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  • 1.
    Andersson, Harald
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Linköpings universitet.
    On the ventilation performance of low momentum confluent jets supply device in a classroom2020In: Energies, E-ISSN 1996-1073, Vol. 13, no 20, article id 5415Article in journal (Refereed)
    Abstract [en]

    The performance of three different confluent jets ventilation (CJV) supply devices was evaluated in a classroom environment concerning thermal comfort, indoor air quality (IAQ) and energy efficiency. The CJV supply devices have the acronyms: high-momentum confluent jets (HMCJ), low-momentum confluent jets (LMCJ) and low-momentum confluent jets modified by varying airflow direction (LMCJ-M). A mixing ventilation (MV) slot jet (SJ) supply device was used as a benchmark. Comparisons were made with identical set-up conditions in five cases with different supply temperatures (TS) (16–18 °C), airflow rates (2.2–6.3 ACH) and heat loads (17–47 W/m2). Performances were evaluated based on DR (draft rating), PMV (predicted mean vote), ACE (air change effectiveness) and heat removal effectiveness (HRE). The results show that CJV had higher HRE and IAQ than MV and LMCJ/LMCJ-M had higher ACE than HMCJ. The main effects of lower Ts were higher velocities, DR (HMCJ particularly) and HRE in the occupied zone as well as lower temperatures and PMV-values. HMCJ and LMCJ produce MV conditions at lower airflow rates (<4.2 ACH) and non-uniform conditions at higher airflow rates. LMCJ-M had 7% higher HRE than the other CJV supply devices and produced non-uniform conditions at lower airflow rates (<3.3 ACH). The non-uniform conditions resulted in LMCJ-M having the highest energy efficiency of all devices.

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  • 2.
    Andersson, Harald
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Sundberg, Mikael
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Senkic, Dario
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Management, Industrial Design and Mechanical Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    FAST-AIR: Fast analytic systems for tracer-gas assessment in indoor research: Development and testing of CO2 tracer-gas system.2024Conference paper (Refereed)
    Abstract [en]

    The time constant of ventilation of rooms in buildings is between 15 minutes (in office spaces) to 2 hours (in residential buildings). Currently, most of the tracer gas system analyzers on the market have a minute-based time constant and depending on the channels a cycle of sampling and analysis may take up to 6 minutes, E.g., 6 channel system. Essentially, only mean values are recorded with most present tracer gas analyzers. This is a hindrance for detailed temporal analysis of conditions in the room and consequently is does not capture the resolution of the influence of the internal flow on air and contaminant distribution. The current paper presents work on the development and testing of a fast response CO2 tracer-gas system with a time constant of 1 second. In contrast to the present analyzers, not only the mean values but also the whole statistical distribution of variables can be recorded, and pulse responses can be analyzed. This makes the system viable for measurement and analysis of not only spatial but also temporal distribution of contaminants. For example, recirculating airflow in the room generated by flooding of ventilation air is possible to be measured and thus making it easy to extend the analyses of the process of ventilation far beyond the possibilities with current systems.

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  • 3.
    Holmgren, Mattias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Langeborg, Linda
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational Health Science and Psychology, Psychology.
    Barthel, Stephan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Colding, Johan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. Beijer Institute of Ecological Economics, The Royal Swedish Academy of Sciences, Stockholm, Sweden.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Deceptive sustainability: Cognitive bias in people's judgment of the benefits of CO2 emission cuts2019In: Journal of Environmental Psychology, ISSN 0272-4944, E-ISSN 1522-9610, Vol. 64, p. 48-55Article in journal (Refereed)
    Abstract [en]

    People's beliefs in the actions necessary to reduce anthropogenic carbon dioxide (CO2) emissions are important to public policy acceptability. The current paper addressed beliefs concerning how periods of small emission cuts contribute to the total CO2 concentration in the atmosphere, by asking participants to rate the atmospheric CO2 concentration for various time periods and emission rates. The participants thought that a time period with higher emission rates combined with a period of lower emission rates generates less atmospheric CO2 in total, compared to the period with high emission rates alone – demonstrating a negative footprint illusion (Study 1). The participants appeared to base their CO2 estimates on the average, rather than on the accumulated sum, of the two periods' emissions – i.e. an averaging bias (Study 2). Moreover, the effect was robust to the wordings of the problem presented to the participants (Study 3). Together, these studies suggest that the averaging bias makes people exaggerate the benefits of small emission cuts. The averaging bias could make people willing to accept policies that reduce emission rates although insufficiently to alleviate global warming.

  • 4.
    Holmgren, Mattias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Marsh, John E.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology. School of Psychology, University of Central Lancashire, Preston, United Kingdom.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    When A+B < A: Cognitive bias in experts' judgment of environmental impact2018In: Frontiers in Psychology, E-ISSN 1664-1078, Vol. 9, article id 823Article in journal (Refereed)
    Abstract [en]

    When ‘environmentally friendly’ items are added to a set of conventional items, people report that the total set will have a lower environmental impact even though the actual impact increases. One hypothesis is that this “negative footprint illusion” arises because people, who are susceptible to the illusion, lack necessary knowledge of the item’s actual environmental impact, perhaps coupled with a lack of mathematical skills. The study reported here addressed this hypothesis by recruiting participants (‘experts’) from a master’s program in energy systems, who thus have bachelor degrees in energy-related fields including academic training in mathematics. They were asked to estimate the number of trees needed to compensate for the environmental burden of two sets of buildings: One set of 150 buildings with conventional energy ratings and one set including the same 150 buildings but also 50 ‘green’ (energy-efficient) buildings. The experts reported that less trees were needed to compensate for the set with 150 conventional and 50 ‘green’ buildings compared to the set with only the 150 conventional buildings. This negative footprint illusion was as large in magnitude for the experts as it was for a group of novices without academic training in energy-related fields. We conclude that people are not immune to the negative footprint illusion even when they have the knowledge necessary to make accurate judgments.

  • 5.
    Holmgren, Mattias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Occupant perception of “green” buildings: Distinguishing physical and psychological factors2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 114, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Studies have found a preference bias for “environmentally friendly” or “green” artifacts and buildings. For example, indoor environments are more favorably viewed when the building is labeled/certified “green”, in comparison with one that is not labeled/certified, even though the two environments are actually identical. The present study explored how physical properties of the indoor environment (high vs. low temperature) and labeling (“green” vs. “conventional”) interacts in their effect on environment perception. Participants performed a series of tasks in four indoor environments with different labels (low vs. high carbon footprint) and different temperatures (23°C vs. 28°C). Label and temperature were manipulated orthogonally. The participants’ environmental concern was also measured. The environmentally concerned participant assigned higher thermal acceptance and satisfaction scores to the environment labeled “low carbon footprint” (i.e., “green” certified) compared to the environment labeled “high carbon footprint” (i.e., not “green” certified), but only in the cooler thermal environment. Environmentally indifferent participants’ perception of the environment did not differ depending on label or room temperature. The results suggest that a “green” label positively influence the perception of the indoor environment for occupants, but only when the temperature is within the acceptable range as proposed in guidelines for “green” buildings.

  • 6.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Are We Overestimating the Benefits of Emission Reduction Measures?2020In: Sustainability, E-ISSN 2071-1050, Vol. 12, no 3, article id 808Article in journal (Refereed)
    Abstract [en]

    When people evaluate the environmental impact of both “environmentally” and “non-environmentally” friendly objects, actions, or behavior, their judgement of the total set in combination is lower than the sum of the individual components. The current communication is a personal perspective article that proposes a human cognitive framework that is adopted during evaluations, which consequently results in wrong reasoning and the reinforcement of misconceptions. The framework gives plausible interpretation of the following: (1) “compensatory green beliefs”—the belief that environmentally harmful behavior can be compensated for by friendly actions; (2) the “negative footprint illusion”—the belief that introducing environmentally friendly objects to a set of conventional objects (e.g., energy efficient products or measures) will reduce the environmental impact of the total set; and (3) “rebound effects”—sustainability interventions increase unsustainable behavior directly or indirectly. In this regard, the framework herein proposes that many seemingly different environmentally harmful behaviors may sprout from a common cause, known as the averaging bias. This may have implications for the success of sustainability interventions, or how people are influenced by the marketing of “environmentally friendly” measures or products and policymaking.

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  • 7.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental Evaluation of Intermittent Air Jet Ventilation Strategy : Cooling Effect Analysis2016In: IAVEQ 2016: 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings, Songdo, South Korea: IAQVEC Committee , 2016Conference paper (Other academic)
    Abstract [en]

    In the built environment climate control is the most energy intensive component and in trying to reduce energy use, occupant satisfaction is compromised.  Identifying strategies that balance the energy use and occupant satisfaction is important. One strategy is optimizing elevated air movements with intermittent air jet strategy (IAJS). The strategy enhances human convective and evaporative cooling resulting in good indoor climate and low energy use. Understanding the systems cooling capabilities is thus important to justify its practical implementation. In this paper, the potential cooling effect of the strategy is estimated with different calculation methods: thermal manikin measurements, measurements with thermal comfort data logger and estimation of the cooling effect with a web application tool (CBE thermal comfort tool). As shown in this study, the obtained cooling effect may differ by as much as 1 oC between estimation/calculation methods. This may have both implications on energy use and occupant satisfaction. 

  • 8.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental study of an intermittent ventilation system in high occupancy spaces2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Spaces with high occupancy density like classrooms are challenging to ventilate and use a lot of energy to maintain comfort. Usually, a compromise is made between low energy use and good Indoor Environmental Quality (IEQ), of which poor IEQ has consequences for occupants’ health, productivity and comfort. Alternative strategies that incorporate elevated air speeds can reduce cooling energy demand and provide occupant’s comfort and productivity at higher operative temperatures. A ventilation strategy, Intermittent Air Jet Strategy (IAJS), which optimizes controlled intermittent airflow and creates non-uniform airflow and non-isothermal conditions, critical for sedentary operations at elevated temperatures, is proposed herein.

    The primary aim of the work was to investigate the potential of IAJS as a ventilation system in high occupancy spaces. Ventilation parameters such as air distribution, thermal comfort and indoor air quality are evaluated and the system is compared with a traditional system, specifically, mixing ventilation (MV). A 3-part research process was used: (1) Technical (objective) evaluation of IAJS in-comparison to MV and displacement ventilation (DV) systems. (2) An occupant response study to IAJS. (3) Estimation of the cooling effect under IAJS and its implications on energy use. All studies were conducted in controlled chambers.

    The results show that while MV and DV creates steady airflow conditions, IAJS has  cyclic airflow profiles which results in a sinusoidal temperature profile around occupants. Air distribution capability of IAJS is similar to MV, both having a generic local air quality index in the occupied zone. On the other hand, the systems overall air change rate was higher than a MV. Thermal comfort results suggest that IAJS generates comfortable thermal climate at higher operative temperatures compared to MV. Occupant responses to IAJS show an improved thermal sensation, air quality perception and acceptability of indoor environment at higher temperatures as compared to MV. A comparative study to estimate the cooling effect of IAJS shows that upper HVAC setpoint can be increased from 2.3 – 4.5 oC for a neutral thermal sensation compared to a MV. This implies a substantial energy saving potential on the ventilation system. In general, IAJS showed a potential for use as a ventilation system in classrooms while promising energy savings.  

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  • 9.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Near-Field Flow Structure and Entrainment of a Round Jet at Low Exit Velocities: Implications on Microclimate Ventilation2020In: Computation, E-ISSN 2079-3197, Vol. 8, no 4, article id 100Article in journal (Refereed)
    Abstract [en]

    This paper explores the flow structure, mean/turbulent statistical characteristics of the vector field and entrainment of round jets issued from a smooth contracting nozzle at low nozzle exit velocities (1.39–6.44 m/s). The motivation of the study was to increase understand of the near field and get insights on how to control and reduce entrainment, particularly in applications that use jets with low-medium momentum flow like microclimate ventilation systems. Additionally, the near field of free jets with low momentum flow is not extensively covered in literature. Particle image velocimetry (PIV), a whole field vector measurement method, was used for data acquisition of the flow from a 0.025 m smooth contracting nozzle. The results show that at low nozzle exit velocities the jet flow was unstable with oscillations and this increased entrainment, however, increasing the nozzle exit velocity stabilized the jet flow and reduced entrainment. This is linked to the momentum flow of the jet, the structure characteristics of the flow and the type or disintegration distance of vortices created on the shear layer. The study discusses practical implications on microclimate ventilation systems and at the same time contributes data to the development and validation of a planned computational turbulence model for microclimate ventilation.

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    10.3390/computation8040100
  • 10.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Cooling energy simulation and analysis of an intermittent ventilation strategy under different climates2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 156, p. 84-94Article in journal (Refereed)
    Abstract [en]

    Energy use on heating, ventilation and air conditioning (HVAC) accounts for about 50% of building energy use. To have a sustainable built environment, energy efficient ventilation systems that deliver good indoor environmental quality are needed. This study evaluates the cooling energy saving potential of a newly proposed ventilation system called Intermittent Air Jet Strategy (IAJS) and compares its performance against a mixing ventilation (MV) system in a classroom located in three cities with different climates, Singapore with ‘hot and humid’, Ahvaz with ‘hot and dry’ and Lisbon with “moderate” climate. The results show a significant reduction of cooling energy need and flexibility in control strategies with IAJS as a primary system in hot and humid climates like Singapore. Hot and dry climate with short cool periods like Ahvaz show possible application and considerable energy savings with IAJS as a primary system under optimized variable setpoints, but moderate climates have an increased risk of occupant discomfort likely due to increased draft especially during the cool season.  Thus, IAJS as a secondary system that operates only during cooling season may be conducive for moderate climates like Lisbon. Additionally, the results show that supply fan energy savings can also be realized if well implemented. 

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  • 11.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Energy simulation and analysis of an intermittent ventilation system under two climates2017In: 10th International Conference on Sustainable Energy and Environmental Protection: Energy Efficiency / [ed] Krope J., Olabi, A.G., Goričanec D. & Božičnik S., Maribor: University of Maribor Press , 2017, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Energy use on heating, ventilation and air conditioning (HVAC) accounts for about 50% of total energy use in buildings.  Energy efficient HVAC systems that do not compromise the indoor environmental quality and at the same time meet the energy reduction directives/policies are necessary and needed. The study herein, evaluates the energy saving potential of a newly proposed ventilation system in spaces with high occupancy density, called Intermittent Air Jet Strategy (IAJS). The aim of the study was to evaluate through simulations the potential energy savings due to IAJS as compared to a mixing ventilation (MV) system in a classroom located in a ‘hot and humid’ climate (Singapore), and in a ‘hot and dry’ climate (Kuwait). The analysis is based on IDA Indoor Climate Energy simulation software. The results herein demonstrate significant reduction of cooling energy use of up 54.5% for Singapore and up to 32.2% for Kuwait with IAJS as compared to MV. Additionally, supply fan energy savings can also be realized if well implemented.

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  • 12.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Andersson, Harald
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Sundberg, Mikael
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Senkic, Dario
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Management, Industrial Design and Mechanical Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Assessing airborne infection risk through a model of airflow evacuation and recirculation dynamics.2024Conference paper (Refereed)
    Abstract [en]

    In a ventilated room, the indoor airflows are complicated but can generally be defined by an internal recirculating airflow generated by flooding of ventilation air. This concept categorizes the internal room flow (air and contaminants) as consist of two populations: One leaving the room and the other recirculating. The one recirculating is spreading the contaminants while the one leaving is evacuating the contaminants, which are quantified by the transfer probability between the source and other locations in the room and by purging flow rate, respectively. This concept accounts for spatial and temporal aspects in risk of airborne infection transmission. The current paper proposes and discusses a revised risk infection model based on this concept and has demonstrated applicability of the model with a test measurement setup with both mixing and displacement ventilation systems. The results emphasize the importance of considering both spatial and temporal factors in assessing airborne infection risks. It underscores the need for dynamic models like the proposed revised Wells-Riley model to provide a more accurate representation of infection risks in various indoor environments. Additionally, it discusses the necessity for longer measurement periods to fully understand the evolving nature of these risks. 

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  • 13.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Chocarro de Erauso, Borja
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental study on augmentation of mixing within a stratified indoor environment by erosion of density interface2023In: E3S Web of Conferences, 2023, Vol. 396, article id 02037Conference paper (Refereed)
    Abstract [en]

    The current study aims to address the problem associated with warm air heating in passive houses. Warm air eating is cheaper and easy to operate in passive houses, however, this creates problems of shortcut ventilation and thermal discomfort due to stratification as warm air is confined to the ceiling. In the current study, we explore a new method of creating resonance between stratification frequency and the periodic variation of the ventilation supply frequency to increase mixing of the supplied warm air and the room air consequently destratifying the room conditions. A basic water model study is used to understand the interaction between the frequency variations and the resulting standing waves with stratification characteristics in a room. Measurements at three different input frequencies and at three input paddle locations have been performed, gathering vertical temperature gradients and visualization data from them. The results show the shift in the inversion point because of an increase augmentation across the inversion between the fluids with different densities close to resonance. There is also a dependency on paddle location showing that the type of ventilation system will have different mixing rates due to different fluid energetic behaviours.  

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  • 14.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Choonya, Gasper
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Window size optimization and shading with photovoltaic panels: Simulation of cooling energy demand in the tropics in the southern hemisphere2021In: 13th International Conference on Sustainable Energy and Environmental Protection: Solar Energy. September 13-16, 2021, Vienna, Austria. / [ed] Christoph Pfeifer, Rafat Al Afif & Abdul Ghani Olabi, 2021Conference paper (Refereed)
    Abstract [en]

     Window size and orientation of holding façade influences the quantity of solar insolation into buildings and consequently the heating/cooling demand and occupant thermal comfort. In cold climates, window optimization (size and the orientation) can reduce the heating requirements if well integrated into the building envelope. However, in hot climates window sizing and orientation poses challenges as it only adds to the cooling energy demand. In addition to design strategies like window size and orientation, passive strategies like blinds or shades are recommended to reduce and control the solar insolation. The current study, through IDA-ICE building simulations, explores optimization of window size, orientation and shading configurations (internal blinds and PV as external shades) and its influence on the cooling energy demand in Harare, Zimbabwe, located in the tropic of Capricorn in the Southern Hemisphere. The results shows that cooling demand and occupant thermal comfort was sensitive to the North facing facades, and slightly on the west, but not on the South and west oriented windows. Shading reduced the cooling demand and use of PV panels proved equally effective although only a slight improvement in thermal comfort level was obtained compared to using internal blinds. However, PV panels produced electricity that could help offset the cooling demand by powering a heat pump or reduce the imported power for other building services. Implications of the results on building design and operation are discussed.

  • 15.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Choonya, Gasper
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Liu, Wei
    KTH Royal Institute of Technology.
    Mulenga, Enock
    Luleå University of Technology.
    Windows of Opportunities: Orientation, Sizing and PV-Shading of the Glazed Area to Reduce Cooling Energy Demand in Sub-Sahara Africa2023In: Energies, E-ISSN 1996-1073, Vol. 16, no 9, article id 3834Article in journal (Refereed)
    Abstract [en]

    In hot climates, such as sub-Sahara Africa, window sizing and orientation pose challenges as they add, through solar insolation, to the building cooling energy demand and thus the cause of indoor overheating risk. This risk can be reduced through passive building-design-integrated measures, e.g., optimizing the window size, orientation and solar shading strategies. Through an IDA-ICE building performance simulation tool, the current study explores the impact of window size, optimization and building-integrated PV panels as shading strategies on cooling energy demands in three cities (Niamey, Nairobi and Harare) in sub-Sahara Africa. Results show that thermal comfort and cooling energy demand are sensitive to a window-to-wall ratio (WWR) > 70%, while the need for artificial lighting is negligible for a WWR > 50%, particularly in the north for cities in the Southern hemisphere and the south in the Northern hemisphere. A WWR > 70% in the east and west should be avoided unless shading devices are incorporated. Internal blinds perform better in improving occupant thermal comfort but increase artificial lighting while integrating PV panels, as external shading overhangs reduce cooling energy but also produce energy that can be utilized for building services, such as air conditioning. In this study, the results and implications of the optimization of window size, orientation and building-integrated shading and operation are discussed.

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  • 16.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Disruption of writing by background speech: a classroom experiment2014Conference paper (Other academic)
    Abstract [en]

    Irrelevant background speech impairs cognitive capabilities such as writing. Laboratory studies wherein participants were tested alone in sound attenuated rooms, showed that ordinary speech, even with relatively low intelligibility (Keus van de Poll, Ljung, Odelius, Sörqvist, 2014), is more distracting than meaningless speech (Sörqvist, Nöstl, & Halin, 2012). Yet, so far research has paid little attention to the manifestation of these effects in classroom environments. The aim of the present study was to investigate the effects of irrelevant background speech on writing in a realistic classroom setting. The hypothesis was that irrelevant background speech would have distracting effects on text production, especially on writing fluency and typing errors. In an experimental within-subjects design, college students (in groups of 10-12 participants), sitting in a classroom, were asked to write short essays (5 minutes per essay) in the software program scriptlog. One essay was written in silence and one in the presence of background speech. As expected, background speech had a (slight) effect, although more participants are needed to increase the experimental power. Comparisons with previous studies on the effects of speech on writing are made and future directions are discussed.

  • 17.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology. Linnaeus Centre HEAD, Swedish Institute for Disability Research, Linköping University, Sweden.
    The effect of heat stress on writing performance in a classroom2014In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 183-188Conference paper (Refereed)
    Abstract [en]

    Studies have shown that heat stress impairs performance. This depends on the mental loading capacity of the task performed and the exposure time. This is a study of a common task in schools and offices: writing task. It also analyses the occupants’ perceived thermal comfort. The experiment was done in two heat conditions: 20 and 25 centigrade. The between participant design was used. ScriptLog was used to perform the writing task, while questionnaires and a Sudoku task were paper based tasks. The results show that the predicted mean vote (PMV) between conditions was significant (p<0.02) and participants perceived the 20 º C condition to be draughty. They however preferred a little more air movements in both conditions. Writing performance only showed a significant difference (p = 0.03) on deleted characters but the other variables considered did not show any significant differences but showed a strong tendency that with a long exposure time it would eventually be impaired.  This shows that writing despite being a complex task is not a high mental loading task and is not quickly impaired by heat stress.

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  • 18.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ogbuagu, Too-Chukwu
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    MacCutcheon, Douglas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. SG Ecophon AB..
    Persson, Torbjörn
    SG Ecophon AB..
    Plenum airflow distribution and its influence on the performance of a diffuse ceiling ventilation2022In: E3S Web Conf. Volume 356, 2022 The 16th ROOMVENT Conference (ROOMVENT 2022) / [ed] Li A., Olofsson T., Kosonen R., Xian, 2022, Vol. 356, article id 01026Conference paper (Refereed)
    Abstract [en]

    Implementation of diffuse ceiling ventilation (DCV) is slowly gaining momentum and applications in building ventilation have taken off with countries like Denmark, Finland and Netherlands taking the lead in Europe. However, DCV is yet to gain a foothold in Sweden and so not many installations are known, and their performance in relation to Swedish building practice is not yet established. A school in southern Sweden was subsequently renovated and two classrooms were equipped with a sound-absorbent suspended ceiling compatible with DCV. DCV has possible benefits for educational environments including improved thermal comfort as well as lower costs and noise levels. However, it is currently still unknown how supply conditions in the plenum affect the diffusion of air and resulting conditions within the room. To assess airflow characteristics and whether these influence flow conditions in the classroom, we investigated and compared the performance of DCV with two different supply conditions in the plenum. Air speeds and temperature distribution measurements in the plenum and classroom were performed with constant temperature anemometers and thermocouples respectively. The general observation from this study and the system setup herein is that airflow and temperature characteristics in the classroom were independent of the airflow conditions in the plenum. Further investigations in a controlled climate chamber are recommended to investigate and optimise system performance in accordance with Swedish building practice.

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  • 19.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Liu, Shichao
    University of California, Berkeley, USA.
    Schiavon, Stefano
    University of California, Berkeley, USA.
    Potential adaptive behaviour to counteract thermal discomfort in spaces with displacement ventilation or underfloor air distribution systems2016In: Proceedings of the 14th international conference of Indoor Air Quality and Climate, Ghent, 2016Conference paper (Refereed)
    Abstract [en]

    Building occupants behave in various adaptive ways to restore thermal comfort when in a state of thermal discomfort. These adaptive actions affect building energy use and indoor environmental quality. This paper reports part of a draft risk study, here we focus on potential adaptive behaviour to counteract discomfort in rooms with displacement ventilation (DV) and underfloor air distribution (UFAD) systems. The most likely adaptive behaviours to be taken are: adjust clothing, open/close windows, adjust thermostat and change workstation. No conclusive relationship was found on whether these behaviours are influenced by overall or ankle thermal sensation. Females stated more frequently than males that they would open/close windows, while more males expressed the intention to use heaters and complain to building managers.

  • 20.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Entrainment and its Implications on Microclimate Ventilation Systems: Scaling the Velocity and Temperature Field of a Round Free Jet2019In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 29, no 2, p. 331-346Article in journal (Refereed)
    Abstract [en]

    Research on microclimate ventilation systems, which mostly involve free jets, point to delivery of better ventilation in breathing zones. While the literature is comprehensive, the influence of contaminant entrainment in jet flows and its implications on the delivery of supplied air is not fully addressed. This paper present and discuss entrainment characteristics of a jet issued from a round nozzle (0.05 m diameter), in relation to ventilation, by exploring the velocity and temperature fields of the jet flow. The results show a trend suggesting that increasing the Reynolds number (Re) reduces ambient entrainment. As shown herein, about 30% concentration of ambient air entrained into the bulk jet flow at Re 2541 while Re 9233 had about 13% and 19% for Re = 6537/12026 at downstream distance of 8 diameters (40 cm). The study discusses that “moderate to high” Re may be ideal to reduce contaminant entrainment, but this is limited by delivery distance and possibly the risk of occupant discomfort. Incorporating the entrainment mixing factor (the ratio of room contaminants entrained into a jet flow) in performance measurements is proposed and further studies are recommended to verify results herein and test whether this is general to other nozzle configurations.

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  • 21.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Measurement of Entrainment into an Axisymmetric Jet using Temperature as a Tracer: A Pilot Study2018In: Excellent Indoor Climate and High Performing Ventilation / [ed] Risto Kosonen, Mervi Ahola and Jarkko Narvanne, 2018, p. 397-402Conference paper (Refereed)
    Abstract [en]

    The current extended abstract is a pilot study of an ongoing experimental and theoretical investigation of ambient entrainment of room air into an axisymmetric free jet using temperature as a tracer. The project aims to investigate, by revisiting the concepts and fundamentals of axisymmetric free Jets and entrainment in ventilation applications, particularly focusing on how to optimize performance of low mixing air distribution systems and to test methods of measuring entrainment in such systems. The study aims to explore a scalar field method using temperature as a tracer to estimate entrainment in axisymmetric free Jets. The results obtained show jet characteristics that slightly differ from what is reported in velocity field measurements and other scalar field studies. Thus, a call is made herein for further investigations to understand entrainment and appropriate methods to determine jet characteristics and its mixing effect. Additionally, more studies are needed to verify whether earlier results are representative of entrainment conditions for low mixing ventilation systems whose operation mode depend on near-filed characteristics of jets.

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  • 22.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sattari, Amir
    School of Technology and Business Studies, Dalarna University, Sweden.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental study on contaminant entrainment in air distribution systems with free jets2017In: Healthy Buildings Europe 2017, ISIAQ , 2017, article id 0040Conference paper (Refereed)
    Abstract [en]

    This is a preliminary study to an ongoing experimental and theoretical study of ambient entrainment of room air into axisymmetric free jets. The study herein aims to understanding characteristic behaviour of free jets, especially in low mixing ventilation technologies in order to get the best of such applications. In this paper, we explore the interaction of a free jet and its ambient, the effect on jet development, characteristics and behaviour at different Reynold numbers. Measurements were done with Particle Image Velocimetry (PIV) under isothermal conditions. As shown, at lower Reynolds numbers the jet is mostly laminar but is unstable consequently shortening the penetration distance into the ambient. As the Reynolds numbers increase the instability reduces and the penetration distance increases, but entrainment increases as vortices are generated closer to the nozzle exit. The current study suggests that’s further investigation is needed to define limits within which low and high mixing can be achieved with free jets, as this will have practical implications on optimization and implementation of free jets.

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  • 23.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Center for the Built Environment, University of California, Berkeley, Berkeley CA, USA.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental Evaluation of Intermittent Air Jet Ventilation Strategy: Cooling effect and the associated energy saving2016Conference paper (Refereed)
    Abstract [en]

    The potential to reduce building energy demand is high especially on building services like ventilation and air conditioning. This potential lies in identifying ventilation strategies that can provide both the required indoor climate and lower the energy use. One of the strategies is optimizing elevated air movements to enhance human convective and evaporative cooling which, as shown in literature, results in reduced energy use on cooling. This paper evaluates the cooling potential and the resulting energy saving of a novel air supply system called intermittent air jet strategy (IAJS). As shown in this study, IAJS with velocities of 0.4 m/s at the breathing height provides a cooling effect equivalent to reducing the ambient temperature in a mixing ventilation system by up to 1.5 oC to achieve a neutral sensation. This translates to a 13% reduction on the cooling demand. The strategy is also shown to have an energy saving potential of up to 50% on the supply fan. 

  • 24.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Center for the Built Environment, University of California, Berkeley, Berkeley CA, USA.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    The influence of heat, air jet cooling and noise on performance in classrooms2015In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 14, no 3, p. 321-332Article in journal (Refereed)
    Abstract [en]

    The quality of indoor environments influences satisfaction, health, and work performance of the occupants. Additional understanding of the theoretical and practical value of individual indoor parameters in relation to health and performance aids indoor climate designers to obtain desired outcomes. This also results in expenditure savings and increased revenue: health care and improved productivity. Here, we report two experiments that investigated how heat, cooling strategy and background noise influence performance in a full-scale classroom mockup setting. The results show that heat and background noise are detrimental to logic-based tasks and to writing, whilst cooling manipulations can protect performance. Implications for indoor environment design are discussed.

  • 25.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Experimental evaluation of an intermittent air supply system – Part 2: Occupant perception of thermal climate2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 108, p. 99-109Article in journal (Refereed)
    Abstract [en]

    A newly proposed intermittent air jet strategy (IAJS) provides satisfactory indoor climate while promising a substantial energy saving potential, as shown in technical (objective) measurements. The strategy creates non-uniform airflow and non-isothermal conditions critical for sedentary operations at elevated temperatures. The current study explored human perception of thermal environment under an IAJS. Assessment of thermal sensation, thermal comfort, and thermal acceptability were collected based on responses from 36 participants. Participants sat in a classroom setup and performed sedentary work. Their clothing had an insulation of 0.51 clo (T-shirt on upper body). Participants were exposed to homogeneous (v < 0.15 m/s) and nonhomogeneous (0.4 m/s < v < 0.8 m/s) velocity conditions across three temperature conditions: 22.5 °C, 25.5 °C and 28.5 °C. The participants found air speeds to be undesirable at lower temperatures, but reported an improved thermal sensation, comfort and acceptability at higher temperatures. As shown here, IAJS generated neutral operable conditions between 24.8 °C and 27.8 °C, within an air speed range of 0.4 m/s to 0.8 m/s. Additionally, air movements induced thermal alliethesia resulting in improved comfort and acceptance of the thermal climate even at lower air speeds in warm temperature conditions. Hence, the current study supports the energy saving potential with IAJS in view of the human perception of the indoor environment.

  • 26.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Human perception of room temperature and intermittent air jet cooling in a classroom2017In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, no 4, p. 528-537Article in journal (Refereed)
    Abstract [en]

    Environments with high temperatures and under steady conditions are perceived poor. The introduction of airflow variations in such environments improves the perception. However the risk of draught is high and to avoid this, variations in high velocity supply is used. This method is far more energy efficient than cooling the entire space as only the occupants are cooled. This paper discusses two studies on occupant cooling conducted at the University of Gävle.  The experiments were performed in a full scale mockup classroom and a total of 85 students participated. In Study 1, students sat in a classroom for about 60 minutes in one of two heat conditions: 20 and 25 º C. In Study 2, the indoor parameters of 25 º C were maintained but airflow variation in the sitting zone was manipulated. In both studies, the participants performed various tasks and answered questionnaires on their perception of the indoor climate. As shown here, higher room temperature deteriorates human perception of the indoor climate in classrooms, and the use of intermittent air jet cooling improves the perception of indoor climate just like cooling by reducing the room air temperature. This study contributes to further knowledge of how convective cooling can be used as a method of cooling in school environments so as to improve on building energy use. 

  • 27.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ljung, Robert
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology. Linnaeus Centre HEAD, Swedish Institute for Disability Research, Linköping University, Sweden.
    Perception of intermittent air velocities in classrooms2014In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 189-191Conference paper (Refereed)
    Abstract [en]

    Classrooms normally host a large number of people and the heat generated provides a challenge cool. Traditional cooling methods by increased low temperature supply airflow rate or use of heat sinks are expensive and mostly inefficient. The strategy of controlled air movements in the occupied zone may prove cheaper and desirable. This research investigates recirculation of room air to provide intermittent velocity cooling in classrooms. The objective of this experiment was to assess how occupants perceive the recirculated intermittent air velocity conditions in classrooms and when the variations should be introduced in the room for optimal results. This was done with a between participant design, accessing how they perceived indoor air quality (IAQ) and the thermal comfort in two velocity conditions: constant low air velocity condition (< 0.15 m/s) and intermittent air velocity condition (0.4 m/s). As shown here; intermittent air velocity has a positive effect on the perceived thermal comfort (p < 0.04) and perception of air quality: less draughty and improved humid perception. The participants perceived the conditions with intermittent velocity to give comfortable feelings and better air quality.  The variations also showed better performance if they were provided at the start of occupancy as opposed to during or after a temperature build up. This strategy can be used in environments where it is rather uneconomical to provide cooling like spaces hosting a group of people: movie theatres, auditoriums, classrooms and perhaps in restaurants.

  • 28.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Center for the Built Environment, University of California, Berkeley, USA.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Experimental evaluation of an intermittent air supply system: Part 1: Thermal comfort and ventilation efficiency2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 95, p. 240-250, article id 4263Article in journal (Refereed)
    Abstract [en]

    Spaces with high occupancy density e.g.; classrooms, auditoriums and restaurants, provide challenges to ventilate at a lower energy use due to elevated temperatures. To meet occupants’ thermal comfort requirements traditional systems use a lot of energy. Alternative ventilation strategies that optimize high air movements in the occupied zone allow human activities at elevated temperatures while attaining improve occupants’ perception and acceptance of the indoor climate at a low energy use. This paper presents an experimental evaluation of a novel ventilation strategy for high occupancy spaces that provides fresh air and thermal comfort in the sitting zone through a controlled intermittent air jet system. The strategy uses ceiling mounted high momentum air jet diffusers (AJD) made from ventilation duct fitted with nozzles that generate confluent jets. The jets coalesce into a single two-dimensional jet which is directed downwards in the sitting zone. This paper presents an experimental evaluation/analysis of the proposed system with regard to ventilation efficiency and thermal comfort measurements in a classroom mockup. Results show that the system qualifies to be used as a primary ventilation system and has local air change index > 1 inside the jet, and a ventilation efficiency > 50%. The system also provides better thermal climate than mixing and displacement ventilation at elevated temperatures.

  • 29.
    Kabanshi, Alan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Yang, Bin
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental psychology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Occupants’ perception of air movements and air quality in a simulated classroom with an intermittent air supply system2019In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 28, no 1, p. 63-76Article in journal (Refereed)
    Abstract [en]

    The study reported herein builds on occupant response to an intermittent air jet strategy (IAJS), which creates periodic airflow and non-isothermal conditions in the occupied zone.  Previous research has highlighted the benefits of IAJS on thermal climate and supports energy saving potential in view of human thermal perception of the indoor environment. In this study, the goal was to explore occupant acceptability of air movements and perceived indoor air quality, and to determine a way of assessing acceptable air movement conditions under IAJS. Thirty-six participants were exposed to twelve conditions: three room air temperatures (nominal: 22.5, 25.5 and 28.5 oC), each with varied air speeds (nominal: <0.15 m/s under mixing ventilation (MV), and 0.4, 0.6 and 0.8 m/s under IAJS) measured at the breathing height (1.1 m). The results show that participants preferred low air movements at lower temperatures and high air movements at higher temperatures. A model to predict percentage satisfied with intermittent air movements was developed, and predicts that about 87% of the occupants within a thermal sensation range of slightly cool (-0.5) to slightly warm (+0.5), in compliance with ASHRAE standard 55, will find intermittent air movements acceptable between 23.7 oC and 29.1 oC within a velocity range of 0.4 – 0.8 m/s.  IAJS also improved participants’ perception of air quality in conditions deemed poor under MV. The findings support the potential of IAJS as a primary ventilation system in high occupant spaces such as classrooms. 

  • 30.
    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
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Nazaroff, William W
    Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
    Predicted Percentage Dissatisfied with Ankle Draft2017In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 27, no 4, p. 852-862Article in journal (Refereed)
    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.

  • 31.
    Liu, Wei
    et al.
    KTH.
    Sun, Haowen
    Dalian University of Technology, China.
    Lai, Dayi
    Shanghai Jiao Tong University, China.
    Xue, Yu
    Dalian University of Technology, China.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Hu, Simon
    Zhejiang University, China.
    Performance of fast fluid dynamics with a semi-Lagrangian scheme and an implicit upwind scheme in simulating indoor/outdoor airflow2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 207, no B, article id 108477Article in journal (Refereed)
    Abstract [en]

    Computational fluid dynamics can be time consuming for predicting indoor airflows and pollutant transport in large-scale problems or emergency management. Fast fluid dynamics (FFD) is able to accomplish efficient and accurate simulation of indoor/outdoor airflow. FFD solves the advection term of the Navier–Stokes equations either by a semi-Lagrangian (SL) scheme or an implicit upwind (IU) scheme. The SL scheme can be highly efficient, but its first-order version is not conservative and introduces significant numerical diffusion. To improve its accuracy, a high-order temporal and interpolation scheme that not only reduces dissipation and dispersion errors but also guarantees the convergence speed should be applied. Otherwise, an IU scheme instead could be used to solve the advection term. The IU scheme is conservative and introduces minor numerical diffusion, but it may increase the computation time. Therefore, this study investigated the performance of FFD with SL scheme using high-order temporal and interpolation schemes and that with IU scheme. The comparisons used experimental data of two indoor airflows and one outdoor airflow. The results showed that FFD with IU scheme was overall more accurate than FFD with SL scheme. In simulating indoor airflow, both methods were robust and the predictions were independent of time step sizes if the Courant number was less than or equal to one. In simulating the outdoor airflow, the FFD with SL scheme performed better than the FFD with IU scheme for large time step sizes. The FFD with IU scheme consumed 44%–61% computing time of the FFD with SL scheme.

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  • 32.
    Mulenga, Enock
    et al.
    Department of Engineering Science and Mathematics, Luleå University of Technology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mupeta, Henry
    Department of Electrical Engineering, The Copperbelt University, Jambo Drive, Riverside, P.O. Box 21692, Kitwe, Zambia.
    Ndiaye, Musa
    Department of Electrical Engineering, The Copperbelt University, Jambo Drive, Riverside, P.O. Box 21692, Kitwe, Zambia.
    Nyirenda, Elvis
    ZESCO Limited, PO Box 33304, Lusaka, Zambia.
    Mulenga, Kabwe
    ZESCO Limited, PO Box 33304, Lusaka, Zambia.
    Techno-economic analysis of off-grid PV-Diesel power generation system for rural electrification: A case study of Chilubi district in Zambia2023In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 203, p. 601-611Article in journal (Refereed)
    Abstract [en]

    The study explores the techno-economic feasibility and viability of a Photovoltaic-Diesel Hybrid system for rural electrification in sub-Sahara Africa with a case study of Chilubi island, a remote district without access to electricity in the Northern Province of Zambia. Using HOMER (Hybrid Optimization of Multiple Electric Renewables) Pro software, the best and most feasible technical solutions through different hybrid system configurations, combinations and the district's rate of access to electricity were considered based on the least Levelized Cost of Energy (LCoE) and life cycle costs of the project. The results show that operating diesel generators as stand-alone is not economically sustainable and has a high LCoE. Influencing factors include variability in diesel pump prices, high fuel transportation costs, high cost of operation and maintenance, among other factors of concern. 100% photovoltaic (PV) with a battery system gave the lowest LCoE. However, the initial capital cost of solar energy projects in Zambia is relatively high compared to the equivalent diesel-based plants, as shown herein. It explains why diesel power plants are favoured for off-grid settlements. On the hand, the low operational cost and LCoE of PV power plants favour rural districts as they offset the high initial capital costs. Additionally, the continued downward trend in the cost of PV installations per kWp has opened discussions among policymakers and energy planners in Zambia to favour rural electrification with renewable energy-based power generation. This study contributes to this discussion.

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  • 33.
    Mupeta, Henry
    et al.
    Copperbelt University.
    Nyirenda, Elvis
    Zambia Electricity Supply Corporation.
    Mulenga, Enock
    Department of Engineering Science and Mathematics, Luleå University of Technology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Techno-economic analysis of PV-Diesel hybrid system as an option for rural electrification in Zambia2021In: 13th International Conference on Sustainable Energy & Environmental Protection: Solar Energy, Vienna, Austria. September 13-16, 2021 / [ed] Christoph Pfeifer, Rafat Al Afif & Abdul Ghani Olabi, 2021Conference paper (Refereed)
    Abstract [en]

    The study explores the viability of the PV-Diesel Hybrid system for rural electrification in Sub-Sahara Africa with a study case of a remote district without access to electricity in the Northern Province of Zambia. Using HOMER (Hybrid Optimization of Multiple Electric Renewables) software, the study investigates the best and most feasible technical solution through different hybrid system configurations and combinations, taking into account the least Levelized Cost of Electricity of the project. The results show that operating diesel generators as stand-alone is not economically sustainable and gives a high LCoE due to variability in diesel pump prices, and a high cost of operation and maintenance. Furthermore, the study shows that the initial capital cost of solar energy projects in Zambia is relatively high compared to the equivalent diesel-based plants. However, the authors project that this will likely change because of the continued downward trend in capital costs of PV per kWp. Additionally, the high initial capital costs are offset by the low operational costs and the clean/environmentally friendly energy from PV systems.

  • 34. Ogbuagu, Cyracus Too-Chukwu
    et al.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    MacCutcheon, Douglas
    SG Ecophon AB, Box 500, 265 03 Hyllinge, Sweden.
    Nilsson, Erling
    SG Ecophon AB, Box 500, 265 03 Hyllinge, Sweden.
    Persson, Torbjorn
    SG Ecophon AB, Box 500, 265 03 Hyllinge, Sweden.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    On the Performance of Diffuse Ceiling Ventilation in Classrooms: A Pre-Occupancy Study at a School in Southern Sweden2023In: Sustainability, E-ISSN 2071-1050, Vol. 15, no 3, article id 2546Article in journal (Refereed)
    Abstract [en]

    The implementation and application of diffused ceiling ventilation (DCV) is gradually gaining momentum, especially in Denmark, Finland, and the Netherlands. In countries such as Sweden, the application is limited despite the favorable conditions for implementation. The current study investigates the performance of DCV and mixing ventilation in a pre-occupancy field study for newly renovated classrooms in Southern Sweden. Two classrooms at the school were installed with diffuse ceiling ventilation while the rest had mixing ventilation. The objective of the study was to compare and evaluate the ventilation performance in terms of indoor environmental quality parameters such as thermal comfort, air quality indexes, airflow, and temperature distribution. Pre-occupancy measurements were performed in two classrooms with similar room characteristics, with one room running under mixing ventilation and the other under DCV. Constant temperature anemometers, thermocouples, and INNOVA thermal comfort were used to measure the indoor air speeds, temperature, and thermal comfort, respectively. Tracer gas measurements, with SF6, were performed to assess air quality. Additionally acoustic measurements were conducted to assess the acoustic benefits of DCV on reducing ventilation noise. The results demonstrate that DCV offers similar indoor environmental conditions to mixing ventilation but has better acoustic performance especially on reducing the ventilation noise. Indoor environmental conditions were very homogeneous under DCV with mixing ventilation showing tendencies for short circuit ventilation. This study demonstrates that DCV has a potential for implementation in Swedish schools with minimal system modification on existing ventilation and air distribution systems.

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  • 35.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Is building ventilation a process of diluting contaminants or delivering clean air?2020In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 29, no 6, p. 768-774Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to discuss the performance of air distribution systems intended for dilution of contaminants (e.g. mixing ventilation) and those intended for delivery of clean air to local regions within rooms (e.g. personalized ventilation). We first start by distinguishing the systems by their visiting frequency behaviour. Then, the performance of the systems with respect to their possibility to influence contaminant concentration in the room or regions within the room is dealt with. Dilution capacity concept for mixing systems is discussed, and delivery capacity concept for systems intended to deliver clean air locally is introduced. Various ways for supply of clean air to regions within the room are presented and their pros and cons are discussed. In delivery capacity systems, the most important single parameter is the entrainment of ambient air into the primary supply flow. Therefore, methods of determining entrainment in these systems need to be defined and the results should be included when describing the performance of the air terminal devices.

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  • 36.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Is Building Ventilation a Process of Diluting Contaminants or Delivering Clean Air?2018In: Excellent Indoor Climate and High Performing Ventilation / [ed] Risto Kosonen, Mervi Ahola and Jarkko Narvanne, 2018, p. 253-258Conference paper (Refereed)
    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.   

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    fulltext
  • 37.
    Yang, Bin
    et al.
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Melikov, A.K.
    International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Denmark.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Zhang, C.
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Bauman, F. S.
    Center for the Built Environment, University of California, Berkeley, CA, United States.
    Cao, G.
    Department of Energy and Process, Norwegian University of Science and Technology, KolbjørnHejesVei 1B, Trondheim, Norway.
    Awbi, H.
    School of Construction Management and Engineering, University of Reading, United Kingdom.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Niu, J.
    School of Architecture, Design and Planning, The University of Sydney, Australia.
    Cheong, K. W. D.
    Department of Building, School of Design and Environment, National University of Singapore, Singapore.
    Tham, K. W.
    Department of Building, School of Design and Environment, National University of Singapore, Singapore.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Nielsen, P. V.
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Kosonen, R.
    Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo, Finland; College of Urban Construction, Nanjing Tech University, Nanjing, China.
    Yao, R.
    School of Construction Management and Engineering, University of Reading, United Kingdom.
    Kato, S.
    Institute of Industrial Science, The University of Tokyo, Tokyo, Japan.
    Sekhar, S. C.
    Department of Building, School of Design and Environment, National University of Singapore, Singapore.
    Schiavon, Stefano
    Center for the Built Environment, University of California, Berkeley, CA, United States.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Li, X.
    Department of Building Science, School of Architecture, Tsinghua University, Beijing, China.
    Lin, Z.
    Division of Building Science and Technology, City University of Hong Kong, Hong Kong, Hong Kong.
    A review of advanced air distribution methods - theory, practice, limitations and solutions2019In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 202, article id 109359Article in journal (Refereed)
    Abstract [en]

    Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review.

  • 38.
    Yang, Bin
    et al.
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Olofsson, Thomas
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Nair, Gireesh
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Outdoor thermal comfort under subarctic climate of north Sweden – A pilot study in Umeå2017In: Sustainable cities and society, ISSN 2210-6707, Vol. 28, p. 387-397Article in journal (Refereed)
    Abstract [en]

    Outdoor microclimate is important to determine the quality of outdoor spaces. Swedish people cherish summer period and prefer more outdoor activities in summer because of long winter with harsh outdoor environments. People in urban areas use parks for recreation and outdoor activities frequently in summer. Under subarctic climate, limited studies have been performed to explore the effect of microclimate environments on usage of outdoor spaces such as parks. The study explored the relationship of microclimate environments, park use and human behavioral patterns in urban area of Umeå, Sweden, which is under subarctic climate. Observations of naturally occurring behavior were recorded. Structured interviews, based on specially designed questionnaires, were performed during July to August in 2015. Measurements of objective parameters for microclimate environments, including air dry bulb temperature, relative humidity, wind speed, solar radiation and globe temperature, were performed. Human subjective responses from the questionnaire survey were compared with objectively measured results. 49% of local persons still prefer higher solar radiation even under “slightly warm” Thermal Sensation Vote (TSV), which reflects their high expectation to solar radiation. Local persons in Umeå, who expose themselves to a wider climate, are more adapted to subarctic climate than non-local persons.

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