| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Gustavsson, Leif, et al.
(författare)
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CO2 Mitigation Costs of Large-scale Bioenergy Technologies in Competitive Electricity Markets
- 2003
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 28:14, s. 1405-1425
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we compare and contrast the impact of recent technological developments in large biomass-fired and natural-gas-fired cogeneration and condensing plants in terms of CO2 mitigation costs and under the conditions of a competitive electricity market. The CO2 mitigation cost indicates the minimum economic incentive required (e.g. in the form of a carbon tax) to equal the cost of a less carbon extensive system with the cost of a reference system. The results show that CO2 mitigation costs are lower for biomass systems than for natural gas systems with decarbonization. However, in liberalized energy markets and given the socio-political will to implement carbon extensive energy systems, market-based policy measures are still required to make biomass and decarbonization options competitive and thus help them to penetrate the market. This cost of cogeneration plants, however, depends on the evaluation method used. If we account for the limitation of heat sinks by expanding the reference entity to include both heat and power, as is typically recommended in life-cycle analysis, then the biomass-based gasification combined cycle (BIG/CC) technology turns out to be less expensive and to exhibit lower CO2 mitigation costs than biomass-fired steam turbine plants. However, a heat credit granted to cogeneration systems that is based on avoided cost of separate heat production, puts the steam turbine technology despite its lower system efficiency at an advantage. In contrast, when a crediting method based on avoided electricity production in natural-gas-fired condensing plants is employed, the BIG/CC technology turns out to be more cost-competitive than the steam turbine technology for carbon tax levels beyond about $ 150/t C. Furthermore, steam turbine plants are able to compete with natural-gas-fired cogeneration plants at carbon tax levels higher than about $ 90/t C.
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| 6. |
- Johansson, Lars, et al.
(författare)
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An open absorption system installed at a sawmill : Description of pilot plant used for timber and bio-fuel drying
- 2000
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 25:11, s. 1067-1079
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a pilot plant and its different parts in a system used for bio-fuel drying and timber drying with an open absorption process. This technique has not been used previously in Sweden in this application. The open absorption system has been installed on four timber dryers and one bio-fuel dryer at a sawmill located in the northern part of Sweden. The annual energy demand for the dryers has decreased considerably. The specific heat demand for a conventional drying system is about 5970 kJ/kg of evaporated water. For the open absorption system, the corresponding value is a heat demand of approximately 1400 kJ/kg of evaporated water. At the same time, an additional 360 kJ/kg of electricity has to be supplied. Here, 45,000 m3 per year of dried bio-fuel has been sold on the market as a result of the decreased heat demand in the wood dryers at the sawmill. The plant has been working well and has had a high availability. The pay-off time for the investment will be approximately 3 years for nondiscounted cash-flows
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| 7. |
- Jonsson, M., et al.
(författare)
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Ammonia-water bottoming cycles : a comparison between gas engines and gas diesel engines as prime movers
- 2001
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 26:1, s. 31-44
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia-water cycles can produce more power than steam Rankine cycles in several applications. One of these applications is as a bottoming cycle to internal combustion engines. In the present study, ammonia-water bottoming cycle configurations for spark-ignition gas engines and compression-ignition gas diesel engines have been compared, Single-pressure Rankine cycles have been used as a basis for the comparison. Low heat source temperatures should increase the difference in power output between the ammonia-water cycle and the Rankine cycle. However, in this study, the results of the simulations show different trends. In most cases, the ammonia-water bottoming cycles with gas engines as prime movers generate more power compared to a Rankine cycle than when gas diesel engines are the prime movers. The temperature of the most important waste heat source, the exhaust gas, is approximately 100 degreesC higher for the gas engines than for the gas diesel engines. Therefore, for the gas engines, most of the waste heat available to a bottoming cycle is in the form of relatively high-temperature exhaust gas, while for the gas diesel engines more of the waste heat is in the form of relatively low-temperature heat sources.
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| 8. |
- Mollersten, K., et al.
(författare)
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Potential and cost-effectiveness of CO2 reductions through energy measures in Swedish pulp and paper mills
- 2003
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 28:7, s. 691-710
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Tidskriftsartikel (refereegranskat)abstract
- Using the two criteria of potential CO2 reduction and Cost Of CO2 reduction, technical energy measures in Swedish pulp. and paper mills are investigated. Principal CO2-reducing measures analysed are: decreased specific energy utilisation, fuel switch, and CO2 capture and sequestration. Among the investigated measures, conventional technologies for electricity conservation and improved electrical conversion efficiency in existing systems for cogeneration of heat and power are identified as the most cost-effective alternatives that also have large CO2 reduction potentials. For commercially available technologies, the results indicate an accumulated reduction potential of up to 8 MtCO(2)/y (14% of the Swedish net emissions). If emerging technologies for black liquor gasification (BLG) with pre-combustion CO2 capture and sequestration are considered, the CO2 reduction potential increases by up to 6 MtCO(2)/y (10% of the Swedish net emissions). Commercialised BLG, CO2 capture and reliable CO2 sequestration technologies are identified as important potential contributors to Swedish compliance with Kyoto Protocol targets, especially in a scenario of nuclear power closure.
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| 9. |
- Möllersten, Kenneth, 1966-, et al.
(författare)
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Potential and cost-effectiveness of CO2-reducing measures in the pulp and paper industry
- 2003
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Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 28:7, s. 691-710
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Tidskriftsartikel (refereegranskat)abstract
- Using the two criteria of potential CO2 reduction and cost of CO2 reduction, technical energy measuresin Swedish pulp and paper mills are investigated. Principal CO2-reducing measures analysed are: decreasedspecific energy utilisation, fuel switch, and CO2 capture and sequestration. Among the investigated measures, conventional technologies for electricity conservation and improved electrical conversion efficiencyin existing systems for cogeneration of heat and power are identified as the most cost-effective alternativesthat also have large CO2 reduction potentials. For commercially available technologies, the results indicatean accumulated reduction potential of up to 8 MtCO2/y (14% of the Swedish net emissions). If emergingtechnologies for black liquor gasification (BLG) with pre-combustion CO2 capture and sequestration areconsidered, the CO2 reduction potential increases by up to 6 MtCO2/y (10% of the Swedish net emissions).Commercialised BLG, CO2 capture and reliable CO2 sequestration technologies are identified as importantpotential contributors to Swedish compliance with Kyoto Protocol targets, especially in a scenario of nuclearpower closure
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| 10. |
- Sundberg, Gunnel, et al.
(författare)
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Interaction effects in optimising a municipal energy system
- 2000
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 25:9, s. 877-891
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Tidskriftsartikel (refereegranskat)abstract
- A study is presented where factorial design is used to find how some selected economic and technical factors affect the profitability of an investment in a combined heat and power plant. The study is performed on a Swedish district heating system. The minimal cost for supplying the demanded heat is calculated with a developed energy system optimisation model, MODEST. The effects on the resulting parameters, such as system cost and optimal size of steam cycle, are calculated from a series of experiments performed using high and low levels of the most relevant factors. The conclusion of the study is that both the main factors and the interactions between them have to be analysed to establish an accurate ranking of the technical and economic factors. (C) 2000 Elsevier Science Ltd. All rights reserved.
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