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  • 1.
    Alanne, K.
    et al.
    Department of Mechanical Engineering, Laboratory of Heating, Ventilating and Air-Conditioning, P.O. Box 1100, 02015 TKK, Finland.
    Salo, A.
    Department of Engineering Physics and Mathematics, Systems Analysis Laboratory, Helsinki University of Technology, P.O. Box 1100, 02015 TKK, Finland.
    Saari, A.
    Department of Civil and Environmental Engineering, Laboratory of Construction Economics and Management, Helsinki University of Technology, P.O. Box 2100, 02015 TKK, Finland.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Energy Systems.
    Multi-criteria evaluation of residential energy supply systems2007In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 39, no 12, 1218-1226 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Gebremedhin, Alemayehu
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Glad, Wiktoria
    Linköping University, Faculty of Arts and Sciences. Linköping University, The Tema Institute, Technology and Social Change.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering.
    Energianalys Solna. Forskningsrapport inom programmet Uthållig kommun.2004Report (Other academic)
  • 3.
    Gebremedhin, Alemayehu
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Glad, Wictoria
    Tema T Linköpings Universitet.
    Energisystemanalys Solna2004Report (Other academic)
  • 4.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Are Earth Tube Heat Exchangers of Interest when Heating Buildings?1993In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 17, no 7, 597-604 p.Article in journal (Refereed)
    Abstract [en]

    It is a well-known fact that the temperature of the soil, some metres below the surface, is relatively stable. If this heat could be utilized by use of an earth tube heat exchanger, significant benefits could occur when space heating for buildings is considered. The inlet ventilation air is then led through a long earth tube in which it will, depending on their relative temperatures, take up heat from, or leave heat to, the surrounding soil. In this paper two case studies are presented. The buildings of concern are sited in the vicinity of Linköping, about 200 km south of Stockholm, Sweden. One of the cases utilizes heat from the earth tube in an air-to-water heat pump, while the other uses an air-to-air heat exchanger. The studies show that the earth tubes only to a very low degree contribute to the need of added heat in order to achieve a desirable indoor climate. Hence, the extra cost for the tube will not be balanced by the decreased cost for space heating. This discouraging result may have depended on heat pipes that were too short or the fact that the difference in temperature between the passing air stream and the surrounding soil was too small.

  • 5.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Carpentry factory and municipal electricity loads1998In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 39, no 3-4, 343-347 p.Article in journal (Refereed)
    Abstract [en]

    Load management of electricity loads has received more interest in recent years. At least in Sweden, this is natural because of a rather cheap energy price, while at the same time, the demand charge is high. If a company could save the precise kWh that build the peak demand, then these would have a value of more than 200 times the off-peak kWh. This paper deals with monitored electricity data for two carpentry industries and one municipality, both situated in the south of Sweden. The ideal ! situation would be if the industry could reduce their peak demand and, at the same time, reduce the peak for the utility. Both participants would, in that case, save money, and the payback time for load management equipment would decrease substantially. If, however, a load management system at the carpentry transfers kWh to peak hours for the utility, the industry will save money, while the utility gets higher costs. The result of the study is that the Swedish electricity rates in use today are a very poor means of encouraging worthwhile load management, and often, they even aggravate the situation.

  • 6.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Climate Influence on District Heat and Electricity Demands1992In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 42, no 4, 313-320 p.Article in journal (Refereed)
    Abstract [en]

    This paper describes the district heating and electricity load of Kalmar, Sweden. Unfortunately, it has not been possible to examine one full year because the monitoring of the energy use for district heating and electricity, and the outdoor temperature, did not exactly overlap. However, more than 7200 h, of the 8760 in a full year, have been examined. It is shown that the district heat load has a far higher correlation with the outdoor temperature (a coefficient of 0·89), than has the electricity load (0·33). Thus, it is much easier to predict the influence of, e.g. an insulation retrofit for the building stock where district heating is used compared with electricity space heating. It is also shown how an estimate can be made of the thermal transmission factor for the total building stock.

  • 7.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Does postponed retrofitting save money?1995In: Heat Recovery Systems and CHP, ISSN 0890-4332, Vol. 15, no 5, 469-472 p.Article in journal (Refereed)
    Abstract [en]

    When a building is to be retrofitted, or refurbished, it is always of importance to study the building as a complete energy system. At least in Sweden, the building process is divided between different professional categories, such as HVAC and ordinary building contractors. It is therefore not surprising that the HVAC contractor wants to maximise his profit by installing large and sophisticated equipment at the same time as the builder or architect wants to design a house with very thick walls and high performing windows. These competing interests will often result in a building where the heating system is not adjusted to the rest of the house, but is instead far too powerful. The recommendation from life-cycle cost analyses has therefore always been to study the building as a whole system and to apply an optimal solution at one specific base year; this is probably always the best solution in order to minimise the life cycle cost, but experience shows that the proprietor of the building often hesitates in doing so. The reason for this is his lack of money. Changing the building into an optimal energy system frequently requires a heavy investment in any one specific year, albeit the best solution in the long run. This paper will discuss what happens to the life-cycle cost when retrofits are postponed so as to fit into the proprietor's “10 yr budget”.

  • 8.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Dubbla vinnare med laststyrning av fjärrvärme2004In: Energimagasinet : teknik, ekonomi, miljö, ISSN 0348-9493, Vol. 25, no 6, 30-32 p.Article in journal (Other (popular science, discussion, etc.))
  • 9.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Economic benefits from load management in a carpentry factory1996In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 16, no 10, 829-834 p.Article in journal (Refereed)
    Abstract [en]

    As a result of a National Referendum and a subsequent parliament decision Sweden will phase out its nuclear power stations before the year 2010. This source of electricity accounts for about half the total electricity usage and therefore other sources must be constructed, or the country must use less electricity. One way to accomplish this, according to economic theory, is to increase the price of electricity, and we will probably be subject to such actions, at least if there is a risk of a shortage of electricity. Hitherto, most interest for saving energy has been emphasised on space and domestic hot water heating in buildings. The major part of electricity, however, is used in industry, and is therefore worth studying in more detail. One small carpentry plant which manufactures wooden staircases and fibreboard panels for ceilings has been studied. Using monitored data for 1 year of their electricity usage and costs, the amount of money which could be saved by the owner of the factory, if different load management measures had been applied, has been calculated. Thus it was possible to find the maximum cost for equipment that can turn off some processes, such as timber dryers, for short periods.

  • 10.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Energieffektivisering i träindustrin.2004In: Energimagasinet : teknik, ekonomi, miljö, ISSN 0348-9493, Vol. 25, 34-37 p.Article in journal (Other (popular science, discussion, etc.))
  • 11.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering.
    Energisparåtgärder vid ytbehandling av planmöbler1999In: Energimagasinet : teknik, ekonomi, miljö, ISSN 0348-9493, Vol. 3, 44-48 p.Article in journal (Other academic)
  • 12.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Energy usage and conservation in surfacing lines2000In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 41, no 15, 1649-1669 p.Article in journal (Refereed)
    Abstract [en]

    This paper deals with energy usage and conservation for a surfacing line in a carpentry factory. In this line, wood panels are coated with paint in a highly automated fashion. The products vary in shapes and the way they shall be coated, and therefore, a number of machines are present in the line which is about 100 m long. Sanding machines, roller coaters, dryers etc. are installed, and all machinery uses electricity for their operation. There are, however, other equipments coupled to the line. One example is the wood dust transportation system, and another is the steam system used for heating purposes. By use of a number of electricity meters, monitoring ventilation flow rates etc., it has been possible to analyze how much energy is used in the surfacing line and also to propose measures to reduce this amount.

  • 13.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Energy Usage in Surfacing Lines2001In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 41, no 5, 1649-1669 p.Article in journal (Refereed)
    Abstract [en]

        

  • 14.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Examensarbete om säker träbearbetning2001Other (Other (popular science, discussion, etc.))
    Abstract [sv]

        

  • 15.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Finite element modelling versus reality for birch chairs1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 5, 355-359 p.Article in journal (Refereed)
    Abstract [en]

    When chairs and other furniture are designed the work is mostly founded on handicraft experience. Calculations based on solid mechanics theory are almost never used in order to find out optimal solutions for different wood members, or the structure as a whole. We have therefore studied a simple chair, made of birch, where the emphasis is laid on its ability to carry different loads. Using the method of finite elements we have predicted the strain and stress at different points on the chair structure. Further, we have manufactured the chair and exposed it to the same load pattern as used in the finite element calculations. The strain has been monitored and compared to the calculated value at the points of most interest. The result shows that part of the calculations corresponded fairly well with the monitored values but also that much work still remains in order to totally predict the accurate structural behaviour for such a simple frame as a chair. Probably, some of the discrepancies depend on the wood material which exhibits so different response for stress in different directions.

     

  • 16.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Fjärrvärme i processindustri2005In: Energimagasinet : teknik, ekonomi, miljö, ISSN 0348-9493, Vol. 26, no 4Article in journal (Other (popular science, discussion, etc.))
  • 17.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Hot Water Heat Accumulators in Single-Family Houses1992In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 12, no 4, 303-310 p.Article in journal (Refereed)
    Abstract [en]

    In Sweden, as in many other countries, there is a significant difference in electricity demand between day and night. In order to encourage the end use consumer to use less electricity during peak situations, time-of-use tariffs have become more common. The price differs from about 0.8 to 0.35 SEK/kWh, taxation included. (1ECU equals about 7 SEK.) If some of the electricity under the high price period, which falls between 0600 and 2200 during November to March, could be transferred to the low price hours, the electricity bill could be reduced. In Sweden it is common to use electricity for space and hot water heating, at least in single-family houses. By use of a hot water accumulator the need for heat could be produced during the cheap hours and the storage could be discharged when the high price hours occur. This paper describes the electricity use for hot water and space heating in a single-family house sited in Linköping, Sweden, where extensive monitoring has been utilized during 1987. Some 30 values for temperatures and electricity demands have been measured each hour, or sometimes even for shorter time intervals. These monitored data have been the base for examining if a water accumulator could be of interest for the proprietor of the building, i.e. if the cost for the accumulator is less than the money saved by the reduced electricity cost.

  • 18.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Indetermined chair frames of ash wood1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 2-4, 255-259 p.Article in journal (Refereed)
    Abstract [en]

    During recent years more interest has been emphasised on wood as a construction material. This is so because wood is a renewable resource and also because problems with waste do not emerge when the wooden structure is taken out of operation. On the contrary this waste is still a resource even if the structure is demolished. Wood could always be used as a biomass fuel which is not expected to contribute to the greenhouse effect. In Sweden most of the interest has been emphasised on our conifers while broad leaved species are much less examined. This paper shows the result from the Finite Element Method applied on indetermined chair frames and compares these findings with actual testing in our laboratory. The conclusion is that there are considerable discrepancies between calculations and real behaviour even for relatively simple structures such as a chair frame. It seems that the real chair is stronger than expected even if the joints between the furniture members must reduce the overall strength found by the FEM calculations.

  • 19.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Load management in municipal electricity systems1997In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 21, no 9, 787-791 p.Article in journal (Refereed)
    Abstract [en]

    Load management is one means of reducing maximum electricity load, and hence also the cost of electricity. In Sweden, the amount charged during the maximum load hour might be about 200 times higher than the standard charge for one kilowatt-hour. If the load could be reduced by certain equipment in factories and buildings, the need for new power stations and higher capacity in the grid would also be decreased. Using electricity load data for one full year and a short computer program, this paper shows by how much the load could be reduced by postponing demand. If part of the load could be postponed by only one hour, this part may need to be only very small for maximum benefit. If longer time segments were practicable, larger chunks could be transferred. The main result of the study is, however, that load management in practice is a very subtle task if an optimal solution is to be achieved

  • 20.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Load management measures in a carpentry factory1998In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 22, no 14, 1267-1274 p.Article in journal (Refereed)
    Abstract [en]

    The wood manufacturing industry in Sweden is not very often the subject of academic research activities. In certain parts of Sweden, generally in rural areas, this industrial branch is of major importance as a local employer. If the companies could grow and prosper it would lead to a more vivid countryside and decrease migration to larger towns and cities. The council of the European Community has therefore introduced certain funds for research projects in such rural areas. This paper describes the use of electricity and heat in a carpentry factory. The result shows that energy conservation measures and load management might be of significant importance in order to make the company more profitable. Even small savings can be the difference between survival or bankruptcy. For the studied factory it is obvious that much equipment for heating purposes are in a poor state. The steam system which could be useful for decreasing the use of electricity heating suffers from leaking steam traps and other imperfections which lead to severe losses in both kilowatt-hours and money. The steam system is therefore not used in an optimal way

  • 21.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Mathematical modelling of district-heating and electricity loads1993In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 46, no 2, 149-159 p.Article in journal (Refereed)
    Abstract [en]

    In recent years it has been more common to use linear or mixed-integer programming methods for finding optimal solutions to the complicated operating options in modern Combined Heat and Power (CHP) networks. Electricity may be bought from the national grid or it may be produced in ordinary condenser or CHP plants owned by the utility. In the same manner, district heat can be produced by the use of waste heat from industries or from a CHP plant. Other options are burning garbage in an incineration plant, using heat pumps in a sewage water plant or just burning fuels in an ordinary boiler. Combining these options and including the possibility of using conservation measures in industry or in the housing stock will result in a very complex situation if one tries to find the optimal solution characterized by the the lowest Life-Cycle Cost (LCC). Load management equipment, such as hot-water accumulators, will aggravate the problem even further. By the use of modern computers, complicated problems can be solved within a reasonable period of time. The bases for the mathematical models are the thermal and electrical loads. Splitting these loads into finer and finer segments will yield a model that will depict reality more closely. Two methods have been used frequently, one where the high and low unit price hours in each month have been lumped together, resulting in 24 segments plus one segment showing the influence of the maximum electricity demand. The other method tries to model the loads by lumping the energy demand in six electricity-tariff segments, but also using about 15 elements for a more versatile picture of the district-heating load. This paper describes the two methods using monitored data for 1990-1991 from Kalmar in the south of Sweden. It also discusses which of the methods is preferable or whether a combination must be elaborated upon in order to model reality closely enough for practical use.

  • 22.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Mechanical properties of some Swedish hard wood species2001In: Proceedings of the Institution of mechanical engineers. Part L, journal of materials, ISSN 1464-4207, E-ISSN 2041-3076, Vol. 215, no L3, 125-131 p.Article in journal (Refereed)
    Abstract [en]

    A large part of Sweden is located within the Taiga Area and hence most of the wood species growing there are included in the division of Coniferales. This has also led to major research activities on the needle-leaved types in the Pinaceae family. There are, however, many broad-leaved trees, but because of their relatively low economic importance only a few researchers have had the opportunity to study such woods. For certain branches of the Swedish wood manufacturing industry the Angiosperms are of vital importance, e.g. the furniture factories. In this paper the mechanical properties of two Swedish hard wood genera, namely Betula and Alnus, are revealed. These findings are also compared with those found in the literature.

  • 23.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Mixed integer linear programming and building retrofits1998In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 28, no 2, 191-196 p.Article in journal (Refereed)
    Abstract [en]

    When a building is subject for refurbishment it is important to add only such measures that will reduce the Life Cycle Cost (LCC), for the building. Even better is to add measures that will, not only reduce the cost, but minimise the LCC. One means for such an optimisation is to use the so called Linear Programming (LP), technique. One drawback with LP models is that they must be entirely linear and therefore two variables cannot be, for example, multiplied with each other. The costs for building retrofits are, however, not very often linear but instead ‘steps’ are present in their cost functions. This calamity can, at least to a part, be solved by introducing binary integers, i.e., variables that only can assume 2 values, 0 or 1. In this paper it is described how to design such a Mixed Integer Linear Programming (MILP), model of a building and how different cost elements of the climate shield influence the optimal solution.

  • 24.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Municipal thermal and electricity loads: A case study in Linköping1998In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 18, no 5, 257-263 p.Article in journal (Refereed)
    Abstract [en]

    Linear programming models used for optimisation of various energy systems have received increased interest during the last ten years. One reason for this is the use of personal computers. Models with thousands of variables and constraints can now be rapidly optimised. If integers are introduced, which are necessary when increments or steps in cost functions are part of the model, the computing power is of even higher interest. However, many scientific authors do not discuss in detail how the model is designed and what basic data lie behind this design. This paper presents an attempt to study municipal thermal and electricity loads, and further how to divide data for one year into useful segments for linear and mixed integer programming purposes

  • 25.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Energy Systems.
    Optimal fenestration retrofits by use of MILP programming technique2001In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 33, no 8, 843-851 p.Article in journal (Refereed)
    Abstract [en]

    When buildings are subject for refurbishment, it is very important to add the optimal strategy at that very moment. If other solutions are chosen and implemented, it will no longer be possible to change the building at a later occasion with the same profitability. A suitable criterion for optimality is the point where the life-cycle cost (LCC) has its minimum value. This point can be calculated by using so-called mixed integer linear programming (MILP). This paper shows how building and possible fenestration retrofits are described in such a MILP program. Changing existing double-glazed windows to triple ditto will of course make the U-values lower, but at the same time less solar radiation is transferred through the glass panes. This must be properly addressed in the MILP model. Of vital importance are also the heating system and the energy tariff connected to it. Nowadays, time-of-use rates are common practice both for district heating and electricity. These facts make it unsuitable to write, optimise and solve the MILP model "by hand", and instead a computer program has been designed for writing the model in the form of a standard MPS data file. This file can in turn be scanned and optimised by MILP-solving programs available at the market today. © 2001 Elsevier Science B.V. All rights reserved.

  • 26.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Energy Systems.
    Optimal use of solar collectors for residential buildings2001In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 25, no 11, 993-1004 p.Article in journal (Refereed)
    Abstract [en]

    Solar radiation is an abundant free resource which may be used in the form of solar heated water. This is achieved in solar collectors which, unfortunately, are expensive devices and, further, the warm water must be stored in accumulators-items which also cost money. This paper shows how we have optimized the situation for a block-of-flats in Sweden. In order to find this point we have used the minimum life-cycle cost (LCC) concept as a criterion. The best solution is therefore found when that cost finds its lowest value. It is also examined under which conditions solar collectors are part of the optimal solution and further it is calculated what happens if this optimal point is abandoned, i.e. how much will the LCC increase if other than optimal solutions are chosen. LCC optimization for multi-family buildings almost always results in a heating system with low operating costs such as district heating or dual-fuel systems where a heat pump takes care of the base load and an oil boiler the peak. The installation cost must, however, be kept to a reasonable level. Expensive solar panel systems are therefore normally avoided if the lowest LCC shall be reached, at least for Swedish conditions. This is so even if the solar system has a very low operating cost. For buildings where the only alternative energy source is electricity, solar collectors seem to be on the rim of profitability, i.e. for an energy price of about 0.6 SEK kWh-1. Copyright © 2001 John Wiley and Sons, Ltd.

  • 27.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Energy Systems.
    Optimization and simulation of building energy systems2000In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 20, no 18, 1731-1741 p.Article in journal (Refereed)
    Abstract [en]

    The Mixed Integer Linear Programming (MILP) technique is a useful tool for the optimization of energy systems. However, the introduction of integers in linear models results in a severe drawback because the ranging process is no longer available. Therefore, it is not possible to study what happens to the solution if input data are changed. In this paper, we compare a MILP model of a building with a simulation model of an identical case. Both models describe a building with a number of possible retrofits. Using the MILP technique, the optimal retrofit strategy is calculated, after which certain input data are changed. The optimization results in the lowest possible Life-Cycle Cost (LCC) of the building, and the paper describes how much the LCC will change if the property owner chooses other solutions. An increase in a particular data value may cause the LCC to increase or decrease. It may also be unchanged. Only a few data reduce the LCC when their values are increased.

  • 28.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Energy Systems.
    Optimization of drying kiln operation2000In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 24, no 1, 19-26 p.Article in journal (Refereed)
    Abstract [en]

    When timber is to be used in the form of furniture it must be dried. Green timber contains many times more water than wood and if it is placed indoors the water will slowly evaporate. When the fibre saturation point is reached the wooden parts start to shrink and the shape of the details will change. If the wood is dried before it is used for furniture parts this calamity is reduced because shrinking has occurred already in the drying kiln when the raw material was in the form of lumber. This drying process uses a lot of heat which is produced by electricity or by firing wood chips or oil in boilers. The cost for these energy sources varies during the season or, for electricity, also during the day. This paper describes how to optimize the use of energy in two drying kilns located at a small carpentry factory in the south of Sweden. Monitored values from the factory are used in order to describe the process in close detail. These values are then used as a basis for a mathematical model which is designed in the form of a mixed integer linear program. The method makes it possible to optimize the operating schemes for the two dryers. Copyright (C) 2000 John Wiley & Sons, Ltd.

  • 29.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Optimization of insulation measures on existing buildings2000In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 33, no 1, 49-55 p.Article in journal (Refereed)
    Abstract [en]

    In Sweden, the activity on building new residences has been decreased for a number of years. The building stock as an average has therefore become older and in the future it will be subject for refurbishment. This paper deals with how to optimize retrofit measures, i.e. how to act in order to minimize the Life-Cycle Cost (LCC) of a building. Insulation measures are emphasized but also other retrofits are dealt with such as changing the heating system. It is shown that the heating system has a vital influence on the optimal amount of extra insulation which is to be applied. District heating is common in Sweden at least for larger buildings such as multi-family block of flats sited in urban areas. The tariffs for district heat must therefore be properly addressed in order to find out if extra insulation is profitable or not. As an example the Navestad area in Norrkoping is used. This residential area is now the subject for extensive retrofitting.

  • 30.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Optimizing ash wood chairs1997In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 31, no 4, 291-301 p.Article in journal (Refereed)
    Abstract [en]

    In Sweden, forest research has been emphasised on mainly two species of wood, i.e. pine and spruce. However, we have also a number of hardwoods which could be utilised for furniture manufacturing, cabinets etc. Nowadays, these hardwoods are a slumbering resource in our country. Most of our broad leafed species are found as small stands inside our soft wood forests and hence not utilised in the most profitable way. For example, much of our birch wood is ground to paper fibres even if it would be perfect for high valued veneer. Instead, most of our birch. veneer is imported from Finland. In order to increase the interest for Swedish hardwoods we therefore have started research in this field and have now designed a chair made of ash wood,Fraxinus excelsior. Most chairs are made up of structural elements called indetermined frames which makes it a rather tedious task to analyse the internal forces in the frame. However, by using the Finite Element Method, FEM, it has been possible to reduce this drawback. This paper shows how a chair could be analysed, and designed, by use of methods common in other disciplines than furniture manufacturing. We also present results, in the form of stress-strain diagrams, from tests made on Swedish ash.

  • 31.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Energy Systems.
    Refurbishment of industrial buildings2006In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 47, no 15-16, 2223-2239 p.Article in journal (Refereed)
    Abstract [en]

    When a building is subject for refurbishment, there is a golden opportunity to change its behavior as an energy system. This paper shows the importance of careful investigations of the processes, the climate shield and the heating systems already present in the building before measures are implemented in reality. A case study is presented dealing with a carpentry factory. The building is poorly insulated according to standards today, and initially it was assumed that a better thermal shield would be of vital importance in order to reach optimal conditions. Instead, it is shown that the main problem is the ordinary heating system. This uses steam from a wood chips boiler and the wood chips come from the manufacturing processes. These wood chips are, therefore, a very cheap fuel. The boiler had, during decades of use, slowly degraded into a poor state. Hence, aero-tempers using expensive electricity have been installed to remedy the situation. These use not only expensive kWh but also very expensive kW due to the electricity tariff. It is shown that electricity for heating purposes must be abandoned and further, that this could be achieved at a surprisingly small cost. By stopping a large waste of steam, it was possible to find resources, in the form of unspent money, for further mending the existing heating system. Not only economy but also environmental hazards in the form of CO2 emissions urges us to abandon electricity and instead use heat from cheap biomass fired boilers. Such equipment saves environment at the same time it saves money. © 2006 Elsevier Ltd. All rights reserved.

  • 32.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Sensitivity analysis of building energy retrofits1998In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 61, no 1, 13-23 p.Article in journal (Refereed)
    Abstract [en]

    When a building is refurbished, energy conservation measures might be profitable to implement. The profitability depends, among other things, on the electricity and district-heating tariffs, the unit price for oil, etc. The cost for the retrofit is of course also important as well as the influence of the retrofit on the demand for heat in the building. By the use of a Mixed Integer Linear Programming model of a building, a number of different optimal retrofit strategies are found depending on the energy cost. The result shows that the Life-Cycle Cost for the building is subject only to small changes as long as the optimal strategies are chosen. Most important is the heating system, while building retrofits such as added insulation, are too expensive to take part in the optimal solution.

  • 33.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Solid mechanics for ash wood1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 5, 373-377 p.Article in journal (Refereed)
    Abstract [en]

    Wood is an anisotropic material and, further, because of its natural origin the mechanical properties might significantly differ also between each of the samples tested. Ordinary methods for evaluation of solid mechanic properties often destroy the tested specimens. It is therefore not common practice to evaluate more than one property, e.g. Young's modulus for tension, at the same time using the same sample. Different tests also have different recommendations of how the test specimens should be designed in order to test the property of interest. When calculations are to be made by e.g. the Finite Element Method values for a number of properties must be included and when the resulting construction is examined after this, it is not easy to decide if discrepancies depend on unreliable input data. This paper therefore describes tension, compression and bending tests for one specific detail, namely a wood beam of ash wood. The applied forces are well under those where rupture occurs and hence the material is assumed to be intact during all testing procedures.

  • 34.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Stability problems in optimized chairs?1996In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 30, no 5, 339-345 p.Article in journal (Refereed)
    Abstract [en]

    Chairs and other furniture are seldom designed by help of structural mechanics and modern computers. Even if the designer uses a sophisticated CAD program, he, or she, will not use for example, finite element programs, FEM, in order to optimise the construction. Most furniture is made of wood or wood composites. Usually, structural mechanics is used for designing wood members in roof constructions and so forth. Because of the consequences of a breakdown, the allowable design stresses must be very low, about one third of the measured breaking strength. Smaller wood details could be chosen with more care and for chairs the result of a break would not necessarily lead to a disaster. However, a lot of the knowledge about how to design small wood structures emanates from the pre-war aeroplane industry. The difference between tensile and compression strength properties in wood also makes ordinary FEM programs hazardous to use because the background theory assumes that these properties are equal in magnitude. In this paper we show how to calculate the internal stresses of an undetermined chair frame and also show some material test results for Swedish alder, Alnus glutinosa.

  • 35.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering, Wood Technology. Linköping University, The Institute of Technology.
    The Strength Properties of Swedish Oak and Beech2010In: Drewno, ISSN 1644-3985, Vol. 53, no 183, 67-83 p.Article in journal (Refereed)
    Abstract [en]

    Because of their economic impact most research on wood in Sweden is aimed at our needle-leaved species, i.e. pine and spruce. Sawmills and other industrial enterprises using these conifers are also in vast majority, both in number of employees and number of companies. However, there is a viable industrial branch in Sweden, i.e. furniture companies, dealing with broad-leaved species such as oak, birch, and alder. Such industries often import all the wood they use, even if the same type of wood grows in the vicinity. In order to make the Swedish broad-leaved trees more interesting to the wood manufacturing sector, we examined the strength properties of some common Swedish woods, viz. oak and beech. The result shows that our oak specimens had a modulus of elasticity of 12.243 MPa measured by using four-point bending. So-called the Young’s modulus was 11.761 MPa for tension and 15.610 MPa for compression in the fibre direction, i.e. there was a very high difference. The stress just before rupture was measured to 85 MPa for tension and 76 MPa for compression, i.e. there was a surprisingly small difference. For beech, our corresponding values were 13.017 MPa for four-point bending, the Young’s modulus during tension was13.954 MPa and 130.4 MPa in maximum stress, whilst under compression these values were 13.101 MPa and 84 MPa, respectively.

  • 36.
    Gustafsson, Stig-Inge
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Träkompositers egenskaper kan skärddarsys2001Other (Other (popular science, discussion, etc.))
    Abstract [en]

      

  • 37.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Andersson, Susanne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Factorial design for energy System Models1994In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 19, no 8, 905-910 p.Article in journal (Refereed)
    Abstract [en]

    Mathematical models are extensively used in energy analysis and have increased in scope as better and faster computers have become available. With complicated systems, it is difficult to predict accurate results if doubtful input data are changed. Traditionally, sensitivity analysis with a change of one or more of the parameters is used. If the influence of a change is very small, the first result is believed to be accurate. Problems may arise when sensitivity analysis is applied to a vast amount of data. The aim of this paper is to examine whether the calculation effort can be decreased by using factorial design. Our model, called Opera (Optimal Energy Retrofit Advisory), is used to find the optimal retrofit strategy for a multi-family building. The optimal solution is characterised by the lowest possible life-cycle cost. Three parameters have been studied here: length of the optimisation period, real interest rate and existing U-value for an attic floor. The first two parameters are found to influence the life-cycle cost significantly, while the last is of minor importance for this cost. We also show that factorial analysis must be used with great care because the method does not reflect the complete situation.

  • 38.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Bojic, M.
    Trifunovic, N.
    Mixed 0-1 sequential linear programming optimization of heat distribution in a district-heating system2000In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 32, no 3, 309-317 p.Article in journal (Refereed)
    Abstract [en]

    A district-heating system transports heat from the heat plant by using primary pipe network, via substation, to secondary pipe network where heat is finally distributed to buildings. When this system is designed its operational characteristics were selected to provide thermal comfort (TC) in all buildings served by this district heating system. After several years of operation, the system characteristics may change and TC in buildings deteriorates, some buildings are overheated and other buildings are underheated. The study investigates an optimum strategy to mitigate the problem caused by changes of three of system characteristics: hydraulic resistance of secondary pipe network, heat transmittance of radiators inside buildings, and heat transmittance of building envelope. A strategy of problem mitigation consists of the adjustment of hydraulic resistance of existing valves and retrofitting the local heating system with new substation heat exchanger and additional pumps. We used a steady state, bottom-up approach and mixed 0-1 sequential linear programming to find optimal mitigation strategy, i.e. optimum combination of valves' hydraulic resistances, new pumps placement and new size of substation heat exchanger. The results indicate that the calculated optimal strategy does not effectively improve TC in buildings only in cases when TC is deteriorated by higher than nominal values of heat transmittance of some building envelopes.

  • 39.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Bojic, Milorad
    University of Kragujevac, Yugoslavia.
    Optimal heating-system retrofits in residential buildings1997In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 22, no 9, 867-874 p.Article in journal (Refereed)
    Abstract [en]

    The optimal heating-system-retrofit strategy for existing buildings differs due to varying prices of energy, building and installation features, climate conditions, etc. We have examined a test building situated in Linköping, Sweden. By using the OPERA model, we were able to arrive at the optimal retrofit strategy, which includes a ground-coupled heat pump using electricity to run the compressor. Unfortunately, the price of electricity differs according to the time of day, month, etc. These variations are not included in the OPERA model. In OPERA, the price should be divided into 12 segments, one for each month of the year since climate data are divided in this manner. Fine tuning of a dual-fuel system (an oil-fired boiler handles the peak load and a heat pump the base thermal load) is optimized using the Mixed Integer Linear Programming (MILP) method. Adding a hot-water accumulator also makes it possible to use low electricity prices for space and domestic hot-water heating. This system competes in the model with traditional heating devices such as district heating. The optimal method of heating the building was found for using the heat pump alone.

  • 40.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Energy Conservation and Optimal Retrofits in Multi-Family Buildings1990In: Energy Systems and Policy, ISSN 0090-8347, Vol. 14, 37-49 p.Article in journal (Refereed)
  • 41.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Heat Accumulators in CHP Networks1992In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 33, no 12, 1051-1061 p.Article in journal (Refereed)
    Abstract [en]

    In a Combined Heat and Power (CHP) network, it is sometimes optimal to install a device for storing heat from one period of time to another. Several possibilities exist. If the electricity demand is high, while at the same time the district heating load is too small to take care of the heat from the CHP plant, it could be optimal to store heat from peak periods and discharge the storage under off-peak. It might also be optimal to store heat during off-peak and use it under the district heating peak load. The storage is then used for decreasing either the district heating demand or for decreasing the electricity load used for space heating. The paper shows how a mixed integer program is developed for use in the optimization process. As a case study, the CHP system of Malmö, Sweden, is used. Further, a sensitivity analysis is elaborated in order to show how the optimal solution will vary due to changes in certain input data.

  • 42.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Insulation and Bivalent Heating System Optimization: Residential Housing Retrofits and Time-Of-Use Tariffs for Electricity1989In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 34, no 4, 303-315 p.Article in journal (Refereed)
    Abstract [en]

    Time-of-use tariffs, which reflect the cost of producing one extra unit of electricity, will be more common in the future. In Sweden the electricity unit price will be high during the winter and cheaper during the summer. A bivalent heating system, where an oil-fired boiler takes care of the peak load, when the electricity price is high, and a heat pump the base load, may decrease the cost of space heating substantially. However, insulation retrofits are also likely to reduce the peak space-heating load in a building. This paper shows how a bivalent heating system can be optimized while also considering the insulation measures. The optimization is elaborated by the use of a mixed integer programming model and the result is compared with a derivative optimization method used in the OPERA (optimal energy retrofit advisory) model. Both models use the life-cycle cost (LCC) as a ranking criterion, i.e. when the lowest LCC for the building is achieved, no better retrofit combination exists for the remaining life of the building.

  • 43.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Is space heating in offices really necessary?1991In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 38, no 4, 283-291 p.Article in journal (Refereed)
    Abstract [en]

    New office buildings in Sweden are thoroughly insulated due to the Swedish building code. This code, however, does not consider the type of activity occurring in the building. This means that the heating equipment is designed as if no activity at all is going on. In modern offices there is a lot of equipment installed which uses electricity. This electricity is converted into heat which can be utilized for heating the premises, mostly in a direct way but also by the use of exhaust-air heat-pumps or heat exchangers. This paper deals with a modern office building plus office hotel complex located in Linköping, Sweden, about 200 km south of Stockholm. The tenants deal with the design of hard- and software for computers. The lighting and computers in the building use electricity which converts into heat. In this paper, it is shown that this electricity is all that is needed during normal conditions, i.e. when people work in the building. The building is also equipped with a district-heating system, which is designed as if no activity goes on in the building, so subsequently the heating equipment is larger than it need be. In this special case, it might have been better to install an electric heating device for hot-water heating and very cold winter conditions, instead of using district heating. This is so even if district heat is about half the unit price compared with that due to the dissipation of electricity. At present, when district heating is used, no measures for saving heat can be profitable due to the low district-heating price. The fact is that the tenants complain of too much heat instead of too little: the prevailing indoor temperature was about 24° C in January 1990 even though 20° C would have been sufficient. There is subsequently a need for a properly working regulation system. The one currently in use is designed to a modern standard, but is not able to maintain temperatures at a modest level.

  • 44.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Life-Cycle Cost Minimization Considering Retrofits in Multi-Family Residences1989In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 14, no 1, 9-17 p.Article in journal (Refereed)
    Abstract [en]

    When a building is to be renovated it is important to implement the optimal retrofit combination. If this strategy is neglected it might not be profitable to change the building in order to improve it as an energy system. This paper deals with energy retrofits and how the strategy can be optimized considering one specific building. The best solution is found when the life-cycle cost for the building is minimal, and building envelope, ventilation and heating system retrofits are combined.

    In order to solve the problem, a mathematical model, OPtimal Energy Retrofit Advisory (OPERA), has been developed. Energy balance calculations are used in which the free energy from solar radiation and from appliances is taken into proper account. The interaction between different retrofits is emphasized. Provided that the optimal solution is implemented, the retrofits in the combination will have a minor interaction which, for most cases, could be neglected. This will also imply that the order of implementation is of no, or minor, importance. A case study for a real building sited in Malmö, Sweden, and a sensitivity analysis for some critical input parameters are discussed.

  • 45.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Linear Programming Optimization in CHP Networks1991In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 11, no 4, 231-238 p.Article in journal (Refereed)
    Abstract [en]

    This paper shows how to simulate a CHP network (CHP = Combined Heat and Power) using the method of linear programming. This method makes it possible to optimize the mathematical model and subsequently find the very best combination of electricity production, electricity purchase and heat production in a district heating system. The optimal solution in the model is characterized by the lowest possible operating cost for year. The paper shows the design of the mathermatical model and furthermore a case study is presented using the district heating net in Malmö, Sweden, as an example.

  • 46.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Natural gas in Optimized Bivalent Heating Sytems1990In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 15, no 11, 993-999 p.Article in journal (Refereed)
    Abstract [en]

    In accordance with a public referendum held in 1980, Sweden will phase out nuclear power completely by 2010. One way to compensate for an immediate, appreciable scarcity of electric power is to construct new fossil-fuel power stations. Another is to reduce the burden on electric power by converting some end-user facilities to operate on natural gas (NG) imported from Denmark through a new pipeline to southern Sweden. We show how an optimal solution can be found for NG operation of a system incorporating an NG boiler and an electric heat pump. Electricity is priced by a time-of-use tariff (TOU) requiring a discrete optimization method. The optimal solution is characterized by the lowest life cycle cost (LCC) for the building as an energy system.

  • 47.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Production or Conservation in CHP Networks1990In: Heat Recovery Systems and CHP, ISSN 0890-4332, Vol. 10, no 2, 151-159 p.Article in journal (Refereed)
    Abstract [en]

    In Sweden, Combined generation of Heat and Power (CHP) is in common practice. Different fuels are burnt in a boiler and the steam is used for generating electricity. The heat that has to be transferred from the condenser in the plant is used in the district heating grid. This grid is thus used as a cooling facility necessary for electricity production. However, energy conservation the Swedish building stock is also encouraged, and if this is utilized in district heated buildings it results in fewer possibilities for electricity production. This might be a major drawback when nuclear power is abolished, as is the result from a consensus some years ago. This paper deals with the question of whether it is better to conserve both heat and electricity, to save only one of the energy forms or if it is cheaper to produce more energy, instead of saving. A case study is presented dealing with Malmö, in the South of Sweden, and it is shown that energy conservation in district heated buildings cannot yield profitability: neither can conservation in the electricity grid, even if it gets closer to profitable savings. It is assumed that the total cost of heating, insulation and electricity is paid by the society and the minimum point for this cost will characterize the best solution.

  • 48.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Why is Life-Cycle Costing Important when Retrofitting Buildings1988In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 12, no 2, 233-242 p.Article in journal (Refereed)
    Abstract [en]

    Using life-cycle costing (LCC) gives us a means to find the best retrofit strategy for an apartment block. This method also shows us how important it is to consider the whole existing building as an energy system. If the best heating system is put into the house almost every shield retrofit is unprofitable. Having heating systems, with high variable costs combined with exhaust ventilation air pumps, sometimes makes it unprofitable to caulk the windows and doors.

    This article also shows the importance of using the accurate prices for the energy. Short-range marginal costs (SMRC) gives different retrofit strategies than normal tariffs used today. This also means that the retrofits do not correspond to the optimal use of the total national energy system and already scarce resources are used unnecessarily.

  • 49.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Window Retrofits: Interaction and Life-Cycle Costing1991In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 39, no 1, 21-29 p.Article in journal (Refereed)
    Abstract [en]

    This paper deals with the interaction between different types of building energy retrofits. The means for finding this interaction has been via the OPERA model, which is used for energy retrofit optimization. The solution is an optimum when the total life-cycle cost, LCC, for the building, i.e. the sum of the building, maintenance and operating costs, is minimized. The model finds the candidates for the optimal strategy by calculating the total LCC for one retrofit after another, i.e., an incremental method is used. All the measures are implemented with respect to the building and the resulting LCC is calculated. Usually, the LCC for this combination is higher than the incremental LCC, i.e. the incremental way of calculation overestimates the savings. However, when window retrofits are considered, the opposite might happen due to the use of shading factors. These factors indicate the decrease in solar radiation through a window when an ordinary one is replaced by a window with enhanced thermal performance. The paper also shows that the interaction between the different measures usually can be neglected, as long as optimal retrofits are introduced.

  • 50.
    Gustafsson, Stig-Inge
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn G
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Sjöholm, Bertil H.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Differential Rates for District Heating and the Influence on the Optimal Retrofit Strategy for Multi-Family Buildings1987In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 7, no 4, 337-341 p.Article in journal (Refereed)
    Abstract [en]

    When renovating existing multi-family buildings it is very important to implement the best retrofit strategy possible in order to minimize the remaining life-cycle cost for the building. If the building is heated with district heating this strategy of course changes due to the energy rate used by the utility. It is also very important for the utility that the consumer is encouraged to save energy when there is a need for it, i.e. during peak load conditions. Our paper shows that an accurate cost differential rate provides all these facilities.

12 1 - 50 of 61
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