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  • 1.
    Arias, Jaime M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Heat recovery and floating condensing in supermarkets2006In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 38, no 2, p. 73-81Article in journal (Refereed)
    Abstract [en]

    Supermarkets are great energy users in many countries. The potential for increased energy efficiency is large. One option is to utilize heat recovery (or heat reclaim) from condensers to heat the premises. Obviously this option is only interesting in relatively cold areas such as northern Europe, Canada, etc. An alternative to heat recovery is floating condensing pressure, which improves the coefficient of performance and decreases the energy consumption of the refrigeration system at lower outdoor temperature. Both heat recovery and floating condensing pressure can be utilized interchangeably depending on the heat requirements of the premises. A computer model that calculates the energy consumption in a supermarket with the possibility to simulate different system solutions for the refrigeration system has been developed at the Royal Institute of Technology, Department of Energy Technology. The software CyberMart is used in the present study to compare the potential of heat recovery and floating condensing in Swedish supermarkets. Measurements of different parameters such as temperatures, relative humidity and compressor power have been carried out in different supermarkets with heat recovery to validate the theoretical calculations. The present study shows that heating requirements can be covered completely by heat reclaim from the condenser. However, practical experiences show that installations are less efficient due to poor system solutions and/or control strategies. According to the results from CyberMart, the highest potential of energy saving is obtained from using a systems solution with both heat recovery and floating condensing.

  • 2.
    Bellander, Rickard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Hed, Göran
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Water-calorimetric measurement on large samples of PCM2005In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178Article in journal (Other academic)
  • 3. Birgisdottir, H.
    et al.
    Moncaster, A.
    Wiberg, A. Houlihan
    Chae, C.
    Yokoyama, K.
    Balouktsi, M.
    Seo, S.
    Oka, T.
    Luetzkendorf, T.
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Sustainability Assessment and Management.
    IEA ESC annex 57 'evaluation of embodied energy and CO2eq for building construction'2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 154, p. 72-80Article in journal (Refereed)
    Abstract [en]

    The current regulations to reduce energy consumption and greenhouse gas emissions (GHG) from buildings have focused on operational energy consumption. Thus legislation excludes measurement and reduction of the embodied energy and embodied GHG emissions over the building life cycle. Embodied impacts are a significant and growing proportion and it is increasingly recognised that the focus on reducing operational energy consumption needs to be accompanied by a parallel focus on reducing embodied impacts. Over the last six years the Annex 57 has 'addressed this issue, with researchers from 15 countries working together to develop a detailed understanding of the multiple calculation methods and the interpretation of their results. Based on an analysis of 80 case studies, Annex 57 showed various inconsistencies in current methodological approaches, which inhibit comparisons of results and difficult development of robust reduction strategies. Reinterpreting the studies through an understanding of the methodological differences enabled the cases to be used to demonstrate a number of important strategies for the reduction of embodied impacts. Annex 57 has also produced clear recommendations for uniform definitions and templates which improve the description of system boundaries, completeness of inventory and quality of data, and consequently the transparency of embodied impact assessments.

  • 4.
    Blomqvist, Claes
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Sandberg, Mats
    Högskolan i Gävle, Avdelningen för inomhusmiljö.
    Conversion of electric heating in buildings An unconventional alternative2008In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 40, no 12, p. 2188-2195Article in journal (Refereed)
    Abstract [en]

    To decrease the electric energy used for heating buildings it has become desirable to convert direct electrical heating to other heat sources. This paper reports on a study of the possibility of using an unconventional method for conversion to avoid installing an expensive hydronic system. The conversion method combines the ventilation and heating systems and uses air instead of water for distribution of heat within the building, taking advantage of thermal forces and the special properties of gravity currents. Full-scale tests have been carried out in a test apartment inside a laboratory hall where the conditions could be controlled. Temperatures and efficiency of ventilation have been measured to ensure that the demands with respect to thermal climate and air exchange were fulfilled. The results show that it is possible to use the method for heating and ventilation when converting the heating system, but further work has to be done to develop a detailed solution that works in practice. (C) 2008 Elsevier B.V. All rights reserved.

  • 5.
    Bohdanowicz, Paulina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martinac, Ivo
    Determinants and benchmarking of resource consumption in hotels: case study of Hilton International and Scandic in Europe2007In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 39, no 1, p. 82-95Article in journal (Refereed)
    Abstract [en]

    This paper reports on a study of resource consumption in 184 Hilton International and Scandic hotels in Europe. An overview of the characteristics of these two brands (upscale and mid-market, respectively), as well as the collective resource consumption in these hotels is presented (2004 data). This is followed by a more detailed analysis of a number of physical and operational factors that may potentially influence the energy and water use in these hotels. A multiple variable regression analysis indicated that, in the absence of climate data, hotel standard, total hotel floor area, number of guest-nights sold and number of food covers sold all affect the energy and water use in these facilities. The survey results further document significant differences in the energy- and water-utilisation in Hilton and Scandic hotels. This indicates that establishing realistic resource consumption benchmarks or models requires classifying hotels (especially those belonging to the upscale brand) into sufficiently specialised sub-groups representing facilities with comparable properties. It is further suggested that benchmarking of facility components may be necessary. The paper concludes with some recommendations on the procedure and criteria for establishing a useful reporting system and benchmarking model.

  • 6. Cauvain, Jenni
    et al.
    Karvonen, Andrew
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Social housing providers as unlikely low-carbon innovators2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 177, p. 394-401Article in journal (Refereed)
    Abstract [en]

    Social housing providers have recently emerged as unlikely innovators of low carbon transitions in the UK residential sector. They tend to have a significant amount of influence over large housing stocks, op- portunities to access funding to retrofit on a large scale, can make explicit connections between reduced carbon emissions and improved quality of life for low-income residents, and foster a close relationship with the place and communities they serve. In effect, social housing providers are ‘middle actors’ who not only facilitate but also realise low carbon transitions through various strategies. This paper uses em- pirical findings from interviews with social housing providers in Greater Manchester to understand the different ways that low carbon and energy efficiency innovation is being undertaken in this sector. The findings reveal that as middle actors, social landlords influence upstream to policy makers and regulators, downstream to individual households, and sideways to other actors in the social housing sector as well as to other building and energy professionals. The findings reveal opportunities for governments to sup- plement their existing policies with recognising and supporting middle actors to accelerate low carbon transitions of the built environment.

  • 7.
    Cehlin, Mathias
    et al.
    KTH, Superseded Departments, Built Environment.
    Moshfegh, B
    Sandberg, M
    Measurements of Air Temperatures Close to a Low-Velocity Diffuser in Displacement Ventilation Using Infrared Camera2002In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 34, p. 687-698Article in journal (Refereed)
    Abstract [en]

    The near zone of supply air diffusers is very critical for the indoor climate. Complaints of draft are often associated with low-velocity diffusers in displacement ventilation because the air is discharged directly into the occupied zone. Today, the knowledge of the near zone of these air supply diffusers is insufficient, causing an increased need for better measuring methods and representation of the occupied zone.

    A whole-field measuring technique has been developed by the authors for visualization of air temperatures and airflow patterns over a large cross-section. In this particular whole-field method, air temperatures are measured with an infrared camera and a measuring screen placed in the airflow. The technique is applicable to most laboratory and field test environments. It offers several advantages over traditional techniques; for example, it can record real-time images within large areas and capture transient events.

    The purpose of this study was to conduct a parameter and error analysis of the proposed whole-field measuring method applied to a flow from a low-velocity diffuser in displacement ventilation. A model of the energy balance, for a solid measuring screen, was used for analyzing the influence of different parameters on the accuracy of the method. The analysis was performed with respect to the convective heat transfer coefficient, emissivity, screen temperature and surrounding surface temperatures.

    Theoretically, the temperature difference between the screen and the ambient air was found to be 0.2–2.4 °C for the specific delimitation in the investigation. However, after applying correction the maximum uncertainty of the predicted air temperature was found to vary between 0.62 and 0.98 °C, due to uncertainties in estimating parameters used in the correction. The maximum uncertainty can be reduced to a great extent by estimating the convective heat transfer coefficient more accurately and using a screen with rather low emissivity.

  • 8.
    Cheng, Xiaogang
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS). Nanjing Univ Posts & Telecommun, Coll Telecommun & Informat Engn, Nanjing 210003, Jiangsu, Peoples R China.
    Yang, Bin
    Hedman, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Media Technology and Interaction Design, MID.
    Olofsson, Thomas
    Li, Haibo
    KTH, School of Electrical Engineering and Computer Science (EECS), Media Technology and Interaction Design, MID.
    Van Gool, Luc
    NIDL: A pilot study of contactless measurement of skin temperature for intelligent building2019In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 198, p. 340-352Article in journal (Refereed)
    Abstract [en]

    Human thermal comfort measurement plays a critical role in giving feedback signals for building energy efficiency. A contactless measuring method based on subtleness magnification and deep learning (NIDL) was designed to achieve a comfortable, energy efficient built environment. The method relies on skin feature data, e.g., subtle motion and texture variation, and a 315-layer deep neural network for constructing the relationship between skin features and skin temperature. A physiological experiment was conducted for collecting feature data (1.44 million) and algorithm validation. The contactless measurement algorithm based on a partly-personalized saturation temperature model (NIPST) was used for algorithm performance comparisons. The results show that the mean error and median error of the NIDL are 0.476 degrees C and 0.343 degrees C which is equivalent to accuracy improvements of 39.07% and 38.76%, respectively.

  • 9. Clarke, J A
    et al.
    Conner, S
    Fujii, Gen
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Geros, V
    Jóhannesson, Gudni
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Johnstone, C M
    Karatasou, S
    Kim, J
    Santamouris, M
    Strachan, P A
    The role of simulation in support of Internet-based energy services2004In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 36, no 8, p. 837-846Article in journal (Refereed)
    Abstract [en]

    The connection of buildings to the Internet broadband network is becoming commonplace. The establishment of such an infrastructure enables the development of a range of new energy, environment and health-related services for people in their homes and workplaces. Telecommunications companies and utilities are actively developing examples of such services, and local authorities and health care providers are supporting trial deployments. Several of the services can be enabled or enhanced through the application of building modelling and simulation. This paper describes the infrastructure for the e-services under test within a European research project and shows the potential for simulation support for these services.

  • 10.
    Einberg, Gery
    KTH, Superseded Departments, KTH Syd.
    The Influence of Airflow Profile and Heat Source Location on Heat Removal EfficiencyIn: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178Article in journal (Other academic)
  • 11.
    Fischer, David
    et al.
    KTH. Fraunhofer Institute for Solar Energy Systems, Germany.
    Haertl, Andreas
    Wille-Haussmann, Bernhard
    Model for electric load profiles with high time resolution for German households2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 92, p. 170-179Article in journal (Refereed)
    Abstract [en]

    Approximately 27% of the European energy consumption is caused by the domestic sector, where 19% of the end use energy demand is caused by electric devices. To investigate the factors at play, a stochastic bottom-up model for the generation of electric load profiles is introduced in this paper. The model is designed for investigating the effects of occupant behaviour, appliance stock and efficiency on the electric load profile of an individual household. For each activity of a person in the household, an electric appliance is used, and its electricity consumption is linked to measured electric load traces with a time resolution of 10 s. Probability distributions are incorporated for when and how often an appliance is operated. Duration of operation is given as probability density conditional on the start time. Shared use of an appliance by multiple persons is included in the model. Seasonal effects are considered by using changing probability sets during the course of the year. For validation, seven subgroups, which reflect typical household configurations, were formed and tested against measured field data from 430 households in 9 different cities across Germany. The results showed an accuracy of 91% and a correlation of up to 0.98.

  • 12. Fischer, David
    et al.
    Lindberg, Karen Byskov
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Wittwer, Christof
    Impact of PV and variable prices on optimal system sizing for heat pumps and thermal storage2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 128, p. 723-733Article in journal (Refereed)
    Abstract [en]

    Heat pump (HP) units coupled to thermal storage offer flexibility in operation and hence the possibility to shift electric load. This can be used to increase PV self-consumption or optimise operation under variable electricity prices. A key question is if new sizing procedures for heat pumps, electric boilers and thermal storages are needed when heat pumps operate in a more dynamic environment, or if sizing is still determined by the thermal demand and thus sizing procedures are already well known. This is answered using structural optimisation based on mixed integer linear programming. The optimal system size of a HP, an electric back-up heater and thermal storage are calculated for 37 scenarios to investigate the impact of on-site PV, variable electricity price, space heat demand and domestic hot water demand. The results are compared to today's established sizing procedures for Germany. Results show that the thermal load profile has the strongest influence on system sizing. In most of the scenarios investigated, the established sizing procedures are sufficient. Only large PV sizes, or highly fluctuating electricity prices, create a need for lager storage. However, allowing the storage to be overheated by 10 K, the need for a larger storage only occurs in the extreme scenarios. (C) 2016 Elsevier B.V. All rights reserved.

  • 13.
    Fischer, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Fraunhofer Inst Solar Energy Syst, Germany.
    Wolf, Tobias
    Scherer, Johannes
    Wilde-Haussmann, Bernhard
    A stochastic bottom-up model for space heating and domestic hot water load profiles for German households2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 124, p. 120-128Article in journal (Refereed)
    Abstract [en]

    In 2013 83% of energy in-the German residential sector is used for the preparation of domestic hot water (13%) and space heating (70%). Thermal demand profiles are essential to correctly determine operation and sizing of heating technologies. In this work, the stochastic bottom-up approach for electric loads is extended to cover domestic hot water (DHW) and space heating demands. The approach is presented for individual buildings and residential areas, validated and compared to currently used approaches. A behavioural model is used to determine DHW tappings, electric appliance use and temperature settings of the building. Building heat load is calculated using a simplified physical model, to allow for realistic energy demand profiles, efficient model parametrisation and fast computation. A randomisation approach for building heat load based on a clustered building typology, a variation of building parameters and heating settings is presented which allows the simulation of larger quantities of similar buildings. Validation against measured data for German single family houses shows a correlation of the typical daily load profile for DHW consumption of 0.92 and a mean relative error of 3% and for space heating 0.89 and 9% respectively.

  • 14.
    Gustafsson, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems. Högskolan Dalarna.
    Dermentzis, Georgios
    University of Innsbruck.
    Myhren, Jonn Are
    Högskolan Dalarna.
    Bales, Chris
    Högskolan Dalarna.
    Ochs, Fabian
    Univeristy of Innsbruck.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Feist, Wolfgang
    Energy performance comparison of three innovative HVAC systems for renovation through dynamic simulation2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 82, p. 512-519Article in journal (Refereed)
    Abstract [en]

    In this paper, dynamic simulation was used to compare the energy performance of three innovativeHVAC systems: (A) mechanical ventilation with heat recovery (MVHR) and micro heat pump, (B) exhaustventilation with exhaust air-to-water heat pump and ventilation radiators, and (C) exhaust ventilationwith air-to-water heat pump and ventilation radiators, to a reference system: (D) exhaust ventilation withair-to-water heat pump and panel radiators. System A was modelled in MATLAB Simulink and systems Band C in TRNSYS 17. The reference system was modelled in both tools, for comparison between the two.All systems were tested with a model of a renovated single family house for varying U-values, climates,infiltration and ventilation rates.It was found that A was the best system for lower heating demand, while for higher heating demandsystem B would be preferable. System C was better than the reference system, but not as good as A or B.The difference in energy consumption of the reference system was less than 2 kWh/(m2a) betweenSimulink and TRNSYS. This could be explained by the different ways of handling solar gains, but also bythe fact that the TRNSYS systems supplied slightly more than the ideal heating demand.

  • 15.
    Gustafsson, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Dalarna University, Sweden.
    Dipasquale, C.
    Poppi, Stefano
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. Högskolan Dalarna, Sverige.
    Bellini, A.
    Fedrizzi, R.
    Bales, C.
    Ochs, F.
    Sié, M.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Economic and environmental analysis of energy renovation packages for European office buildings2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 148, p. 155-165Article in journal (Refereed)
    Abstract [en]

    A large share of the buildings in Europe are old and in need of renovation, both in terms of functional repairs and energy efficiency. While many studies have addressed energy renovation of buildings, they rarely combine economic and environmental life cycle analyses, particularly for office buildings. The present paper investigates the economic feasibility and environmental impact of energy renovation packages for European office buildings. The renovation packages, including windows, envelope insulation, heating, cooling and ventilation systems and solar photovoltaics (PV), were evaluated in terms of life cycle cost (LCC) and life cycle assessment (LCA) through dynamic simulation for different European climates. Compared to a purely functional renovation, the studied renovation packages resulted in up to 77% lower energy costs, 19% lower total annualized costs, 79% lower climate change impact, 89% lower non-renewable energy use, 66% lower particulate matter formation and 76% lower freshwater eutrophication impact over a period of 30 years. The lowest total costs and environmental impact, in all of the studied climates, were seen for the buildings with the lowest heating demand. Solar PV panels covering part of the electricity demand could further reduce the environmental impact and, at least in southern Europe, even reduce the total costs.

  • 16.
    Hassanie, Samer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Martinac, Ivo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Long-term performance assessment of autonomous demand controlled ventilation units: A case study of an office building in SwedenIn: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178Article in journal (Refereed)
  • 17.
    Hed, Göran
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Bellander, Rickard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Mathematical modelling of PCM air heat exchanger2006In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 38, no 2, p. 82-89Article in journal (Refereed)
    Abstract [en]

    In order to cool a room with a cold night air phase change material, PCM, is stored in an air heat exchanger. During night the PCM crystallises, energy is released. During daytime air is circulated in the unit, energy is absorbed and the indoor air is cooled. The characteristic of PCM is that there is an increase of the specific heat over a limited temperature span. This is the principle that is used in the design of the PCM air heat exchanger unit.

    The action of a PCM storage unit will act differently depending of the thermal properties of the material. In an ideal material the phase transition occurs at a given temperature. On the market, compounds containing PCM are available which, in order to create a suitable melting temperature, are mixtures of different products. In these materials, the transition from liquid to solid takes place over a temperature span, i.e. the specific heat varies with the temperature. This can be represented by a c(p)(T) curve, specific heat as a function of the temperature.

    In this paper, the development of a mathematical model of the PCM air heat exchanger is presented. Considerations are taken to different shapes of the cp(T) curve. The mathematical model is verified with measurement on a prototype heat exchanger.

    The development of the equipment is part of the CRAFT project Changeable Thermal Inertia Dry Enclosures (C-TIDE) the possibility of use of phase change materials integrated into a building is explored.

  • 18.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Bourdakis, Eleftherios
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Experimental study of energy performance in low-temperature hydronic heating systems2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, p. 108-114Article in journal (Refereed)
    Abstract [en]

    Energy consumption, thermal environment and environmental impacts were analytically and experimentally studied for different types of heat emitters. The heat emitters studied were conventional radiator, ventilation radiator, and floor heating with medium-, low-, and very-low-temperature supply, respectively. The ventilation system in the lab room was a mechanical exhaust ventilation system that provided one air change per hour of fresh air through the opening in the external wall with a constant temperature of 5 °C, which is the mean winter temperature in Copenhagen. The parameters studied in the climate chamber were supply and return water temperature from the heat emitters, indoor temperature, and heat emitter surface temperature. Experiments showed that the mean supply water temperature for floor heating was the lowest, i.e. 30 °C, but it was close to the ventilation radiator, i.e. 33 °C. The supply water temperature in all measurements for conventional radiator was significantly higher than ventilation radiator and floor heating; namely, 45 °C. Experimental results indicated that the mean indoor temperature was close to the acceptable level of 22 °C in all cases. For energy calculations, it was assumed that all heat emitters were connected to a ground-source heat pump. Analytical calculations showed that using ventilation radiator and floor heating instead of conventional radiator resulted in a saving of 17% and 22% in heat pump's electricity consumption, respectively. This would reduce the CO2 emission from the building's heating system by 21 % for the floor heating and by 18% for the ventilation radiator compared to the conventional radiator.

  • 19.
    Hjortling, Camilla
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. Vattenfall AB, Sverige.
    Björk, Folke
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Berg, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. Vattenfall AB, Sverige.
    af Klintberg, Tord
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. Vattenfall AB, Sverige.
    Energy mapping of existing building stock in Sweden - Analysis of data from Energy Performance Certificates2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 153, p. 341-355Article in journal (Refereed)
    Abstract [en]

    This study contributes to defining the current energy consumption baseline for buildings in Sweden. The data used for the analysis are extracted from the database of the Swedish National Board of Housing, Building and Planning and consists of 186,021 measured energy performance certificates issued for commercial buildings (355 Mm(2)), collected during 2007-2015. The results from this study for certain building types, construction periods, climate zones and energy use is presented. Building codes have influence of the buildings energy performance. When new building codes have been adopted and energy performance requirement been stricter the measured energy consumption have been lowered compared to buildings built earlier. New buildings have nevertheless often higher energy consumption than stipulated by the building code. Climate zone have less impact on energy consumption than type of building. Building units in the warmer climate zones generally have slightly lower energy consumption than those in colder zones. This implies that the buildings are well adapted to the climates at hand. The results may help public authorities to plan future business strategies and energy policies. The Swedish Energy Performance Certificates are quite reliable because they are based on energy bills and not on theoretical calculations.

  • 20.
    Holmstedt, Louise
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Nilsson, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Mäkivierikko, Arman
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Brandt, Nils
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Stockholm Royal Seaport moving towards the goals—Potential and limitations of dynamic and high resolution evaluation data2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 169, p. 388-396Article in journal (Refereed)
    Abstract [en]

    Cites have been identified as one key arena to meet future sustainability challenges. However, if cites are to be part of the transition it must become possible to confirm results of ongoing actions. By the introduction information and communication technologies, it has become easier to collect performance parameters from the built environment, thereby enable more detailed evaluation. The aim of this paper is therefore to examine the potential and limitation of using dynamic and high resolution meter data for evaluation of energy consumption in buildings and households. The novelty of this approach is that dynamic and high resolution meter data can increase the level of detail in evaluation results and ease detection of deviations in the structures performance. However, most benefits are found from the occupant perspective, as more detailed evaluation information enable better inclusion of this stakeholder group. Furthermore this study has shown that the commonly used indicator energy use per heated floor area is an insufficient communication tool when taking holistic approach to building energy evaluation. Limitation to full use of dynamic and high resolution meter data have been identified to data collection and management, preservation of personal integrity and incentives to react on the given evaluation information.

  • 21.
    Hårsman, Björn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Daghbashyan, Zara
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Chaudhary, Parth
    On the quality and impact of residential energy performance certificates2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 133, p. 711-723Article in journal (Refereed)
    Abstract [en]

    This paper addresses quality and impact issues concerning Energy Performance Certificates (EPC) by means of a dataset based upon the Swedish EPCs for single-family houses. Assuming that the quality of the certificates plays an important role for their impact, we examine to what extent various characteristics of the firms and experts issuing the certificates are influencing their assessments of energy consumption and energy conservation. Exploiting the information on biased assessments, we also investigate the relationship between the transaction price of a house and its EPC label. Doing so, we distinguish the attributes that can be observed by visiting the house and those that a buyer only can inform herself about through the EPC. Applying regression analyses we find that firm and expert characteristics matter quite a lot implying that the EPC-quality could be improved considerably by increasing the inter-rater reliability. The results also show that the price impact of the energy label is related to information that the buyers can obtain by visiting the house rather than to information uniquely provided by the EPCs. Hence, the EPCs per se are unlikely to stimulate energy conservation through the price mechanism.

  • 22.
    Karami, Peyman
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Al-Ayish, Nadia
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. CBI, Swedish Cement.
    Gudmundsson, Kjartan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    A comparative study of the environmental impact of Swedish residential buildings with vacuum insulation panels2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, p. 183-194Article in journal (Refereed)
    Abstract [en]

    A large part of the energy consumption in the European Union member states is related to space heating, a significant share of which is due to transmission losses through the building envelope. Vacuum insulation panels (VIPs), with unique thermal insulation properties, do therefore provide an interesting alternative for the building industry. This paper presents the results of a life cycle analysis (LCA) study that compares the environmental impact of three hypothetical buildings, a standard residential building, a regular well-insulated building and a building insulated with VIPs. The environmental impact includes the global warming potential (GWP) and the primary energy (PE) use, from the material production stage to the building operational phase (50 years). The cradle-to-gate environmental impact categories of ozone depletion potential (ODP), acidification potential (AP) and eutrophication potential (EP) of all building components are also assessed. The study shows a comparatively lower operational energy for the VIP insulated building and a relatively lower total greenhouse gas emission as well as the possibility to save significant living space. The results also show that the VIPs have measurable environmental impact during the product stage while the core material of the VIPs has considerable impact on the results.

  • 23.
    Karami, Peyman
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Twumasi Afriyie, Ebenezer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Norberg, Peter
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. University of Gävle, Sweden.
    Gudmundsson, Kjartan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    A study of the thermal conductivity of granular silica materials for VIPs at different levels of gaseous pressure and external loads2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 85, p. 199-211Article in journal (Refereed)
    Abstract [en]

    Fast and reliable methods for the determination of thermal properties of core materials for vacuum insu-lation panels (VIPs) are needed. It is of great importance to know the thermal performance of a VIP core atdifferent levels of vacuum and external loads. In this study a new self-designed device, consisting of twocylindrical cavities connected to a Transient Plane Source instrument, is used to determine the thermalconductivity of low-density nanoporous silica powders, from atmospheric pressure down to 0.1 mbarwhile applying different levels of external pressure up to 4 bars. The study includes a brief theoreticaldiscussion of methods. The TPS is validated through comparison with available data for commercial silicaas well as through independent stationary measurements with a hot plate apparatus and with a TransientHot Bridge method. The different materials illustrate clear but different trends for the thermal conductiv-ity as a function of the level of vacuum and external pressure. The analysis of experimental results showsthat the transient methods are less suitable for measuring the thermal conductivity of low-density sil-ica powders, especially for the cases when the density is less than a limit at which the heat transfer byradiation becomes dominant compared to pure conduction.

  • 24. Khalid, W.
    et al.
    Rogstam, Jörgen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Energy usage prediction model comparing outdoor vs. indoor ice rinks2013In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 67, p. 195-200Article in journal (Refereed)
    Abstract [en]

    The overall aim of the project was to reduce energy usage in ice rinks. The specific scope of this study is to develop a comparison tool for indoor and outdoor ice rinks based on an energy usage prediction model. The refrigeration system cooling capacity, heat loads on ice surface and their correlation is studied in detail for an outdoor bandy (Bandy is a team winter sport played on ice, in which skaters use sticks to direct a ball into the opposing team's goal) ice rink for season 2010-2011. Climate data input has been validated along with performance analysis of refrigeration system. The cooling capacity and heat loads on ice surface are calculated, compared and analysed considering energy usage affecting parameters and weather parameters like temperature, wind speed, relative humidity and solar load. The deviation between total cooling energy produced and total heat load energy is found 19% and 27% for four warm days and season. The developed model provides a decision tool to choose between alternatives.

  • 25.
    Lai, Dayi
    et al.
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, Tianjin 300072, Peoples R China..
    Chen, Chuanming
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, Tianjin 300072, Peoples R China..
    Liu, Wei
    Zhejiang Univ, Zhejiang Univ Univ Illinois Urbana Champaign Inst, Int Campus, Haining 314400, Peoples R China..
    Shi, Yifu
    Georgia Inst Technol, Coll Architecture, Atlanta, GA 30332 USA..
    Chen, Chun
    Chinese Univ Hong Kong, Dept Mech & Automat Engn, Shatin 999077, Hong Kong, Peoples R China..
    An ordered probability model for predicting outdoor thermal comfort2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 168, p. 261-271Article in journal (Refereed)
    Abstract [en]

    Outdoor thermal comfort in urban spaces is gaining increasing research attention because it is associated with the quality of life in cities. This paper presents an ordered probability model for predicting the probability distribution of thermal sensation votes (TSVs) based on 1549 observations obtained from a large-scale field survey conducted at a park in Tianjin, China. With a given set of inputs, the developed model can predict the probability that people will feel cold, cool, slightly cool, neutral, slightly warm, warm, or hot. The predictive capability of the ordered probability model was systematically assessed by comparing it with the survey data and a traditional multivariate linear model. Both models had a similar accuracy in predicting single-value TSVs. However, the ordered probability model performed much better than the multivariate linear model in predicting the probability distribution of TSVs. A sensitivity analysis of the ordered probability model revealed that outdoor air temperature was the most important influencing factor. The impacts of global radiation, relative humidity, and activity level on predicted thermal sensation depended on the outdoor air temperature. The developed ordered probability model was used to predict suitable time periods for holding outdoor activities in Tianjin across a whole year. This new model is a more informative tool for predicting outdoor thermal comfort. (C) 2018 Elsevier B.V. All rights reserved.

  • 26. Lindberg, Karen Byskov
    et al.
    Doorman, Gerard
    Fischer, David
    KTH.
    Korpas, Magnus
    Anestad, Astrid
    Sartori, Igor
    Methodology for optimal energy system design of Zero Energy Buildings using mixed-integer linear programming2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 127, p. 194-205Article in journal (Refereed)
    Abstract [en]

    According to EU's Energy Performance of Buildings Directive (EPBD), all new buildings shall be nearly Zero Energy Buildings (ZEB) from 2018/2020. How the ZEB requirement is defined has large implications for the choice of energy technology when considering both cost and environmental issues. This paper presents a methodology for determining ZEB buildings' cost optimal energy system design seen from the building owner's perspective. The added value of this work is the inclusion of peak load tariffs and feed-in tariffs, the facilitation of load shifting by use of a thermal storage, along with the integrated optimisation of the investment and operation of the energy technologies. The model allows for detailed understanding of the hourly operation of the building, and how the ZEB interacts with the electricity grid through the characteristics of its net electric load profile. The modelling framework can be adapted to fit individual countries' ZEB definitions. The findings are important for policy makers as they identify how subsidies and EPBD's regulations influence the preferred energy technology choice, which subsequently determines its grid interaction. A case study of a Norwegian school building shows that the heat technology is altered from HP to bio boiler when the ZEB requirement is applied.

  • 27. Lindberg, Karen Byskov
    et al.
    Fischer, David
    KTH.
    Doorman, Gerard
    Korpas, Magnus
    Sartori, Igor
    Cost-optimal energy system design in Zero Energy Buildings with resulting grid impact: A case study of a German multi-family house2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 127, p. 830-845Article in journal (Refereed)
    Abstract [en]

    Zero Energy Buildings (ZEBs) are considered as one of the key elements to meet the Energy Strategy of the European Union. This paper investigates cost-optimal solutions for the energy system design in a ZEB and the subsequent grid impact. We use a Mixed Integer Linear (MILP) optimisation model that simultaneously optimises the building's energy system design and the hourly operation. As a ZEB have onsite energy generation to compensate for the energy consumption, it is both importing and exporting electricity. The hourly time resolution identifies the factors that influence this import/export situation, also known as the building's grid impact. An extensive case study of a multi-family house in Germany is performed. The findings show that the energy system design and the grid impact greatly depend on the ZEB definition, the existing policy instruments and on the current energy market conditions. The results indicate that due to the feed-in-tariff for PV, the cost-optimal energy design is fossil fuelled CHP combined with a large PV capacity, which causes large grid impacts. Further, we find that heat pumps are not a cost-optimal choice, even with lower electricity prices or with increased renewables in the electric power system.

  • 28.
    Liu, Wei
    et al.
    Zhejiang University, Haining, 314400, China.
    Zhao, Xingwang
    Chen, Qingyan
    A novel method for measuring air infiltration rate in buildings2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 168, p. 309-318Article in journal (Refereed)
    Abstract [en]

    Measuring the air infiltration rate in buildings is essential for reducing energy use and improving indoor air quality. This rate has traditionally been determined by means of the blower door method, which is disruptive to building occupants, cannot identify the location of infiltration, cannot provide the infiltration rate for a section of the envelope, and requires considerable effort for setup and tear-down. Therefore, this study has developed a novel technique to measure air infiltration in buildings using an infrared camera. A thermographic image of a building envelope produced by an infrared camera and the measured indoor/outdoor air parameters (velocity, temperature, and pressure) were used to identify the effective crack size and air infiltration rate by means of theoretical heat transfer and fluid mechanics analyses. The proposed method was validated by experimental measurements in an environmental chamber and an office. The experiment in the environmental chamber constructed a small-scale room with known crack size. The experimental setup was comparable to actual conditions. The proposed method was able to predict the crack size within a relative error of 20%. For the experiment in the office, this study used the tracer-gas decay method to measure the air infiltration rate, and the relative error of the calculated air infiltration rate was only 3%.

  • 29.
    Lu, Hai
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems. Electric Power Research Institute, Yunnan Electric Power and Research Institute (Group), Kunming, China .
    Yu, Z.
    Alanne, K.
    Zhang, L.
    Fan, L.
    Xu, X.
    Martinac, Ivo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Transition path towards hybrid systems in China: Obtaining net-zero exergy district using a multi-objective optimization method2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 85, p. 524-535Article in journal (Refereed)
    Abstract [en]

    A hybrid energy system including both off-site and distributed energy sources, energy conversion technologies and operation methods, is a necessary step on a transition path towards a sustainable energy system. The challenge is to identify such a combination of design options that result in minimum life cycle cost (LCC) and maximum exergy efficiency (EE) at each phase of the transition path. In this paper, a time-effective multi-objective optimization method based on genetic algorithm (GA), is proposed for the transition path problem. The proposed model makes use of a fitness function approach to reduce the model into one objective function and to reduce the computational time. In a case study, the model is applied to a potential net-zero exergy district (NZEXD) in Hangzhou, China. Here, three possible hybrid energy scenarios and three preference treatment strategies are analyzed. The study suggests that the proposed approach is workable for the identification of the most feasible options to be gradually integrated in an NZEXD in a multi-stage process. In the Hangzhou case, with the reduction of investments in distributed energy components and escalating market prices of fossil fuels, distributed energy system (DES) may have more feasibility in the near future.

  • 30.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A descriptive and comparative analysis of three common control techniques for an on/off controlled Ground Source Heat Pump (GSHP) system2013In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 65, p. 1-9Article in journal (Refereed)
    Abstract [en]

    In the present paper, three common methods in order to control an on/off controlled Ground Source Heat Pump (GSHP) system called "Constant hysteresis", "Floating hysteresis", and "Degree-Minute" methods are comprehensively described. Then, the generic model already developed by the authors is used in order to do the dynamic simulation of the systems with three different control methods over a year and making the comparison between them. The results from annual modeling of the systems show that the mean temperature of the heating water supplied to the building for the system controlled with degree-minute method is always close to the required temperature, regardless of the climatic boundary conditions over a typical year, whereas, the average supply temperature for the system with constant hysteresis method is mostly higher or lower than the required temperature, depending on the boundary condition. Regarding the annual energy use, the degree-minute and constant hysteresis methods have the lowest and highest annual energy use respectively. Switching from constant hysteresis to floating hysteresis method, the annual energy use will become lower and the mean temperature of the heating water supplied to the building will be closer to the required one.

  • 31. Mader, Gunda
    et al.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity control in air-water heat pumps: Total cost of ownership analysis2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 81, p. 296-304Article in journal (Refereed)
    Abstract [en]

    Adjusting capacity to changing demand by variable speed control is known to offer efficiency improvement over classical on/off control. With a total cost of ownership analysis the economic viability of both control schemes is assessed for residential air-water heat pumps operating in different climate zones. Component sizes are optimized for both control methods individually. Results show optimal compressor displacement volumes to be smaller for variable speed than for on/off control. The optimal ratio of evaporator to condenser size is smaller for the variable speed system. Variable speed control is shown to be uneconomic for space heating in warmer climate while for average climate cost-effectiveness depends on the economic framework. For colder climate variable speed control is the more profitable choice in all considered cases; savings of up to 5000 EUR compared to on/off control can be achieved within 15 years of operation.

  • 32.
    Malmqvist, Tove
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Nehasilova, Marie
    Czech Tech Univ, Univ Ctr Energy Efficient Bldg, Prague, Czech Republic..
    Moncaster, Alice
    Open Univ, Sch Engn & Innovat, Milton Keynes, Bucks, England..
    Birgisdottir, Harpa
    Aalborg Univ, Danish Bldg Res Inst, Copenhagen, Denmark..
    Rasmussen, Freja Nygaard
    Aalborg Univ, Danish Bldg Res Inst, Copenhagen, Denmark..
    Wiberg, Aoife Houlihan
    Norwegian Univ Sci & Technol, Dept Architectural Design Hist & Technol, Trondheim, Norway..
    Potting, Jose
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Design and construction strategies for reducing embodied impacts from buildings - Case study analysis2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 166, p. 35-47Article in journal (Refereed)
    Abstract [en]

    The dominance of operational energy and related greenhouse gas (GHG) emissions of most existing buildings is decreasing in new construction, when primary fossil energy of building operation decreases as result of the implementation of energy efficiency measures as well as a decarbonisation of national energy mixes. Stakeholders therefore have a growing interest in understanding the possibilities for reducing embodied impacts in buildings. In the LEA EBC project 'Annex 57' a broad call for case studies was launched with the aim to identify design strategies for reducing embodied energy and GHG emissions (EEG) from buildings. The aim of this paper is to identify and provide a collected and comprehensive overview of quantitative reduction potentials of the particular EEG reduction strategies which should be considered by the stakeholders engaged in, and with the capacity to influence the outcome of, individual building projects. This is done by a systematic analysis of the Annex 57 case study collection as well as additional scientific literature. While it should be noted that the actual EEG savings at building level illustrated in this collection of studies are only applicable to each specific case, importantly this multiple cross-case analysis has provided rigorous evidence of the considerable potential to reduce embodied impacts in the design and construction of new and refurbished buildings.

  • 33. Manyumbu, Edson
    et al.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Fransson, Torsten H.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    A parametric analysis on the regeneration performance of silica gel in a proposed comfort provision strategy for a typical office space in Harare, Zimbabwe2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 126, p. 104-112Article in journal (Refereed)
    Abstract [en]

    This paper reports the influence, design and climate parameters have on the regeneration performance of a proposed strategy for passive comfort provision for an office space. Solar regeneration of an external silica gel bed is later followed by regeneration of internal surfaces laden with silica gel. The internal surfaces regeneration is effected utilizing air dried by the external bed. External bed regenerating air conditions are evaluated based on simple energy balance and buoyancy models. Thermal efficiency is formulated based on its fundamental definition. Silica gel drying models are obtained from literature. MS Excel Spreadsheet program is applied in the present simulations. Internal surfaces regeneration depends largely on; ventilation rate, initial dryness and mass of external silica gel bed. There is an optimum ventilation rate for a given mass of silica gel in the external bed for particular initial moisture content. Channel depth is quite critical to the regeneration effect on the external silica gel bed, with an average influence coefficient of 200%. The specific humidity of the regenerating air has the least coefficient of influence of 82%. Considering the foregoing, the design of the proposed system calls for simulation to estimate performance.

  • 34. Marimón, M. A.
    et al.
    Arias, Jaime
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Bruno, J. C.
    Coronas, A.
    Integration of trigeneration in an indirect cascade refrigeration system in supermarkets2011In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 43, no 6, p. 1427-1434Article in journal (Refereed)
    Abstract [en]

    This article presents an energy and economic analysis of a trigeneration configuration for supermarket applications. The energy system in a supermarket is relatively complex, because it includes lighting, air conditioning, cabinets, refrigeration system, etc. A trigeneration system could be used to simultaneously satisfy heating, refrigeration and electricity demands in supermarkets. More specifically, this article studies the integration of a trigeneration system and an indirect refrigeration cascade compression system in a supermarket in Barcelona. The trigeneration system consists of a cogeneration engine and an ammonia/water absorption chiller unit. The results of simulating energy usage, life cycle costs and CO2 emissions have been compared with a conventional indirect refrigeration cascade compression system for the supermarket studied. Several trigeneration configurations have been studied. They all show a payback time of less than 6 years but the profitability of the investment depends strongly on the ratio between the prices of natural gas and electricity. This study shows that this novel trigeneration system is economically feasible and environmentally more viable than conventional supermarket systems.

  • 35.
    Molinari, Marco
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Lazzarotto, Alberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Björk, Folke
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    The application of the parametric analysis for improved energy design of a ground source heat pump for residential buildings2013In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 63, p. 119-128Article in journal (Refereed)
    Abstract [en]

    Energy use in buildings represents a major share of the overall energy used in developed countries. The reduction of the energy demand and the efficient energy use are often seen as feasible ways for a more sustainable energy use in the built environment. Ground source heat pumps (GSHPs) are efficient systems to supply heating and cooling energy to buildings but their design is critical for their performance. Furthermore, their performance depends on the cooling and heating demand and on the environmental conditions. The need for the end-use energy for a building supplied with GSHP has been studied with regard to four parameters in two different locations. The effect of two building performance parameters, roof and external walls insulation, and of two parameters affecting the performance of GSHP, boreholes spacing and number of boreholes, have been investigated by means of factorial analysis. Results show that from an energy point of view the optimal configurations of the boreholes change depending on the variation of building parameters such as insulation. The methodology proposed allows to quantify the impact of different design configurations on the need for end-use energy.

  • 36.
    Monzó, Patricia
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Puttige, Anjan Rao
    KTH.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Mogensen, Palne
    KTH.
    Cazorla, Antonio
    Instituto de Ingeniería Energética, Universidad Politécnica de Valencia, Camino de Vera s/n, Valencia 46022, Spain.
    Rodriguez, Juan
    EnergyLab, Fonte das Abelleiras s/n, Campus Universidad de Vigo, Vigo 36310, Spain.
    Montagud, Carla
    Instituto de Ingeniería Energética, Universidad Politécnica de Valencia, Camino de Vera s/n, Valencia 46022, Spain.
    Cerdeira, Fernando
    Universidad de Vigo, Maxwell 16, Vigo 36310, Spain.
    Numerical modeling of ground thermal response with borehole heat exchangers connected in parallel2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 172, p. 371-384Article in journal (Refereed)
    Abstract [en]

    With bore fields for energy extraction and injection, it is often necessary to predict the temperature response to heat loads for many years ahead. Mathematical methods, both analytical and numerical, with different degrees of sophistication, are employed. Often the g-function concept is used, in which the borehole wall is assumed to have a uniform temperature and the heat injected is constant over time. Due to the unavoidable thermal resistance between the borehole wall and the circulating fluid and with varying heat flux along the boreholes, the concept of uniform borehole wall temperature is violated, which distorts heat flow distribution between boreholes. This aspect has often been disregarded. This paper describes improvements applied to a previous numerical model approach. Improvements aim at taking into account the effect of thermal resistance between the fluid and the borehole wall. The model employs a highly conductive material (HCM) embedded in the boreholes and connected to an HCM bar above the ground surface. The small temperature difference occurring within the HCM allows the ground to naturally control the conditions at the wall of all boreholes and the heat flow distribution to the boreholes. The thermal resistance between the fluid and the borehole wall is taken into account in the model by inserting a thermally resistive layer at the borehole wall. Also, the borehole ends are given a hemispherical shape to reduce the fluctuations in the temperature gradients there. The improvements to the HCM model are reflected in a changed distribution of the heat flow to the different boreholes. Changes increase with the number of boreholes. The improvements to the HCM model are further illustrated by predicting fluid temperatures for measured variable daily loads of two monitored GCHP installations. Predictions deviate from measured values with a mean absolute error within 1.1 and 1.6 K

  • 37.
    Myhren, Jonn Are
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators2009In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 41, no 1, p. 92-100Article in journal (Refereed)
    Abstract [en]

    Performance of heat emitters in a room is affected by their interaction with the ventilation system. A radiator gives more heat output with increased air flow along its heat transferring surface, and with increased thermal difference to surrounding air. Radiator heat output and comfort temperatures in a small one-person office were Studied using different positions for the ventilation air inlet. In two of the four test cases the air inlet was placed between radiator panels to form ventilation-radiator systems. Investigations were made by CFD (Computational Fluid Dynamics) simulations, and included visualisation of thermal comfort conditions, as well as radiator heat output comparisons. The room model was exhaust-ventilated, with an air exchange rate equal to what is recommended for Swedish offices (71 s(-1) per person) and cold infiltration air (-5 degrees C) typical of a winter day in Stockholm. Results showed that under these conditions ventilation-radiators were able to create a more stable thermal climate than the traditional radiator ventilation arrangements. In addition, when using ventilation-radiators the desired thermal climate could be achieved with a radiator surface temperature as Much as 7.8 degrees C lower. It was concluded that in exhaust-ventilated office rooms, ventilation-radiators can provide energy and environmental savings.

  • 38.
    Myhren, Jonn Are
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Flow patterns and thermal comfort in a room with panel, floor and wall heating2008In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 40, no 4, p. 524-536Article in journal (Refereed)
    Abstract [en]

    Thermal comfort aspects in a room vary with different space heating methods. The main focus in this study was how different heating systems and their position affect the indoor climate in an exhaust-ventilated office under Swedish winter conditions. The heat emitters used were a high and a medium-high temperature radiator, a floor heating system and large wall heating surfaces at low temperature. Computational fluid dynamics (CFD) simulations were used to investigate possible cold draught problems, differences in vertical temperature gradients, air speed levels and energy consumption. Two office rooms with different ventilation systems and heating needs were evaluated. Both systems had high air exchange rates and cold infiltration air.

    The general conclusions from this study were that low temperature heating systems may improve indoor climate, giving lower air speeds and lower temperature differences in the room than a conventional high temperature radiator system. The disadvantage with low temperature systems is a weakness in counteracting cold down-flow from ventilation supply units. For that reason the location of heat emitters and the design of ventilation systems proved to be of particular importance. Measurements performed in a test chamber were used to validate the results from the CFD simulations.

  • 39.
    Myrefelt, Sonny
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    The reliability and availability of heating, ventilation and air conditioning systems2004In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 36, no 10, p. 1035-1048Article in journal (Refereed)
    Abstract [en]

    Reliability theory has been applied to building HVAC facilities. In order to do this, the type of probability distribution for "mean time to repair", "mean time between failures" and "decision time" was first studied, and it has been shown that the log-normal type of distribution applies here. This was evaluated from a large amount of data collected from buildings belonging to seven large real estate operators. Based on those results and assumptions, a "model" using standard reliability theory equations was deducted. The model has been used in a study of the seven large real estate operators. The study shows that the model can give a good picture of the reliability and availability of HVAC systems. The study also gave interesting results about the status of the studied HVAC systems: the operational availability is high, almost 100%; the decision time of the maintenance staff is large compared to repair time; the system reliability depends strongly on the technical solutions and the number of components; and the functional availability of the systems was low, partly because of malfunction of the ventilation systems. (Note: this depends, naturally, on the function criteria.) Values of functional availability depend strongly on the function criteria. In this study, criteria connected to the actual buildings were used and no evaluation of the criteria themselves was made. The measurements were taken from different buildings both connected and not connected to the seven studied organisation.

  • 40.
    Mäkivierikko, Aram
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Shahrokni, Hossein
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kordas, Olga
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Designing energy feedback for a local social network2019In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 199, p. 88-101Article in journal (Refereed)
    Abstract [en]

    Engaged households are needed for the future ‘smart grids’ to function, but it is difficult to engage residents in their household electricity consumption. Building on earlier research suggesting that a local social network could provide a suitable context for energy feedback, this paper examines how feedback presented in a social network should be designed in order to be better understood by the residents and encourage long-term engagement. A review of the literature on design principles and cases where they had been implemented identified 24 principles. A prototype feedback design adapted for a local social network was made, based on design principles deemed suitable for the screens designed. End-user feedback on the prototype was collected through a stakeholder consultation workshop. In the workshop dis- cussions, 17 identified principles were mentioned and there was support for 15 of these, one was both supported and contested and two were contested. Based on comments and suggestions from end-users, a revised version of the feedback prototype was made for implementation in a pilot study in Sweden and Portugal.

  • 41. Müller, A.
    et al.
    Kranzl, L.
    Tuominen, P.
    Boelman, E.
    Molinari, Marco
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Entrop, A.G.
    Estimating exergy prices for energy carriers in heating systems: Country analyses of exergy substitution with capital expenditures2011In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 43, no 12, p. 3609-3617Article in journal (Refereed)
    Abstract [en]

    Exergy represents the ability of an energy carrier to perform work and can be seen as a core indicator for measuring its quality. In this article we postulate that energy prices reflect the exergy content of the underlying energy carrier and that capital expenditures can substitute for exergy to some degree. We draw our line of argumentation from cost and technology data for heating systems of four European countries: Austria, Finland, The Netherlands, and Sweden. Firstly, this paper shows that the overall consumer costs for different heating options, widely installed in those countries, are in the same range. In this analysis we derived an overall standard deviation of about 8%. Secondly, additional analysis demonstrates that the share of capital costs on total heating cost increases with lower exergy input. Based on the data used in this analysis, we conclude that for the case of modern cost effective heating systems the substitution rate between exergy and capital is in the vicinity of 2/3. This means that by reducing the average specific exergy input of the applied energy carriers by one unit, the share of capital costs on the total costs increases by 2/3 of a unit.

  • 42.
    Nilsson, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Wester, Misse
    Lazarevic, David
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Brandt, Nils
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Smart homes, home energy management systems and real-time feedback- Lessons for influencing household energy consumption from a Swedish field study2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 179, p. 15-25Article in journal (Refereed)
    Abstract [en]

    Home energy management systems (HEMS), providing energy feedback and smart features through in-home displays, have the potential to support more sustainable household decisions concerning energy consumption. However, recent findings from European smart metering trials have reduced the optimism, suggesting only modest savings from energy feedback. In this paper, we investigate the potential of HEMS to foster reductions in energy use, focusing on a population segment of particular relevance; high-income and highly educated households, considered as early adopters of smart grid technologies. Covering 154 households participating in a field trial in a sustainable city district in Stockholm, Sweden during one year, this study draws on the analyses of smart meter electricity and hot tap water data and in-depth interviews to provide an increased understanding of how feedback and features are perceived, used, and acted upon, and resulting effects on awareness, behavior, and consumption. Our results show that impact on energy consumption varies widely across individual households, suggesting that households respond to energy feedback highly individually. Although HEMS may lead to increased awareness of energy consumption, as well as increased home comfort, several obstacles for energy consumption behavioral change are identified. Drawing from these findings, we suggest policy implications and key issues for future research.

  • 43.
    Persson, Johannes
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Phase change material cool storage for a Swedish Passive House2012In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 54, p. 490-495Article in journal (Refereed)
    Abstract [en]

    Passive Houses have gained popularity the last 10 years as a way of improving the energy efficiency in the housing stock. The combination of a highly insulating building envelope and large solar heat gains summertime can, however, result in excessive temperatures. The aim of this paper is to evaluate a comfort cooling strategy for attaining good indoor climate summertime while maintaining good energy efficiency. The studied strategy is a night cool storage with phase change material (PCM). To evaluate this, a Matlab code was used for the analysis of climate files along with the thermodynamical properties of PCM storages and then used with IDA Indoor Climate and Energy for building simulations. The building model is based on an actual Passive House in the district of Lambohov in Linköping, Sweden, where continuous logging of temperatures are available. Without comfort cooling the simulations show excessive temperatures summertime, which is consistent with the field measurements from the actual house. The results show that the PCM can remove a substantial share of the degree hours with excessive temperatures.

  • 44.
    Persson, Tomas
    et al.
    Högskolan i Dalarna.
    Nordlander, Svante
    Högskolan i Dalarna.
    Rönnelid, Mats
    Högskolan i Dalarna.
    Electrical savings by use of wood pellet stoves and solar heating systems in electrically heated single-family houses2005In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 37, no 9, p. 920-929Article in journal (Refereed)
    Abstract [en]

    This study investigates how electrically heated single-family houses can be converted to wood pellets- and solar heating using pellet stoves and solar heating systems. Four different system concepts are presented and system simulations in TRNSYS evaluate the thermal performance and the electrical savings possible for two different electrically heated single-family houses. Simulations show that the electricity savings using a wood pellet stove are greatly affected by the level of comfort, the house plan, the system choice and if the internal doors are open or closed. Installing a stove with a water-jacket connected to a radiator system and a hot water store has the advantage that heat can be transferred to domestic hot water and be distributed to other rooms. Such systems leads to that more electricity can be replaced, especially in houses having a traditional plan. Though it is unnecessary to have too many radiators connected to a stove with a low fraction of energy heating the water jacket. Today's most common control strategy for stoves (the on/off-control) results in unnecessarily high emissions. A more advanced control varying the heating rate from maximum to minimum to keep a constant room temperature reduces the number of starts and stops and thereby the emissions.

  • 45.
    Ploskić, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-temperature ventilation pre-heater in combination with conventional room heaters2013In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 65, p. 248-259Article in journal (Refereed)
    Abstract [en]

    The main focus of the present study was to find design requirements for an air-heater that would be able to operate at low pressure loss and low-temperature water supply. The idea was to combine this low-temperature air-heater with existing radiator systems so that they can operate at similar low-temperature supply as used in floor heating systems. Results indicated that the proposed air-heater was able to lift the temperature of supply air at 10 l/s from -15 degrees C to 18.7 degrees C using 40 degrees C water supply. In addition, a thermal performance analysis showed that radiator systems equipped with the proposed air-heater could meet a space heat loss of 35.6 W per square meter floor area, using supply water of 40 degrees C. It was also shown that the heat pump efficiency in the hydronic system with proposed air-heater was 8-18% higher than in system without air-heater. All results in the present study were obtained by analytical (semi-empirical) and numerical (Computational Fluid Dynamics - CFD) calculations.

  • 46. Rahnama, S.
    et al.
    Afshari, A.
    Bergsøe, N. C.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Aalborg University, Denmark.
    Experimental study of the pressure reset control strategy for energy-efficient fan operation: Part 1: Variable air volume ventilation system with dampers2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 139, p. 72-77Article in journal (Refereed)
    Abstract [en]

    This paper is the first part of a two-part series which investigate the energy saving potentials in a novel mechanical ventilation system by replacing terminal dampers with decentralized fans. In Part 1, a conventional variable air volume (VAV) ventilation system with dampers is studied as a reference for comparison with the novel ventilation system in Part 2. The present study (Part 1) proposes a new method to implement the pressure reset strategy in practice. A common strategy to control the supply fan speed in a VAV system is to install a pressure sensor in the supply duct system. Then the fan speed is controlled such that a constant static pressure is maintained at the sensor location. Further energy saving can be obtained by resetting the pressure setpoint to a lower value at partial load conditions. This strategy is known as pressure reset control or critical zone reset strategy in the literature. The proposed method has been evaluated through an experimental mock-up in a laboratory environment. Experimental results show a minimum reduction of about 20% in fan power demand with applying the reset strategy compared to a constant static pressure setpoint.

  • 47. Rasmussen, F. N.
    et al.
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Moncaster, A.
    Wiberg, A. H.
    Birgisdóttir, H.
    Analysing methodological choices in calculations of embodied energy and GHG emissions from buildings2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 158, p. 1487-1498Article in journal (Refereed)
    Abstract [en]

    The importance of embodied energy and embodied greenhouse gas emissions (EEG) from buildings is gaining increased interest within building sector initiatives and on a regulatory level. In spite of recent harmonisation efforts, reported results of EEG from building case studies display large variations in numerical results due to variations in the chosen indicators, data sources and both temporal and physical boundaries. The aim of this paper is to add value to existing EEG research knowledge by systematically explaining and analysing the methodological implications of the quantitative results obtained, thus providing a framework for reinterpretation and more effective comparison. The collection of over 80 international case studies developed within the International Energy Agency's EBC Annex 57 research programme is used as the quantitative foundation to present a comprehensive analysis of the multiple interacting methodological parameters. The analysis of methodological parameters is structured by the stepwise methodological choices made in the building EEG assessment practice. Each of six assessment process steps involves one or more methodological choices relevant to the EEG results, and the combination potentials between these many parameters signifies a multitude of ways in which the outcome of EEG studies are affected.

  • 48.
    Sandels, Claes
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Widén, Joakim
    Uppsala Universitet.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Andersson, Enar
    Department of Energy Technology, SP Technical Research Institute of Sweden.
    Day-Ahead Predictions of Electricity Consumption in a Swedish Office Building from Weather, Occupancy, and Temporal data2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 108Article in journal (Refereed)
    Abstract [en]

    An important aspect of Demand Response (DR) is to make accurate predictions for the consumption in the short term, in order to have a benchmark load profile which can be compared with the load profile influenced by DR signals. In this paper, a data analysis approach to predict electricity consumption on load level in office buildings on a day-ahead basis is presented. The methodology is: (i) exploratory data analysis, (ii) produce linear models between the predictors (weather and occupancies) and the outcomes (appliance, ventilation, and cooling loads) in a step wise function, and (iii) use the models from (ii) to predict the consumption levels with day-ahead prognosis data on the predictors. The data has been collected from a Swedish office building floor. The results from (ii) show that occupancy is correlated with appliance load, and outdoor temperature and a temporal variable defining work hours are connected with ventilation and cooling load. It is concluded from the results in (iii) that the error rate decreases if fewer predictors are included in the predictions. This is because of the inherent forecast errors in the day-ahead prognosis data. The achieved error rates are comparable with similar prediction studies in related work.

  • 49.
    Sevencan, Suat
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Economic feasibility study of a fuel cell-based combined cooling, heating and power system for a data centre2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 111, p. 218-223Article in journal (Refereed)
    Abstract [en]

    The energy use of data centres is increasing as the data storage needs increase. One of the largest items in the energy use of these facilities is cooling. A fuel cell-based combined cooling, heating and power system can efficiently meet such a centre's need for cooling and in the meantime generate enough electricity for the centre and more. In this paper the economic feasibility of a fuel cell-based combined cooling, heating and power system that meets the energy demands of such a facility is investigated using operational data from an existing data centre in Stockholm, Sweden. The results show that although the system is not feasible with current energy prices and technology it may be feasible in the future with the projected changes in energy prices.

  • 50.
    Shahrokni, Hossein
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Levihn, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Brandt, Nils
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Big meter data analysis of the energy efficiency potential in Stockholm's building stock2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 78, p. 153-164Article in journal (Refereed)
    Abstract [en]

    The City of Stockholm is making substantial efforts towards meeting its climate change commitments including a GHG emission target of 3 tonnes per capita by 2020 and making its new eco-district Stockholm Royal Seaport a candidate of Clinton Climate Initiative's Climate Positive Program. Towards achieving these policies, this study evaluated the energy efficiency potential in the city, in collaboration with the district heating and electricity utility Fortum. Drawing on their vast billing meter data on the housing stock in Stockholm, a new understanding of energy use in the city emerged. Analysis of the energy efficiency potential of different building vintages revealed that the retrofitting potential of the building stock to current building codes would reduce heating energy use by one third. In terms of market segmentation, the greatest reduction potential in total energy was found to be for buildings constructed between 1946 and 1975. This is due to the large number of buildings constructed during that era and their poor energy performance. However, the least energy-efficient buildings were those built between 1926 and 1945 in contradiction to commonly held beliefs. These findings indicate the need for a shift in public policy towards the buildings with highest retrofitting potential.

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