directed away from the EH nozzle, i.e. when the velocity component in the direction towards the EH opening is negative. The recorded PNV values correlated well with the corresponding CE values, attained at the tracer gas tests. Thus, measuring PNV might be a convenient alternative or complement to tracer gas measurements.

  • 163.
    Mattsson, Magnus
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Linden, Elisabet
    Högskolan i Gävle, Akademin för teknik och miljö, BMG-labbet.
    Test av luftrenare i Visby domkyrka2016Rapport (Annet vitenskapelig)
    Abstract [sv]

    Efter den senaste renoveringen av Visby domkyrka, som bl a innefattade rengöring av innerväggar (våren 2014), noterades en oväntat snabb försmutsning av rengjorda väggytor, orsakad av avsättning av partiklar i inneluften. Med syfte att minska försmutsningstakten installerades två fristående luftrenare av elektrostatisk modell i kyrkan i oktober 2015. Föreliggande studie har haft som främsta syfta att utvärdera dessa luftrenares effektivitet i att rena inneluften på luftburna partiklar, framför allt från levande ljus. Utvärderingen har gjorts genom att mäta hur partikelhalten i kyrksalen förändrades vid olika driftfall på luftrenarna. Två olika flödesinställningar på luftrenarna provades: maxflöde resp. lågflöde, där maxflödet provades med både horisontellt och vertikalt riktat utblås av den renade luften. Anledningen till att även ett lägre luftreningsflöde provades var att luftrenarna bullrade så mycket vid maxflöde att detta driftförhållande endast torde bli aktuellt utanför besökstid. Studien har även inkluderat luftomsättningsmätning med spårgasteknik, luft- och yttemperaturmätningar, samt kallrasmätning vid vägg. Även ett vädringstest via portöppning har ingått. 

    Resultaten tyder på att luftrenarna har en klart renande effekt avseende luftburna partiklar i kyrksalen. Den minskning i antalet partiklar som luftrenarna åstadkom (partikelrenings-effektiviteten) varierade emellertid med partikelstorleken. I lågflödesfallet erhölls en reduktion av de minsta partiklarna (ultrafina, 0,02-0,3 µm) med ca 31 %, medan den för större partiklar (0,3-10 µm) var av storleksordningen 65‑75 %. I maxflödesfallet blev motsvarande siffror ca 58 % för de minsta partiklarna och 80‑90 % för de större. I välbesökta kyrkor där levande ljus ofta tänds – som i Visby domkyrka – utgör emissionerna från ljusen förmodligen den största partikelkällan. För dessa tycks de minsta partiklarna dominera avseende partikelyta (som kan tänkas täcka/försmutsa invändiga ytor), varför den sammantagna partikelreningseffektiviteten avseende försmutsning hamnar närmare den för de minsta partiklarna. Det är dock troligt att partikelreningseffektivitet blir något högre sommartid, då de riktigt stora besökarskarorna kommer i fallet Visby domkyrka.

    Riktningen på utblåset på luftrenarna hade ingen nämnvärd inverkan på partikelrenings-effektiviteten. Dock indikerade mätningarna av kallras (nedfallande luft) längs yttervägg i kyrkan att detta blir något större vid uppåtriktat utblås på luftrenarna, vilket riskerar att öka partikelavsättningstakten vid ytan. Detta fenomen behöver dock studeras närmare. Testet med vädring genom portöppning indikerade att ett avsevärt luftutbyte erhölls med denna metod, och att tillfällig vädring därför kan vara en lämplig åtgärd (även som komplement till luftrenare) vid tillfällen med många besökare och/eller mycket ljusbränning. Både partikel- och spårgasmätningarna påvisade god luftomblandning i kyrksalen, vilket är positivt för spridningen av den renade luften, och detta bidrar till att placeringen av luftrenarna är mindre kritisk. Sommartid kan dock luftomblandningen bli sämre; detta kan behöva undersökas närmare. Förutom minskad försmutsning kan luftrenarna förväntas bidra till en hälsosammare innemiljö ett minskat städbehov i kyrkan.

  • 164.
    Milić, Vlatko
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Ekelöw, Klas
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    On the performance of LCC optimization software OPERA-MILP by comparison with building energy simulation software IDA ICE2018Inngår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 128, s. 305-319Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From an economic point of view, it is crucial to minimize the life cycle costs (LCC) of buildings undergoing energy renovations, hence an optimization approach is needed. Building energy use and power demand as well as energy efficiency measures are important issues while performing an LCC optimization. Thus it is of great importance to accurately predict the building energy use and power demand before and after energy renovation. This paper aims to address the performance of an in-house LCC optimization software, OPERA-MILP, which has a rather fast optimization procedure. The aim is fulfilled through comparison with building energy simulation software IDA ICE before and after cost-optimal energy renovation. Three historic buildings with different layout and construction properties are used as a case study. The results show good agreement in the calculations of buildings’ power demand and energy use between OPERA-MILP and IDA ICE. The percentage difference in calculated annual energy use and buildings’ power demand with OPERA-MILP compared to IDA ICE is shown to be maximum 11% and 8% for the studied climate zones, respectively. Total impact on LCC is estimated to be equal to or less than 8%.

  • 165.
    Myhr, Hampus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Energiförluster i vattenkraftstunnlar och älvsträckor: Hur påverkas Manningtalet när skrovlighetens geometri är stor i förhållande till tvärsektionens geometri?2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    When water travels along a channel is the bottom which the water is in direct contact with, defined by a coefficient named

    Manning’s coefficient of friction. This coefficient explains the roughness of the channel bed. A rough surface equals a low Manning’s coefficient. The purpose of this thesis is to study how Manning’s coefficient differs when different waterflows and depths is obtained. The Manning equation is depend-ent on using a constant Manning’s coefficient based on experience and tables. The experience in the line of business knows that the coefficient holds a different value in channels with similar bathymetry and different flow conditions, and the thesis will cover these questions.

    At Vattenfall Research & Development in Älvkarleby, a flume made for fluid me-chanic experiments has been built, which is perfectly suitable for the experiments for this thesis. The flume has a roughness that has been programmed mathematically with a purpose of looking like a real channel bed or a blasted rock-tunnel. This is where all the measurements were made.

    The measurements were made in totally 14 cross-sections with a few different flows and depths. The depth was controlled by a hatchway downstream the flume and the flow were controlled by the pumps. Depending on which setting the hatchway ob-tained measurements between 1.6 l/s to 280 l/s were made. The different settings that were used for the hatch was 100 %, 85 %, 75 %, 60 % and 30 % open hatch. The most obvious results appeared when the hatch was 100 % open, since the differ-ence in depth between each cross-section was large and the faults in the equipment

    weren’t that important. 30 % open hatch generated such calm flow and a deep depth, so the errors were too big to include in the report. These different flow conditions were used to gain a big variation and accuracy, with the purpose of getting as good result as possible.

    The measurements show that for every hatch-setting, the Manning coefficient gets lower when a lower depth and flow are held. If the results are plotted from all the hatch-settings, especially 100 % open in a graph with the Manning coefficient as a function of the flow, the results follow an obvious shape with a trend where the Man-ning coefficient reduces with lower flows. The same thing with the depth. Shallower depth equals lower Manning coefficient. This is because of the roughness elements that has a bigger part of the entire cross-sectional area, so that a bigger part of the cross-sectional area is affected by phenomenon caused by the roughness elements.

    Key words: Manning’s coefficient,

    streaming losses, energy losses, Vattenfall

  • 166.
    Nashih, Samuel K.
    et al.
    Instituto de Telecomunicações, Lisboa, Portugal .
    Fernandes, Carlos A. F.
    Instituto de Telecomunicações, Lisboa, Portugal .
    Torres, João Paulo N.
    Instituto de Telecomunicações, Lisboa, Portugal .
    Gomes, João
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Branco, P. J. Costa
    Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal .
    Validation of a Simulation Model for Analysis of Shading Effects on Photovoltaic Panels2016Inngår i: Journal of solar energy engineering, ISSN 0199-6231, E-ISSN 1528-8986, Vol. 138, nr 4, artikkel-id 044503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Numerical simulation results and modeling on the electrical features of concentrating photovoltaic-thermal (PVT) using the free circuit simulation package from linear technology corporation (LTSPICE) are presented. The effects of partial shading of cell strings and temperature are analyzed, showing very good agreement with the results obtained experimentally in lab, at Lisbon University, and under outdoor testing using similar receivers, at the SME Solarus Sunpower AB, a Swedish company whose mission is the development, production, and marketing of concentrated solar technology to the world market. The potential of the used methodology for the design of the solar cell configuration is emphasized as an important tool to optimize PV and PVT performances in the energy conversion process. 

  • 167.
    Neophytou, M. K-A.
    et al.
    Department of Civil and Environmental Engineering, Environmental Fluid Mechanics Laboratory, University of Cyprus, Nicosia, Cyprus .
    Fernando, H. J. S.
    Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, IN, United States .
    Batchvarova, E.
    National Hydrometeorological Institute, National Academy of Sciences, Sofia, Bulgaria .
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Lelieveld, J.
    Max Planck Institute for Chemistry, Mainz, Germany .
    Tryphonos, E.
    Department of Civil and Environmental Engineering, Environmental Fluid Mechanics Laboratory, University of Cyprus, Nicosia, Cyprus.
    A scaling law for the Urban Heat Island phenomenon: deductions from field measurements and comparisons with existing results from laboratory experiments2014Inngår i: ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels, 2014, s. V01DT28A009-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report results from a multi-scale field experiment conducted in Cyprus in July 2010 in order to investigate the Urban Heat Island (UHI) in Nicosia capital city and its interaction with multiscale meteorological phenomena taking place in the broader region. Specifically, the results are analysed and interpreted in terms of a non-dimensional/scaling parameter dictating the urban heat island circulation reported from laboratory experiments (Fernando et al, 2010). We find that the field measurements obey the same scaling law during the day, in the absence of any other flow phenomena apart from the urban heating. During the night we find that the deduced non-dimensional value reduces to half (compared to that during the day); this is due to the presence of katabatic winds from Troodos mountains into the urban center of Nicosia and their cooling effect superimposed on diurnal urban heating. Based on this deduction, the impact of various proposed heat island mitigation measures in urban planning can be evaluated.

  • 168.
    Nkweto, Henry
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Energy Audit in two Multifamily Buildings and Economical Evaluation of possible Improvements: Case Study of District-heated Buildings with Mechanical Ventilation located in middle Sweden2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The energy performance of the buildings is important for economic and environmental aspect. The building energy use is gradually increasing. This is due to economical growth and increase in population. There are various energy efficiency measures that can be implemented provided they are economically feasible. Several Studies show that the implementation of energy saving measures such as thermal insulation results in more energy saving. However, most of the outlined measures are not economically viable.

    The paper outlines the energy efficiency measures through the use of the computer IDA ICE software. The evaluation of energy performance of two multifamily houses was conducted and possible suggestions such as thermal insulation, change of the windows, installing new air handling unit, installing heat exchange in the showers, improving the thermal bridges and change of schedules were presented.

    The economic feasibility of the suggestions is analysed using the life cycle cost to determine the economic viability of the energy measures. This involved determine the investment cost and life cycle saving cost to decide the best option. The most important factor in determining life-cycle saving is the modified uniform net present factor.  The addition of attic insulation, replacement of lighting bulbs, installing heat exchange in the showers and change of schedules, meet the economical requirement within the required time frame.

    The total energy saving from the measures that meet the economical requirement was approximately 71 MWh/year for Centralgatan 14 and 54 MWh/year of Tebogatan 5 corresponding to 24 % for Centralgatan 14 and 20.4 % of Tebogatan 5 reduction in heating demand. Replacement of lighting bulbs results in 5 MWh/year and 7.51 MWh/year  electricity energy saving for Tebogatan 5 and Centralgatan 14 respectively. The integration of energy measures has less impact on thermal comfort. The energy measures implementaed are within the acceptable limit of < 15 % PPD for thermal comfort apart from the combined effect of adding 200 mm external insulation plus lowering indoor temperature.

    Key word: energy audit, economical anaylysis, life cycle savings, investment cost, energy efficiency, IDA ICE

  • 169.
    Nordin, Malin
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Kan restvärme från rörtillverkning tas tillvara till intern fjärrvärme?: En fallstudie för Rörverk 2012 på Sandvik ABs nordvästra industriområde i Sandviken i samarbete med ÅF.2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Den globala uppvärmningen ökar i takt med utsläppen från det växande konsumtionssamhället och världen står inför en stor utmaning i att bromsa den negativa utvecklingen. Stålindustrin i Sverige står för industrins näst största energianvändning, efter massaindustrin, och stor del energi går förlorad som restvärme. Restvärme kan definieras som ”värme bunden till vätskor och gaser som släpps ut från en process till omgivningen och som inte utnyttjas”.

    Ett sätt att ta tillvara restvärme är genom fjärrvärme. En önskad temperatur för att restvärme direkt ska kunna växlas till ett fjärrvärmenät är enligt tidigare studier 90 oC. Lägre temperaturer kan uppgraderas med värmepump för att användas till ändamålet.

    Examensarbetets syfte var att identifiera potentialen för att använda restvärme från Rörverk 2012 till intern fjärrvärme inom Rörverk 68, Rörverk 98, Rörverk 2012 och transsportavdelningens lokaler. Metoden för arbetet har varit en litteraturstudie och en fallstudie baserad på intervjuer och flödes- och temperaturmätningar i Rörverk 2012. Några tekniska lösningar har inte undersökts närmare.

    För fallstudien har kartlagts vilka energiflöden som går in i byggnaden och vilka som går ut, även storleken på dessa har bestämts. Både fastighetsrelaterade och processrelaterade flöden har identifierats. Värt att nämna är att lokalen har övertemperaturer under stora delar av året och att den rymmer en ugn som håller 80 oC i ytan dygnet runt, vilket ger ett stort värmetillskott. De höga temperaturerna i lokalen ökar drivkraften för värmetransport genom väggar, vilket kallas transmissionsförluster och okontrollerad ventilation via otätheter och vädring.

    Undersökningen visar att inte några av energiflödena ut ur byggnaden anses tillräckliga för återvinna värme ur. Om energi däremot skulle tas tillvara ur den varma inomhusluften skulle problemet med övertemperatur i lokalen lösas och drivkrafterna för transmission och okontrollerad ventilation skulle minska, vilket även ger mindre energiförluster. Det finns potential att ta tillvara ca 1,1 GWh ur inomhusluften/år. Detta skulle kunna göras genom att temperaturen uppgraderas med värmepump och förs över till värmesystemet, som binds samman med de andra byggnaderna. Detta skulle ge ökad komfort i lokalen, samt minskad energianvändning för uppvärmning i byggnaderna omkring. Fortsatt undersökning för teknisk lösning behöver göras.

  • 170.
    Olsson, Jonna
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Energikartläggning av 30-tals villa i Ljusdal: Utredning av värme- och ventilationssystem samt lönsamhetsanalys av solcellsanläggning2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna energikartläggning syftar till att presentera förslag på passande ventilations- och uppvärmningslösning, samt att undersöka möjligheterna att installera en solcellsanläggning

    för en fastighet i Våxäng, Ljusdal. Fastigheten är en 30-tals stenvilla med krypgrund som ska totalrenoveras och byggas ut inklusive byte av fönster till 3-glasfönster, golven renoveras och ventilation skall installeras. Energikartläggningen avser fastighet i renoverat skick. Intill fastigheten finns byggnad med takyta i söderläge, lämplig för installation av solceller.

    Beräkningarna för energikartläggningen baseras på uppgifter om fastighetsdata, husritningar, samt uppgifter från fastighetsägare. Där fastighetsdata saknas har brukarindata används. Nuvärdesmetoden har använts för lönsamhetsberäkning av solcellsanläggning. Som metod för att avgöra en solcellsanläggnings lämplighet har även solcellssimuleringsprogrammet PVGis använts.

    Resultatet av energikartläggningen visar att värmepump tillsammans med frånluftsventilation i form av frånluftsmodul med värmeåtervinning är det lämpligaste och mest lönsamma alternativet. Detta jämfördes mot värmepump med FTX- ventilation, som energimässigt är likvärdigt, men ekonomiskt och installationsmässigt är dyrare.

    En solcellsanläggning kommer att ha en ungefärlig återbetalningstid på 20 år. Dess lönsamhet är beroende av elkostnader, subventioner, ränteläge, anläggnings- och installationskostnader.

    Fortsatt skulle det vara av intresse att undersöka en solcellsanläggnings eventuella lönsamhet om något år baserat på fastighetens verkliga elanvändning och då rådande kostnader, elpriser och subventioner. Det skulle även vara intressant att undersöka en solcellsanläggnings miljönytta, vilket inte behandlas i denna rapport då det ligger utanför energikartläggningens syfte.

  • 171.
    ORBADIA BUKENYA, RICHARD
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Improvement of the performance of a Demonstration Thermal Power Plant2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Power generation with steam as the working fluid has been proven technology in many developed countries around the world. The advantages in using this technology include its ability to use a wide range of fuel and using the cheapest material (water) as a working fluid. This means that if this technology is invested in it can boost the levels of power generation especially in developing countries where only the minority of the population has access to electricity.

    Currently there is no power plant in Uganda which uses steam technology despite Uganda being endowed with vast sources of fuel ranging from solar, biomass, geothermal and the recently discovered oil in the Albertan region. Blessed by nature, Uganda has a lot of potential to generate power using steam technologies which power when generated can boost the economic development of the country.

    Due to a low technology level in the country in areas of power generation, there are few commercial steam power plants which are mainly owned by sugar manufacturers and some of them generate power which is supplied to the National grid. There are however accessible demonstration steam power plants in the engineering faculties at both Makerere and Kyambogo Universities. However, the one at Makerere University is malfunctioned and one can only make a study of the performance of these power plants using the plant at Kyambogo University. This study can help the researcher understand the exact challenges of steam power plants, the performance and how to improve efficiency of performance.

  • 172.
    Pedrosa, Ane
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Development of a stove to meet the new environmental requirements2018Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
  • 173.
    Peiris, Ambagaha Pathirage Thanushka Sandaruwan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Feasibility Study of Production of Bio Methane from Bio Wastes in Sri Lanka and Develop Cost Model for the Production Process2016Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Generation of wastes as a result of expanding economic activities and change life styles of people is on the increase from recent times in Sri Lanka, especially in urban areas. The government authorities, both national and provincial, have no firm plans to manage the generation of wastes as well as safe disposal of unavoidable wastes. The wastes composition of the country is fortunately rich of biodegradable substances and it is a good indication that these wastes could be utilized in anaerobic digestion systems for the generation of biogas. Sri Lanka has over four decade’s history of using anaerobic digestion (AD) with a little expansion to deal the situation of high level of wastes being accumulated in most of the cities. Further, AD technology is not developed to the same scale as of the western countries due to various reasons related to technological know-how, economic, social and cultural practices together with misconceptions with regard to the economic benefits that could be derived from AD. This research work mainly focused on two objectives, namely to evaluate the feasibility of production of biomethane under Sri Lankan context and to develop a cost model for the production process, i.e. investor decision tool for the biomethane projects. During the study, it was considered that the overall process from input feedstock to a biogas plant to produce cleaned and upgraded biogas (biomethane), has over 95% of CH 4 . It was also considered two main end products based on purified biogas (biomethane) such as bottled biomethane and generation of electricity from combustion of biomethane on a generator coupled to an internal combustion engine or a gas turbine. Revenues of the project are made by said one product or both products. There were number of algorithms or logics made for quantifying capital cost (CAPEX) and operational expenses (OPEX) of a considered project. After estimating the revenue of such a project, net present value, internal rate of return and simple payback period for own investment were calculated (a calculation guide for those indicators provided). Those indicators are used as guides to select a successful project. It was important that co-digestion of various substrates (mainly municipal solid wastes) were considered during the development of a model.

  • 174.
    Ramirez Villegas, Ricardo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Dalarna University.
    A methodology to assess impacts of energy efficient renovation: a Swedish case study2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The European Union aims to reduce energy use and CO2-emissions by 40 % by the year 2030. The building sector has been identified as having a great potential to reduce emission of CO2 by increasing its energy efficiency. Also, there is a growing concern of the buildings environmental performance, that lead to the development of building environmental assessment tools. However, different types of energy sources and confusing environmental impacts affect the decision making when renovating for improved energy efficiency. This study develops and tests a methodology to help decision-makers when considering major renovation of their building stock when connected to adistrict heating system. The proposed methodology is applied and used to investigate how different renovation scenarios affects the building environmental impacts in terms of CO2 emissions and identify and discuss future improvements of the methodology.

    The novelty of the method is the expanded system boundaries that include both the distribution and production of district heating and the energy use at a building level. In this way it is possible to compare and weight measures made both at the energy system level and the building level. This work has limited its approach to energy use in buildings, but it is important to bring the life cycle thinking to the methodology. During the choice of the renovation methods it was noticed that the environmental impact of the production of some components in order to reduce the energy use of a building are not insignificant. Even if all the renovation measures considered in this case study are feasible, it is important to determine in which order they are desirable or achievable from an economic point of view. Uncertainty in the future development of energy, and limited economic resources can play an important role in the possibility of energy efficient renovation.

  • 175.
    Ruan, Wenbo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Energy survey on replacing a direct electrical heating system with an alternative heating system2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With the ever-growing energy demand that world is currently going through and the danger of climate change around the corner, wagering in renewable energy seems to be the right path to create a more smart and green future.

    Sweden has put great effort on decreasing its dependency on oil, in fact in 2012 more than 50 % of its electricity came from the renewable source and has a plan in making it 100 % in 2040. However, when it comes to heating systems Sweden depends greatly on district heating, and situations which buildings are located outside the district heating system’s reach is not uncommon, hence for those buildings, other options such as solar power or heat pumps are considered.

    Many buildings located in Skutskär suffer from the problem stated above. The particular building analyzed in this thesis uses electrical radiator and furnace as sources of heat, which implies high energy uses and financial expenses. For this reason technical and financial analysis of using each alternative system for a single family house located in Skutskär had been done.

    Using solar powered system is deemed to be quite ineffective, as Sweden has poor solar radiation. In order to compensate the poor sun hours during the winter, 51 photovoltaic (PV) panels or 19 solar thermal panels would be required. This high initial investment needs long period of time in order to be profitable, 15 years for solar thermal system and 21 years for solar PV system.

    On the other hand, the results from the heat pumps are quite satisfactory, the fastest payback period is around 4 years. This is achieved by using air source heat pump (ASHP), the annual saving in this case is three times higher than using solar photovoltaic panels, making the usage of ASHP more attractive than any solar energy system. However, when annual saving is concerned, the ground source heat pump (GSHP) system is capable of generating even higher saving, but the initial investment is significantly higher, extending the payback period to 6 years.

  • 176.
    Ruiz Bello, Elsa
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Design of a PV-system with batteries connected building for a grid2017Independent thesis Advanced level (degree of Master (Two Years)), 10 poäng / 15 hpOppgave
  • 177.
    Sadrizadeh, Sasan
    et al.
    Division of Fluid and Climate Technology, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Stockholm, Sweden; Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark.
    Afshari, Alireza
    Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark.
    Karimipanah, Taghi
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Håkansson, Ulf
    Skanska AB, Stockholm, Sweden.
    Nielsen, Peter
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre2016Inngår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 110, s. 140-147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Airborne particles released from surgical team members are major sources of surgical site infections. To reduce the risk of such infections, ultraclean-zoned ventilation systems have been widely applied, as a complement to the ventilation of the main operating theatre. The function of ventilation in an operating theatre is usually determined without considering the influence of the staff members’ posture and movements. The question of whether the surgeon's posture during an on-going operation will influence particle distribution within the surgical area has not yet been explored in depth or well documented. In the present study we analysed data from investigation of two positions (bending and straightened up), which represent the most common surgeon and staff-member postures. The investigation was performed by applying the computational fluid dynamics methodology to solve the governing equations for airflow and airborne particle dispersion. Ultraclean-zoned ventilation systems were examined as an addition to the conventional operating theatre. We examined three distinct source strengths (mean value of pathogens emitted from one person per second) due to the variety of staff clothing systems. In the upright posture, the screen units reduced the mean air counts of bacteria and the mean counts of sedimenting bacteria to a standard level for infection-prone surgeries in the surgical area. However, the performance of this system could be reduced drastically by improper work experience. Surgical garments with a high protective capacity result in lower source strength and thus reduces the particle concentration within the surgical area. These results are useful for developing best practices to prevent or at least reduce the infection rate during a surgical intervention.

  • 178.
    Samuelsson, Kalle
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Barthel, Stephan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Social-ekologisk stadsbyggnad: perspektiv på urban resiliens och hållbar utveckling2016Rapport (Annet vitenskapelig)
  • 179.
    Sandalidi, Elisavet
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Building energy pre-design based on multi-criteria decision analysis2017Independent thesis Advanced level (degree of Master (One Year)), 40 poäng / 60 hpOppgave
    Abstract [en]

    The successful energy design of buildings requires that special attention be paid to the conceptual stage. However, it is a difficult task to find the most promising design alternatives satisfying several conflicting criteria. This thesis presents a simple multi-criteria decisions analysis method that could assist designers in green building design. Variables in the model include those alternatives that are common options when a residential building is to be constructed. The individual components that are considered are the building envelope, heating, ventilation and air conditioning (HVAC) system, service water heating, power and lighting. The key actors, objectives and methodology of multi-criteria decisions analysis are presented and finally a case study for a residential building in Athens is performed. The criteria by which to evaluate each building component of the newly built construction were identified by the decision-makers. Subsequently, decision frameworks for the selection of roof, walls, windows, heating system, energy source for heating system, power source, lighting and service water heating system were built. The method is followed step-by-step to conclude on the optimal building components based on their score. Due to the equal scoring of the windows and an inapplicable combination of electric underfloor heating with air-to-water heat pump, the method is characterized by low accuracy. The fact that the building components have been treated individually sets the method as a basic one and indicates that a more complex one should be preferred when more trustworthy results are needed.

  • 180.
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Indoor Environmental Quality — Ventilation2017Inngår i: Encyclopedia of Sustainable Technologies / [ed] Martin Abraham, Amsterdam: Elsevier, 2017, s. 231-241Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    The primary goal of ventilation is to provide dilution capacity for diluting contaminants generated within a room. The properties of the dilution curve are discussed first; this is the concentration as a function of the ventilation flow rate and the varying efficiency of dilution at different levels of concentration. The purging flow rate is the flow rate at which ventilates are introduced. In situations where the air supply is laden with the contaminant that is going to be removed it is important to distinguish between the purging flow rate and the flow rate supplied by the ventilation system. The trade-off between control of contaminant levels by ventilation and source control is addressed. Factors that may diminish the dilution capacity, such as short circuiting and direct loss of air, are discussed. A sensation of draft may be counteracted by the occupants' manipulation of the ventilation system, which may lead to reduced dilution capacity. Situations where there is a risk of draft occurs are identified and design parameters are introduced whose use in design can help in avoiding systems that cause draft. Communication about how ventilation works is important for avoiding mistakes and having the wrong expectations about what can be achieved with ventilation. © 2017 Elsevier Inc. All rights reserved.

  • 181.
    Sandberg, Mats
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Mattsson, Magnus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Wigö, Hans
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Hayati, Abolfazl
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Claesson, Leif
    Högskolan i Gävle, Akademin för teknik och miljö, BMG-labbet.
    Linden, Elisabet
    Högskolan i Gävle, Akademin för teknik och miljö, BMG-labbet.
    Khan, Mubashar
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Viewpoints on wind and air infiltration phenomena at buildings illustrated by field and model studies2015Inngår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, s. 504-517Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ventilation and infiltration caused by wind are difficult to predict because they are non-local phenomena: driving factors depend on the surrounding terrain and neighbouring buildings and on the building orientation with respect to the wind direction. Wind-driven flow through an opening is complex because wind can flow through the opening or around the building, in contrast to buoyancy driven flow. We explored wind and air infiltration phenomena in terms of pressure distributions on and around buildings, stagnation points, flow along façades, drag forces, and air flow through openings. Field trials were conducted at a 19th-century church, and wind tunnel tests were conducted using a 1:200 scale model of the church and other models with openings.

     

    The locations of stagnation points on the church model were determined using particle image velocimetry measurements. Multiple stagnation points occurred. The forces exerted on the church model by winds in various directions were measured using a load cell. The projected areas affected by winds in various directions were calculated using a CAD model of the church. The area-averaged pressure difference across the church was assessed. A fairly large region of influence on the ground, caused by blockage of the wind, was revealed by testing the scale model in the wind tunnel and recording the static pressure on the ground at many points. The findings of this study are summarized as a number of steps that we suggest to be taken to improve analysis and predictions of wind driven flow in buildings.

  • 182.
    Sandberg, Mats
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Wigö, Hans
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Kabanshi, Alan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Is Building Ventilation a Process of Diluting Contaminants or Delivering Clean Air?2018Inngår i: Excellent Indoor Climate and High Performing Ventilation / [ed] Risto Kosonen, Mervi Ahola and Jarkko Narvanne, 2018, s. 253-258Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The purpose of the paper is to discuss the performance of air distribution systems intended for dilution of contaminants and those intended for delivery of clean air to local regions within rooms. At first the systems are distinguished by their visiting frequency behaviour. The performance of the systems with respect to their possibility to influence the concentration due to contaminants is dealt with by the concept dilution capacity for mixing systems and by introduction of the concept delivery capacity for systems intended for delivery of clean air locally. Various ways of realizing systems for supply of clean air to regions within a room are presented and their pros and cons are discussed.  The most important single parameter is the entrainment of ambient air into the primary flow that drives the airflow in the room.   

  • 183.
    Sattari, Amir
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. KTH, Installations- och energisystem.
    Investigations of Flow Patterns in Ventilated Rooms Using Particle Image Velocimetry: Applications in a Scaled Room with Rapidly Varying Inflow and over a Wall-Mounted Radiator2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis introduces and describes a new experimental setup for examining the effects of pulsating inflow to a ventilated enclosure. The study aimed to test the hypothesis that a pulsating inflow has potential to improve ventilation quality by reducing the stagnation zones through enhanced mixing. The experimental setup, which was a small-scale, two-dimensional (2D), water-filled room model, was successfully designed and manufactured to be able to capture two-dimensional velocity vectors of the entire field using Particle Image Velocimetry (PIV). Using in-house software, it was possible to conclude that for an increase in pulsation frequency or alternatively in the flow rate, the stagnation zones were reduced in size, the distribution of vortices became more homogeneous over the considered domain, and the number of vortices in all scales had increased. Considering the occupied region, the stagnation zones were moved away in a favorable direction from a mixing point of view. In addition, statistical analysis unveiled that in the far-field occupied region of the room model, stronger eddies were developed that we could expect to give rise to improved mixing. As a fundamental experimental study performed in a 2D, small-scale room model with water as operating fluid, we can logically conclude that the positive effect of enhanced mixing through increasing the flow rate could equally be accomplished through applying a pulsating inflow.

    In addition, this thesis introduces and describes an experimental setup for study of air flow over a wall-mounted radiator in a mockup of a real room, which has been successfully designed and manufactured. In this experimental study, the airflow over an electric radiator without forced convection, a common room-heating technique, was measured and visualized using the 2D PIV technique. Surface blackening due to particle deposition calls for monitoring in detail the local climate over a heating radiator. One mechanism causing particle deposition is turbophoresis, which occurs when the flow is turbulent. Because turbulence plays a role in particle deposition, it is important to identify where the laminar flow over radiator becomes turbulent. The results from several visualization techniques and PIV measurements indicated that for a room with typical radiator heating, the flow over the radiator became agitated after a dimensionless length, 5.0–6.25, based on the radiator thickness.

    Surface properties are among the influencing factors in particle deposition; therefore, the geometrical properties of different finishing techniques were investigated experimentally using a structured light 3D scanner that revealed differences in roughness among different surface finishing techniques. To investigate the resistance to airflow along the surface and the turbulence generated by the surfaces, we recorded the boundary layer flow over the surfaces in a special flow rig, which revealed that the types of surface finishing methods differed very little in their resistance and therefore their influence on the deposition velocity is probably small. 

  • 184.
    Sattari, Amir
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. KTH, Installations- och energisystem, Stockholm.
    Particle Image Velocimetry Visualization and measurement of Air Flow over a Wall-Mounted Radiator2015Inngår i: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 14, nr 3, s. 289-302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A common room-heating technique involves the use of a wall-mounted radiator without forced convection. The cold surrounding air passes adjacent to the warm surfaces of the radiator where it absorbs heat and gains momentum to rise along the wall surface and finally circulate in the entire room. Understanding the properties of heated airflows is important for several purposes. To understand the flow process it is important to identify where the transition from laminar to turbulent flow occurs and to quantify the turbulent fluctuations. With the objective to characterize the airflow in the vicinity of wall surfaces, the local climate over the radiator was visualized and measured using a two-dimensional particle image velocimetry technique. The PIV technique yields 2D vector fields of the flow. The resulting vector maps were properly validated and post-processed using in-house software to provide the average streamlines and other statistical information such as standard deviation, average velocity, and covariance of the entire vector field. The results show that, for a room with a typical heating power, the airflow over the radiator becomes agitated after an ordinate of N = 5 - 6.25 over the radiator upper level, in which N is the dimensionless length based on the thickness of the radiator. Practical problems encountered in near-wall PIV measurements include generating a homogeneous global seeding that makes it possible to study both plume and entraining region, as well as optical problems due to near-surface laser reflection that makes the measurement process more complicated.

  • 185.
    Sattari, Amir
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. KTH, Installations- och energisystem.
    Sandberg, Mats
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Particle image velocimetry (PIV) visualization of air flow over a wall-mounted radiator2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A common room heating technique is to use a wall-mounted radiator without forced convection. The cold surrounding air passes adjacent to the warm surfaces of the radiator, gets heated, and the buoyancy difference gives this heated air a momentum to rise along the wall surface (as plume) and finally circulate and get mixed into the whole room. The properties of heated plumes are important for assessing the risk of soiling of the wall surfaces through particle deposition driven by thermophoresis and turbophoresis. It is important to identify where there is a transition from laminar to turbulent flow. With the objective to characterize the plume of heated air flow in the vicinity of wall surface, the airflow over the radiator is visualized and measured using the two-dimensional Particle Image Velocimetry (2D PIV) technique. The PIV technique yields two-dimensional vector fields of the flow. The resulted vector maps are size and peak validated and post processed using in house developed software to provide the average streamlines. In the near wall PIV measurements there are practical problems; generating a homogeneous global seeding that makes it possible to study both the plume and the surrounding entrainment region, and optical problems due to strong laser reflection from the wall surface which limits the investigation area. These issues are dealt with in the present study. In addition to visualization with PIV, visualization with a CMOS video camera was also conducted.

  • 186.
    Schössler, Torsten
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Evaluation of an Asymmetric Concentrating Solar Photovoltaic Thermal (C-PVT) Installation: Case Study of an Installation in the Netherlands2018Independent thesis Advanced level (degree of Master (Two Years)), 10 poäng / 15 hpOppgave
  • 187.
    Skeppstedt, Tobias
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Dimensionering och optimering av ett PV-system för en elintensiv industribyggnad i södra Norrland: En fallstudie med avseende på teknik, ekonomi och klimat2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Utbyggnaden av PV‑system (solcellsanläggningar) har ökat exponentiellt under senare år, både internationellt och i Sverige. Några av anledningarna till detta är framförallt att tekniken blir billigare och allt mer effektiv, samt att tekniken ses som en av lösningarna på problematiken kring klimatförändringar. Trots detta behövs ändå i många fall ekonomiska bidrag för att solcellsanläggningar ska bli lönsamma, och även om solceller inte ger upphov till utsläpp av växthusgaser i driftsfasen så är emissionerna betydande i tillverkningsprocessen av systemkomponenterna.

    I denna fallstudie framläggs en elintensiv industribyggnad i södra Norrland som föremål för att undersöka tekniska, ekonomiska och klimatrelaterade aspekter vid en potentiell installation av solceller.

    Det huvudsakliga syftet var att först dimensionera lämpliga PV‑system för att sedan kunna utföra nödvändiga beräkningar gällande ekonomiska återbetalningstider för att kunna fastslå om solcellsanläggningar kan göras lönsamma inom tillverkningsindustrin. Dessutom skulle en omfattande klimatpåverkansanalys utföras för dessa typer av system.

    Dimensioneringen utfördes genom att först insamla data av kvantitativ karaktär genom mätningar och undersökningar av studieobjektet. Simuleringar utfördes därefter för att fastställa optimala villkor varpå olika system kunde utformas av väletablerade aktörer på solcellsmarknaden. Dessa system fungerade sedan som grund för beräkningarna av återbetalningstider. För klimatpåverkansanalysen jämfördes tre utsläppsscenarion från PV‑system med olika fall av rådande elmix. Dessa data var insamlade genom en omfattande litteraturstudie.

    Resultatet visar att det går att få solcellsanläggningar ekonomiskt lönsamma inom tillverkningsindustrin, men sannolikt endast med hjälp av ekonomiska bidrag. Även med bidrag så tycks lönsamheten vara betydligt sämre än för exempelvis privata hushåll. Utöver detta kan tillverkningsindustrier i vissa fall tjäna mer på att sälja el till nätet än att spara el, vilket är det diametralt motsatta andra aktörer.

    Klimatpåverkansanalysen visar att PV‑system genererar en uppenbar klimatnytta utanför Sveriges gränser, men tycks också påvisa att dessa potentiellt kan öka utsläppen i den svenska elmixen. Detta kan innebära att solceller i Sverige ger en negativ klimatpåverkan lokalt, men en positiv globalt, tack vare ökad export av el till följd av en utbyggnad av solcellsanläggningar.

    Nyckelord: PV‑system, dimensionering, optimering, tillverkningsindustri, ekonomisk återbetalningstid, växthusgasutsläpp, elmix.

  • 188.
    Solanes Bosch, Júlia
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Investigation of the Performance of a Large PV system2017Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    One of the main social challenges that society is facing nowadays is the energy crisis. So, head towards renewable energy resources such as solar, hydraulic, wind, geothermal and biomass, could be the best solution. Solar photovoltaic is one of the most promising sources to produce electricity due to its cleanness, noiselessness and sustainability, and the fact that it is inexhaustible. However, the power output of the PV systems varies notably because of the ambient conditions: temperature and solar radiation.

    The main aim of this thesis is to study if the PV system installed on the wall of the new football arena Gavlehov in Gävle is providing the amount of power promised before the installation. To achieve reliable results, the first step is to develop and install a monitoring system for recording the real power of the system and the ambient conditions at the same time. After that, an evaluation of the performance of the system during one week will be done, comparing the theoretical power and the real power obtained. The theoretical power will be calculated in two ways: using the data from a pyranometer and on the other hand, from a reference solar cell. This will permit to compare which one matches better with the reality.

    Different factors such as the temperature, the irradiance and the angle of incidence are studied to know the real influence that they have on the performance of a PV installation. The results obtained show that the measurement system installed is reliable and that the model used to evaluate the system is correct.

    It can be concluded that using a reference solar cell to calculate the theoretical power of the system is easier to align and it has the same angular behaviour as a PV module than employing a pyranometer. Regarding the installation, all the panels work similarly and the system works at nominal power. So, it provides the amount of power promised before the installation.

    Key words: Renewable energy, PV system, solar radiation, nominal power, pyranometer, solar cell.

  • 189.
    Somasundara, D. H. G. S. R.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Waste from instant tea manufacturing as a fuel for process steam generation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    An existing furnace oil fired boiler is used to supply process steam to an instant tea manufacturing factory. The instant tea is manufactured the Broken Mixed Fannings (BMF) through extraction and other required processes. The average steam consumption of the plant is 6000 kg/h at 10 barg pressure. During the process, tea waste is generated at a nominal rate of 50,000 kg/day, about 2000 kg/h at around 70% MC content on wet basis. At the moment this waste tea is either dumped in the surrounding area by spending money or sent to landfilling purposes, which create environmental issues.  

    The tea waste coming out at 70% MC wet basis, is looked at to press through continuous belt press to reduce the moisture content to about 55% on wet basis. The water removed from this pressing process is sent to effluent treatment plant at the factory. The output from the belt press is sent to a steam operated  The average generation of tea waste from the instant tea manufacturing process process is about 2000 kg/h, after pressing in the belt press an output rate of about 1,400 kg/h at 55% MC.

    This amount of tea waste at 55% MC is sent to a rotary steam tube dryer and the MC is reduced from 55% to 30% and the output rate from the steam tube dryer is about 857 kg/h. The amount of steam consumed by the rotary steam tube dryer at 6 barg pressure is 760 kg/h. Then the tea waste from the rotary tube dryer is mixed with firewood of 30% MC and fed to the boiler to generate process steam, out of which 857 kg/h steam at 6 barg pressure is sent back to the rotary steam dryer.

    From tea waste alone, a steam amount of 2,472 kg/h can be supplied after giving steam to the rotary steam dryer. The balance steam amount of 3,528 kg/h for the process requirement is supplied by burning additional firewood at 30% MC content. The tea waste fuel and firewood in combination have an overall moisture content of 30% on wet basis. The boiler is rated at 10,000 kg/h F & A 100 deg C with an actual generating capacity of about 9000 kg/h at 10 barg operating pressure at 70 deg C feed water temperature.

    By implementing the combination of belt press, rotary steam tube dryer and firewood boiler in place of the existing furnace oil fired boiler, an annual monetary saving of 168 Mn SLR/year can be achieved with a simple payback period of 21 months which is a highly feasibly project.

  • 190.
    Steen Englund, Jessika
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Akander, Jan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Björling, Mikael
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Moshfegh, Bahram
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Division of Energy Systems, Department of Management and Engineering, Linköping Unviersty, Linköping, Sweden.
    Assessment of Airflows in a School Building with Mechanical Ventilation Using Passive Tracer Gas Method2017Inngår i: Mediterranean Green Buildings & Renewable Energy: Selected Papers from the World Renewable Energy Network’s Med Green Forum / [ed] Sayigh, Ali, Springer, 2017, 1, s. 619-631Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The focus of this study is to assess the airflows in a school building built in 1963 in Gävle, Sweden, which is subject to energy conservation measures (ECMs) in a forthcoming renovation. Today, the school building is mainly ventilated by several mechanical ventilation systems, which are controlled by a constant air volume (CAV) strategy. Schedules and presence sensors impose a high operation mode during the day and a low operation mode at night, on weekends and on holidays. The homogeneous tracer gas emission method with passive sampling is used to measure the average local mean age of air (τ) during different operation modes. Temperature, relative humidity and CO2 concentration are simultaneously measured. The calculated relative uncertainty for the average local mean age of air in every measured point is approx. ±20 %. The results during low operation mode show an average value of τ of approx. 8.51 h [corresponding to 0.12 air changes per hour (ACH)], where τ in various zones ranges between 2.55 and 16.37 h (indicating 0.06–0.39 ACH), which is related to the unintentional airflow in the school. The results during mixed operation mode show an average value of τ of approx. 4.60 h (0.22 ACH), where τ in various zones ranges between 2.00 and 8.98 h (0.11–0.50 ACH), which is related to both unintentional and intentional airflows in the school. Corridors, basement and attic rooms and entrances have lower τ compared to classrooms, offices and other rooms. High maximums of the CO2 concentration in some rooms indicate an imbalance in the mechanical ventilation systems. During a regular school week of mixed operation, which includes both high and low operation modes, it is found that mainly the low operation modes show up in the results. The dynamics of the highly varying airflows in the building cannot be identified using the passive sampling technique.

  • 191.
    Strand, Simon
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Utredning om hur 4:e generationens fjärrvärmeteknik kan implementeras i Borlänge Energis fjärrvärmenät2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    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.

  • 192.
    Sumner, Jonathon
    et al.
    École de technologie supérieure, Department of Mechanical Engineering.
    Garcia, Bibiana
    Cehlin, Mathias
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Bechmann, Andreas
    Risø National Laboratory / Technical University of Denmark.
    Prospathopoulos, John
    Masson, Christian
    École de technologie supérieure, Department of Mechanical Engineering.
    Cabezon, Daniel
    Sanz Rodrigo, Javier
    Odemark, Ylva
    Sørensen, Niels
    Risø DTU, Wind energy departmernt.
    Politis, Evangelos
    Chaviaropoulos, Panagiotis
    RANS simulations of Bolund2011Inngår i: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824Artikkel i tidsskrift (Fagfellevurdert)
  • 193.
    Sylva, Kappina Kasturige Kamani
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. OUSL.
    Modeling and Optimization of Energy Utilization of Air Ventilation System of an Auditorium2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Maintaining IAQ (Internal Air Quality) and thermal comfort of occupants in buildings have been a challenge to overcome satisfying the two ends: criteria for sustainability and cost effectiveness. Although there was a movement for mechanical ventilation systems in the recent past, in addition to the cost involved, they are found to not deliver the desired air quality, lead to social consequences such as sick building syndrome, contribute to environmental consequences related to ozone-depleting substances with increasing energy consumption, generate noise and having difficulties in cleaning and maintaining. These consequences compelled research on natural ventilation systems, which were used in ancient buildings. Although it has been found that natural ventilation of buildings can become a substantial architectural design tool that leads to “breathing architecture,” fluctuations in indoor temperature and air quality makes depending entirely on natural ventilation less effective. The combination of natural and mechanical ventilation, the hybrid ventilation or mixed-mode ventilation, systems utilizes advantages and eliminates drawbacks from both mechanical and entirely dependent natural ventilation systems. Hybrid ventilation systems, which have been utilized in historical buildings, with less investment cost and reduction of energy usage have been found to be a solution to provide acceptable standards of IAQ and thermal comfort through natural air circulation in buildings. This research study was carried out to verify the effectiveness of a hybrid ventilation system in an auditorium built around 60 years back for its effectiveness as a provider of thermal comfort to its occupants. Computational Fluid Dynamic (CFD) modeling was carried out on a Finite Element (FE) model owing to its capability of offering a wide range of flexible analytical solutions, lower realization time and comparative cost effectiveness to experimental methods of modeling. This verification of the system has revealed that hybrid ventilation systems could provide effective thermal comfort in buildings designed specifically to allow circulation of air through the system. The results of the study were in agreement with measured data and the expected flow of air through the building when the thermal load due to metabolism of occupants was not included in the analysis. In addition, the expected results complied with similar studies on natural/hybrid ventilation systems. With the addition of the thermal load, as a uniform heat flux from the flow of the auditorium, it was observed that the conditioning of the air throughout the space was better than the without thermal load scenario. In the case modeling people as cylinders, with a convective heat flux, it was observed that the air flow direction changes and the seating level of the auditorium do not get sufficient air flow to maintain a comfortable air quality.  Ineffective simulation of the inlet louver was assumed to be the primary reason for this scenario and other reasons such as the seating arrangement modeling too could have effects on the result. As conclusions of the study it was found that the whole building system properties have to be selected, as the control component to produce operating commands, to circulate air through the building in accordance with the air flow: both velocity and patterns, required to maintain thermal comfort of all occupants. Air inflow could be through windows as acquisition components to collect indoor and outdoor climatic parameters and air outflow could be mechanically controlled through exhausted fans turning on or off as the operating component in the system. The result of the study ensures the method of solutions through CFD to be utilized to provide effective and less costly path to verify systems such as natural or hybrid air flow systems through buildings.  The whole system studied could be applied with suitable contextual modifications to any new location, with similar cost effective modeling, to produce less fuel consuming building systems leading to sustainability of built environment. 

  • 194.
    Säker, Robin
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Lönsamheten för energiåtervinning i ventilation Kv. Bordsgossen: Undersökning kring lönsamheten av att installera energiåtervinning i ett 60-tals flerbostadshus2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Sedan oljekrisen på 1970-talet har västvärlden strävat efter att hitta energieffektiva     metoder för uppvärmning i fastigheter. I EU står bostadssektorn för ca 40% av det totala energibehovet och den enskilt största delen i människans ekologiska fotavtryck är koldioxidutsläpp, främst via förbränning av fossila bränslen där energisektorn historiskt stått för en stor del av dess utsläpp. Oljan har som uppvärmningsmedel så gott som fasats ut och på ventilationssidan har det de senaste 30 åren hänt fantastiskt mycket där man hela tiden strävar efter att hitta effektivare och miljömässigt hållbara system. Man har så gott som helt lyckats att få bort fossila bränslen som uppvärmningskälla från bostadssektorn och på ventilationssidan har man kommit så långt att man till och med börjar återgå från stora komplexa system till de något enklare systemen som man lyckats optimera  bl.a frånluftsvärmepumpar. Just frånluftsvärmepumpar spås en fortsatt god framtid där effektiviteten på pumparna, det så kallade COP-värdet (coefficient of performance) tros kunna fördubblas.

    Kv. Bordsgossen är ett flerfamiljsbostadshus i centrala Gävle och består av fem huskroppar fördelade på 53 lägenheter och därutöver kontors- och butikslokaler på bottenplan. Fastigheten som är från 1963 saknar helt energiåtervinning och fastighetsägaren Svedinger Fastigheter vill nu ändra på detta. Denna rapport tar vid där en tidigare energikartläggning slutar och i denna rapport har det undersökts om det finns lönsamhet i frånluftsvärmepump för fastighetens lägenheter, samt lönsamheten i värmeväxlare för fastighetens garage och en värmeväxlare för den butikslokal som inhyser företaget Arkitektkopia. Resultatet visar att det vid uppskattad installationskostnad finns god ekonomi i att installera frånluftsvärmepump i fastigheten samt att installera värmeväxlare för den lokal som inhyser Arkitektkopia och för fastighetens garage. Det som fastighetsägaren måste ta hänsyn till är att den uppskattade installationskostnaden nödvändigtvis inte är korrekt, utan bör ses som en fingervisare. Svedinger Fastigheter bör även hålla ett öga på den eventuella flödestaxa som den lokala fjärrvärmedistributören funderar på att tillämpa, som om den tas i anspråk antas kunna ha stor påverkan på den ekonomiska vinning som finns att hämta i energieffektivisering. Vidare behöver ventilationen i fastigheten injusteras och om fastighetsägaren beslutar att skrida till verket med ett fönsterbyte ska man ha klart för sig att det kommer att påverka fastighetens termiska komfort och energibehov.

  • 195.
    Taghi, Karimipanah
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Sandberg, Mats
    The confinement effects on jet kinetic momentum flux quantified by measuring the reaction force2014Inngår i: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 13, nr 3, s. 285-298Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A turbulent jet is the most important flow element in mechanical ventilation. Mixing ventilation is basedon the properties of turbulent jets. By entrainment into the jet the ambient air is set into motion. For ajet supplied within a room the enclosure may affect the jet in several ways, through: a) Coanda effect which is the tendency of a fluid to be attracted to a nearby surface. A free jet is turned into a wall jet and the momentum flux of the jet decreases by friction against the room surfaces.b) The jet collides with the opposing wall and the jet is transformed into a wall jet. c) The size of the cross sectional area relative to the supply opening will affect the flow pattern withinthe enclosure. One can expect the direction of the inflow (entrainment) to the jet to be affected. d) Location of supply and extract. The location of the supply is a factor that influences the pressure gradient within the room. This paper considers the items b), c) and d). The main characteristic of a jet is its momentum flux, but determining the momentum flux is not an easy task and has lead to contradicting results. Standard methods require velocity field measurements which have their restrictions and uncertainties. To overcome these problems a direct and more reliable method was used by recording the flow force, caused by an impinging jet, with a digital balance. Thetests were carried out both for unenclosed (free jet) and enclosed cases. In the latter case tests were conducted with supply and extract both located on the same wall and located on opposite walls. Detailed pressure measurements were conducted to describe the details of the reaction force. There was a clear effect of the confinement on the reaction force and a Reynolds number dependence.

  • 196.
    Thollander, Patrik
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem. Department of Management and Engineering, Division of Energy Systems, Linköping University, Linköping, Sweden.
    Palm, Jenny
    Department of Thematic Studies—Technology and Social Change, Linköping University, Linköping, Sweden.
    Industrial Energy Management Decision Making for Improved Energy Efficiency: €”Strategic System Perspectives and Situated Action in Combination2015Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, nr 6, s. 5694-5703Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Improved industrial energy efficiency is a cornerstone in climate change mitigation. Research results suggest that there is still major untapped potential for improved industrial energy efficiency. The major model used to explain the discrepancy between optimal level of energy efficiency and the current level is the barrier model, e.g., different barriers to energy efficiency inhibit adoption of cost-effective measures. The measures outlined in research and policy action plans are almost exclusively technology-oriented, but great potential for energy efficiency improvements is also found in operational measures. Both technology and operational measures are combined in successful energy management practices. Most research in the field of energy management is grounded in engineering science, and theoretical models on how energy management in industry is carried out are scarce. One way to further develop and improve energy management, both theoretically as well as practically, is to explore how a socio-technical perspective can contribute to this understanding. In this article we will further elaborate this potential of cross-pollinating these fields. The aim of this paper is to relate energy management to two theoretical models, situated action and transaction analysis. We conclude that the current model for energy management systems, the input-output model, is insufficient for understanding in-house industrial energy management practices. By the incorporation of situated action and transaction analysis to the currently used input-output model, an enhanced understanding of the complexity of energy management is gained. It is not possible to find a single energy management solution suitable for any industrial company, but rather the idea is to find a reflexive model that can be adjusted from time to time. An idea for such a reflexive model would contain the structural elements from energy management models with consideration for decisions being situated and impossible to predict.

  • 197.
    Tillman, Joacim
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Kategorisering av byggnader i Gävles fjärrvärmenät utifrån dess effektsignaturer: En fallstudie2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Gävle Energi har nyligen implementerat en ny prismodell till fjärrvärmen med en säsongsprismodell som kom 2018 och en kapacitetsprismodell som kommer 2019. Den nya prismodellen ska återspegla kostnaden för att producera fjärrvärmen samt belöna kunder som utför effektiviseringsåtgärder. Kapacitetsprismodellen, som denna studie fokuserar på, kommer att baseras på anläggningens energibehov vid -10 grader. Då kapacitetspriset är samma för samtliga kunder så kommer priset kunden betalar att återspegla hur stort energibehov byggnaden har vid -10 grader. I denna studie har det undersökts om en uppskattning kan utföras för att ta reda på hur stort energibehov en nyansluten kunds byggnad behöver vid -10 grader utifrån tidigare anslutna kunder. Signaturer för 115 tidigare anslutna kunder med byggnader byggda från 2000 – 2018 användes vid denna studie. Byggnaderna kategoriserades för att kunna jämföra energibehovet för varje kund med en liknande byggnad. Utifrån detta skapades uppvärmningssignaturer för varje enskild byggnad, vilka sammanställdes i diagram uppdelade på varje byggnadskategori. Med detta var tanken att en standardsignatur kunde skapas för varje kategori för att sedan kunna använda denna signatur vid kapacitetsberäkning av en ny kunds byggnad. Då resultatet inte blev som tänkt kunde dessa standardsignaturer dock inte skapas, utan en djupare analys för varje byggnad ser ut att behöva utföras. Hade en standardsignatur skapats utifrån befintliga resultat hade ett felaktigt energibehov tilldelats kunder med hög respektive låg energianvändning. Två olika metoder användes för att beräkna energibehovet bakom uppvärmningssignaturerna, dels med boarean för byggnaderna, dels med omslutande arean då tanken var att den omslutande arean skulle ge ett bättre resultat. Användningen av den omslutande arean vid framtagandet av signaturerna visade sig dock inte vara av bättre användning då resultaten varierade för mycket.

  • 198.
    Torres, João Paulo N.
    et al.
    Instituto de Telecomunicações, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
    Fernandes, Carlos A. F.
    Instituto de Telecomunicações, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
    Gomes, João
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Luc, Bonfiglio
    Ecole Polytechnique Universitaire de Montpellier, Montpellier, France.
    Carine, Giovinazzo
    Ecole Polytechnique Universitaire de Montpellier, Montpellier, France.
    Olsson, Olle
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Branco, P. J. Costa
    Associated Laboratory for Energy, Transports and Aeronautics, Institute of Mechanical Engineering (LAETA, IDMEC), Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
    Effect of reflector geometry in the annual received radiation of low concentration photovoltaic systems2018Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, nr 7, artikkel-id 1878Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solar concentrator photovoltaic collectors are able to deliver energy at higher temperatures for the same irradiances, since they are related to smaller areas for which heat losses occur. However, to ensure the system reliability, adequate collector geometry and appropriate choice of the materials used in these systems will be crucial. The present work focuses on the re-design of the Concentrating Photovoltaic system (C-PV) collector reflector presently manufactured by the company Solarus, together with an analysis based on the annual assessment of the solar irradiance in the collector. An open-source ray tracing code (Soltrace) is used to accomplish the modelling of optical systems in concentrating solar power applications. Symmetric parabolic reflector configurations are seen to improve the PV system performance when compared to the conventional structures currently used by Solarus. The parabolic geometries, using either symmetrically or asymmetrically placed receivers inside the collector, accomplished both the performance and cost-effectiveness goals: for almost the same area or costs, the new proposals for the PV system may be in some cases 70% more effective as far as energy output is concerned.

  • 199.
    Torres, João Paulo N.
    et al.
    University of Lisbon, Lisbon, Portugal.
    Nashih, Samuel K.
    University of Lisbon, Lisbon, Portugal.
    Fernandes, Carlos A. F.
    University of Lisbon, Lisbon, Portugal.
    Leite, João C.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    The effect of shading on photovoltaic solar panels2018Inngår i: Energy Systems, Springer Verlag, ISSN 1868-3967, E-ISSN 1868-3975, Vol. 9, nr 1, s. 195-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A modelling description of photovoltaic (PV) modules in a PSPICE environment is presented. To validate the simulation model, a lab prototype is used to create similar conditions as those existing in real photovoltaic systems. The effects of partial shading of solar cell strings and temperature on the performance of various PV modules are analyzed. The simulation results show a very good agreement with those obtained experimentally in similar conditions, either in lab, at Lisbon University, and under outdoor testing in Sweden, using PV solar collectors manufactured by Solarus Sunpower AB. The potential of the simulation analysis is highlighted as a flexible and powerful tool for the design of new and more competitive PV module configurations for the collectors in solar panels.

  • 200.
    Vaarama Danielsson, Adam
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Ahmedi, Omed
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Energisystem.
    Energikartläggning av kvarteret Bordsgossen i Gävle.Undersökning av energieffektiviseringsåtgärder passande flerbostadshus.2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
12345 151 - 200 of 219
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf