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- How do road grade, road type and driving aggressiveness impact vehicle fuel consumption? Assessing potential fuel savings in Lisbon, PortugalPublication . Faria, Marta; Duarte, Gonçalo; Varella, Roberto A.; Farias, Tiago; Baptista, PatriciaThe transportation sector contributes significantly to energy consumption with inherent consequences in terms of emission of local pollutants, which is associated with air quality deterioration. Considering that driving behavior significantly influences fuel consumption, this work goal was to assess how driving aggressiveness is influenced by the type of road and by the road grade, and consequently their impacts on fuel consumption. For that purpose, 47 drivers were monitored in the Lisbon Metropolitan Area during 6 months, allowing building an extensive 1 Hz real world driving database (similar to 33,000 trips, totalizing 28.9 million seconds). This database provided distinctive and representative data, allowing assessing the impacts on fuel consumption rates. Results showed that both road context and aggressive driving behavior impact fuel consumption rates significantly. However, for non-aggressive driving behavior fuel consumption rates increased more with road grade increments (up to 3 times) than for aggressive driving behavior (up to 2.3 times). Furthermore, this study results demonstrated that aggressiveness influences fuel consumption differently across road grades. Aggressiveness impacts are higher for lower road grades, with increased fuel consumption rates by up to 255%. The key findings associated to this research work are that aggressiveness on roads with lower grades tends to correlate with higher percent increase on fuel consumption for all speed ranges. Moreover, aggressiveness seems to correlate with higher fuel consumption on urban streets. Consequently, a reduction in driving under these conditions can offer significant savings in fuel consumption.
- Evaluation of technological solutions for compliance of environmental legislation in light-duty passenger: a numerical and experimental approachPublication . Taborda, A. M.; Varella, R. A.; Farias, T. L.; Duarte, GonçaloThis work includes an original approach that combines on-road experimental fuel use and emission maps and a numerical analysis to assess the impacts of fuel efficiency and NOx emission reduction technologies on a light-duty passenger vehicle. The solutions analyzed include Stop/Start, vehicle mass reduction up to 100 kg, drag coefficient reduction, as well as SCR and Lean NOx Trap systems. For this purpose, a reference EURO 6 diesel vehicle was monitored under real world driving conditions with a PEMS and the experimental data obtained allowed building engine maps of fuel use and NOx emission to be used on AVL Cruise software. The results obtained with Cruise were firstly validated with the experimental data (with errors up to 10,6% on fuel and 17,5% on NOx) and then the solutions implemented were tested individually and simulated on 48 real-world driving cycles. The results pointed to Stop/Start, mass reduction of 100 kg and SCR as the most effective solutions in reducing fuel consumption and NOx emission up to 14,6% and 57,5%, respectively, depending on driving context. The combination of these technologies was tested and the results showed maximum fuel savings of 17% on urban context and a maximum reduction of 58% on NOx on combined driving cycles. Despite all the efforts, real-world driving presents NOx emissions not yet compliant with standards, indicating the need for new strategies in order to face the environmental challenges.
- Engine cold start analysis using naturalistic driving data: City level impacts on local pollutants emissions and energy consumptionPublication . Faria, Marta; Varella, Roberto A.; Duarte, Gonçalo; Farias, Tiago L.; Baptista, PatriciaThe analysis of vehicle cold start emissions has become an issue of utmost importance since the cold phase occurs mainly in urban context, where most of the population lives. In this sense, this research work analyzes and quantifies the impacts of cold start in urban context using naturalistic driving data. Furthermore, an assessment of the influence of ambient temperature on the percentage of time spent on cold start was also performed. Regarding the impacts of ambient temperature on cold start duration, a higher percentage of time spent on cold start was found for lower ambient temperatures (80% of the time for 0 °C and ~50% for 29 °C). Results showed that, during cold start, energy consumption is >110% higher than during hot conditions while emissions are up to 910% higher. Moreover, a higher increase on both energy consumption and emissions was found for gasoline vehicles than for diesel vehicles. When assessing the impacts on a city perspective, results revealed that the impacts of cold start increase for more local streets. The main finding of this study is to provide evidence that a higher increase on emissions occurs on more local streets, where most of the population lives. This kind of knowledge is of particular relevance to urban planners in order to perform an informed definition of public policies and regulations to be implemented in the future, to achieve a cleaner and healthier urban environment.
- Assessment of wireless charging impacts based on real-world driving patterns: Case study in Lisbon, PortugalPublication . Duarte, Gonçalo; Silva, André; Baptista, PatríciaIn the current transition to a smarter and more efficient transportation system, battery electric vehicle mileage and the time required for charging are still two main constraints that need to be overcome to enable a larger penetration of electric vehicles. Moreover, the few charging stations available are a consequence of the "supply and demand" problem. Consequently, wireless dynamic recharging can be a complementary solution to address the problems of light-duty electric mobility and an added-value towards autonomous vehicles. Consequently, this paper presents an innovative approach based on real world mobility patterns collected for a sample in the city of Lisbon, Portugal, to assess users' electric vehicle feasibility by assessing different recharging scenarios, comparing stationary and dynamic recharging scenarios. The results indicate that at least 15 % more drivers would be eligible to own an electric vehicle if wireless charging was available. Moreover, wireless charging reduces the range of battery used, with stationary charging requiring circa 3.2 times more battery range. The developed approach confirms that wireless dynamic recharging can significantly change the framework of current electric mobility limitations, reducing range anxiety issues, contributing to redesign electric vehicle battery capacity and overcome barriers in stationary charging deployment and availability.
- Including engine data for energy and pollutants assessment into the vehicle specific power methodologyPublication . Mera, Zamir; Varella, Roberto; Baptista, Patrícia; Duarte, Gonçalo; Rosero Obando, FredyVehicle emission models are relevant for evaluating the performance of vehicle technologies and help in the definition of environmental policies. This paper presents an improved emissions modelling approach (named VSP+M) by combining the vehicle specific power (VSP) with load-regime engine maps for each VSP mode. The new modelling enabled to link tailpipe emissions to vehicle and engine operating conditions, obtained from real driving emission (RDE) tests and on-board diagnosis (OBD) data. The parameters for the sizing of engine maps were optimised by means of Pareto frontiers to solve the trade-off between the minimisation of RMSE and emission factor errors in urban sections and total RDE trips. The CO2 emission factors errors were reduced up to 63% and 45% for urban and RDE sections, respectively. The NOx emission factor errors were reduced up to 15%, maintaining the same RMSE levels. Optimal engine maps sizing was found for every tested vehicle and for each engine type to be applied in other vehicles. This study demonstrates the potential to address declinations of the conventional VSP model based on engine operation or proxies to those variables by using the proposed approach.
- Driving for decarbonization: Assessing the energy, environmental, and economic benefits of less aggressive driving in Lisbon, PortugalPublication . Faria, Marta; Duarte, Gonçalo; Varella, Roberto A.; Farias, Tiago; Baptista, PatriciaThis work assesses the impacts of aggressive driving behavior on pollutants emissions and energy consumption at a city level. Furthermore, it performs an economic analysis considering the potential avoided emissions and fuel savings and discusses potential policy measures to address this topic. The results showed that aggressive driving significantly impacts energy consumption and emissions, with energy consumption increasing by more than similar to 200% and emissions by 330% for aggressive driving compared to non-aggressive driving (in MJ/km and in g/ km, respectively). This increment was found to be even higher for diesel vehicles than for gasoline vehicles. On the contrary, gasoline vehicles showed higher percentages of increase for most emissions (CO, NOx and NO). Results also revealed that aggressive driving impacts are higher for local streets when examining the city level. Moreover, the economic analysis showed that significant cost reductions may be achieved by avoiding aggressive driving, reaching up to 52.5 k(sic) on a daily basis. In conclusion, this study is of particular relevance to policy makers and urban planners, enabling to obtain a comprehensive overview of the impacts of aggressive driving behaviors at a city level and providing new insights to perform further developments and to assess the feasibility of the implementation of policy measures.
- Energy assessment of a plug-in hybrid vehicle propulsion management systemPublication . Campino, Miguel; Henriques, Nuno; Duarte, GonçaloPlug-In hybrid vehicles have a complex propulsion system management, trying to manage the conventional and electric motorization in the most energy efficient way according to the driving dynamics, topography and battery charge state. In this sense, the aim of this work is to analyze the energy performance of plug-in hybrid vehicles, based on road tests, under real conditions of use, focusing on the management system of the two energy sources present, varying the level of battery charge at the start of the test to visualize the impact of this change. To complement the analysis and in order to better understand the operation of the management system, a methodology for applying the VSP parameter is used, which allows the load state to be approximated according to the vehicle’s operating mode, alternating between the three modes according to the conditions at the time in question, prioritizing the electric motor when the state of charge of the battery is maximum. These results confirm the fact that plug-in hybrid vehicles allow better electricity management due to the diversity of external or internal charging sources, which makes this type of vehicle more efficient and versatile than conventional hybrids, allowing a reduction in fossil fuel consumption and consequently a reduction in the emission of pollutant gases, making this type of vehicle a very competitive alternative in the transport sector in view of the current challenges due to the goals present in the current European regulations.
- Assessment of influential operational parameters in the mitigation of CO2 emissions in a power plant: case study in PortugalPublication . Balanuta, Vítor; Baptista, Patrícia; Carreira, Fernando; Duarte, Gonçalo; Casaca, Cláudia S. S. L.The European decarbonization goals and requirement for energy independence are mostly relying on intermittent renewable energy sources for electrification. A numerical model was developed to simulate the operation of a steam generator, allowing a study of the potential impacts of retrofitting existing coal-fired power plants to operate with biomass or coal–biomass mixtures on combustion parameters and CO2 emissions. The results obtained using the operational parameters of the Sines power plant indicate that a mixture of 25% coal and 75% pine sawdust allow operation at λ = 1.8, demonstrating that a small amount of coal allows operation near the coal combustion parameters (λ = 1.9). These conditions have the drawback of a reduction of 8.7% in adiabatic flame temperature but a significant reduction of 57.5% in CO2 emissions, considering the biomass as carbon-neutral.
- Comparison of portable emissions measurement systems (PEMS) with laboratory grade equipmentPublication . Varella, Roberto Aliandro; Giechaskiel, Barouch; Sousa, Luís; Duarte, GonçaloReal-driving emissions (RDE) testing with portable emissions measurement systems (PEMS) during the type approval and in-service conformity of light-duty vehicles was recently introduced in the European Union legislation. In this paper, three PEMS were compared with laboratory analyzers connected to the tailpipe and the dilution tunnel. The tests were conducted with two Euro 6 vehicles (one gasoline and one diesel) performing the World harmonized Light vehicles Test Cycle (WLTC) and a pre-recorded RDE cycle on a chassis dynamometer. The results showed that the differences of the PEMS gas analyzers compared to the laboratory references were typically within 2% for CO2 and 5% for NOx. The CO2 and NOx mass emissions were within 10% and 15%, respectively, with only a few exceptions. The exhaust flow rate measurements were within 10% at low speeds (urban conditions), and 5% at higher speeds. These results confirm the legislated permitted tolerances and the 2017 PEMS uncertainty estimates.
- Assessing electric mobility feasibility based on naturalistic driving dataPublication . Faria, Marta; Duarte, Gonçalo; Baptista, PatriciaIn a context where electric mobility is gaining increasing importance as a more sustainable solution for urban environments, this work presents an analysis of electric mobility feasibility and adequacy based on private users' naturalistic driving data. Several scenarios were tested to evaluate different charging event opportunities and their impacts on electric mobility feasibility. In more detail, scenario 1 considered that vehicles would recharge whenever they are stopped for 2, 4 or 6 h, either on weekdays or weekend days; scenario 2 tested the hypothesis of recharging only during the night period; and scenario 3 assumed that vehicles would recharge during the day on weekdays. Furthermore, the potential energy impacts of electric mobility at a city level, by applying a driver and street level approach, were also estimated. Results revealed that electric mobility is highly feasible for weekday urban trips, while weekend trips due to their higher average distance are less suitable to be performed by EVs. Scenario 1, due to its higher recharging opportunities was found to be the best-case scenario. In this case, the percentage of eligible trips was found to be equal to or higher than 94% and 88% on weekdays and weekend days, respectively. Results showed also the lower electric mobility feasibility if considering only daytime charging, on weekdays (scenario 3). However, if considering night charging (scenario 2), the electric mobility eligibility was found to improve significantly. When considering a street level analysis, the potential reduction in energy consumption ranges in average from −60 to −70%, enabling the visualization of higher EV potential, with increasing potential for reducing energy consumption for increasing road grades. Concluding, since electric mobility is particularly suited for urban driving and most households detain 2 or more vehicles, there is a high potential to replace at least one ICEV by an EV. In this case, people may adapt their driving behavior, using the EV for their day-to-day urban driving while the ICEV would be used for longer trips. Nonetheless, the capacity to recharge during night plays a significant role on trips eligibility. Therefore, the availability of home-charge set-ups or a much higher deployment of public charging stations at residential locations are required in order to incentivize drivers to shift towards electric mobility.