| 1. |
- Alanne, K., et al.
(författare)
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Multi-criteria evaluation of residential energy supply systems
- 2007
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 39:12, s. 1218-1226
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the selection of a residential energy supply system as a multi-criteria decision-making problem, which involves both financial and environmental issues. Specifically, we compare micro-CHP (micro-cogeneration) heating with traditional heating systems through an evaluation that accounts for: (i) the decision-makers' subjective preferences, (ii) uncertainties in the performance of micro-CHP heating systems (which are partly caused by the lack of long-term operational experiences) and (iii) the context-dependency of life-cycle costs and environmental burdens of heating systems. Motivated by these considerations, we employ the PAIRS multi-criteria decision-making methodology that captures incomplete information by way of interval-valued parameters and provides support for sensitivity analyses, too. Our comparative analysis of alternative heating systems suggests that micro-CHP is a reasonable alternative to traditional systems, particularly from the environmental point of view. © 2007 Elsevier B.V. All rights reserved.
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| 2. |
- Arias, Jaime M., et al.
(författare)
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Heat recovery and floating condensing in supermarkets
- 2006
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 38:2, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
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| 4. |
- Blomqvist, Claes, et al.
(författare)
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Conversion of electric heating in buildings An unconventional alternative
- 2008
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 40:12, s. 2188-2195
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Bohdanowicz, Paulina, et al.
(författare)
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Determinants and benchmarking of resource consumption in hotels : case study of Hilton International and Scandic in Europe
- 2007
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 39:1, s. 82-95
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Gustafsson, Stig-Inge, 1948-, et al.
(författare)
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Optimal heating of large block of flats
- 2008
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 40:9, s. 1699-1708
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Tidskriftsartikel (refereegranskat)abstract
- District heating is used in many urban areas in Sweden. Almost always, the district heating utility is owned by the municipality and the municipality naturally encourages proprietors to connect their buildings to the grid, even if they cannot really force them to do so. The building owners are free to choose the best system, i.e. the cheapest one, for their need. Unfortunately, it is not always so easy to find the best solution. Mixed integer linear programming (MLIP) models might here come to help. By such computer programs it is possible to find the absolutely cheapest system of available alternatives, or even combinations among them. This paper shows how to design such a model and further how to closely depict the district heating, and electricity tariff. This is of course very important because the only interface between the proprietor of the building and the utility is found in this bureaucratic instrument. If the tariff is too high the building owners will choose other heating systems than district heating, or even worse, combining district heating with alternative base load sources. In Sweden, this has been of interest because ground-water coupled heat pumps can be profitable, operated by use of the relatively low electricity prices. In this paper we show that dual-fuel, and sometimes even triple-fuel systems, are of interest when the proprietor aims at minimising the cost for space and domestic hot-water heating. © 2008 Elsevier B.V. All rights reserved.
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| 7. |
- Gustavsson, Leif, et al.
(författare)
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Energy conservation and conversion of electrical heating systems in detached houses
- 2007
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 39:6, s. 717-726
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a Swedish house built in 1974, heated with resistance heaters was analysed. Different options for changing the heating system and electricity production were compared for this type of detached house, assuming coal-based electricity production as a reference. Changes in the fuel used, the electricity production technology, the end-use heating technology and the heat demand were analysed. The aim was to show how these different parts of the energy system interact and to evaluate the cost-effectiveness of reducing CO2 emission and primary energy use by different combinations of changes. The results showed that the CO2 emission and primary energy use could be reduced by 95 and 70%, respectively, without increased heating costs in a national economic perspective. The choice of end-use heating system had a greater influence than the energy conservation measures on the parameters studied. The energy conservation measures were less cost-effective in combination with the more energy-efficient heating systems, although the fact that they reduced the heat demand, and thus also the investment cost of the new heating system, was taken into account.
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| 8. |
- Hed, Göran, et al.
(författare)
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Mathematical modelling of PCM air heat exchanger
- 2006
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 38:2, s. 82-89
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Hellström, Bengt, et al.
(författare)
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Description of ParaSol v3.0 and comparison with measurements
- 2007
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Ingår i: Energy and Buildings. - : Elsevier BV. - 1872-6178 .- 0378-7788. ; 39:3, s. 279-283
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Tidskriftsartikel (refereegranskat)abstract
- Parasol is a computer program for calculating the solar and thermal properties of windows with sunshades and the energy demands of a room with a window/shading system. The program has three main features. One of them is a calculation of g, T and U for normal incidence of beam irradiation, which is performed as soon as a window or an internal/interpane sunshade is selected. The other two are based on yearly simulations, using DEROB-LTH, a building energy simulation program on which ParaSol is based. One of the applications gives the monthly average of g and T for the window glazing and the glazing/sunshade system. The other application gives the heating and cooling demands for a room with a window, with and without a sunshade, where input data are given for the internal heat, ventilation settings, shading control and temperature set-points. Version 3.0 of Parasol, which has some new and improved models, is described in this paper. The g-values obtained with this program version are compared with measurements on windows with internal/interpane screens/venetian blinds. The absolute deviation is less than 0.03 for the venetian blinds. The measured values of dark internal screens with closed air gaps exceed those simulated by Parasol, but are lower than the ones simulated with open air gaps. (C) 2006 Elsevier B.V. All rights reserved.
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| 10. |
- Karlsson, Fredrik, et al.
(författare)
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Energy demand and indoor climate in a low energy building : changed control strategies and boundary conditions
- 2006
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788. ; 38:4, s. 315-326
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Tidskriftsartikel (refereegranskat)abstract
- Energy demand in the built environment is an important issue. In Sweden, 39% of energy use originates from the building sector, and this figure is increasing. Several attempts have been made to improve the energy use, for example low-energy houses, which are built with the aim of decreasing the use of energy, but still providing a good environment for the occupants. An energy simulation program, ESP-r, was used for simulation of the energy requirement and indoor climate in a well-insulated terraced house in Sweden. The building model was compared to measured values from the real object. A computational fluid dynamics (CFD)-model for one room was used to simulate and visualize the airflow and temperature pattern. Increased set-point temperature increases the power demand by about 200 kWh/°C. Thinner insulation increases the heat demand but decreases the demand for passive cooling by airing and deteriorates the indoor climate. Different types of windows affect both the energy demand and the indoor climate significantly. Load management was simulated by restriction on the heating possibilities and an economical comparison was made to investigate the advantage of such an operation. The extra insulation has a payoff time of about 38 years at common Swedish energy prices.
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