| 1. |
- Gustafsson, Stig-Inge
(författare)
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Load management in municipal electricity systems
- 1997
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Ingår i: International Journal of Energy Research. - : John Wiley & Sons. - 0363-907X .- 1099-114X. ; 21:9, s. 787-791
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 2. |
- Gustafsson, Stig-Inge
(författare)
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Load management measures in a carpentry factory
- 1998
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Ingår i: International Journal of Energy Research. - : John Wiley & Sons. - 0363-907X .- 1099-114X. ; 22:14, s. 1267-1274
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 3. |
- Mattsson, Niclas, 1967, et al.
(författare)
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Assessing New Energy Technologies Using an Energy System Model with Endogenized Experience Curves
- 1997
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Ingår i: International Journal of Energy Research. - 1099-114X .- 0363-907X. ; 21, s. 385-393
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Tidskriftsartikel (refereegranskat)abstract
- Most energy systems models treat reductions of technology investment costs exogenously. In these models, investments may be postponed until the costs become low. This model behaviour is unreasonable, since early investments are necessary to realize the cost reductions, a phenomenon known as the experience effect. We have developed a global energy systems model with endogenized experience curves, and have conducted a pilot study to demonstrate the new insights which can be obtained with the model. In this initial application, we study the emergence of new energy technologies such as photovoltaics and fuel cells, competition between technologies and technology lock‐in effects
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| 4. |
- Zhu, Bin
(författare)
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Applications of hydrofluoride ceramic membranes for advanced fuel cell technology
- 2000
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Ingår i: International Journal of Energy Research. - 0363-907X .- 1099-114X. ; 24:1, s. 39-49
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Tidskriftsartikel (refereegranskat)abstract
- New types of materials, hydrofluoride-alumina ceramic composites containing one hydride component, CaH2, have been studied for fuel cell applications. Excellent fuel cell performances were achieved for a peak power density of 180 mW cm(-2) at 300 mA cm(-2), and a short-circuit current density near 1000 mA cm(-2). In fuel cell measurements the conductivity and ionic transport properties of the hydrofluoride-based electrolytes have also been investigated. During fuel cell operation, water was often observed at the cathode (air side), indicating that proton conduction occurs in these electrolyte materials. The experiments show an interesting chance for the future development of innovative fuel cell technology for commercialization.
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| 5. |
- Abbas, Ghazanfar, et al.
(författare)
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Electrochemical study of nanostructured electrode for low-temperature solid oxide fuel cell (LTSOFC)
- 2014
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 38:4, s. 518-523
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Tidskriftsartikel (refereegranskat)abstract
- Zn-based nanostructured Ba0.05Cu0.25Fe0.10Zn0.60O (BCFZ) oxide electrode material was synthesized by solid-state reaction for low-temperature solid oxide fuel cell. The cell was fabricated by sandwiching NK-CDC electrolyte between BCFZ electrodes by dry press technique, and its performance was assessed. The maximum power density of 741.87 mW-cm(-2) was achieved at 550 degrees C. The crystal structure and morphology were characterized by X-ray diffractometer (XRD) and SEM. The particle size was calculated to be 25 nm applying Scherer's formula from XRD data. Electronic conductivities were measured with the four-probe DC method under hydrogen and air atmosphere. AC Electrochemical Impedance Spectroscopy of the BCFZ oxide electrode was also measured in hydrogen atmosphere at 450 degrees C.
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| 6. |
- Ahlström, Johan, 1990, et al.
(författare)
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Bark as feedstock for dual fluidized bed gasifiers. Operability, efficiency, and economics
- 2019
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 43:3, s. 1171-1190
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Tidskriftsartikel (refereegranskat)abstract
- The demand for biofuels and biochemicals is expected to increase in the future, which will in turn increase the demand for biomass feedstock. Large gasification plants fueled with biomass feedstock are likely to be a key enabling technology in a resource-efficient, bio-based economy. Furthermore, the costs for producing biofuels and biochemicals in such plants could potentially be decreased by utilizing inexpensive low-grade residual biomass as feedstock. This study investigates the usage of shredded tree bark as a feedstock for the production of biomethane in the GoBiGas demonstration plant in Gothenburg, Sweden, based on a 32 MWth industrial dual fluidized bed gasification unit. The plant was operated with bark feedstock for 12 000 hours during the period 2014 to 2018. Data from the measurement campaign were processed using a stochastic approach to establish the plant's mass and energy balances, which were then compared with operation of the plant with wood pellets. For this comparison, an extrapolation algorithm was developed to predict plant performance using bark dried to the same moisture content as wood pellets, ie, 8%w.b. Plant operation with bark feedstock was evaluated for operability, efficiency, and feedstock-related cost. The gas quality achieved during the test period was similar to that obtained for operation with wood pellets. Furthermore, no significant ash sintering or agglomeration problems were observed more than 750 hours of operation. The calculated biomass-to-biomethane efficiency is 43% to 47% (lower heating value basis) for operation with wet bark. However, the predicted biomass-to-biomethane efficiency can be increased to 55%–65% for operation with bark feedstock dried to 8% moisture content, with corresponding feedstock costs in the range of 24.2 to 32.7 EUR/MWh; ie, a cost reduction of about 40% compared with wood pellets.
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| 7. |
- Alamia, Alberto, 1984, et al.
(författare)
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Performance of large-scale biomass gasifiers in a biorefinery, a state-of-the-art reference
- 2017
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 41:14, s. 2001-2019
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Tidskriftsartikel (refereegranskat)abstract
- The Gothenburg Biomass Gasification plant (2015) is currently the largest plant in the world producing biomethane (20 MWbiomethane) from woody biomass. We present the experimental data from the first measurement campaign and evaluate the mass and energy balances of the gasification sections at the plant. Measures improving the efficiency including the use of additives (potassium and sulfur), high-temperature pre-heating of the inlet streams, improved insulation of the reactors, drying of the biomass and introduction of electricity as a heat source (power-to-gas) are investigated with simulations. The cold gas efficiency was calculated in 71.7%LHVdaf using dried biomass (8% moist). The gasifier reaches high fuel conversion, with char gasification of 54%, and the fraction of the volatiles is converted to methane of 34%mass. Because of the design, the heat losses are significant (5.2%LHVdaf), which affect the efficiency. The combination of potential improvements can increase the cold gas efficiency to 83.5%LHVdaf, which is technically feasible in a commercial plant. The experience gained from the Gothenburg Biomass Gasification plant reveals the strong potential biomass gasification at large scale.
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| 8. |
- Andersson, Viktor, 1983, et al.
(författare)
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Integration of algae-based biofuel production with an oil refinery: Energy and carbon footprint assessment
- 2020
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 44:13, s. 10860-10877
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Tidskriftsartikel (refereegranskat)abstract
- Biofuel production from algae feedstock has become a topic of interest in the recent decades since algae biomass cultivation is feasible in aquaculture and does therefore not compete with use of arable land. In the present work, hydrothermal liquefaction of both microalgae and macroalgae is evaluated for biofuel production and compared with transesterifying lipids extracted from microalgae as a benchmark process. The focus of the evaluation is on both the energy and carbon footprint performance of the processes. In addition, integration of the processes with an oil refinery has been assessed with regard to heat and material integration. It is shown that there are several potential benefits of co-locating an algae-based biorefinery at an oil refinery site and that the use of macroalgae as feedstock is more beneficial than the use of microalgae from a system energy performance perspective. Macroalgae-based hydrothermal liquefaction achieves the highest system energy efficiency of 38.6%, but has the lowest yield of liquid fuel (22.5 MJ per 100 MJalgae) with a substantial amount of solid biochar produced (28.0 MJ per 100 MJalgae). Microalgae-based hydrothermal liquefaction achieves the highest liquid biofuel yield (54.1 MJ per 100 MJalgae), achieving a system efficiency of 30.6%. Macro-algae-based hydrothermal liquefaction achieves the highest CO2 reduction potential, leading to savings of 24.5 resp 92 kt CO2eq/year for the two future energy market scenarios considered, assuming a constant feedstock supply rate of 100 MW algae, generating 184.5, 177.1 and 229.6 GWhbiochar/year, respectively. Heat integration with the oil refinery is only possible to a limited extent for the hydrothermal liquefaction process routes, whereas the lipid extraction process can benefit to a larger extent from heat integration due to the lower temperature level of the process heat demand.
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| 9. |
- Arjmand, Mehdi, et al.
(författare)
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Exergetic efficiency of high-temperature-lift chemical heat pump (CHP) based on CaO/CO2 and CaO/H2O working pairs
- 2013
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Ingår i: International Journal of Energy Research. - : Wiley-Blackwell. - 0363-907X .- 1099-114X. ; 37:9, s. 1122-1131
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Tidskriftsartikel (refereegranskat)abstract
- The use of reversible chemical reactions in recuperation of heat has gained significant interest due to higher magnitude of reaction heat compared to that of the latent or sensible heat. To implement chemical reactions for upgrading heat, a chemical heat pump (CHP) may be used. A CHP uses a reversible chemical reaction where the forward and the reverse reactions take place at two different temperatures, thus allowing heat to be upgraded or degraded depending on the mode of operation. In this work, an exergetic efficiency model for a CHP operating in the temperature-level amplification mode has been developed. The first law and the exergetic efficiencies are compared for two working pairs, namely, CaO/CO2 and CaO/H2O for high-temperature high-lift CHPs. The exergetic efficiency increases for both working pairs with increase in task, TH, decrease in heat source, TM, and increase in condenser, TL, temperatures. It is also observed that the difference in reaction enthalpies and specific heats of the involving reactants affects the extent of increase or decrease in the exergetic efficiency of the CHP operating for temperature-level amplification.
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| 10. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
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Profitability and off-site CO2-emission reduction from energy savings in the pulp and paper industry in different future energy markets
- 2012
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 36:9, s. 975-986
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies by the authors have shown that energy savings in pulp and paper mills offer opportunities forincreased electricity production on-site or wood fuel export. The energy export implies reductions in CO2 emissions off-site, where fossil fuel or fossil-fuel-based electricity is replaced. To assess this potential and the related profitability for a future situation, four energy market scenarios were used. For a typical Scandinavian mill, the potential for CO2-emission reductions was 15–140 kton year-1 depending on the scenario and the form of energy export. Extrapolated to all relevant mills in Sweden, the potential was 0.4–3.1 Mton year-1, which is in the order of percent of the Swedish CO2 emissions. Wood fuel export implies larger reduction in CO2 emissions in most scenarios. In contrast, electricity export showed better economy in most of the cases studied; with annual earnings of 5–6Mh, this is an economically robust option. In the market pulp mill investigated, the wood fuel export was in the form of lignin. Lignin could possibly be valued as oil, regarding both price and potential for CO2-emissionreduction, making lignin separation an option with good profitability and large reductions of CO2 emissions.
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| 11. |
- Börjesson, Martin, 1980, et al.
(författare)
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Assessment of transport fuel taxation strategies through integration of road transport in an energy system model — the case of Sweden
- 2012
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 36:5, s. 648-669
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Tidskriftsartikel (refereegranskat)abstract
- Road transport is responsible for a large and growing share of CO2 emissions in most countries. A number of new fuel-efficient vehicle technologies and renewable transport fuels are possible alternatives to conventional options but their deployment relies strongly on different policy measures. Even though a future higher use of transport biofuels and electric vehicles is likely to increase the interaction between the transportation sector and the stationary energy system (heat, power, etc.), these systems are often analysed separately. In this study, a transport module is developed and integrated into the MARKAL_Nordic energy system model. The transport module describes a range of vehicle technologies and fuel options as well as different paths for conversion of primary energy resources into transport fuels. The integrated model is utilized to analyse the impact of transport fuel tax designs on future cost-effective fuel and technology choices in the Swedish transportation sector, as well as the consequences of these choices on system costs and CO2 emissions. The model, which is driven by cost-minimization, is run to 2050 with various assumptions regarding transport fuel tax levels and tax schemes. The results stress the importance of fuel taxes to accelerate the introduction of fuel-efficient vehicle technologies such as hybrids and plug-in hybrids. Tax exemptions can make biofuels an economically favourable choice for vehicle users. However, due to limitations in biomass supply, a too strong policy-focus on transport biofuels can lead to high system costs in relation to the CO2 abatement achieved. The modelling performed indicates that the effects caused by linkages between the transportation sector and the stationary energy system can be significant and integrated approaches are thus highly relevant.
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| 12. |
- Carlson, Annelie
(författare)
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On cost-effective technical measures to avoid environmental damage of regional energy systems
- 2002
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 26:12, s. 1103-1115
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Tidskriftsartikel (refereegranskat)abstract
- The production of heat and electricity can cause large environmental impacts and, hence, large costs for society. Those are costs that are seldom taken into consideration. An important question is how the future technical energy systems should be formed if environmental costs were considered as any other good or service, such as raw material, capital and labour. This study comprises cost-effective technical measures when monetary values of external effects are included in an energy system analysis. It is an analysis of how the present energy system can for society be cost-effectively reconstructed to be more sustainable. A regional energy system model has been developed to perform the study and it concentrates upon production of heat in single-family houses, multi-dwelling buildings, non-residential promises and district heating systems. The analysis adopts a business economic perspective, using present prices of energy carriers, and a more socio-economic perspective, in which external costs are included. The result of the analysis is the optimal mix of energy carriers as well as new and existing heating plants that minimizes the costs of satisfying a demand for heat. The results show that it is profitable to invest in new heating plants fuelled with woody biomass. Furthermore, the external costs arising with satisfying the demand for heat can decrease substantially, 60%, by carrying through with the investments that are cost-effective according to the institutional rules valid today. When monetary values of external costs are taken into consideration, this number is additional 5-percentage points lower. It is shown that if environmental costs are included it is more expensive to continue with business as usual than it is to reconstruct and run a more sustainable energy system.
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| 13. |
- Choi, Seung Young, et al.
(författare)
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Nanostructure-property relationship of two perfluorinated sulfonic acid (PFSA) membranes
- 2022
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 46:8, s. 11265-11277
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Tidskriftsartikel (refereegranskat)abstract
- The physicochemical properties of perfluorinated sulfonic acid (PFSA) polymers are closely correlated with their nanostructure. However, their real nano-structural morphology is still controversial because it is difficult to observe their accurate morphology at the nanoscale. Moreover, studies on the nanostructures of the PFSA membranes have been mainly focused on the ionic domain. On this basis, here we describe the crystalline domain of two PFSA membranes as well as their ionic domain based on small-angle X-ray scattering results. Both ionic and crystalline domains showed significant alterations during hydration, and the different behaviors based on the side-chain length of the two PFSA membranes are also described. The short side chain-tethered PFSA membrane (higher ion exchange capacity (IEC)) showed a widespread ionic domain and lacking crystalline domain with their relatively temperature-dependent tendency compared to the flexible long side chain-tethered PFSA membrane (lower IEC). On this basis, the correlation between nanostructure and membrane properties is described from various perspectives.
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| 14. |
- Dahlquist, Erik, et al.
(författare)
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Alternative Pathways to a Fossil-Fuel Free Energy System in the Mälardalen region of Sweden
- 2007
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 31:12, s. 1226-1236
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study on alternative pathways to a fossil-fuel free regional energy system in the Mälardalen region of Sweden with a population of 3 million inhabitants. We describe and address how the region can be made independent of fossil fuels by integration of resource management, technology advances, and behaviour change in energy use. First we investigate the consumption pattern of the inhabitants. Then we study what resources are available, and how these can be used to fulfil the different demands. If we just use the resources in a pattern of business as usual today without changing the behaviour, the balance between demands and resources is difficult to reach. By combining a slightly different behaviour and a change of crops we can fulfil the needs and it might even be possible to have a surplus of resources. Some advanced technological solutions have also been proposed. For example, dedicated biomass energy plants such as Salix, straw, hemp and some cereals can be used for ethanol production and the residues can be gasified to produce dimethylether (DME), which is good as a replacement for diesel fuel. Still the fueldemand for transport is high, and the vehicle weight could be further reduced. For example, by going back to the car size we had only 10 years ago the weight would be 25-30% less, and fuelconsumption would be at least 15% lower. With diesel engines instead of Otto engines the fuel consumption could be reduced by 35%, and with hybrid technology additional 20% fuel reduction could be gained. Improved public transportation will also give a positive effect especially for those commuting between the larger cities and between the cities and the suburbs. The results of our calculations show that it would be possible to accomplish a fossil-free energy system in the Mälardalen region. The results of this study are important since it shows that an energy balance without fossil fuels could be possible for an area with a population in the order of 3 million people, which would also be valuable in studies of other areas in the world.
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| 15. |
- Danielsson, Oskar, et al.
(författare)
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Study of a Longitudinal Flux Permanent Magnet Linear Generator for Wave Energy Converters
- 2006
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 30:14, s. 1130-1145
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Tidskriftsartikel (refereegranskat)abstract
- A directly coupled linear permanent magnet generator of longitudinal flux-type is investigated. The generator will be used for power take-off in a wave energy converter. A combined field- and circuit model, solved by a time stepping finite element technique, is used to model and analyse the electromagnetic behaviour of the machine. A large number of simulations form the basis of a design study where the influence of armature current level, number of cables per slot, and pole width is investigated with respect to efficiency, generator size, and the load angle. A case study is performed for a chosen generator design. The electromagnetic behaviour is examined both for nominal load and for overloads. The generator has a nominal output power of 10 kW for a constant piston speed of 0.7 m s(-1). The electromagnetic efficiency at nominal load is 86.0%, the load angle 6.6 degrees, and the power fluctuation 1.3%. At 300% overload the load angle barely exceeds 12 degrees and the cable temperature is below 25 degrees C provided that the stator back is thermally connected to the sea water. The numerical calculations have been verified for small speeds by experiments.
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| 16. |
- Eriksson, Lina, et al.
(författare)
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A feasibility study of improved heat recovery and excess heat export at a Swedish chemical complex site
- 2018
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 42:4, s. 1580-1593
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Tidskriftsartikel (refereegranskat)abstract
- New ambitious targets for reduced greenhouse gas emissions and increased energy efficiency in industry and in the stationary energy sector provide incentives for industrial plants to investigate opportunities for substantially increasing recovery and use of excess heat from their operations. This work investigates the economic feasibility of recovering industrial excess heat at a Swedish chemical complex site for increased site internal heat recovery or export to a regional district heating (DH) network. The work is based on investment cost data estimated in previous work by the authors. A site-wide heat collection and distribution system based on circulating hot water was envisioned, which is also connected to a regional DH network. With the help of multiobjective optimization, the optimal heat contributions from the individual plant sites were identified that minimize the total system cost for a large range of options involving different quantities of internally recovered heat and heat export to the DH system. A payback period analysis was conducted together with a risk assessment to take into account uncertainty regarding utility steam production cost and heat sale price. The results of the study indicate that a payback period of around 3 years can be achieved for a number of cases in which 30% to 50% of the total excess heat produced by the site plants is recovered. Although it seems more profitable to recover heat at the site rather than exporting heat to the DH system only, profitability appears to be maximized by hybrid solutions that allow a share of the excess heat to be sold to the DH system and some heat to be recovered at the site simultaneously.
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| 17. |
- Fan, L., et al.
(författare)
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Role of carbonate phase in ceria-carbonate composite for low temperature solid oxide fuel cells : A review
- 2016
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Ingår i: International Journal of Energy Research. - : John Wiley & Sons. - 0363-907X .- 1099-114X.
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Tidskriftsartikel (refereegranskat)abstract
- Ceria-salt composites represent one type of promising electrolyte candidates for low temperature solid oxide fuel cells (LT-SOFCs), in which ceria-carbonate attracts particular attention because of its impressive ionic conductivity and unique hybrid ionic conduction behavior compared with the commonly used single-phase electrolyte materials. It has been demonstrated that the introduction of carbonate in these new ceria-based composite materials initiates multi new functionalities over single-phase oxide, which therefore needs a comprehensive understanding and review focus. In this review, the roles of carbonate in the ceria-carbonate composites and composite electrolyte-based LT-SOFCs are analyzed from the aspects of sintering aid, electrolyte densification reagent, electrolyte/electrode interfacial 'glue' and sources of super oxygen ionic and proton conduction, as well as the oxygen reduction reaction promoter for the first time. This summary remarks the significance of carbonate in the ceria-carbonate composites for low temperature, 300-600°C, SOFCs and related highly efficient energy conversion applications.
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| 18. |
- Feng, Bo, et al.
(författare)
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Nitrogen oxides emission from a circulating fluidized bed combustor
- 1998
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Ingår i: International Journal of Energy Research. - 1099-114X .- 0363-907X. ; 20:11, s. 1015-1025
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were carried out in a pilot-scale circulating fluidized bed (CFB) coal combustor to investigate the mechanism of N,O formation, nitrogen oxides (including NO, and N,O) emission and the effect of temperature, excess air ratio, recirculation ratio, etc. The concentrations of nitrous oxide and nitric oxide were measured along the height of the CFB furnace. N,O concentration increased with height, and in the exit of the combustor N,O reached the highest level. NO,, however, decreased with height, showing the inverse trend compared with N,O. The N,O emission decreased sharply with the rise of temperature at the bottom of the combustor; at the same time, the NO, concentration increased.
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| 19. |
- Fiedler, Frank, et al.
(författare)
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Comparison of carbon monoxide emissions and electricity consumption of modulating and non-modulating pellet and solar heating systems
- 2007
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 31:10, s. 915-930
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Tidskriftsartikel (refereegranskat)abstract
- Emission and electricity consumption are important aspects of a pellet heating system. Low noxious emissions, particularly carbon monoxide, are a measure of a well-performing system. High carbon monoxide emissions are often caused by unnecessary cycling of the burner, poor adjustment of the combustion air and insufficient maintenance. The carbon monoxide output, the thermal performance and the electricity consumption for modulating and non-modulating operation mode have been investigated by simulations of four stoves/boilers as part of combined solar and pellet heating systems. The systems have been modelled with the simulation programme TRNSYS and simulated with the boundary conditions for space heating demand, hot water load and climate data as used in earlier research projects. The results from the simulations show that operating the pellet units with modulating combustion power reduces the number of starts and stops but does not necessarily reduce the carbon monoxide output. Whether the carbon monoxide output can be reduced or not depends very strongly on the reduction of starts and stops and how much the carbon monoxide emissions increase with decreased combustion power, which are in turn dependent on the particular settings of each pellet burner and how the heat is transferred to the building. However, for most systems the modulating operation mode has a positive impact on carbon monoxide emissions. Considering the total auxiliary energy demand, including the electricity demand of the pellet units, the modulating combustion control is advantageous for systems 1 and 4 for the used boundary conditions. The study also shows that an appropriate sizing of the stove or boiler has a huge potential for energy saving and carbon monoxide emission reduction.
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| 20. |
- Fu, Jie, et al.
(författare)
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Nanoporous CoP nanowire arrays decorated with carbon-coated CoP nanoparticles: the role of interfacial engineering for efficient overall water splitting
- 2022
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Ingår i: International Journal of Energy Research. - : WILEY. - 0363-907X .- 1099-114X. ; 46:8, s. 11359-11370
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Tidskriftsartikel (refereegranskat)abstract
- The innovative construction of bifunctional non-noble electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is imperative for electrochemical water splitting. Herein, we provide a collaborative self-templating method to prepare a hybrid catalyst of nanoporous CoP nanowire (NWs) arrays decorated with carbon-coated CoP nanoparticles (NPs). Its found that the unique structure and morphology of the resultant catalyst can provide abundant available active sites and faciliatate the rapid H-2/O-2 transmission. Additionally, the N-doped carbon improves the conductivity of the catalyst and prevents the aggregation and deactivation of CoP nanoparticles. Forthermore, the strong coupling and synergistic effects by interface engineering are also conducive to the electrochemical performance. Benefiting from these advantages, the CoP NWs/CoP NPs@NC/CC only needs a low overpotential of 103 mV to achieve 10 mA cm(-2) with a small Tafel slope of 87 mV dec(-1) for HER. When employed in an electrolytic cell as an electrocatalyst for overall water splitting, a low voltage of 1.60 V is required to drive 10 mA cm(-2). This study may provide a novel way to fabricate transitionmetal-based catalysts for water splitting.
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| 21. |
- Gao, Zhan, et al.
(författare)
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Composite electrolyte based on nanostructured Ce0.8Sm0.2O1.9 (SDC) for low-temperature solid oxide fuel cells
- 2009
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 33:13, s. 1138-1144
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured Ce0.8Sm0.2O1.9 (SDC) is investigated for low-temperature solid oxide fuel cells based on SDC- 30 wt% (53 mol% Li2CO3:47 mol % Na2CO3) composite electrolyte in this work. SDC is prepared by the combined citrate and EDTA complexing method. X-ray powder diffraction shows that it forms a well-cubic fluorite structure after being sintered at 700 degrees C for 2 h. The particle is about 12 nm detected by the transmission electron microscopy. Conductivity for the composite is much higher than the pure SDC at comparable temperatures. A transition of ionic conductivity occurs at 450 degrees C for the composite electrolyte. The single cells are fabricated by a simple dry-pressing process and tested at 450-600 degrees C. A maximum power density of 900 mW cm(-2) and the open-circuit voltage of 0.92 V are achieved at 600 degrees C. The conduction mechanism has been discussed by comparing the conductivity of composite electrolyte under different conditions. AC impedance for single cell indicates that the electrochemical process involving cathode and anode reactions is the rate-limiting step.
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| 22. |
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| 23. |
- Gao, Zhan, et al.
(författare)
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Development of methanol-fueled low-temperature solid oxide fuel cells
- 2011
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 35:8, s. 690-696
-
Tidskriftsartikel (refereegranskat)abstract
- Low-temperature solid oxide fuel cell (SOFC, 300-600 degrees C) technology fueled by methanol possessing significant importance and application in polygenerations has been developed. Thermodynamic analysis of methanol gas-phase compositions and carbon formation indicates that direct operation on methanol between 450 and 600 degrees C may result in significant carbon deposition. A water steam/methanol ratio of 1/1 can completely suppress carbon formation in the same time enrich H(2) production composition. Fuel cells were fabricated using ceria-carbonate composite electrolytes and examined at 450-600 degrees C. The maximum power density of 603 and 431 mW cm(-2) was achieved at 600 and 500 degrees C, respectively, using water steam/methanol with the ratio of 1/1 and ambient air as fuel and oxidant. These results provide great potential for development of the direct methanol low-temperature SOFC for polygenerations.
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| 24. |
- Gebremedhin, Alemayehu, 1962-, et al.
(författare)
-
Modelling and optimization of district heating and industrial energy system - An approach to a locally deregulated heat market
- 2004
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 28:5, s. 411-422
-
Tidskriftsartikel (refereegranskat)abstract
- Regions with densely concentration of industries and district heating systems (DHS) could be interesting study object from the light of an integrated heat market on local basis. System analysis with a widened system boundary could be used as an approach to evaluate the benefit of an integrated heat supply system. In this study, an energy system model consisting of totally seven different participants is designed and the optimization results of the system analysis are presented. With applied data and assumptions, the study shows that a significant amount of the heat demand within two sub-systems can be covered by heat supply from the heat market (the entire heat comes from two industries). Shadow prices, which can be used for heat pricing, indicate the advantage of an integrated system. The system cost reduction through integration and the availability of several actors with diverse energy supply system, makes the region under study an interesting area to prove a locally deregulated heat market.
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| 25. |
- Gierse, Martin, et al.
(författare)
-
Operation control of circulating fluidized bed boilers
- 1996
-
Ingår i: International Journal of Energy Research. - 1099-114X .- 0363-907X. ; 20:10, s. 839-851
-
Tidskriftsartikel (refereegranskat)abstract
- The heat balance of different circulating fluidized bed boiler designs is investigated for variations in input parameters, such as specific flue-gas amount and ash content of the fuel. A simple model and a corresponding diagram are developed to describe the boiler behaviour when conditions deviate from the nominal ones. The model shows how the furnace temperature is influenced in different ways in different boiler designs by changes of furnace heat transfer and of the mass flow of particles and flue gases. The model results are verified by measurements in one type of boiler. Finally, it is shown how the desired stable furnace temperature and stable heat flux distribution are in conflict during variations of the input parameters. As a consequence, a two-dimensional boiler control strategy is suggested.
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| 26. |
- Gong, Mei, 1967-
(författare)
-
Exergy analysis of a pulp and paper mill
- 2005
-
Ingår i: International Journal of Energy Research. - Chichester : John Wiley & Sons. - 0363-907X .- 1099-114X. ; 29:1, s. 79-93
-
Tidskriftsartikel (refereegranskat)abstract
- Different energy and exergy concepts and methods are presented and applied to a Swedish pulp and paper mill. Flow diagrams show that the exergy content is mostly much less than the energy content of the flows. The largest exergy losses appear in the boilers. Heating processes are highly exergy inefficient. A limited Life Cycle Exergy Analysis (LCEA) shows that the exergy output amounts to over 3 times the spent exergy as non-sustainable resources. By replacing the present use of non-sustainable resources, mostly fuel oil, the mill could move towards a truly sustainable process. Copyright © 2005 John Wiley & Sons, Ltd.
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| 27. |
- Grönkvist, Stefan, et al.
(författare)
-
Models for assessing net CO2 emissions applied on district heating technologies
- 2003
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 27:6, s. 601-613
-
Tidskriftsartikel (refereegranskat)abstract
- Methodologies to assess the effects of energy projects on global carbon dioxide emissions will be an important feature of a future international carbon dioxide trading system. In this paper, we present and discuss four different models for assessing the net carbon dioxide emissions resulting from a certain energy project. These models are applied to different district heating technologies. To judge the mitigation performance of a project, the amount of carbon dioxide released in kilograms is expressed per megawatt-hour of useful district heating produced. All the models consider the marginal change caused by the project on the electric power system. The different model perspectives are discussed, and it is shown that the choice of model is very critical for assessing the net carbon dioxide emissions from an energy project.
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| 28. |
- Gunasekara, Saman Nimali, 1982-, et al.
(författare)
-
Thermal conductivity measurement of erythritol, xylitol, and their blends for phase change material design : A methodological study
- 2019
-
Ingår i: International Journal of Energy Research. - : John Wiley & Sons. - 0363-907X .- 1099-114X. ; 43:5, s. 1785-1801
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents and discusses a detailed thermal conductivity assessment of erythritol, xylitol, and their blends: 25 mol% erythritol and 80 mol% erythritol using the transient plane source (TPS) method with a Hot Disk Thermal Constants Analyzer TPS‐2500S. Thereby, the thermal conductivities of xylitol, 25 mol% erythritol, 80 mol% erythritol, and erythritol were here found for respectively in the solid state to be 0.373, 0.394, 0.535, and 0.589 W m−1 K−1 and in the liquid state to be 0.433, 0.402, 0.363, and 0.321 W m−1 K−1. These obtained results are comprehensively and critically analyzed as compared to available literature data on the same materials, in the phase change materials (PCMs) design context. This study clearly indicates that these thermal conductivity data in literature have considerable discrepancies between the literature sources and as compared to the data obtained in the present investigation. Primary reasons for these disparities are identified here as the lack of sufficiently transparent and repeatable data and procedure reporting, and relevant standards in this context. To exemplify the significance of such transparent and repeatable data reporting in thermal conductivity evaluations in the PCM design context, here focused on the TPS method, a comprehensive measurement validation is discussed along various residual plots obtained for varying input parameters (ie, the heating power and time). Clearly, the variations in the input parameters give rise to various thermal conductivity results, where choosing the most coherent result requires a sequence of efforts per material, because there are no universally valid conditions. Transparent and repeatable data and procedure reporting are the key to achieve comparable thermal conductivity results, which are essential for the correct design of thermal energy storage systems using PCMs.
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| 29. |
- Gustafsson, Stig-Inge
(författare)
-
Are Earth Tube Heat Exchangers of Interest when Heating Buildings?
- 1993
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 17:7, s. 597-604
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 30. |
- Gustafsson, Stig-Inge
(författare)
-
Optimal use of solar collectors for residential buildings
- 2001
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 25:11, s. 993-1004
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 31. |
- Gustafsson, Stig-Inge, et al.
(författare)
-
Optimization models and solution methods for load management
- 2004
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 28:4, s. 299-317
-
Tidskriftsartikel (refereegranskat)abstract
- The electricity market in Sweden has changed during recent years. Electricity for industrial use can now be purchased from a number of competing electricity suppliers. Hence, the price for each kilowatt-hour is significantly lower than it was just two years ago and interest in electricity conservation measures has declined. However, part of the electricity tariff, i.e. the demand cost expressed in Swedish Kronor (SEK) for each kilowatt, is almost the same as before. Attention has thereby been drawn to load management measures in order to reduce this specific cost. Saving one kWh might lead to a monetary saving of between SEK 0.22 and SEK 914, this paper demonstrates how to eliminate only those kWh that actually save a significant amount of money. A load management system has been installed in a small carpentry factory that can turn off equipment based on a pre-set priority and number of minutes each hour. The question now is what level of the electricity load is optimal in a strictly mathematical sense, i.e. how many kW should be set in the load management computer in order to maximise profitability? In this paper, we develop a mathematical model that can be used as a tool both to find the most profitable subscription level and to control the choices to be made. Numerical results from a case study are presented. Copyright (C) 2004 John Wiley Sons, Ltd.
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| 32. |
- Gustafsson, Stig-Inge
(författare)
-
Optimization of drying kiln operation
- 2000
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Ingår i: International Journal of Energy Research. - 0363-907X .- 1099-114X. ; 24:1, s. 19-26
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 33. |
- Gustafsson, Stig-Inge, et al.
(författare)
-
Why is Life-Cycle Costing Important when Retrofitting Buildings
- 1988
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 12:2, s. 233-242
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 34. |
- Han, Song, et al.
(författare)
-
Techno-economic analysis of an integrated biorefinery system for poly-generation of power, heat, pellets and bioethanol
- 2014
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 38:5, s. 551-563:38, s. 551-563
-
Tidskriftsartikel (refereegranskat)abstract
- Bioethanol is an alternative to fossil fuels in the transportation sector. The use of pellet for heating is also an efficient way to mitigate greenhouse gas emissions. This paper evaluates the techno-economic performance of a biorefinery system in which an existing combined heat and power (CHP) plant is integrated with the production of bioethanol and pellet using straw as feedstock. A two-stage acid hydrolysis process is used for bioethanol production, and two different drying technologies are applied to dry hydrolysis solid residues. A sensitivity analysis is performed on critical parameters such as the bioethanol selling price and feedstock price. The bioethanol production cost is also calculated for two cases with either 10 year or 15 year payback times. The results show that the second case is currently a more feasible economic configuration and reduces production costs by 36.4%-77.3% compared to other types of poly-generation plants that are not integrated into existing CHP plants.
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| 35. |
- He, Qiao, et al.
(författare)
-
A study on latent heat storage exchangers with the high-temperature phase-change material
- 2001
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 25:4, s. 331-341
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a theoretical analysis and an experimental test on a shell-and-tube latent heat storage exchanger. The heat exchanger is used to recover high temperature waste heat from industrial furnaces and off-peak electricity. It can also be integrated into a renewable energy system as an energy storage component. A mathematical model describing the unsteady freezing problem coupled with forced convection is solved numerically to predict the performance of the heat exchanger. It provides a basis for optimum design of the heat exchanger. The experimental study on the heat exchanger is carried out under various operating conditions. Effects of various parameters, such as the inlet temperature, the mass flow rate, the thickness of the phase change material and the length of the pipes, on the heat transfer performance of the unit are discussed by combining with theoretical prediction. Criterion for analyzing and evaluating the performance of heat exchanger is also proposed.
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| 36. |
- Heinisch, Verena, 1991, et al.
(författare)
-
Organizing prosumers into electricity trading communities: Costs to attain electricity transfer limitations and self‐sufficiency goals
- 2019
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 43:13, s. 7021-7039
-
Tidskriftsartikel (refereegranskat)abstract
- Among household electricity end users, there is growing interest in local renewable electricity generation and energy independence. Community‐based and neighborhood energy projects, where consumers and prosumers of electricity trade their energy locally in a peer‐to‐peer system, have started to emerge in different parts of the world. This study investigates and compares the costs incurred by individual households and households organized in electricity trading communities in seeking to attain greater independence from the centralized electricity system. This independence is investigated with respect to: (i) the potential to reduce the electricity transfer capacity to and from the centralized system and (ii) the potential to increase self‐sufficiency. An optimization model is designed to analyze the investment and operation of residential photovoltaic battery systems. The model is then applied to different cases in a region of southern Sweden for year 2030. Utilizing measured electricity demand data for Swedish households, we show that with a reduced electricity transfer capacity to the centralized system, already a community of five residential prosumers can supply the household demand at lower cost than can prosumers acting individually. Grouping of residential prosumers in an electricity trading community confers greater benefits under conditions with a reduced electricity transfer capacity than when the goal is to become electricity self‐sufficient. It is important to consider the local utilization of photovoltaic‐generated electricity and its effect on the net trading pattern (to and from the centralized system) when discussing the impact on the electricity system of a high percentage of prosumers.
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| 37. |
- Heyne, Stefan, 1979, et al.
(författare)
-
Extending existing combined heat and power plants for synthetic natural gas production
- 2012
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 36:5, s. 670-681
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, integration of a synthetic natural gas (SNG) production process with an existing biomass CHP steam power cycle is investigated. The paper assesses two different biomass feedstock drying technologies-steam drying and low-temperature air drying-for the SNG process. Using pinch technology, different levels of thermal integration between the steam power cycle and the SNG process are evaluated. The base case cold gas efficiency for the SNG process is 69.4% based on the lower heating value of wet fuel. The isolated SNG-related electricity production is increased by a factor of 2.5 for the steam dryer alternative, and tenfold for the low-temperature air dryer when increasing the thermal integration. The cold gas efficiency is not affected by the changes. Based on an analysis of changes to turbine steam flow, the integration of SNG production with an existing steam power cycle is deemed technically feasible.
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| 38. |
- Heyne, Stefan, 1979, et al.
(författare)
-
Impact of choice of CO2 separation technology on thermo-economic performance of Bio-SNG production processes
- 2014
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 38:3, s. 299-318
-
Tidskriftsartikel (refereegranskat)abstract
- Three different CO2 separation technologies for production of synthetic natural gas (SNG) from biomass gasification – amine-based absorption, membrane-based separation and pressure swing adsorption – are investigated for their thermo-economic performance against the background of different possible future energy market scenarios. The studied scale of the SNG plant is a thermal input of 100 MWth,LHV to the gasifier at a moisture content of 20 wt-% with a preceding drying step reducing the biomass' natural moisture content of 50 wt-%. Preparation of the CO2-rich stream for carbon capture and storage is investigated for the amine-based absorption and the membrane-based separation technology alternatives. The resulting cold gas efficiency ηcg for the investigated process alternatives ranges between 0.65 and 0.695. The overall system efficiency ηsys ranges from 0.744 to 0.793, depending on both the separation technology and the background energy system. Amine-based absorption gives the highest cold gas efficiency whereas the potential for cogeneration of electricity from the process' excess heat is higher for membrane-based separation and pressure swing adsorption. The estimated specific production costs for SNG cSNG for a process input of 90.3 MWth,LHV at 50 wt-% moisture vary between 103–127 €2010/MWhSNG. The corresponding production subsidy level csubsidy needed to achieve end-user purchase price-parity with fossil natural gas is in the range of 56–78 €2010/MWhSNG depending on both the energy market scenario and the CO2 separation technology. Sensitivity analysis on the influence of changes in the total capital cost for the SNG plant on the production cost indicates a decrease of about 12% assuming a 30% reduction in total capital investment. Capture and storage of biogenic CO2 – if included in the emission trading system – only becomes an option at higher CO2 charges. This is due to increased investment costs but, in particular, due to the rather high costs for CO2 transport and storage that have been assumed in this study.
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| 39. |
- Höök, Mikael, 1982-, et al.
(författare)
-
A review on coal to liquid fuels and its coal consumption
- 2010
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 34:10, s. 848-864
-
Forskningsöversikt (refereegranskat)abstract
- Continued reliance on oil is unsustainable and this has resulted in interest in alternative fuels. Coal-to-Liquids (CTL) can supply liquid fuels and have been successfully used in several cases, particularly in South Africa. This article reviews CTL theory and technology. Understanding the fundamental aspects of coal liquefaction technologies are vital for planning and policy-making, as future CTL systems will be integrated in a much larger global energy and fuel utilization system. Conversion ratios for CTL are generally estimated to be between 1-2 barrels/ton coal. This puts a strict limitation on future CTL capacity imposed by future coal production volumes, regardless of other factors such as economics, emissions or environmental concern. Assuming that 10% of world coal production can be diverted to CTL, the contribution to liquid fuel supply will be limited to only a few Mb/d. This prevents CTL from becoming a viable mitigation plan for liquid fuel shortage on a global scale. However, it is still possible for individual nations to derive significant shares of their fuel supply from CTL, but those nations must also have access to equally significant coal production capacities. It is unrealistic to claim that CTL provides a feasible solution to liquid fuels shortages created by peak oil. For the most part, it can only be a minor contributor and must be combined with other strategies.
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| 40. |
- Jia, Yuxin, et al.
(författare)
-
A parametric comparison of temperature uniformity and energy performance of a PEMFC having serpentine wavy channels
- 2019
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 43:7, s. 2722-2736
-
Tidskriftsartikel (refereegranskat)abstract
- Proton exchange membrane fuel cells (PEMFCs) are regarded as alternative energy sources because they are environment friendly and deliver no harmful emission. As its reliability and power generating efficiency is largely influenced by the temperature distribution, it is necessary to improve the temperature uniformity which is crucial in PEMFCs. To this end, this numerical study presents an attempt to optimize the flow channels via introducing wavy shape flow channels at the ribs. The numerical model is validated by experimental data available in the open literature. Two kinds of wavy shape flow channels are designed while straight flow channel is set as a reference. In the PEMFCs with wavy shape flow channels, the effects of the amplitude and wavelength on the thermal performance are simulated and analyzed. Results show that wavy shape flow channels provide better performance not only for thermal uniformity but also for PEMFC output power and efficiency. With lower amplitude and wavelength of wavy shape flow channels, the power can be promoted up to 3.69% and 7.26% for two kinds of wavy shaped flow channels compared with straight flow channel, respectively. The influences of amplitude and wavelength on the thermal uniformity and the output power are also analyzed. This paper provides a new insight to PEMFC flow channel designers.
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| 41. |
- Johannes, Schmidt, et al.
(författare)
-
Potential of biomass-fired combined heat and power plants considering the spatial distribution of biomass supply and heat demand
- 2010
-
Ingår i: International Journal of Energy Research. - : Wiley. - 0363-907X .- 1099-114X. ; 34:11, s. 970-985
-
Tidskriftsartikel (refereegranskat)abstract
- Combined heat and power (CHP) plants fired by forest wood can significantly contribute to attaining the target of increasingthe share of renewable energy production. However, the spatial distribution of biomass supply and of heat demand limits thepotentials of CHP production. This article assesses CHP potentials using a mixed integer programming model that optimizeslocations of bioenergy plants. Investment costs of district heating infrastructure are modeled as a function of heat demanddensities, which can differ substantially. Gasification of biomass in a combined cycle process is assumed as productiontechnology. Some model parameters have a broad range according to a literature review. Monte-Carlo simulations havetherefore been performed to account for model parameter uncertainty in our analysis. The model is applied to assess CHPpotentials in Austria. Optimal locations of plants are clustered around big cities in the east of the country. At current powerprices, biomass-based CHP production allows producing around 3% of the total energy demand in Austria. Yet, the heatutilization decreases when CHP production increases due to limited heat demand that is suitable for district heating.Production potentials are most sensitive to biomass costs and power prices.
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| 42. |
- Jönsson, Johanna, 1981, et al.
(författare)
-
Comparison of options for utilization of a potential steam surplus at kraft pulp mills - Economic performance and CO2 emissions
- 2013
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 37:9, s. 1017-1035
-
Tidskriftsartikel (refereegranskat)abstract
- This paper compares different energy-related investment options that can be implemented in a kraft pulp mill with a potential steam surplus. The options investigated include lignin extraction, electricity production, capturing of CO2 and black liquor gasification with production of electricity or biofuels, here DME. The investment options are compared with respect to annual net profit and global CO2 emissions for different future energy market scenarios. A further analysis of how different parameters such as policy instruments and investment costs affect the different technologies also is included. The results show that, generally, for reasonable levels of biofuel support, the best economic performance among the studied technologies is achieved by extraction of lignin valued as oil. However, if the level of support for biofuels is high, black liquor gasification with DME production generally has the best economic performance among the studied options. All the investment options investigated decrease global CO2 emissions significantly. Capturing and storing CO2 from the recovery boiler flue gases result in the highest CO2 emissions reduction and also is an economically attractive option in scenarios with a high CO2 emissions charge.
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| 43. |
- Karamoozian, Amirhossein, et al.
(författare)
-
Risk assessment of renewable energy projects using uncertain information
- 2022
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 46:13, s. 18079-18099
-
Tidskriftsartikel (refereegranskat)abstract
- The majority of countries attempting to switch from conventional energy sources to renewable energy sources have decided to make significant investments in these projects. Considering renewable energy is an industry with a high level of investment expenses, assessing investment risks is critical to making efficient investment strategies. Howbeit, since risk assessment is dependent on expert opinions, uncertainty in the judgment of the consultants should be avoided. In this study, a novel hybrid failure mode and effect analysis approach is proposed to assess the investment risks of renewable energy projects. Results indicated that wind energy is the most appropriate alternative considering technical, marketability, environmental, economic, social aspects. Moreover, the sensitivity analysis is carried out and the robustness and validity of results from the proposed approach are examined. Finally, six different scenarios are considered and the results are interpreted accordingly. The findings of this study will be valuable to authorities, investors, and enterprises involved in the renewable energy projects and evaluating their investment.
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| 44. |
- Karlsson, Magnus, 1966-, et al.
(författare)
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Sensitivity analysis of investments in the pulp and paper industry : on investments in the chemical recovery cycle at a board mill
- 2002
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 26:14, s. 1253-1267
-
Tidskriftsartikel (refereegranskat)abstract
- In the pulp and paper industry, energy costs represents a relatively large proportion of the value of production. When investing in new equipment, considerations concerning boundary conditions, such as electricity and oil prices, are therefore of great importance. A vital requirement is the identification of other key parameters influencing production costs as well as possible interaction between these parameters. In this paper, a sensitivity analysis is accomplished by using an optimization model that minimizes the system cost combined with a systematic approach involving a statistical method.The paper analyses the possibilities of investing in a new chemical recovery cycle, including a new recovery boiler and evaporation plant, at a Swedish board mill. The study includes a survey of future changes, together with forecasts of boundary conditions, such as changes in the price of electricity and oil. Interactions between different parameters are also examined.
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| 45. |
- Kharseh, Mohamad, et al.
(författare)
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Sustainable heating and cooling systems for agriculture
- 2011
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 35:5, s. 415-422
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Tidskriftsartikel (refereegranskat)abstract
- Space heating/cooling systems account for approximately 40% of the global energy consumption. Such systems contribute to global warming by emitting 4×1010 MWh of heat and 3×1010 tons of CO2. There is a general understanding that the way to reduce global warming is a more efficient use of energy and increased use of renewable energy in all fields of the society. Ground-coupled heating/cooling systems, which have proven to make huge contributions in reducing energy consumption in Europe and North America, is here applied for poultry industry in Syria, as an example for the Middle East. There are e.g. 13 000 chicken farms in Syria producing 172 000 tons of meat per year. This industry employs directly almost 150 000 people. The total investments in chicken farming are 130 BSP (2 B). The annual mean air temperature in Syria is 15-18°C with winter temperatures close to freezing during two months. The chickens need a temperature of 21-35°C, depending on age, and the heating of all Syrian chicken plants consume 173×103 tons of coal (1196 GWh). In the summer time, the ambient air temperature in Syria could reach above 45°C. The chicken farms have no cooling systems since conventional cooling system is too expensive. The elevated temperature inside the farms reduces the chicken growth and lots of chicken die of overheating. The ground temperature at 10 m depth is roughly equal to the annual mean air temperature. Using the ground as a heat source means a sustainable and less expensive heating of the chicken farms. During the summer, the ground is used as a source for free cooling, i.e. used directly for cooling of the plants without any cooling machines. Current study shows the design and simulated operation of a ground-coupled heating/cooling system for a typical chicken farm in Syria. Performed national potential study showed that the implementation of such ground coupled heating and cooling systems in the Syrian poultry sector would mean increased poultry production and considerable savings in money, energy, and the environment.
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| 46. |
- Klugman, Sofia, et al.
(författare)
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Modeling an industrial energy system : Perspectives on regional heat cooperation
- 2008
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Ingår i: International Journal of Energy Research. - Chichester, West Sussex, United Kingdom : John Wiley & Sons. - 0363-907X .- 1099-114X. ; 32:9, s. 793-807
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Tidskriftsartikel (refereegranskat)abstract
- Through energy efficiency measures, it is possible to reduce heat surplus in the pulp and paper industry. Yet pulp and paper mills situated in countries with a heat demand for residential and commercial buildings for the major part of the year are potential heat suppliers. However, striving to utilize the heat within the mills for efficient energy use could conflict with the delivery of excess heat to a district heating system. As part of a project to optimize a regional energy system, a sulfate pulp mill situated in central Sweden is analyzed, focusing on providing heat and electricity to the mill and its surrounding energy systems. An energy system optimization method based on mixed integer linear programming is used for studying energy system measures on an aggregated level. An extended system, where the mill is integrated in a regional heat market (HM), is evaluated in parallel with the present system. The use of either hot sewage or a heat pump for heat deliveries is analyzed along with process integration measures. The benefits of adding a condensing unit to the back-pressure steam turbine are also investigated. The results show that the use of hot sewage or a heat pump for heat deliveries is beneficial only in combination with extended heat deliveries to an HM. Process integration measures are beneficial and even increase the benefit of selling more heat for district heating. Adding a condensing turbine unit is most beneficial in combination with extended heat deliveries and process integration.
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| 47. |
- Koksal, M., et al.
(författare)
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Thermal Aspects a Circulating Fluidized Bed with Air Staging
- 2005
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Ingår i: International Journal of Energy Research. - : John Wiley & Sons, Ltd.. - 0363-907X .- 1099-114X. ; 29:10, s. 923-935
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Tidskriftsartikel (refereegranskat)abstract
- In this study, effects of air staging on wall-to-bed heat transfer were investigated in a laboratory scale circulating fluidized bed (0.23m ID, 7.6m high). The bed was operated under ambient conditions with silica sand particles (dp=89 mm, rp=2650 kgm_3). Two different designs of secondary air (SA) injectors were used for air staging: radial and tangential. Bed-to-wall heat transfer measurements were carried out at three elevations above the SA injection port. The results indicate that similar to non-SA operation, the heat transfer with air staging depends strongly on the cross-sectional average suspension density. Tangential secondary injection was found to increase the bed-to-wall heat transfer above the SA injection port significantly due to increased suspension density compared with non-SA operation.
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| 48. |
- Larsson, Mikael, et al.
(författare)
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System gains from widening the system boundaries : analysis of the material and energy balance during renovation of a coke oven battery
- 2004
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 28:12, s. 1051-1064
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Tidskriftsartikel (refereegranskat)abstract
- The coke oven plant has a central role in the iron and steel making process in an integrated steel plant. The subject of this research is to study how the production and energy system at the steel industry, with a connected combined heat and power plant, is affected by renovation of the coke oven. The aim is to investigate the interaction between the different processes and how the choice of system boundary affects the operation practice for the steel plant. MILP-based optimization models have been developed and used for the evaluation. The analysis shows that it is very important to take the interactions between the different production units in the system into consideration when making the analysis. A system optimization with a boundary including the whole system has a greater potential for minimizing the total system cost than one that only includes the processes where the actual changes are made. Conclusions are also drawn regarding the production practice for the specific system.
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| 49. |
- Leckner, Bo G, 1936
(författare)
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Optimization of emissions from fluidized bed boilers
- 1992
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Ingår i: International Journal of Energy Research. - 1099-114X .- 0363-907X. ; 16:5, s. 351-363
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Tidskriftsartikel (refereegranskat)abstract
- The experiences of emissions of SO,, NO, and N,O from fluidized bed boilers obtained from extensive measurements by the Department of Energy Conversion, Chalmers University of Technology, are briefly summarized. In addition, results from secondary methods to reduce NO and N,O emissions are shown. With this background, possibilities for decreasing the N,O emissions by the optimization of boiler parameters involving the use of secondary methods are discussed. The problem lies in the increase in the SOz and NO emissions when a measure is taken to reduce the N,O emission. In particular, the influence of excess air and temperature is considered in comparison with selective noncatalytic reduction of NO.
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| 50. |
- Leduc, Sylvain, et al.
(författare)
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Optimal location of wood gasification plants for methanol production with heat recovery
- 2008
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 32:12, s. 1080-1091
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Tidskriftsartikel (refereegranskat)abstract
- Second generation biofuels from wood gasification are thought to become competitive in the face of effective climate and energy security policies. Cost competitiveness crucially depends on the optimization of the entire supply chain-field-wheel involving optimal location, scaling and logistics. In this study, a linear mixed integer programming model has been developed to determine the optimal geographic locations and sizes of methanol plants and gas stations in Austria. Optimal locations and sizes are found by the minimization of costs with respect to biomass and methanol production and transport, investments for the production plants and the gas stations. Hence, the model covers competition in all levels of a biofuel production chain including supply of biomass, biofuel and heat, and demand for bio- and fossil fuels.The results show that Austria could be self-sufficient in the production of methanol for biofuels like M5, M10 or M20, using up to 8% of the arable land share. The plants are optimally located close to the potential supply of biomass (i.e. poplar) in Eastern Austria, and produce methanol around 0.4 is an element of(-1). Moreover, heat production could lower the methanol cost by 12%.
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