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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "C: Energy Economics and Policy".

Deadline for manuscript submissions: closed (31 March 2020) | Viewed by 39159

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Prof. Dr. Carla Silva

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Department of Geographic, Geophysic and Energy Engineering, Faculdade de Ciências, Universidade de Lisboa, Campo Grande 1749–016 Lisboa, Portugal
Interests: new fuels; biomass; biorefinery systems; alternative powertrains; alternative road vehicle simulation; system energy and emissions; life cycle assessment; indicators for sustainable mobility

Special Issue Information

Dear colleagues,

Cities have increased their goals of becoming smart, air pollution-free, carbon neutral, and energy self-sufficient. Citizens’ mobility plays a major role in the cities’ metabolisms, consuming more than 30% of the energy and generating heat, CO₂, and mostly PM2.5 and NOx regulated emissions. Car/bus exhaust aftertreatment devices increase unregulated emissions such as ammonia (NH₃) a PM2.5 precursor, and black carbon (which provokes local climate change phenomena by absorbing sunlight).

Solar energy and biofuels, from urban metabolism waste, together with public and shared transportation, could pave the way towards a more sustainable mobility system that helps to ensure smart city targets.

Latin American countries are enforcing their flex-fuel fleets and boosting sugar-cane/agriculture waste biorefineries for ethanol production. In Europe, the RED II agreement states that at least 14% of transportation fuel must come from renewable sources by 2030, crop-based biofuels cannot exceed 7%, and advanced biofuels must be at least 3.5% by 2030. Biorefineries from urban metabolism waste streams, e.g., solid urban waste/urban wastewaters, can be explored for transport-related material building blocks and advanced biofuels.

Papers are welcomed in the following areas:

Plug-in hybrid and pure electric bus systems simulation and monitoring of PM2.5, NOx, NH₃, and black carbon;
Ethanol hybrid ED95 bus and flex-fuel vehicles simulation and monitoring of PM2.5, NOx, and NH₃, and black carbon;
Shared mobility systems and evaluation of their success in supressing conventional private modes;
Low-cost sensor networks for traffic related air quality monitoring and historical trends;
Biorefinery systems for sustainable transportation (biopolymers and biofuels from waste resources);
Solar powered charging stations for e-mobility;
Well-to-wheels of alternative transport systems.

Prof. Dr. Carla Silva
Guest Editor

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Keywords

electricity
biogas
biodiesel
ethanol
hydrogen
plug-in hybrid
hybrid, flex-fuel engine
real-time monitoring networks

Published Papers (11 papers)

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Research

17 pages, 2858 KiB

Open AccessArticle

Ground Level Ozone Formation Near a Traffic Intersection: Lisbon “Rotunda De Entrecampos” Case Study

by Angelo Roldão Soares, Duarte Neto, Tiago Avelino and Carla Silva

Energies 2020, 13(7), 1562; https://doi.org/10.3390/en13071562 - 27 Mar 2020

Cited by 4 | Viewed by 2891

Abstract

Ground-level ozone in cities is increasing mainly due to traffic exhaust aftertreatment devices, i.e., tailpipe catalytic converters. The chemical reaction of O₃ formation indicates radiation and nitrogen oxides as main players. Thus, we investigate correlations between O₃, global radiation, nitrogen oxides, temperature, and precipitation in several periods of the year (2017) near a traffic roundabout in Lisbon city (coordinates 38°44’55’’ lat, −9°08’56’’ long). The weekend effect, school break versus school period, day and night, and seasonal effect were explored. Low-cost sensors (LCS) of O₃, NO_x, and temperature were tested to see if they can be used to get historical data on other cities and locations. The main innovation is the calibration of the sensor directly with real data (uncontrolled environment). Raw data were compared and led us to conclude that MQ-131 has a better performance than the MICS-4514 sensor. The results indicate that the diurnal cycle of ozone concentration has a mid-day peak around 1–2 pm and a lower nighttime concentration below 5 ppb Weekends and school break period (251 days a year) have the highest values of Ozone, this is due to lower NO_x emissions and thus lower levels of ozone destruction reaction (NO_x-titration reaction). August is a hotspot month with a maximum concentration of 71 ppb. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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12 pages, 3143 KiB

Open AccessArticle

Plug-in Electric Vehicles for Grid Services Provision: Proposing an Operational Characterization Procedure for V2G Systems

by Ângelo Casaleiro, Rodrigo Amaro e Silva and João Serra

Energies 2020, 13(5), 1240; https://doi.org/10.3390/en13051240 - 07 Mar 2020

Cited by 2 | Viewed by 2414

Abstract

Plug-in electric vehicles (PEVs) are expected to play a role as power grid ancillary service providers through vehicle-to-grid (V2G) chargers, enabling higher levels of renewable electricity penetration. However, to fully exploit the storage capacity of PEVs and fast responsiveness, it is crucial to understand their operational characteristics. This work proposes a characterization procedure for V2G systems providing grid services. It extends the existing literature on response time, AC/DC conversion and reactive power assessment. Illustrative results were obtained by implementing the procedure using a Nissan Leaf battery electric vehicle (BEV) connected to a remotely operated commercial V2G CHAdeMO charger. The V2G system was characterized as having a relative inaccuracy and variability of response inferior to 3% and 0.4%, respectively. Its average communication and ramping times are 2.37 s and 0.26 s/kW, respectively. Its conversion efficiency and power factor both showed degradation in the power values below 50% of the charger’s nominal power. Moreover, the proposed visualizations revealed that: i) the V2G system implements power requests for the DC power flow; ii) the power factor control algorithm was nonoperational; and iii) the acquired data can leverage statistical models that describe the operation of V2G systems (which is of extreme value for researchers and operators). Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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23 pages, 4181 KiB

Open AccessArticle

Variability in Measured Real-World Operational Energy Use and Emission Rates of a Plug-In Hybrid Electric Vehicle

by H. Christopher Frey, Xiaohui Zheng and Jiangchuan Hu

Energies 2020, 13(5), 1140; https://doi.org/10.3390/en13051140 - 04 Mar 2020

Cited by 21 | Viewed by 2717

Abstract

Compared to comparably sized conventional light duty gasoline vehicles (CLDGVs), plug-in hybrid electric vehicles (PHEVs) may offer benefits of improved energy economy, reduced emissions, and the flexibility to use electricity as an energy source. PHEVs operate in either charge depleting (CD) or charge sustaining (CS) mode; the engine has the ability to turn on and off; and the engine can have multiple cold starts. A method is demonstrated for quantifying the real-world activity, energy use, and emissions of PHEVs, taking into account these operational characteristics and differences in electricity generation resource mix. A 2013 Toyota Prius plug-in was measured using a portable emission measurement system. Vehicle specific power (VSP) based modal average energy use and emission rates are inferred to assess trends in energy use and emissions with respect to engine load and for comparisons of engine on versus engine off, and cold start versus hot stabilized running. The results show that, compared to CLDGVs, the PHEV operating in CD mode has improved energy efficiency and lower CO₂, CO, HC, NO_x, and PM_2.5 emission rates for a wide range of power generation fuel mixes. However, PHEV energy use and emission rates are highly variable, with periods of relatively high on-road emission rates related to cold starts. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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18 pages, 5131 KiB

Open AccessArticle

Exploratory Research of CO₂, Noise and Metabolic Energy Expenditure in Lisbon Commuting

by Angelo Soares, Cristina Catita and Carla Silva

Energies 2020, 13(4), 861; https://doi.org/10.3390/en13040861 - 16 Feb 2020

Cited by 8 | Viewed by 2651

Abstract

The lower cost of sensors is making possible the acquisition of big data sets in several applications and research areas. Indoor air quality and commuter exposure to pollutants are some of these areas, which can have impacts on our livelihood. The main objective of this exploratory research was to assemble portable equipment along with a prototype, one low-cost and easy to replicate in any location worldwide. We answer how CO₂, noise and energy expenditure compare in different transportation modes with indoor environments (metro, bus and car). It was intended to be carried by a subject on all commutes. The low-cost equipment assembled has the ability to measure ambient CO₂, noise levels, heart rate and geographic coordinates. The field campaign was conducted on an urban commuting route, in Lisbon city, between Rossio (downtown of Lisbon city) and Campo Grande (near FCUL campus). It took place during 3 weeks in school break and 3 weeks in the school period to grasp some differences between these periods of the year. The heart rate data was used to calculate the subject energy expenditure and the geographic coordinate data allowed for time and spatial analysis using a geospatial software package. Our measurements totaled 70 one-way trips and 358,140 data points. Temporal and spatial analysis yielded the following results: The metro presents the lowest median CO₂ concentrations of 693 ppm and the bus the highest with 1085 ppm. The bus had an equivalent continuous sound average (L_eq) of 75 dBA, while the metro had 85.2 dBA. Based on the metabolic equivalent of task (MET) calculations, the metro displays the least sedentary behavior, while the bus presents the most sedentary behavior with up to 96.5% of its commute spent in this classification. The metro was the fastest mode of transportation based on the consistency of its travel times compared to the bus, which despite also being consistent, was slower by 1.8 times. The car measurement values reside in the middle of the metro and bus results. Despite this, it is considered the worst mode of transportation, as it goes against the idea of a less congested and clean city. It also has a highly variable commuting time, which sometimes makes it slower than the metro, especially during the school period. According to our results, we concluded that the metro had efficient indoor ventilation while the bus did not. There were several instances of inefficient ventilation with concentrations exceeding 1000 ppm, particularly between Restauradores and Saldanha due to overcrowding. Referring to the health impacts of noise, the metro dBA levels are not sustained for enough time to have any measurable negative impact. Sensor performance was considered acceptable for the CO₂ sensor. The dBA and heart rate (HR) sensors were considered acceptable to sometimes irregular in nature, which was expected and taken into consideration. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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18 pages, 2633 KiB

Open AccessArticle

Development and Assessment of an Over-Expanded Engine to be Used as an Efficiency-Oriented Range Extender for Electric Vehicles

by F. P. Brito, Jorge Martins, Francisco Lopes, Carlos Castro, Luís Martins and A. L. N. Moreira

Energies 2020, 13(2), 430; https://doi.org/10.3390/en13020430 - 16 Jan 2020

Cited by 6 | Viewed by 3218

Abstract

A range extender (RE) is a device used in electric vehicles (EVs) to generate electricity on-board, enabling them to significantly reduce the number of required batteries and/or extend the vehicle driving range to allow occasional long trips. In the present work, an efficiency-oriented RE based on a small motorcycle engine modified to the efficient over-expanded cycle, was analyzed, tested and simulated in a driving cycle. The RE was developed to have two points of operation, ECO: 3000 rpm, very high efficiency with only 15 kW; and BOOST: 7000 rpm with 35 kW. While the ECO strategy was a straightforward development for the over-expansion concept (less trapped air and a much higher compression ratio) the BOOST strategy was more complicated to implement and involved the need for throttle operation. Initially the concepts were evaluated in an in-house model and AVL Boost^® (AVL List Gmbh, Graz, Austria), and proved feasible. Then, a BMW K75 engine was altered and tested on a brake dynamometer. The running engine proved the initial concept, by improving the efficiency for the ECO condition in almost 40% in relation to the stock engine and getting well over the required BOOST power, getting to 35 kW, while keeping an efficiency similar to the stock engine at the wide open throttle (WOT). In order to protect the engine during BOOST, the mixture was enriched, while at ECO the mixture was leaned to further improve efficiency. The fixed operation configuration allows the reduction, not only of complexity and cost of the RE, but also the set point optimization for the engine and generator. When integrated as a RE into a typical European light duty vehicle, it provided a breakthrough consumption reduction relatively to existing plug-in hybrid electric vehicles (PHEVs) in the market in the charge sustaining mode. The very high efficiency of the power generation seems to compensate for the loss of efficiency due to the excess electricity production, which must be stored in the battery. The results indicate that indeed it is possible to have an efficient solution, in-line with the electric mobility sustainability paradigm, which can solve most of the shortcomings of current EVs, notably those associated with batteries (range, cost and charging time) in a sustainable way. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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19 pages, 3273 KiB

Open AccessArticle

Evaluation of the Brake’s Performance Dependence Upon Technical Condition of Car Tires as a Factor of Road Safety Management

by Olga Orynycz, Karol Tucki, Andrzej Wasiak, Robert Sobótka and Arkadiusz Gola

Energies 2020, 13(1), 9; https://doi.org/10.3390/en13010009 - 18 Dec 2019

Cited by 13 | Viewed by 3830

Abstract

The social cost, as one of the factors determining sustainability of socio-economic development, is strongly dependent upon a number of casualties and mortality in road accidents. The condition of car tires appears to be one of the important factors determining the occurrence of accidents. The vast majority of vehicles are tested every year at vehicle inspection stations. One of the elements affecting the result of the technical condition test and basically the quality of vehicle braking is the technical condition of the tires. Their technical condition is a very important factor responsible for the quality of acceleration, braking, maintaining, or changing the direction of driving. As a consequence, it has a significant impact on road safety. The aim of the study is to examine the impact of tires on the results of tests performed at a vehicle inspection station. The study presents the results of bench measurements of the impact of selected features of tire condition of two vehicles during routine periodic inspections at a vehicle inspection station (VIS). The focus was on an attempt to assess the impact of inflation pressure, age, and tire tread wear on the braking process. The technical studies performed might be a source for legal steps assuring better management of road safety. It can also be expected that the tire choice and condition may affect fuel consumption, and therefore the amount of energy consumed by the road transport. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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20 pages, 11157 KiB

Open AccessArticle

Solar Glare Vulnerability Analysis of Urban Road Networks—A Methodology

by Paula Redweik, Cristina Catita, Frederico Henriques and Alexandre Rodrigues

Energies 2019, 12(24), 4779; https://doi.org/10.3390/en12244779 - 14 Dec 2019

Cited by 5 | Viewed by 3179

Abstract

Solar glare on roads is responsible for momentaneous deterioration of a driver’s view, interfering with driving capacity and causing accidents. The situation of a driver being affected by solar glare on a road is a spatial-temporal variable, since it depends not only on the time of the day and the day of the year, which are determinant for the local Sun position (temporal factors), but also on the local slope and azimuth of the road in the driven direction (spatial factors). The present work describes a method for producing road glare maps along a road network, as well as retrieving glare information from urban roads so that solar glare vulnerability can be easily accessed. Input data are a 1m resolution Digital Surface Model from Light Detection and Ranging data and the road network. Spatial parameters are processed in a Geographic Information System environment. The Urban Glare Algorithm detects glare and outputs temporal matrices and glare maps. Shadows cast by buildings and trees are considered as well as the driver’s eyes height. The method is tested in an area of Lisbon (Portugal). This work is a contribution to road safety systems implementation and constitutes a relevant basis for warning drivers of glare through car navigation systems. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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17 pages, 1302 KiB

Open AccessArticle

Life Cycle Costing and Eco-Efficiency Assessment of Fuel Production by Coprocessing Biomass in Crude Oil Refineries

by Pedro L. Cruz, Diego Iribarren and Javier Dufour

Energies 2019, 12(24), 4664; https://doi.org/10.3390/en12244664 - 08 Dec 2019

Cited by 13 | Viewed by 4143

Abstract

Biobased liquid fuels are becoming an attractive alternative to replace, totally or partially, fossil ones in the medium term, mainly in aviation and long-distance transportation. In this regard, coprocessing biomass-derived feedstocks in conventional oil refineries might facilitate the transition from the current fossil-based transport to a biobased one. This article addresses the economic and environmental feasibility of such a coprocessing strategy. The biomass-based feedstocks considered include bio-oil and char from the fast pyrolysis of lignocellulosic biomass, which are coprocessed in fluid catalytic cracking (FCC), hydrocracking, and/or cogasification units. The assessment was based on the standardized concept of eco-efficiency, which relates the environmental and economic performances of a system following a life-cycle approach. Data from a complete simulation of the refinery process, from raw materials to products, were used to perform a life cycle costing and eco-efficiency assessment of alternative configurations of the coprocessing strategy, which were benchmarked against the conventional fossil refinery system. Among other relevant results, the eco-efficiency related to the system’s carbon footprint was found to improve when considering coprocessing in the hydrocracking unit, while coprocessing in FCC generally worsens the eco-efficiency score. Overall, it is concluded that coprocessing biomass-based feedstock in conventional crude oil refineries could be an eco-efficient energy solution, which requires a careful choice of the units where biofeedstock is fed. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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22 pages, 2159 KiB

Open AccessFeature PaperArticle

The Development of Electromobility in Poland and EU States as a Tool for Management of CO₂ Emissions

by Karol Tucki, Olga Orynycz, Antoni Świć and Mateusz Mitoraj-Wojtanek

Energies 2019, 12(15), 2942; https://doi.org/10.3390/en12152942 - 31 Jul 2019

Cited by 60 | Viewed by 4972

Abstract

The article analyzes the dynamics of the development of the electromobility sector in Poland in the context of the European Union and due to the economic situation and development of the electromobility sector in the contexts of Switzerland and Norway. On the basis of obtained data, a forecast was made which foresees the most likely outlook of the electric car market in the coming years. The forecast was made using the creeping trend method, and extended up to 2030. As part of the analysis of the effect of the impact of electromobility, an original method was proposed for calculating the primary energy factor (PEF) primary energy ratio in the European Union and in its individual countries, which illustrates the conversion efficiency of primary energy into electricity and the overall efficiency of the power system. The original method was also verified, referring to the methods proposed by the Fraunhofer-Institut. On the basis of all previous actions and analyses, an assessment was made of the impact of the development of the electromobility sector on air quality in the countries studied. Carbon dioxide tank-to-wheels emission reductions which result from the conversion of the car fleet from conventional vehicles to electric motors were then calculated. In addition to reducing carbon dioxide emissions, other pollutant emissions were also calculated, such as carbon monoxide (CO), nitrogen oxides (NO_x) and particulate matter (PM). The increase in the demand for electricity resulting from the needs of electric vehicles was also estimated. On this basis, and also on the basis of previously calculated primary energy coefficients, the emission reduction values have been adjusted for additional emissions resulting from the generation of electricity in power plants. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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18 pages, 3124 KiB

Open AccessArticle

Global Warming Potential of Biomass-to-Ethanol: Review and Sensitivity Analysis through a Case Study

by Rui Pacheco and Carla Silva

Energies 2019, 12(13), 2535; https://doi.org/10.3390/en12132535 - 01 Jul 2019

Cited by 39 | Viewed by 5363

Abstract

In Europe, ethanol is blended with gasoline fuel in 5 or 10% volume (E5 or E10). In USA the blend is 15% in volume (E15) and there are also pumps that provide E85. In Brazil, the conventional gasoline is E27 and there are pumps that offer E100, due to the growing market of flex fuel vehicles. Bioethanol production is usually by means of biological conversion of several biomass feedstocks (first generation sugar cane in Brazil, corn in the USA, sugar beet in Europe, or second-generation bagasse of sugarcane or lignocellulosic materials from crop wastes). The environmental sustainability of the bioethanol is usually measured by the global warming potential metric (GWP in CO₂eq), 100 years time horizon. Reviewed values could range from 0.31 to 5.55 gCO₂eq/L_ETOH. A biomass-to-ethanol industrial scenario was used to evaluate the impact of methodological choices on CO₂eq: conventional versus dynamic Life Cycle Assessment; different impact assessment methods (TRACI, IPCC, ILCD, IMPACT, EDIP, and CML); electricity mix of the geographical region/country for different factory locations; differences in CO₂eq factor for CH₄ and N₂O due to updates in Intergovernmental Panel on Climate Change (IPCC) reports (5 reports so far), different factory operational lifetimes and future improved productivities. Results showed that the electricity mix (factory location) and land use are the factors that have the greatest effect (up to 800% deviation). The use of the CO₂ equivalency factors stated in different IPCC reports has the least influence (less than 3%). The consideration of the biogenic emissions (uptake at agricultural stage and release at the fermentation stage) and different allocation methods is also influential, and each can make values vary by 250%. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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14 pages, 2535 KiB

Open AccessArticle

Exploring the Introduction of Plug-In Hybrid Flex-Fuel Vehicles in Ecuador

by Danilo Arcentales and Carla Silva

Energies 2019, 12(12), 2244; https://doi.org/10.3390/en12122244 - 12 Jun 2019

Cited by 6 | Viewed by 2909

Abstract

In Europe, diesel combustion is being banned due to the NO_x and PM_2.5 emissions impact on air quality. The bus sector is being electrified and is increasing its use of alternative fuels, such as natural gas (in spark ignition engines) and bioethanol (in compression ignition engines), to reduce such harmful emissions. Even if a diesel bus is equipped with selective catalytic reduction (SCR), its NO_x emissions are reduced its but produces more NH₃ emissions that are PM_2.5 precursors. In developing countries, the air quality is still barely monitored, however, the air quality issue is well known and is being addressed. Moreover, the Ecuadorian sugar cane industry is seeking ways to increase its ethanol production. This is the ideal framework to explore a new technology and energy source in developing economies such as Ecuador. This paper explores the impact of the Ecuadorian diesel bus fleet conversion to hybrid compression ignition ethanol (HEV-ED95), hybrid diesel and plug-in hybrid flex-fuel using electricity and internal combustion engine ICE-E20 and ICE-E100. The impacts are measured in terms of final energy consumption, criteria pollutant emissions (NH₃, NO_x, PM_2.5) and 100 years global warming potential in a well-to-wheels framework. For the tank-to-wheels data the method follows the typical values of conversion efficiency from final to useful energy (cross checked with a microsimulation model), the Tier 2 European Environmental Agency approach combined with ethanol influence on compression ratio, lower heating value, criteria emissions taken from a literature review, and well-to-tank emission factors for electricity (10–58% thermal natural gas or coal powerplant contribution), for ethanol from banana industry wastes (ED95, E20 and E100), gasoline and diesel from US databases. A discussion on whether sugarcane biorefineries are necessary is highlighted in the results. All input parameters have an uncertainty range between a minimum and a maximum and the probability for each is giving by a uniform distribution. Full article

(This article belongs to the Special Issue Smart Mobility and Energy Transitions)

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