| 1. |
- Andersson, Maria, 1965-, et al.
(författare)
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Cost-effective incentives for cooperation between participants in the electricity market
- 1996
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 54:4, s. 301-313
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Tidskriftsartikel (refereegranskat)abstract
- In the Swedish electricity system there is a great potential for increasing the cost efficiency of electricity use. Today economic incentives, offered for instance by existing electricity tariffs, are too weak to improve the use of the system. On the Swedish electricity market, there are at least three different participants, the power producer, the distributor and the customer. Today these participants act separately owing to low awareness of the costs for electricity over the year and the day. If the participants are aware of the real electricity costs, cost-effective incentives for cooperation will arise. When participants cooperate, the introduction of end-use measures will reduce system costs for those participants that are involved in cooperation. We present a system analysis for cooperation between distributor and customers. We also present results from a project, where behaviours of an existing distributor and existing customers have been analysed. The results show that there exist cost-effective incentives for cooperation when end-use measures are introduced.
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| 2. |
- Gebremedhin, Alemayehu, et al.
(författare)
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Optimisation of merged district - heating systems - Benefits of co - operaion in the light of externality costs
- 2002
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Ingår i: Applied Energy. - 0306-2619 .- 1872-9118. ; 73:3-4, s. 223-235
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Tidskriftsartikel (refereegranskat)abstract
- Studies have shown that separate actors can benefit from co-operation around heat supply. Such co-operation, for example, might be between an industry selling waste heat to a districtheating system or two district-heating systems interconnecting their respective systems. Cooperation could also be expected to reduce the environmental impacts of the energy systems by choosing the plants with the lowest emissions. It is widely accepted that the production of heat and electricity causes damage to the environment. This damage often imposes a cost on society, but not on company responsible. In general, using a broader system perspective when analysing local energy systems results in a lower total cost, more e.cient use of plants and a greater potential for producing electricity in combined heat-and-power (CHP) plants. Internalising the externality costs in the energy system model facilitates the study of what cooperation can mean for reducing emissions. This study shows that co-operation between the two systems is on the whole cost-effective, but the benefits are greater when external costs are not included in the calculation. Considering externality costs in combination with current electricity prices would lead to a higher system cost, but the quantity of emission gases will be lower. If, on the other hand, the calculation is made taking externality costs and corresponding adjusted electricity prices (the adjustment being necessary to compensate for the additional cost due to externality costs) into consideration, the quantities of emission gases will rise because more heat-and-power will be generated by one of the CHP plants. © 2002 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Gustafsson, Stig-Inge
(författare)
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Climate Influence on District Heat and Electricity Demands
- 1992
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 42:4, s. 313-320
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Gustafsson, Stig-Inge, et al.
(författare)
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Insulation and Bivalent Heating System Optimization : Residential Housing Retrofits and Time-Of-Use Tariffs for Electricity
- 1989
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 34:4, s. 303-315
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Gustafsson, Stig-Inge, et al.
(författare)
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Is space heating in offices really necessary?
- 1991
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 38:4, s. 283-291
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Gustafsson, Stig-Inge
(författare)
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Mathematical modelling of district-heating and electricity loads
- 1993
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 46:2, s. 149-159
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Gustafsson, Stig-Inge
(författare)
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Sensitivity analysis of building energy retrofits
- 1998
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 61:1, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Gustafsson, Stig-Inge, et al.
(författare)
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Window Retrofits : Interaction and Life-Cycle Costing
- 1991
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Ingår i: Applied Energy. - 0306-2619 .- 1872-9118. ; 39:1, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Johansson, Lars, et al.
(författare)
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Energy efficient bio fuel drying with an open absorption system : parameter study in order to reduce investment costs
- 2000
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Ingår i: Applied Energy. - 0306-2619 .- 1872-9118. ; 67:3, s. 231-244
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Tidskriftsartikel (refereegranskat)abstract
- A pilot plant using the open absorption system for drying of timber and bio fuel has been realized at a sawmill located in the northern part of Sweden. The technique decreases the energy demand for the dryers considerably and the system has an availability of about 8000 h per year. Compared with other drying techniques, the investment cost is high due to large airflow and therefore large apparatus. The main part of the investment cost, i.e. about 70% originates from the bio fuel dryer and the absorbers. In order to decrease the initial cost a parameter study has been made to investigate the possibilities to reduce the airflow of the drying process, i.e. bio fuel dryer and absorber. Parameters studied are drying temperature, salt concentration and cooling of the airflow during the absorption process. Measured values from the pilot plant have been used as a reference case. The results show that it is possible to decreases the airflow by 31% when using a higher drying temperature. Higher salt concentration decreases the airflow by approximately 32% and cooling during absorption makes it possible to decrease the airflow by 50%. In order to minimize the airflow, the three parameters were combined. In this case it is possible to decrease the airflow by approximately 60%. The electrical input for the plant is also high due to large air and solution flows. By decreasing the airflow, the required electrical input will also decrease since the fan power is proportional to the volume airflow. The results clearly show that it is possible to reduce the airflow and therefore the investment costs compared with the pilot plant.
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| 10. |
- Johansson, Lars, et al.
(författare)
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Energy savings in indoor swimming-pools : comparison between different heat-recovery systems
- 2001
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Ingår i: Applied Energy. - 0306-2619 .- 1872-9118. ; 70:4, s. 281-303
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Tidskriftsartikel (refereegranskat)abstract
- In indoor swimming-pool facilities, the energy demand is large due to ventilation losses with the exhaust air. Since water is evaporated from the pool surface, the exhaust air has a high water content and specific enthalpy. Because of the low temperature, the heat from the evaporation is difficult to recover. In this paper, the energy demand for the conventional ventilation technique in indoor swimming pools is compared to two different heat-recovery techniques, the mechanical heat pump and the open absorption system. The mechanical heat-pump is the most widely used technique in Sweden today. The open absorption system is a new technique in this application. Calculations have been carried out on an hourly basis for the different techniques. Measurements from an absorption system pilot-plant installed in an indoor swimming pool in the northern part of Sweden have been used in the calculations. The results show that with the mechanical heat pump, the electrical input increases by 63 MWh/year and with the open absorption system 57 MWh/year. However, a mechanical heat-pump and an open absorption system decrease, the annual energy demand from 611 to 528 and 484 MWh respectively, which correspond to decreases of approximately 14 and 20% respectively. The electricity input will increase when using heat-recovery techniques. Changing the climate in the facility has also been investigated. An increased temperature decreases the energy demand when using the conventional ventilation technique. However, when either the mechanical heat-pump or the open absorption system is used, the energy demand is increased when the temperature is increased. Therefore increasing the temperature in the facility when using the conventional technique should be considered the first measure to reduce the energy demand.
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