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- Björnsson, Lars Henrik, 1984
(författare)
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Assessment of PHEV potential to reduce fuel use in Sweden using GPS data for car movements
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Roughly 30% of Sweden’s total greenhouse gas emissions originate from transport. These emissions need to be reduced to be able to reach the by The Swedish parliament adopted goal of a carbon neutral society in 2050. The plug-in hybrid electric vehicle (PHEV) allows for a major share of the fuel to be replaced by electricity from the grid and can thereby reduce greenhouse gas emissions, local pollutants, and energy insecurity. But the expected share of electric driving for a given battery size is dependent on the individual car’s movement. In this thesis we assess the potential to reduce fuel use in Swedish passenger car transport through an introduction of plug-in hybrid electric vehicles (PHEVs) by utilising a comprehensive data set on Swedish car movements logged by GPS.In paper I we analyse how individuality in movement patterns may affect the battery design and viability of PHEVs and enable electrification of vehicle kilometres in Sweden. We found that both optimal battery sizes and savings vary substantially between individual car movement patterns. As expected better economic conditions meant more cars with batteries, larger batteries and larger savings. Better charging options lead to a higher battery utilization and therefore to more cars viable as PHEVs and higher savings. We also found that the PHEV viability is dependent on the battery-capacity-independent investment cost, which if high can delay the introduction of PHEVs to the market. Due to good possibilities for recharging, regularity in movement pattern and in general higher yearly mileage, the commuters are on average reaching higher savings and their cars are in majority among the first to be viable as PHEVs. Therefore, commuters are likely to be the first drivers for whom the PHEV will be cost-effective. Paper II focuses on how different actors’ interest possibly could influence battery sizing and the resulting fleet TCO savings, electric drive fraction, and number of PHEVs. Our results suggest that different objectives among stakeholder could result in very different optimal battery sizes. Some interest can therefore be conflicting, while others can work together. The resulting fleet could for example reach a high share of PHEVs without reaching a high share of electric driving.The aim of paper III was to analyse the possibilities for regeneration in Swedish car driving. We found that the individual differences in energy use at the wheel and in braking power are large. Also the discrepancies in braking power profile between test cycles and real world driving were found to be considerable.
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| 2. |
- Björnsson, Lars Henrik, 1984
(författare)
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Car movement patterns and the PHEV
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Roughly 30% of Sweden’s total greenhouse gas emissions originate from transport and a majority of them from cars. The plug-in hybrid electric vehicle (PHEV) avoids the range limitation of the fully electric vehicle while still allowing for a major share of the fuel to be replaced by electricity from the grid and can thereby reduce greenhouse gas emissions, local pollutants and energy security concerns. The expected share of electric driving for a given battery size is however dependent on the individual car’s movement. In this thesis, the potential to reduce fuel use in Swedish passenger car transport through an introduction of PHEVs is assessed by utilizing a comprehensive data set on Swedish car movements logged by GPS.In paper I, we analyze how individuality in movement patterns may affect optimal battery design, economic viability and potential for fuel substitution. Both optimal battery sizes and savings are found to vary substantially between drivers. Commuters are found to be among the first to reach viability for PHEVs.In paper II we analyze how different objectives can affect optimal battery range, viability, savings and share of electric driving. Our results suggest that different objectives among stakeholders could result in different optimal battery sizes and that a high share of PHEVs in a vehicle fleet is not enough to ensure a high share of electric driving.In paper III we evaluate the relative benefit of a PHEV in comparison to a BEV in a two-car household. The results suggest that the BEV in general is economically favored over the PHEV in two-car households if the vehicle usage is optimized within the household. The difference in potential share of electric driving between a PHEV and a BEV is in general small.In paper IV we analyze the potential for brake energy regeneration in Swedish driving conditions. We find that city drivers have the highest potential to regenerate energy per km of driving, but long distance drivers have the largest potential to regenerate energy on a yearly basis. Also, extra energy gains from higher regeneration power capacity were found to fall off quickly.
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| 3. |
- Björnsson, Lars Henrik, 1984, et al.
(författare)
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Electrification of the two-car household: PHEV or BEV?
- 2017
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Ingår i: Transportation Research, Part C: Emerging Technologies. - : Elsevier BV. - 0968-090X. ; 85, s. 363-376
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Tidskriftsartikel (refereegranskat)abstract
- In previous works, we have shown two-car households to be better suited than one-car households for leveraging the potential benefits of the battery electric vehicle (BEV), both when the BEV simply replaces the second car and when it is used optimally in combination with a conventional car to overcome the BEV’s range limitation and increase its utilization. Based on a set of GPS-measured car movement data from 64 two-car households in Sweden, we here assess the potential electric driving of a plug-in hybrid electric vehicle (PHEV) in a two-car household and compare the resulting economic viability and potential fuel substitution to that of a BEV. Using estimates of near-term mass production costs, our results suggest that, for Swedish twocar households, the PHEV in general should have a higher total cost of ownership than the BEV, provided the use of the BEV is optimized. However, the PHEV will increasingly be favored if, for example, drivers cannot or do not want to optimize usage. In addition, the PHEV and the BEV are not perfect substitutes. The PHEV may be favored if drivers require that the vehicle be able to satisfy all driving needs (i.e., if drivers don’t accept the range and charge-time restrictions of the BEV) or if drivers requires an even larger battery in the BEV to counter range anxiety. We find that, given a particular usage strategy, the electric drive fraction (EDF) of the vehicle fleet is less dependent on whether PHEVs or BEVs are used to replace one of the conventional cars in two-car households. Instead, the EDF depends more on the usage strategy, i.e., on whether the PHEV/BEV is used to replace the conventional car with the higher annual mileage (“the first car”), the less used car (“the second car”), or is used flexibly to substitute for either in order to optimize use. For example, from a fuel replacement perspective it is often better to replace the first car with a PHEV than to replace the second with a BEV.
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| 4. |
- Björnsson, Lars Henrik, 1984, et al.
(författare)
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Objective functions for plug-in hybrid electric vehicle battery range optimization and possible effects on the vehicle fleet
- 2018
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Ingår i: Transportation Research, Part C: Emerging Technologies. - : Elsevier BV. - 0968-090X. ; 86, s. 655-669
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Tidskriftsartikel (refereegranskat)abstract
- While a hybrid electric vehicle (HEV) mainly runs on the same fuel as a conventional combustion engine, a plug-in hybrid electric vehicle (PHEV) has the potential to replace most of that fuel with electricity from the grid. Further, the driving-range limitations associated with a pure battery electric vehicle (BEV) do not apply to the PHEV. This makes the PHEV an interesting option for reducing greenhouse gas (GHG) emissions and local air pollutants as well as energy dependence, without sacrificing performance. However, how large fuel reduction that could be expected from PHEVs strongly depends on the battery range and driving and charging patterns (Björnsson and Karlsson, 2015). To maximize fuel reduction, battery capacity should be designed to reach a high share of electric driving. However, maximizing fuel reduction might not be the main objective for all stakeholders when optimizing battery range. Car owners could be more interested in reaching a low total cost of ownership (TCO), while manufacturers might focus on a battery range that suits as many potential buyers as possible. In this study, we analyze how the optimal battery range for the PHEV and the resulting vehicle fleet properties vary with the choice of objective function under various techno-economic conditions and policy options.
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| 5. |
- Björnsson, Lars Henrik, 1984, et al.
(författare)
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Plug-in hybrid electric vehicles: How individual movement patterns affect battery requirements, the potential to replace conventional fuels, and economic viability
- 2015
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 143, s. 336-347
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Tidskriftsartikel (refereegranskat)abstract
- Using GPS data logged for a representative sample of individual vehicles in private use, we assess the viability of plug-in hybrid electric vehicles (PHEVs) in Sweden for a wide range of techno-economic conditions. We determine requirements for PHEVs with the aid of a simple parameterization used to analyze the GPS data covering number of trips, driving distance per trip, and parking times, logged for 30 days or longer, for 432 conventional Swedish cars. Good opportunities for charging and regular distances traveled between rechargings increase the potential for battery-powered driving and, along with a high annual mileage, enhance the viability of the PHEV. Therefore, commuters are likely to be the first drivers for whom the PHEV will be cost-effective. Making charging infrastructure available at work places would enhance the opportunity for this group of early adopters, as we show that charging while at work is comparable at the-initial stage to halving the marginal battery costs for the average commuter.
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| 6. |
- Björnsson, Lars Henrik, 1984, et al.
(författare)
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The potential for brake energy regeneration under Swedish conditions
- 2016
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 168, s. 75-84
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Tidskriftsartikel (refereegranskat)abstract
- The ability to regenerate energy when braking is a valuable advantage of hybrid and fully electric vehicles. The regeneration potential mainly depends on how a car is driven and on the capacity of the drivetrain. Detailed studies of the regeneration potential based on brake energy in real-world driving are needed to better understand the potential gains of car-electrification, since test cycles do not take individual driving characteristics or route elevation into account. This study uses a model of a normalized vehicle and a highly detailed and representative data set of individual car movements including elevation to analyze the potential for energy regeneration in cars when driven under current real-world Swedish conditions.The ultimate energy regeneration potential (defined as the braking energy at the wheels) varies by about a factor of six among individual movement patterns, with an average of 0.033 kW h/km, corresponding to 27% of the total average energy supplied at the wheels. Earlier studies have shown a higher energy regeneration potential per km for cars driving under urban conditions with low average velocity and many starts and stops. Our results confirm this but also point out that a low average velocity and a high share of city driving are not very well correlated with the yearly energy savings; for this the yearly mileage is a more important indicator. This suggests that drivers who rack up the miles should be targeted as potential early adopters of regenerative technologies rather than city drivers per se. The results from real-world driving are compared to the NEDC and WLTP test cycles.
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