| 1. |
- Börjesson, Pål, et al.
(författare)
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Regional Production and Utilisation of Biomass in Sweden
- 1996
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 21:9, s. 747-764
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Tidskriftsartikel (refereegranskat)abstract
- Regional production and utilization of biomass in Sweden is analysed, considering the potential of replacing fossil fuels and producing new electricity. Extensive utilization of biomass will decrease biomass-transportation distances. The average distance for biomass transportation to a large-scale conversion plant suitable for electricity or methanol production will be 30–42 km when the conversion plant is located in the centre of the biomass production area. The total energy efficiency of biomass production and transportation will be 95–97% and the emissions of air pollutants will be small. In areas where energy crops from agriculture constitute the main part of the biomass, the transportation distance will be two to three times shorter than in areas where logging residues from forestry dominate. When present Swedish fossil-fuel use for heat and electricity production is replaced, more than 75% of the biomass required can be produced locally within the county. The average transportation distance of the remaining part will be between 130 and 240 km, increasing the cost of this biomass by 15–20%. Increased use of biomass by 430 PJ/yr, the estimated potential for increased utilization of energy crops, logging residues and straw, will lead to an excess of about 200 PJ/yr biomass after fossil fuels for electricity and heat production have been replaced. This biomass could be used for methanol or electricity production. The production of biomass-based methanol will lead to a low demand for transportation, as the methanol produced from local biomass can mainly be used locally to replace petrol and diesel. If the biomass is used for electricity production, however, the need for transportation will increase if the electricity is cogenerated in district heating systems, as such systems are usually located in densely populated areas with a deficit of biomass. About 60% of the biomass used for cogenerated electricity must be transported, on average, 230 km. Changing transportation mode when transporting biomass over large distances, compared with short distances, however, will lead to rather low specific transportation costs and environmental impact, as well as high energy efficiency. Replacing fossil fuels with biomass for heat and electricity production is typically less costly and leads to a greater reduction in CO2 emission than substituting biomass for petrol and diesel used in vehicles. Also, cogeneration of electricity and heat is less costly and more energy efficient than separate electricity and heat production.
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| 2. |
- Christiansson, Lena
(författare)
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Time Dynamics of Electricity Demand in Air-Distribution Systems for Commercial Buildings in Sweden
- 1996
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 21:10, s. 879-888
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Tidskriftsartikel (refereegranskat)abstract
- This paper illustrates the potential for reducing future electricity demand for air distribution in commercial buildings in Sweden. We have developed a general, quantitative, scenario-based framework to describe electricity demand for air distribution and to analyze how governmental and utility-sponsored policy measures affect electricity demand. The results suggest that higher electricity prices will not be very effective in reducing electricity demand, whereas significant electricity savings can be achieved by implementing desirable policy programs.
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| 3. |
- Gustavsson, Leif, et al.
(författare)
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Heating Detached Houses in Urban Areas
- 2003
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 28:8, s. 851-875
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Tidskriftsartikel (refereegranskat)abstract
- District heating systems using cogeneration, as well as local fuel-based and electric heating systems for detached houses, are analysed. The analysis includes the whole energy system, from the natural resource to the end user, with respect to primary energy use, emission and cost. The end-use technologies studied are heat pumps, resistance heaters and boilers. It was assumed that the base-load electricity, except for the cogenerated electricity, was produced in stand-alone power plants using wood chips or natural gas, while peak-load electricity and fuel used for transportation were produced from crude oil. The heat pump and district heating systems are found to be most energy efficient, followed by the local fuel-based systems. The wood-fuel-based systems emit about one tenth of the greenhouse gases emitted by the natural-gas-based systems. The sulphur and nitrogen oxide emission, however, is higher for wood-fuel-based systems. Systems based on natural gas are less expensive than the corresponding wood-fuel-based systems. Decarbonization and carbon dioxide sequestration, however, do not reduce the carbon dioxide emission to the low level of the wood-fuel-based systems and, in addition, make the natural-gas-based systems more expensive than the wood-fuel-based systems.
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| 4. |
- Johansson, Bengt, et al.
(författare)
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Energy and environmental costs for electric vehicles using CO2-neutral electricity in Sweden
- 2000
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 25:8, s. 777-792
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Tidskriftsartikel (refereegranskat)abstract
- Electric vehicles (EVs) may provide an alternative for CO2-neutral transportation services. This article analyses the cost of energy and emissions from using electricity produced from Swedish renewable energy sources in electric vehicles, and compares it with the cost of an alternative in which biomass-based methanol is used in internal combustion engine vehicles (ICEVs). These costs do not include vehicle and battery costs. Cost estimates of electricity, calculated using a marginal cost perspective, include production costs as well as the cost of distribution and vehicle recharging. The energy cost per km for vehicles using electricity is calculated to be 30-70% of the cost of biomass-based methanol, depending on the general level of electricity demand, the need for grid upgrading, and the assumed cost of biomass-based methanol. A high general electricity demand in society would require expensive condensing plants to supply the vehicles, whereas with a lower demand, cheaper cogeneration and wind power plants could be utilised. An electric vehicle, used as the average Swedish car, would, during its lifetime, have energy and environmental costs 30 000-40 000 SEK ($4000-5400) lower than the current state-of-the art ICEVs using biomass-based methanol. An electric vehicle used mainly in the city centre might have energy and environmental costs which are 130 000-140 000 SEK ($17 000-19 000) lower than a current methanol-fuelled car. With future improvements in the energy efficiency and environmental performance of ICEVs the difference will be significantly reduced. If battery costs were included in the cost calculations, EVs would not be cost competitive with future ICEVs, even if battery costs are reduced to $100/kWh. (C) 2000 Elsevier Science Ltd. All rights reserved.Electric vehicles (EVs) may provide an alternative for CO2-neutral transportation services. This article analyses the cost of energy and emissions from using electricity produced from Swedish renewable energy sources in electric vehicles, and compares it with the cost of an alternative in which biomass-based methanol is used in internal combustion engine vehicles (ICEVs). These costs do not include vehicle and battery costs. Cost estimates of electricity, calculated using a marginal cost perspective, include production costs as well as the cost of distribution and vehicle recharging. The energy cost per km for vehicles using electricity is calculated to be 30-70% of the cost of biomass-based methanol, depending on the general level of electricity demand, the need for grid upgrading, and the assumed cost of biomass-based methanol. A high general electricity demand in society would require expensive condensing plants to supply the vehicles, whereas with a lower demand, cheaper cogeneration and wind power plants could be utilized. An electric vehicle, used as the average Swedish car, would, during its lifetime, have energy and environmental costs 30 000-40 000 SEK ($4000-5400) lower than the current state-of-the art ICEVs using biomass-based methanol. An electric vehicle used mainly in the city centre might have energy and environmental costs which are 130 000-140 000 SEK ($17 000-19 000) lower than a current methanol-fuelled car. With future improvements in the energy efficiency and environmental performance of ICEVs the difference will be significantly reduced. If battery costs were included in the cost calculations, EVs would not be cost competitive with future ICEVs, even if battery costs are reduced to $100/kWh.
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| 5. |
- Johansson, Bengt
(författare)
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Will Swedish Biomass be Sufficient for Future Transportation Fuel Demands?
- 1996
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 21:12, s. 1059-1069
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Tidskriftsartikel (refereegranskat)abstract
- There is a potential to increase the annual use of biomass in Sweden by 125 TWh between 1994 and 2015. 125 TWh of biomass would satisfy most of the transportation-fuel demand in Sweden in 2015. Even if the biomass is primarily used for heat and electricity production, a significant fraction will be available for transportation-fuel production, if other non-fossil energy sources are utilized for electricity production and/or substantial energy-efficiency improvements are realized. Improved energy efficiency and the use of renewable energy sources will be required in all sectors to achieve CO2 emission reductions greater than 50%.
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| 6. |
- Andersson, Maria, 1965-
(författare)
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Shadow prices for heat generation in time-dependent and dynamic energy systems
- 1994
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 19:12, s. 1205-1211
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Tidskriftsartikel (refereegranskat)abstract
- Shadow prices for heat generation are used to study the impact of changes in heat demand on the total system cost of an existing district-heating system in Sweden. The energy system may be considered to be both dynamic, because there is energy storage, and time-dependent since the electricity tariff is time-differentiated and the heat demand varies over the year and day. The energy system has been analysed with and without energy storage. The analysis shows that despite a reduction in system cost, the use of energy storage can result in higher shadow prices for heat generation in some time periods.
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| 7. |
- Dai, X W, et al.
(författare)
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Pyrolysis of waste tires in a circulating fluidized-bed reactor
- 2001
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 26:4, s. 385-399
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Tidskriftsartikel (refereegranskat)abstract
- Using a circulating fluidized bed (CFB) as the main reactor, an integrated process development unit was operated aiming at the pyrolysis of waste tires. The main chemical processes in the CFB can be divided into two zones corresponding to pyrolysis and secondary reactions. The pyrolysis of tire powder was carried out at various pyrolysis temperatures, particle sizes of tire powder and feed positions. The effects of temperature, residence time and heating rate on pyrolysis were analyzed based on the experimental data. The main trends are that (1) a long residence time contributes to secondary reactions and (2) lower temperature and heating rate favor carbonization, which reduces the oil yield. Analysis of the pyrolytic oil shows that the predominant components are aromatics, followed by alkanes, non-hydrocarbons and asphalt.
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| 8. |
- Gong, Mei
(författare)
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Optimization of industrial energy systems by incorporating feedback loops into the MIND method
- 2003
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 28:15, s. 1655-1669
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Tidskriftsartikel (refereegranskat)abstract
- The MIND (Method for analysis of INDustrial energy system) method has been developed for multi-period cost optimization of industrial energy systems. Existing industrial processes can be represented at the desired level of accuracy, i.e. one modeling unit may represent a part of the production process or the whole plant. The optimization method includes both energy and material flows. Nonlinear relations, energy conversion efficiencies and investment costs are linearized by mixed-integer linear programming. A flexible time-scale facilitates the performance of long- and short-term analyses. In order to meet the requirements with regard to sustainable development, the recycling of energy and material flows is becoming more common in many industrial processes. The recycling or reuse of energy and material is managed by feedback loops, which are incorporated into the original MIND method to improve the model and reduce the calculation time. The improved MIND/F method (MIND method with feedback loops) model is applied to a pulp and paper mill in Sweden. A comparison between the original MIND method with manual handling of the feedback loops and the MIND/F method gives highly satisfactory results. Cost optimization using the improved MIND method is well within the given accuracy and computer time and manual calculation time are both reduced considerably. The reuse of energy and material resources is not only an economic advantage, but also implies a reduction of the environmental impact.
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| 9. |
- Gustafsson, Stig-Inge, et al.
(författare)
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Factorial design for energy System Models
- 1994
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 19:8, s. 905-910
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Gustafsson, Stig-Inge, et al.
(författare)
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Natural gas in Optimized Bivalent Heating Sytems
- 1990
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 15:11, s. 993-999
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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