| 1. |
- Eidehall, Andreas, et al.
(författare)
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Joint Road Geometry Estimation and Vehicle Tracking
- 2007
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Ingår i: Control Engineering Practice. - Linköping : Elsevier. - 0967-0661 .- 1873-6939. ; 15:12, s. 1484-1494
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Tidskriftsartikel (refereegranskat)abstract
- Detection and tracking of other vehicles and estimation of lane geometry will be required for many intelligent driver assistance systems in the future. By combining the processing of these two features into a single filter, better utilisation of the available information can be achieved. For instance, it is demonstrated that it is possible to improve the road shape estimate by including information about the lateral movement of leading vehicles. Statistical evaluation is done by comparing the estimated parameters to true values in varying road and weather conditions. The performance is also related to typical requirements of active safety applications such as adaptive cruise control and a new safety function called emergency lane assist.
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| 2. |
- Birgersson, Erik, et al.
(författare)
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A quantitative study of the effect of flow-distributor geometry in the cathode of a PEM fuel cell
- 2006
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 153:1, s. 76-88
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Tidskriftsartikel (refereegranskat)abstract
- An isothermal three-dimensional model describing mass, momentum and species transfer in the cathode of a proton exchange membrane fuel cell has been used to study four different flow-distributors: interdigitated, coflow and counterflow channels, and a foam. A quantitative comparison of the results shows; that the interdigitated channels can sustain the highest current densities, followed in descending order by the foam, the counterflow and the coflow channels. The foam yields the most uniform current density distribution at higher currents, but care should be taken as to its permeability to avoid unreasonably high-pressure drops.
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| 3. |
- Bodén, Andreas, et al.
(författare)
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Conductivity of SDC and (Li/Na)2CO3 composite electrolytes in reducing and oxidising atmospheres
- 2007
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 172:2, s. 520-529
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Tidskriftsartikel (refereegranskat)abstract
- Composite electrolytes made of samarium-doped cerium oxide and a mixture of lithium carbonate and sodium carbonate salts are investigated with respect to their structure, morphology and ionic conductivity. The composite electrolytes are considered promising for use in so called intermediate temperature solid oxide fuel cells (IT-SOFC), operating at 400-600 degrees C. The electrolytes are tested in both gaseous anode (reducing) and cathode (oxidising) environments and at different humidities and carbon dioxide partial pressures. For the structure and morphology measurements, it was concluded that no changes occur to the materials after usage. From measurements of melting energies, it was concluded that the melting point of the carbonate salt phase decreases with decreasing fraction of carbonate salt and that a partial melting occurs before the bulk melting point of the salt is reached. For all the composites, two regions may be observed for the conductivity, one below the carbonate salt melting point and one above the melting point. The conductivity is higher when electrolytes are tested in anode gas than when tested in cathode gas, at least for electrolytes with less than half the volume fraction consisting of carbonate salt. The higher the content of carbonate salt phase, the higher the conductivity of the composite for the temperature region above the carbonate melting point. Below the melting point, though, the conductivity does not follow this trend. Calculations on activation energies for the conductivity show no trend or value that indicates a certain transport mechanism for ion transport, either when changing between the different composites or between different gas environments.
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| 4. |
- Bodén, Andreas, et al.
(författare)
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The solubility of Ni in molten Li2CO3–Na2CO3 (52/48) in H2/H2O/CO2 atmosphere
- 2007
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 166:1, s. 59-63
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Tidskriftsartikel (refereegranskat)abstract
- In this work the solubility of a Ni-Al anode for MCFC has been studied at atmospheric pressure and two different temperatures using various gas compositions containing H-2/H2O/CO2. It is well known that nickel is dissolved at cathode conditions in an MCFC. However, the results in this study show that nickel can be dissolved also at the anode, indicating that the solubility increases with increasing CO2 partial pressure of the inlet gas and decreasing with increasing temperature. This agrees with the results found by other authors concerning the solubility of NiO at cathode conditions. The dissolution of Ni into the melt can proceed in two ways, either by the reduction of water or by the reduction of carbon dioxide.
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| 5. |
- Brown, Shelley, et al.
(författare)
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Cycle Life Evaluation of 3 Ah LixMn2O4-based Lithium-Ion Secondary Cells for Low-Earth-Orbit Satellites : II. Harvested Electrode Examination
- 2008
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Ingår i: Journal of Power Sources. - Amsterdam : ELSEVIER. - 0378-7753 .- 1873-2755. ; 185:2, s. 1454-1464
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-ion batteries area candidate for the energy storage system onboard low-earth-orbit satellites. Terrestrial experiments are able to capture the performance degradation of cells in orbit, therefore providing the opportunity for lifetime investigations. The lifetime performance of 3 Ah commercial LixMn2O4-based pouch cells was evaluated in a matrix of different cycling depths-of-discharge (DODs: 0, 20,40%) and temperatures (25, 45 degrees C). Aged cells were disassembled and the electrochemical performance of harvested electrodes investigated with two- and three-electrode pouch cells. The positive electrode had a larger decrease in capacity than the negative electrode. Both the positive and negative electrode contributed to the increase of cell impedance measured at high states-of-charge (SOCs). The data at low SOCs indicated that the increase of cell impedance was associated with the positive electrode, which showed a significant increase in the magnitude of the high-frequency semi-circle. This SOC-dependence was observed for cells cycled for either extended periods of time or at higher temperatures with a 40% DOD swing. Low-current cycling of positive electrodes revealed a change in the second potential plateau, possibly reflecting a structural change of the LixMn2O4. This could impact on the electrode kinetics and provide a possible explanation for the SOC-dependent change of the impedance.
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| 6. |
- Brown, Shelley, et al.
(författare)
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Cycle Life Evaluation of 3 Ah LixMn2O4-based Lithium-Ion Secondary Cells for Low-Earth-Orbit Satellites : I. Full Cell Results
- 2008
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 185:2, s. 1444-1453
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-ion batteries are a candidate for the energy storage system onboard low-earth-orbit satellites. Cycle life performance under both orbital and terrestrial conditions must be investigated in order to evaluate any inadvertent effects due to the former and the validity of the latter, with a successful comparison allowing for the extension of terrestrial experimental matrices in order to identify the effects of ageing. The orbital Performance of LixMn2O4-based pouch cells onboard the microsatellite REIMEI was monitored and compared with terrestrial experiments, with the cells found to be unaffected by orbital conditions. A lifetime matrix of different cycling depths-of-discharge (DODs: 0,20,40%) and temperatures (25, 45 degrees C) was undertaken with periodic reference performance tests. A decrease in both the cell end of-discharge cycling voltage and capacity was accelerated by both higher temperatures and larger DODs. Impedance spectra measured for all ageing conditions indicated that the increase was small, manifested in a state-of-charge dependent increase of the high-frequency semi-circle and a noticeable increase in the high-frequency real axis intercept. An evaluation of the change of both the resistance and capacity of 3 Ah cells led to the development of a potential prognostic state-of-health indicator. The use of elevated temperatures to accelerate cell ageing was validated.
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| 7. |
- Bryngelsson, Hanna, et al.
(författare)
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How dynamic is the SEI?
- 2007
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 174:2, s. 970-975
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Tidskriftsartikel (refereegranskat)abstract
- The surface chemistry of graphite and intermetallic AlSb has been studied by XPS (X-ray photoelectron spectroscopy) in a Li-ion battery context using LiPF6 in EC/DEC as electrolyte. The main results for graphite are as follows: the SEI (solid electrolyte interphase) is different for the lithiated state after 3 cycles (0.01 V) compared to the delithiated state (1.5 V); after 50 cycles the SEI is thicker; there are more Li2CO3 or semi-carbonates on the surface of the delithiated sample (1.5 V) than on the lithiated sample (0.01 V); LiF is continuously formed during the first cycles but a steady state is reached after 50 cycles; a new peak in the C 1s spectra indicating a fluorine-containing compound is found at high photon energies (292 eV). The main results for AlSb are as follows: the SEI is different for the lithiated state (0.01 V) compared to the delithiated state (1.2 V) after 3 cycles; after 50 cycles the surface layer thickness is slightly larger but significantly thinner than for graphite; contrary to graphite, more Li2CO3 or semi-carbonates are found on the surface of the lithiated sample; also here a new peak indicating a fluorine-containing compound is found in the C 1s spectra at 292 eV. The general result is that the SEI has many similar features between graphite and AlSb but also important differences. The carbonaceous layer is dynamically shifting in chemical composition during cycling for both samples.
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| 8. |
- Fleury, E., et al.
(författare)
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Fe-based amorphous alloys as bipolar plates for PEM fuel cell
- 2006
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 159:1, s. 34-37
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Tidskriftsartikel (refereegranskat)abstract
- Two compositions of Fe-based Fe50Cr18Mo8Al2Y2C14B6 and Fe44Cr15Mo14Y2C15B6N4 amorphous alloys were developed as alternative bipolar plate material for polymer electrolyte membrane fuel cell (PEMFC). In this paper, we present results of an investigation on the electrical, mechanical, corrosion properties and processing ability of these amorphous alloys. The combination of excellent properties indicated that Fe-based amorphous alloys could be potential candidate materials as bipolar plates in PEMFC.
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| 9. |
- Gustavsson, Marie, et al.
(författare)
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Thin film Pt/TiO2 catalysts for the polymer electrolyte fuel cell
- 2007
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 163:2, s. 671-678
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Tidskriftsartikel (refereegranskat)abstract
- Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3-6 mu g cm(-2)). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nation increases the performance compared to a Pt film deposited directly on Nation. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nalion and in addition, substantial proton conduction through the thin Ti02 layer. It is also shown that deposition order and the film thickness affects the performance.
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| 10. |
- Haraldsson, Kristina, et al.
(författare)
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Effects of Ambient Conditions on Fuel Cell Vehicle Performance
- 2005
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 145:2, s. 298-306
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Tidskriftsartikel (refereegranskat)abstract
- Ambient conditions have considerable impact on the performance of fuel cell hybrid vehicles. Here, the vehicle fuel consumption, the air compressor power demand, the water management system and the heat loads of a fuel cell hybrid sport utility vehicle (SUV) were studied. The simulation results show that the vehicle fuel consumption increases with 10% when the altitude increases from 0 m up to 3000 m to 4.1 L gasoline equivalents/100 km over the New European Drive Cycle (NEDC). The increase is 19% on the more power demanding highway US06 cycle. The air compressor is the major contributor to this fuel consumption increase. Its load-following strategy makes its power demand increase with increasing altitude. Almost 40% of the net power output of the fuel cell system is consumed by the air compressor at the altitude of 3000 m with this load-following strategy and is thus more apparent in the high-power US06 cycle.Changes in ambient air temperature and relative humidity effect on the fuel cell system performance in terms of the water management rather in vehicle fuel consumption. Ambient air temperature and relative humidity have some impact on the vehicle performance mostly seen in the heat and water management of the fuel cell system. While the heat loads of the fuel cell system components vary significantly with increasing ambient temperature, the relative humidity did not have a great impact on the water balance. Overall, dimensioning the compressor and other system components to meet the fuel cell system requirements at the minimum and maximum expected ambient temperatures, in this case 5 and 40 degrees C, and high altitude, while simultaneously choosing a correct control strategy are important parameters for efficient vehicle power train management.
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