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A probabilistic fleet analysis for energy consumption, life cycle cost and greenhouse gas emissions modelling of bus technologies
Abstract
Introducing alternative bus fleet technologies requires investigation into life cycle impacts, risks and benefits. Previous modelling approaches comparatively assess individual vehicle energy demands and life cycle impacts, assuming alternative technologies can fulfil identical life cycle functions to a diesel baseline. This assumption neglects the influence that service frequency, capacity and range limitations have on daily operations and fleet and infrastructure sizing. The goal of this study was to develop a framework to investigate bus fleet operation in terms of the risk and uncertainty of an alternative drivetrain technology’s ability to mitigate life cycle costs and greenhouse gas emissions. Probabilistic simulation enabled risk and uncertainty quantification of diesel, micro-hybrid, mild-hybrid and battery-electric fleet scenarios for a UK case study. The fleet analysis approach revealed decreased potential to reduce life cycle costs and greenhouse gas emissions from battery-electric buses. Compared to a baseline single-deck diesel fleet at low risk levels, the micro-hybrid double-deck fleet delivers the largest life cycle cost savings (18.7%). The largest life cycle greenhouse gas emissions savings come from the mild-hybrid lithium-titanate single-deck fleet (20.8%). Double-deck micro and mild hybrid fleets are the most effective at saving both life cycle costs and greenhouse gas emissions. The modelling approach adds a novel probabilistic capability for making comparative fleet-wide assertions, supporting the decision-making process for implementing new sustainable fleet technologies.
... Regarding environmental aspects, LCC analysis serves as an important tool to evaluate the vehicle utilization impact on GHG emissions [21]. The total amount of GHG emissions is calculated based on four aspects, including: ① well-to-tank (WTT) emissions, which represents the electricity delivery from the source to the bus energy storage system; ② tank-to-wheel (TTW) emissions, which comprises energy conversion and distribution inside the bus, where the TTW stage is emission-free for a battery EB recharged from the grid; ③ glider emissions, which includes bus production, maintenance, and recycling processes; and ④ powertrain emissions, which consists of motor, battery, and electronics production. ...
... For buses of the same type, the schedule is the same. The objective function is shown in Eq. (21), which ensures that minimizing the bus fleet size is equivalentto minimizing the number of schedules covered by each bus. Eq. (22) ensures that each trip is covered in the optimal schedule plan. ...
Despite rapid advances in urban transit electrification, the progress of systematic planning and management of the electric bus (EB) fleet is falling behind. In this research, the fundamental issues affecting the nascent EB system are first reviewed, including charging station deployment, battery sizing, bus scheduling, and life-cycle analysis. At present, EB systems are planned and operated in a sequential manner, with bus scheduling occurring after the bus fleet and infrastructure have been deployed, resulting in low resource utilization or waste. We propose a mixed-integer programming model to consolidate charging station deployment and bus fleet management with the lowest possible life-cycle costs (LCCs), consisting of ownership, operation, maintenance, and emissions expenses, thereby narrowing the gap between optimal planning and operations. A tailored branch-and-price approach is further introduced to reduce the computational effort required for finding optimal solutions. Analytical results of a real-world case show that, compared with the current bus operational strategies and charging station layout, the LCC of one bus line can be decreased significantly by 30.4%. The proposed research not only performs life-cycle analysis but also provides transport authorities and operators with reliable charger deployment and bus schedules for single-and multi-line services, both of which are critical requirements for decision support in future transit systems with high electrification penetration, helping to accelerate the transition to sustainable mobility.
... Nordelöf et al. (2019) [18] have studied the life cycle carbon emission level of city buses, which is found to be dependent on the degree of electrification, electricity supply mix and choice of diesel or hydrogenated vegetable oil for average operation in Sweden, the European Union and the United States of America. Harris et al. (2020) [29] have estimated the GHG emissions of buses with different technologies in the UK and revealed the decreasing potential to reduce GHG emissions from BEBs. Other determinants of the carbon emission difference between BEBs and FFBs have been discussed by many more scholars [30][31][32][33][34][35]. ...
... Many scholars (e.g., [36][37][38][39][40][41][42]) have studied the costs or benefits of bus electrification for BEBs to replace FFBs. Moreover, some other scholars (e.g., [17,25,29,[43][44][45]) have evaluated both the economic characteristics of bus electrification and the corresponding emission reduction, to analyse the advantages of BEBs or FFBs in different countries. To discuss the relation between the cost of bus electrification and the corresponding emission reduction in a unified system, Xu [24], to evaluate the economic value of carbon emission reduction of bus electrification on the perspective of direct carbon emissions. ...
The economic value of carbon emission reduction in the electrification of buses is of concern in practical and academic fields. The aim of this paper, which focuses on direct and indirect carbon emissions, is to study the economic value of the carbon emission reduction of bus electrification in an operational lifecycle carbon footprint, with the empirical data sourced from the bus electrification in Macau. First, it proposes the methodology to evaluate the operational lifecycle carbon value of bus electrification (OLCVBE). Second, it analyses the distinct impacts of internal determinants on OLCVBE. Third, it discusses the determinants’ characteristics for OLCVBE. The results indicate that (1) OLCVBE may be a carbon debt, but it is not a carbon asset in some situations; (2) OLCVBE is determined by the carbon emission coefficients of both electric power and fossil fuel, buses’ electric or fossil fuel consumption levels, buses’ terminations, carbon price and discounted rate; and (3) as a comparison, electric power’s embedded carbon emission coefficient has the biggest impact on OLCVBE, then carbon price and the electric consumption have the second or third biggest impacts, and the annual driving distance of buses has relative less impact. This paper provides a new perspective to study the economic and environmental effects of bus electrification.
... The current high level of air pollution worldwide is an undeniable phenomenon. Among the various causes, the transportation sector is one of the largest contributors to the increase in greenhouse gas levels and other pollutants in ambient air [1]. Emissions from internal combustion engine (ICE) vehicle exhausts during the operational phase of vehicles are particularly significant, even though the environmental impact of the transportation sector begins with prior phases, which are the extraction of materials and the manufacturing of transportation equipment [2], [3]. ...
Substituting diesel technology with eco-technologies in public buses is one of the prominent efforts being made to achieve a sustainable transportation system goal. Among these eco-technologies, commonly used ones include electric vehicles, natural gas fuel, hydrogen fuel, and bio-diesel fuel technology. However, the performance comparison between these technologies in reducing environmental impact at each location where they are implemented remains unanswered by previous studies. Research to measure the effectiveness of each of the eco-technologies in reducing environmental issues has been conducted extensively, employing various methods and metrics. This study conducted a systematic review of 94 articles that met the predefined inclusion criteria to obtain performance comparisons among these technologies. As a result, a general trend has been observed that eco-technologies have successfully achieved their intended goals with various success rates, although electric bus technology has advantages over other technologies based on the articles. However, its effectiveness relies on specific aspects to optimize its environmental performance. Therefore, the suitability of implementation in a region will depend on many factors. This article contributes to determining the extent to which eco-technologies are implemented in buses worldwide, serving as a consideration for decision-makers, and identifying research gaps in this topic.
... Vehicle fleet data are biased due to partial information on vehicle fleet characteristics, driving behavior, and vehicle movements and mileage [89]. Alternative bus fleet research evaluates individual characteristics of vehicles, neglecting the frequency of service, daily operating constraints, and fleet size [90]. Various models have been used to forecast the development of electric transport technologies. ...
Diverse measures related to the electrification of transport fleets have been implemented in many countries due to the increasing consumption of fossil fuels and their negative impact on the climate and human health. Such transformation is effective if electric energy is sourced from renewable sources. The rate of transport electrification is determined mainly by legislative and financial incentives, charging infrastructure density, and fuel price. The main aims of the study are to present financial support for investments in low-emission transport infrastructure and to provide forecasts of the fleet of urban electric buses and the expected demand for electricity consumed by them in Poland. The main source of data was statistical reports published by Statistics Poland. Because the available sample was short, basic statistical models were used. The results obtained indicate the stable growth of investments in regional low-emission transport infrastructure, characterized by strong heterogeneity. The foreseen number of electric buses in urban public transport in the realistic variants ranges between 1486 and 1626. In the optimistic variants, the forecast values are significantly higher. However, they can only be achieved if there is a significant increase in investment. The electricity demand forecast for the realistic variant shows a demand of 341,266.50 MWh.
... An LCC analysis for investments in public buses presents a main challenge given the issues with identifying the end-of-life costs for electric buses. Previous studies investigating LCC for electric buses assumed no residual value or overlooked the problem (Harris et al., 2020;Lajunen, 2014Lajunen, , 2018Nurhadi et al., 2014;Bor en, 2020). The only study we retrieved that provides insight into how to account for these costs, Yusof et al. (2021), suggests that the impact of end-of-life costs on total LCC is irrelevant. ...
Purpose
With more cities aiming to achieve climate neutrality, identifying the funding to support these plans is essential. The purpose of this paper is to exploit the present of a structured green bonds framework in Sweden to investigate the typology of abatement projects Swedish municipalities invested in and understand their effectiveness.
Design/methodology/approach
Marginal abatement cost curves of the green bond measures are constructed by using the financial and abatement data provided by municipalities on an annual basis.
Findings
The results highlight the economic competitiveness of clean energy production, measured in abatement potential per unit of currency, even when compared to other emerging technologies that have attracted the interest of policymakers. A comparison with previous studies on the cost efficiency of carbon capture storage reveals that clean energy projects, especially wind energy production, can contribute to the reduction of emissions in a more efficient way. The Swedish carbon tax is a good incentive tool for investments in clean energy projects.
Originality/value
The improvement concerning previous applications is twofold: the authors expand the financial considerations to include the whole life-cycle costs, and the authors consider all the greenhouse gases. This research constitutes a prime in using financial and environmental data produced by local governments to assess the effectiveness of their environmental measures.
... (Xu et al., 2015) showed the relevance of local geographical and operating condition when assessing the overall impact of current and incoming alternative fleets. The same applies for public transport service characteristics, such as frequency or capacity of the transit unit (Harris et al., 2020). Lastly, (McKenzie and Durango-Cohen, 2012) indicates how the purchase of clean-fuel buses, instead of traditional ones, come at both emission savings and an increase in investment costs (both for vehicles and charging infrastructures). ...
... Some studies employed real-world urban bus fleets to simulate the adoption of various technologies scenarios, with the primary objective of evaluating fleet's energy consumption, environmental impact, and lifecycle costs (Harris et al., 2018(Harris et al., , 2020Mohamed et al., 2017;Teoh et al., 2018). Previous studies have also established scenarios for the long-term effects of electrifying bus fleets, which incorporated different assumptions about various energy and environmental parameters in the future (Correa et al., 2017;Lotfi et al., 2020). ...
The electrification of public transit is one of the key actions in the transportation sector. This study proposed an innovative framework for analyzing the effectiveness and emission reduction potential of electrifying transit policies. The future energy consumption, GHG emissions, and pollutant emissions of bus fleets in representative Canadian cities were analyzed. Under the high oil price scenarios, this study incorporated the upfront infrastructure costs, the social costs of pollution, and the dynamics of carbon prices and fuel prices, allowing for a comprehensive analysis of carbon reduction costs during transition. Compared to the BAU scenarios, the cumulative GHG emissions from 2019 to 2030 of bus fleet in ESD scenarios in Toronto, Montreal, Edmonton, and Halifax had a reduction of 18.7 %, 30.1 %, 21.3 % and 34.6 %, respectively. The findings have implications for the trade-off management of climate policies at the provincial level and can help understand polycentric governance from multiple resource perspectives.
... A. Jagiełło (2021) notices that the operating costs of conventional and electric buses are most often examined in the light of total cost of ownership (TCO) or life cycle cost (LCC) which makes it possible to compare the operating costs of different types of buses in terms of vehicle costs, maintenance, operation and decommissioning, but it does not take into account the non-cost differences in operation between electric and conventional buses such as passenger capacity or level of technical readiness. Similarly, A. Harris et al. (2020) criticise a conventional vehicle-by-vehicle comparison between conventional and electric buses pointing out that it "neglects the influence that passenger capacity and range limitations have on fleet and infrastructure sizing, underestimating capital costs and greenhouse gas emissions of these phases". Hence, a broader view of electric bus implementation in the context of the entire given transport system is needed. ...
Transport activities are a significant factor in environmental pollution, especially in cities. Therefore, measures aimed at electrification of public transport are particularly important. The aim of the paper is to present the origins, status and development dynamics of electromobility in Polish cities, especially the second generation of electromobility, i.e. vehicles that do not require continuous connection to the energy source. In practice the second-generation electric vehicles can be identified with battery-powered vehicles, hydrogen and hybrid vehicles. The study was prepared on the basis of an analysis of literature, industry documents or development strategies. In addition, a database of information on zero- and low-emission vehicles in public transport (i.e. electric and hybrid buses) was compiled to analyse the phenomenon. The study shows that the implementation of electromobility in Poland has already emerged from the initial phase. The possibilities for developing battery technology vary in cities of different sizes. In 2021 in Poland, the share of low-emission buses in the public transport fleet was several times higher than that of electric vehicles among passenger vehicles. It is most likely that the Polish road to electromobility leads primarily through public transport. The following factors influencing the development of electromobility were identified: these were primarily EU and Polish legislation and regulations, the presence of manufacturers of rolling stock and electrotechnical equipment, and – at the local scale – organisational, economic and social issues.
... The literature on the subject also raises the following objections regarding the use of TCO and LCCA analyses to compare the costs of DBs and BEBs [48][49][50][51]: Some of the analyses do not take into account the need to operate a larger fleet of BEBs than DBs (due to the limited range of vehicles). Analyses often neglect service frequency, capacity, and range. ...
The electrification of public transport is an overwhelming trend, representing the first step in the energy transition of the transport sector. The transport sector is characterized by the prevalence of public ownership and the significant influence of the public sector. Accordingly, tendering procedures are widely utilized to identify the most efficient bus delivery options. This paper compares, evaluates, and identifies the differences in criteria used in tenders for battery electric buses and diesel buses in Poland based on a deep bus market analysis supported by in-depth individual interviews. The article also attempts to determine whether the weight of the “vehicle price” criterion corresponds to the share of the vehicle price in its life cycle cost or total cost of ownership. The results indicate no significant difference in the tender criteria between battery electric buses and diesel buses. In the vast majority of cases, institutions that had previously developed diesel bus acquisition patterns transferred these patterns to tenders for battery electric bus purchases. Therefore, the criteria and their weights used in tenders do not consider the advantages and disadvantages of both technologies. Tendering procedures are adapted to local conditions and operational requirements. Electric buses often replace conventionally powered vehicles on existing routes and schedules. Thus, operational requirements are known. As a result, the necessary number of vehicles and the basic technical and operational parameters (e.g., selection of the optimal charging method and battery capacity) can be determined. In turn, the charging method will influence the total cost of ownership, with overnight charging favored for shorter assignments and opportunity charging favored for longer mileages.
... (Xu et al., 2015) showed the relevance of local geographical and operating condition when assessing the overall impact of current and incoming alternative fleets. The same applies for public transport service characteristics, such as frequency or capacity of the transit unit (Harris et al., 2020). Lastly, (McKenzie and Durango-Cohen, 2012) indicates how the purchase of clean-fuel buses, instead of traditional ones, come at both emission savings and an increase in investment costs (both for vehicles and charging infrastructures). ...
In the last decade, the concept of ‘cohesion’ has become increasingly important to study the distributional effects of infrastructure investment between different population groups, i.e., social cohesion, or between different zones inside a study area, i.e., territorial cohesion. Nevertheless, despite a growing interest, in the literature there is still a lack of consolidated methodologies and guidelines to assess the impacts on cohesion of transport infrastructure. In the attempt to bridge up this gap, this paper proposes a method based on the estimation of zonal accessibility variations as proxy for the effectiveness of the investment, and on statistical indices estimating accessibility dispersion as a proxy for the territorial cohesion. Two case studies are presented: the completion of the High-Speed Rail (HSR) line between Turin–Venice (Northern-Italy) and the construction of the new HSR line between Naples and Bari (Southern-Italy). The application shows that the investment in the more industrialized and densely populated areas of North Italy turns out to be more effective in terms of accessibility improvement than in less developed Southern ones. However, while the former increases inequalities in terms of accessibility and risks to amplify the gap between North and South of the Country, the latter (Naples–Bari) tends to reduce such disparities.KeywordsTransport equity assessmentAccessibilityGini index
... In addition to the investment costs for vehicles and infrastructure, the crew costs for drivers are the main cost component in public transport. Thus, in their probabilistic comparison of the life-cycle costs of different technologies at the fleet level, Harris et al. [21] observe that driver costs are the highest cost component in all scenarios. ...
Approach to solve the integrated electric vehicle and crew scheduling problem. • Influence of vehicle and crew scheduling on the design of electric buses. • Comparing electric bus concepts taking into account local conditions. • Case study investigation for a real-world bus route. • Most cost-effective electric bus concept depends on the crew scheduling assumptions. A R T I C L E I N F O Keywords: Public transportation Electric bus Depot and opportunity charging Integrated vehicle and crew scheduling Adaptive large neighborhood search Total cost of ownership A B S T R A C T Encouraged by international efforts to reduce greenhouse gases and local emissions, many public transport operators are converting their fleets to battery-powered electric buses. Public transport operators can choose between different electric bus concepts, with the total cost of ownership being the most important decision criterion. The associated strategic decisions regarding charging strategy, vehicle concept, and charging infrastructure have a significant impact on the operational planning of the electric buses. Motivated by this, this paper aims to analyze the interactions between electrification and operational planning , especially vehicle scheduling and crew scheduling. This allows us to make a more comprehensive comparison of different electrification concepts. Prior work has addressed the impact of electrification on vehicle scheduling but has neglected the interactions with crew scheduling. Crew scheduling dominates operational costs and planning for many public transport operators and must therefore be considered in all strategic decisions. For this reason, in this work we focused on integrated electric vehicle and crew scheduling problem. This allows us to calculate the total cost of ownership of different electric bus concepts under better representation of local conditions. We deal with the electric vehicle and crew scheduling problem with a metaheuristic based on Adaptive Large Neighborhood Search. We tested the developed methodology for a real-world bus route. Our results indicate that the constraints for crew scheduling significantly impact the total cost of ownership and the required number of vehicles of the different electrification concepts. Our case study suggests that the choice of the most cost-effective concept depends significantly on crew scheduling constraints. These findings imply that crew scheduling constraints should be considered as part of the local framework for bus fleet electrification.
... Additionally, while comparing alternatively powered HGVs on an individual basis is a necessary first step, we assume in this work that the alternative powertrains assessed can replace current fleets in a likefor-like manner. In reality this may not be the case, as factors such as refuelling schedules, fleet capacity and route frequency may have an impact on fleet composition [105] . A full fleet analysis would again provide stakeholders with improved insights into the differences between conventional HGV fleets and alternative powertrains. ...
Uncertainty surrounding the total cost of ownership, system costs, and life cycle environmental impacts means that stakeholders may lack the required information to evaluate the risks of transitioning to low-carbon fuels and powertrains. This paper assesses the life cycle costs and well-to-wheel environmental impacts of using electricity and electrofuels in Heavy Good Vehicles (HGVs) whilst considering input parameter uncertainty. The complex relationship between electricity cost, electrolyser capacity factor, CO2 capture cost and electricity emissions intensity is assessed within a Monte Carlo based framework to identify scenarios where use of electricity or electrofuels in heavy goods vehicles makes economic and environmental sense. For vehicles with a range of less than 450 km, battery electric vehicles achieve the lowest total cost of ownership for an electricity cost less than 100 €/MWh. For vehicles that require a range of up to 900 km, hydrogen fuel cell vehicles represent the lowest long-term cost of abatement. Power-to-methane and power-to-liquid scenarios become economically competitive when low-cost electricity is available at high-capacity factors and CO2 capture costs for fuel synthesis are below 100 €/tCO2; these fuels may be more applicable to decarbonise shipping and aviation. Battery electric HGVs reduce greenhouse gas emissions by 50% compared to the diesel baseline with electricity emissions of 350 gCO2e/kWh. Electricity emissions less than 35 gCO2e/kWh are required for the power-to-methane and power-to-liquid scenarios to meet EU emissions savings criteria. High vehicle capital costs and a lack of widespread refuelling infrastructure may hinder initial uptake of low-carbon fuels and powertrains for HGVs.
... Dessa maneira, soluções eficientes relacionadas a mobilidade urbana tem sido prioridade para muitas cidades para atingir objetivos de desenvolvimento sustentável. Por sua vez, os ônibus elétricos reduzem a poluição do ar local, a vibração e ruídos (LI, CASTELLANOS, MAASSEN, 2018;HARRIS et al., 2020;TARGINO et al., 2020). ...
O conceito de ‘smart city’ tem atraído o interesse da ciência, indústria e da sociedade nos últimos anos. As cidades inteligentes são caracterizadas pela implementação de tecnologias diversificadas para atender aos padrões de sustentabilidade e têm principalmente 6 critérios a serem considerados: pessoas, governo, economia, mobilidade, meio ambiente e vida. Este trabalho terá como foco a mobilidade, uma vez que é notável a crescente demanda por tecnologias avançadas e mais sustentáveis no transporte urbano, especialmente no que diz respeito à redução significativa nas emissões de gases de efeito estufa (GEE). Para um desenvolvimento sustentável adequado em uma cidade, é necessário planejar. A melhoria da qualidade de vida da população é consequência de práticas sustentáveis implementadas em ‘smart cities’. A cidade de Curitiba está localizada no sul do Brasil, desde os anos 70 é considerada como uma ‘smart city’, devido ao projeto pioneiro do sistema BRT (Bus Rapid Transit). Curitiba é referência mundial por seu planejamento urbano e iniciativas sustentáveis e inovadoras relacionadas à mobilidade urbana. Curitiba e comprometeu a introduzir ônibus de baixa emissão em sua frota para substituir o sistema BRT por híbrido-elétrico, com foco na redução de emissões de GEE e de sua energia sustentável. Como forma de contribuir para minimizar as consequências das mudanças climáticas, Curitiba tem enfrentado desafios para se tornar uma cidade cada vez mais sustentável e menos vulnerável aos efeitos climáticos. Portanto, para ser caracterizada como uma ‘smart city’, não se trata apenas de mudanças, mas de necessidades de planejamento. Este trabalho tem como foco a mobilidade, considerando fontes renováveis de energia para alimentar o transporte público urbano. Para um desenvolvimento sustentável adequado em uma cidade, é necessário planejar. A melhoria da qualidade de vida da população é consequência de práticas sustentáveis implementadas nas ‘smart cities’. Curitiba é uma das cidades que tem enfrentado os grandes desafios para se tornar uma cidade cada vez mais sustentável e menos vulnerável aos efeitos climáticos. Nesse cenário, o presente estudo visa analisar características do transporte público de Curitiba relacionado-o ao uso de fontes renováveis de energia. Considerando os padrões estabelecidos para ser caracterizada como ‘smart city’, Curitiba atende aos pré-requisitos necessários.
... This study is focused on the technical and the economical aspect of vehicle electrification. The economic aspect is crucial for evaluating a technology feasibility to penetrate the market [36]. If the technology is costly, it will face a significant challenge in penetrating the market despite its technical advantages [19]. ...
Recently, many countries have set the target for the automakers to sell only vehicles with zero tailpipe emissions in the future, like in Europe, the United Kingdom, as well as the United States of America, promoting a major shift towards electric vehicles globally. But the electric vehicles do have emissions during their entire life cycle, these emissions vary from country to country, depending mainly on their electricity generation mix. Moreover, considering the cost aspect, an Electric Vehicle with a driving range of 500 km costs way higher than an Internal Combustion Engine Vehicle offering twice the range. Hence, in this study, a numerical evaluation is done for conventional diesel, hybrid and electric sports utility vehicles, on real drive cycles in the six largest automotive markets, namely, China, United States of America, Europe, Japan, India and Brazil, to assess the degree of electrification suitable for lowest life cycle emissions and total cost of ownership in each country. The global results for diesel, hybrid and electric vehicles of life cycle CO2 emissions are 0.21–0.29 kg/km, 0.13–0.20 kg/km and 0.08–0.20 kg/km while for total cost of ownership are 0.21–0.33 €/km, 0.23–0.34 €/km and 0.37–0.47 €/km, respectively. Thus, although the long-range Electric Vehicles can be emitting lowest in few markets, its total cost of ownership will still be the highest.
... MPEG-7 technology, embedded DB technology, and synchronization technology can be effectively combined based on XML. Three specific core technologies based on XML are embedded in MPEG-7 database management technology, XML-based MPEG-7 document validation check technology, and MPEG-7 data synchronization technology [4]. In this paper, we develop and use MPEG-7 schema-based Smart Home digital contents management and operation system (SDCMOS: Smart Home Digital Contents Management and Operation System) to effectively process multimedia in a Smart Home environment by mixing these technologies [5]. ...
With the development of high-speed wireless LAN, the use of multimedia-type digital contents is increasing significantly even in the smart home environment. Therefore, it is very important to efficiently process and manage the use of digital content in the form of multimedia. In order to effectively process multimedia digital contents in the wireless LAN environment of a smart home, a server higher than the PC level is required. There is also a need for a support system that can exchange multimedia digital contents between clients of home appliances. Therefore, in this paper, we propose a Smart Home Digital Contents Management and Operation System (SDCMOS) that effectively processes and supports multimedia digital contents. This system is designed to effectively process real-time multimedia processing in home service in a wireless LAN environment. In addition, it was made possible to efficiently search multimedia information directly from the home server. SDCMOS is designed to be usable in fields such as biomedical image search, history museums, art exhibition halls, tourism information, geographic information, and e-commerce.
... In addition to all this, the increase in the demand for electricity generation to power the new electrified fleet of buses will be too high to be satisfied with the renewable energy generation supply [21,22]. Hence, it is especially important to do an overall life cycle analysis of each powertrain technology [23], considering all its relevant characteristics to assess its impact correctly [24,25]. Life cycle assessment for transportation sector can be found in the literature in large numbers [26,27]. ...
To control the global warming by ensuring the greenhouse gas emissions reduction of the automotive sector, the standards or norms are getting ever stricter globally, specifically in the past few years. In view of this, great emphasis is currently being given to the shift towards electric vehicles. However, it is very important to critically evaluate the overall life cycle of different powertrain technologies. In this study, such analysis has been carried out for the bus rapid transit networks in the 4 largest cities of Spain: Madrid, Barcelona, Valencia and Seville. Ten different lines were selected from each city and their driving-cycles were designed by extracting real time data from GPS used for simulating 3 different bus powertrains (diesel, hybrid and electric) for real-life results of the vehicles on each route. A life cycle analysis of the different bus configurations was done considering a wide perspective from manufacturing, use, maintenance to end-of-life stages, to compare the CO₂ footprints of the 3 evaluated powertrains using the database of the software GREET. The CO₂ footprints of the electric bus was also estimated for the years 2030 and 2050, using the predictions for cleaner electricity grids for future perspective. Compared to the standard diesel bus results, the overall results for hybrid and electric bus show 40% decrement and 30% increment of CO₂ well-to-tank emissions, respectively, 40% and 60% decrement of CO₂ life cycle emissions; 30% increment and 60% decrement of the buses’ driving range and, 2.5% and 30% addition in the life cycle cost
... The paper [4] provides a proper decision-making procedure regarding the process of replacing a diesel fleet with alternative-technology buses by using a deterministic mixed-integer programming model. The study [5] develops a framework to investigate the bus fleet operation risks by using probabilistic simulations. In the research [6], the problem of dispatching time control in rolling horizons is modeled, following a periodic optimization approach. ...
One of the main problems to be solved by the transport operators is the substantiation of the vehicle models servicing the transport lines. A game-theoretical approach is proposed in this paper to justify the bus model choice based on the passengers' preferences and the structure of the passenger flows. To estimate the customers' preferences, the membership functions for fuzzy sets of the optimal vehicle models were defined. The simulation experiment aiming to estimate the city fleet structure in terms of the vehicles' capacity was conducted for the Talas city (Kazakhstan) based on the proposed approach with the use of the corresponding software implementation of the developed mathematical models. As a result of the experimental studies, the impact of the passengers' flow structure and the number of carriers on the rational structure of the city bus fleet was studied in the paper. (online version) research is to determine the optimal carrier strategy (in terms of the choice of bus models) that guarantees the biggest possible market share.
... It is also conducive to realizing the unified quantification of heterogeneous energy. The life cycle (LC) theory can coordinate the economic benefits of each stage in the whole LC of the IES (Harris et al., 2020). This is beneficial in obtaining the full LC assessment of economic benefits in the planning process based on the LC theory. ...
Integrated energy system (IES) is of great significance in the construction of the modern energy system. Reasonable planning is one of the important means to improve the economy of the IES and promote the consumption of renewable energy. However, the complex coupling characteristics between energy sources make it difficult to quantify the production efficiency of multi-energy heterogeneous resources uniformly in the economic benefit model during the planning cycle. Quantifying the production efficiency of the IES for planning is currently an urgent problem to be solved. This study proposes a planning method for the IES based on the life cycle and emergy theory. First, emergy theory is applied to quantify the production efficiency of the IES. A complete economic benefit model is established based on life cycle theory. Second, a bi-level planning model of the IES is established. The upper-level model aims at minimizing the whole life cycle cost of the IES to plan the capacity and location of the coupling equipment. The lower-level model aims at maximizing the emergy yield ratio of the IES to provide the operating data for the upper level. Finally, comparing experimental evaluations with traditional planning schemes considering annual average cost and energy quality coefficient, the method in this study reduces planning costs by 23.16% and increases the consumption rate of renewable energy by 4.26%. It can be seen that the planning method proposed in this study improves the planning economy and the level of renewable energy consumption of the IES.
... Fast charging can be used with a special pantograph, the design of which allows the driver to connect the vehicle to the power supply safely without leaving the vehicle. Moreover, there is also a wireless solution-inductive charging [61]. Unfortunately, fast charging requires the bus schedule to allow for sufficient charging time in certain locations [22]. ...
The development of urban transport in recent years has become one of the most important issues related to improving the quality of life in Polish cities. Excessive pollution in the form of greenhouse gases and other harmful substances from buses affects people’s health as does the excessive noise. This article analysed the measures being taken to reduce emissions, and the results showed that it is possible to reduce CO2 emissions by more than 28 thousand megagrams (Mg) per annum. Policymakers in Poland should consider limiting electricity generation through coal combustion and recognize, at least temporarily, CNG/LNG-powered buses as low-carbon rolling stock and co-finance their purchase and the necessary infrastructure.
... However, such methods have not been widely applied in the development of buses. The majority of publications on electric buses study and compare the lifecycle costs and GHG emissions of Battery-Electric Buses against Diesel and Hybrid powertrains and discuss the potential of using alternative powertrain technologies [28][29][30]. Due to the high costs of the battery technology and charging infrastructure, other studies [31][32][33] investigate the influence of the battery size, charging method such as depot and opportunity charging, on costs and analyze the optimal vehicle and charging schedules [34,35]. ...
Autonomous electric buses (AEB) have widely been envisioned in future public transportation systems due to their large potential to improve service quality while reducing operational costs. The requirements and specifications for AEBs, however, remain uncertain and strongly depend on the use case. To enable the identification of the optimal vehicle specifications, this paper presents a holistic design optimization framework that explores the impacts of implementing different AEB concepts in a given set of routes/network. To develop the design optimization framework, first, a multi-objective, multi-criteria objective function is formulated by identifying the attributes of bus journeys that represent overall value to the stakeholders. Simulation models are then developed and implemented to evaluate the overall performance of the vehicle concepts. A genetic algorithm is used to find the concepts with the optimal trade-off between the overall value to the stakeholders and the total cost of ownership. A case study is presented of a single bus line in Singapore. The results show an improvement in the waiting time with the use of a smaller sized AEB with a capacity of 20 passengers. However, the costs and emissions increase due to the requirement of a larger fleet and the increase in daily distance traveled compared to a 94-passenger capacity AEB.
... The second major contribution of this study is to apply the LCXM model framework in the current economic context of an urban bus service provider in California as a case in point. Urban transit bus fleets have received considerable attention in the transportation literature as well as in the urban planning and policy-making communities [8,27,28]. Relying on recent measurements of cost and operational performance per bus in the provider's fleet as well as real-time protocols for bus dispatches to routes served, this study specifically contrasts the life-cycle cost of battery-electric buses with that of diesel buses. While the former entail a substantially higher acquisition cost, they result in a lower life-cycle cost compared to diesel buses, provided the annual utilization rate is at least around 1300 hours, with the exact cut-off depending on the characteristics of the particular route served. ...
Comprehensive global decarbonization requires that transportation services cease to rely on fossil fuels for power generation. This paper develops a generic, time-driven life-cycle cost model for mobility services to address two closely related questions central to the emergence of clean energy transportation services: (i) the utilization rates (hours of operation) that determine how alternative drivetrains rank in terms of their cost, and (ii) the cost-efficient share of clean energy drivetrains in a vehicle fleet composed of competing drivetrains. The model compares alternative drivetrains with different environmental and economic characteristics in terms of their life-cycle cost for any given duty cycle. The critical utilization rate that equates any two drivetrains in terms of their life-cycle cost is shown to also provide the optimization criterion for the efficient mix of vehicles in a fleet. This model framework is then calibrated in the context of urban transit buses, on the basis of actual cost-and operational data for an entire bus fleet. In particular, our analysis highlights how the economic comparison between diesel and battery-electric transit buses depends on the specifics of the duty cycle (route) to be served. While electric buses entail substantially higher upfront acquisition costs, the results show that they obtain lower life-cycle costs once utilization rates exceed only 20% of the annual hours, even for less favorable duty cycles. At the same time, the current economics of the service profile examined in our study still calls for the overall fleet to have a one-third share of diesel drivetrains.
This study aims to examine the expansion of the electric vehicle fleet in the context of transport electrification in the European Union. We assessed the car market, following demand and sales trends for electric and hybrid cars. It was explored the possibility of a causal relationship among the percentage of BEV + PHEV in the total fleet and purchasing power, loading infrastructure, government support, the level of education and the degree of digitalization. To achieve the main objectives of the research to assess the existence and magnitude of the causal effects of the considered variables on the percentage of BEV + PHEV in the total fleet, we conducted a cross-sectional analysis in 2020 among the European Union (EU) countries. Five research hypotheses were formulated and tested. The results confirmed that the economic and social development of a region, the charging infrastructure, the government support measures, and the degree of digitalization positively influence the desire of the EU population to buy electric cars.
We study optimal degree of bus system electrification for Stockholm’s longest high-frequency bus line. We evaluate the welfare effects of opportunity and depot charging fleet configurations with batteries charged during dwell times at terminal stations or during the operating pause in the bus depot, respectively. Electric buses (e-buses) significantly reduce carbon and health damaging emissions of transit services. However, e-buses are presently not welfare improving, because their lower external costs do not offset the higher supply costs (e.g., capital cost of charging infrastructures and batteries). Instead, we find that optimising bus fares and frequencies and road pricing is more effective in improving social welfare and carbon emissions. E-buses significantly reduce surplus of bus operators, which thus are reluctant to adopt these technologies without direct public support. Sensitivity analysis shows that: (i) technological developments to substantially reduce capital costs can make e-buses perform well from a social welfare perspective; (ii) efficiency gains obtained in the operation of the service, e.g., by optimizing on-board conditioning systems, but also bus routing and driving style, can have a greater impact on the cost performance of e-bus fleet configurations than simply reducing capital costs. An argument for e-buses is the efforts in coordinating a transition to electrified vehicles, aiming at reducing the risk of futile investments in charging infrastructure.
Intelligent transportation systems enhance the potential for sustainable, user-friendly, and efficient transport. By eliminating driver costs, autonomous buses facilitate the redesign of networks, timetables, and fleet structure in a cost-effective manner. The electrification of bus fleets offers the opportunity to further improve the environmental sustainability of transportation networks, but requires adjustments to vehicle schedules due to the limited range and charging requirements. This paper examines the intricate relationship between electrification and autonomous buses. To this end, timetables for autonomous electric buses of different sizes were developed for a real bus route in Aachen, Germany. The resulting electric vehicle scheduling problem was then solved using an adaptive large neighborhood search to determine the number of vehicles needed and the total cost of ownership. By eliminating driver costs, vehicles with lower passenger capacity become much more attractive, albeit at a slightly higher cost. In comparison, the incremental costs of electrification are low if the right approach is taken. Fluctuations in typical passenger numbers can be used to modify timetables and vehicle schedules to accommodate the charging needs of autonomous electric buses. In particular, electric bus concepts with fewer charging stations and lower charging power benefit from adapting the timetable to passenger numbers. The results demonstrate that the specific requirements of electric buses should be considered when adapting networks and timetables in order to design a sustainable transport network.
With the accelerating electrification of public transit systems, the number of electric buses (EBs) in China has increased substantially. The operation management of EBs is of great significance for reducing the carbon emissions of the public transit system. Herein, we firstly introduce the development history of EBs in China and Western countries, and summarize the existing issues in the EB operation management in practice. Then a framework of EB operation management is proposed, and current studies are summarized from the perspectives of energy consumption estimation, vehicle scheduling, energy-efficient driving, resource allocation and benefit evaluation. We point out the techniques and methods down the road on EB operation management. Finally, the challenges are systematically summarized. We conclude that the future works that need to be focused on include: electric bus network planning, battery life estimation based on actual data, intelligent scheduling, and adoption of new power supply and charging modes.
This Working Group III contribution to the IPCC Sixth Assessment Report provides a comprehensive and transparent assessment of the literature on climate change mitigation. The report assesses progress in climate change mitigation options for reducing emissions and enhancing sinks. With greenhouse gas emissions at the highest levels in human history, this report provides options to achieve net zero, as pledged by many countries. The report highlights for the first time the social and demand-side aspects of climate mitigation, and assesses the literature on human behaviour, lifestyle, and culture, and its implications for mitigation action. It brings a wide range of disciplines, notably from the social sciences, within the scope of the assessment. IPCC reports are a trusted source for decision makers, policymakers, and stakeholders at all levels (international, regional, national, local) and in all branches (government, businesses, NGOs). Available as Open Access on Cambridge Core.
This paper aims to analyze overall economic and environmental performances of alternative bus powertrains by focusing on U.S. active fleets in different urban contexts. We define a life cycle cost model related to bus technologies by referring to real-world data of 256 transport operators, which provide more than 80% of total vehicle revenue miles produced by urban transit mode across the U.S. in 2019. The proposed method includes some service parameters that significantly affect the supply cost (e.g., service speed, annual mileage), on which we perform scenario and sensitivity analysis. Results show that electric buses are cost-competitive in large cities and metropolises, where urban bus routes are characterized by a high level of congestion, high service frequency, and the highest marginal impact of harmful emissions. In towns and suburban areas, where bus routes are longer and faster, full electric technology still faces both economic and technical barriers.
Sustainable fleet management seeks to deliver the best service with a standard of service defined by state regulatory bodies by utilizing and managing large fleets of vehicles in the most efficient, productive, and cost-effective way. Public transport service providers thus seek alternative ways to minimize cost as well as air pollution and carbon emissions from the transportation sector. This study develops a total cost of ownership (TCO) framework for evaluation of different alternative fuel options (diesel, compressed natural gas [CNG], and electric) for bus public transportation based on real-world driving conditions. Electric, CNG, and diesel buses are compared from the life cycle perspective by quantifying a set of sustainability indicators including global warming potential, particulate matter formation, human health impacts, and TCO. According to the results, it was found that TCO of electric buses is less than that of diesel and CNG buses. Specifically, TCO of electric buses is 15% less than that of diesel buses, and compared with CNG it is 5% less over a period of 10 years of use. The proposed framework provides a quantitative basis for a sustainable fleet management approach for public bus service providers.
This paper examines the impact of geographical location on the energy consumption of double deck battery electric buses operating in four UK cities. By considering seasonal variation in ambient temperature and an assumed battery degradation process, the implications on operational cost and carbon emissions were investigated. Using a MATLAB/Simulink model the total energy demand of a vehicle operating on the UKBC was simulated. Energy consumption was combined with hourly seasonal averages of carbon intensity (gCO2/kWh) and wholesale electricity costs (£) to assess charging at different times of the day and year. At the beginning of life, the range could decrease by up to 17.3% due to heating load requirements. From beginning of life to end of life, range was predicted to decrease by up to 26%. Whilst the average operational costs are relatively consistent across the four regions, the average carbon emissions can be five times higher depending on location.
The energy consumption supervision is required for each smart home to ensure the highest power quality and to enhance the stability of the whole grid. In this paper, a various-goal energy management system is proposed to arrive at a compromise solution for smoothing the smart home power profile, reducing the electricity bill (E.B) and obtaining a free charging of Plug-in Electric Vehicles (PEVs) from home and renewable energy sources (RES). This control has been structured into two hierarchical layers. The first aims to maintain an appropriate balance of the Photovoltaic Generator (PVG) power that is scattered into three essential paths: home, vehicles and grid. The second destinates to coordinate the PEVs charging/discharging modes from and to the smart home. Both optimization layers of the proposed framework are executed using Particle Swarm Optimization (PSO) algorithm. Four scenarios are presented in different seasons with different demand profiles, different electricity prices and illuminations in north Africa, and different PEVs connections states. The simulation results have demonstrated the obtention of smooth home power profiles. As well, the inhabitant can achieve a total daily bill reduction of 26% in autumn, 15.57% in winter, 31.68% in summer and 25% in spring including almost a free charging of PEVs which prove the efficiency of the proposed strategy.
Alternatives to conventional diesel engines in medium/heavy-duty commercial trucks offer promising solutions to decarbonize road freight. We compare the life cycle greenhouse gas (GHG) emissions from diesel, battery electric (BEV) and hydrogen fuel cell (FCV) medium-duty urban delivery trucks (gross vehicle weight 3.5 – 7 metric tonnes) in Singapore, including the vehicle and fuel production, use phase and end-of-life stages. Use phase energy demand was estimated by simulating energy consumption on local real-world driving cycles. BEVs powered by the 2019 electricity mix had up to 11% lower GHG emissions than conventional diesel, but doubling battery capacity to meet travel range requirements resulted in up to 12% higher emissions. FCVs using gaseous hydrogen via steam methane reforming achieved 23 – 30% GHG reductions while satisfying range requirements. Efforts in obtaining updated and reliable data on vehicle production remain critical for assessments of emerging technologies and enacting evidence-based policies to decarbonize road freight.
Energy consumption, economic growth, and eco-environment protection of urban agglomeration is full of contradictions and continues to be challenges faced by decision makers. It is desired to develop effective methods to realize coordinated management of energy economy and eco-environment nexus (EEEN) system. In this study, a copula-based stochastic multi-level programming (CSMP) approach is first developed, where the conflicting objectives with multiple hierarchical levels and the uncertainty presented as random variables with different probability distributions can be tackled. CSMP can also reflect the complex interactions among random variables and examine the risk of violating joint-probabilistic constraints. The CSMP is then applied to planning EEEN system of Pearl River Delta (PRD) urban agglomeration (China) during the period of 2021–2035. Six scenarios based on joint and individual risk levels for violating energy consumption and GDP constraints are analyzed. Results reveal that the share of tertiary industry and high-tech industry would attain to 62.4% and 14.9% by 2035, the energy and CO2 intensity would decrease by 45.1% and 56.9%, and ecological land would expand to absorb more CO2, indicating that EEEN system would develop towards energy saving, economy and eco-environment friendly pattern. Results also disclose that decisions at high risk level would lead to high GDP, energy consumption and CO2 emissions, occupy ecological land and reduce CO2 absorption, and reduce the reliability of fulfilling system requirements.
Globally, many cities are seeking to meet their greenhouse gas (GHG) reduction targets in urban transport systems. Several strategies have been proposed for this sector, such as battery-electric buses (BEBs), and today numerous companies and cities are transitioning to greener bus fleets. However, the global adoption of electric buses is limited in large scale due to some implementation barriers. This analysis focuses on scholarly research and reports that present case studies, interviews with the interested parties and preliminary results of BEBs implementation for public transport. A casual loop diagram (CLD) and an analysis of the dimensions of sustainability were developed pointing out implications for behavioral patterns. The discussion here addresses general barriers (technological, financial and institutional), impacts on the power grid, energy consumption, fleet operation, fire safety and people’s willingness to pay, and summarizes the experiences and lessons learned from real-world implementation. The article’s most significant recommendations for the successful use of BEBs in cities are new protocols to facilitate financing and contracting, support for institutional innovation policies and the construction of facilities. The findings are useful to both researchers and policymakers.
Buses account for almost 60% of the total public transport services in Europe, and most of the vehicles are diesel fuelled. Regional transport administrators, under pressure by governments to introduce zero-emission buses, require analytical tools for identifying optimal solutions. In literature, few models combine location analysis, least cost planning, and emission assessment, taking into account multiple technologies which might achieve emission reduction goals. In this paper, an existing optimal location model for electric urban transport is adapted to match the needs of regional transport. The model, which aims to evaluate well-to-wheel carbon emissions as well as airborne emissions of NO x and PM10, is applied to a real case study of a regional bus transport service in North Eastern Italy. The optimization has identified electric buses with relatively small (60 kWh) batteries as the best compromise for reducing carbon equivalent emissions; however, under current economic conditions in Italy, the life cycle cost of such vehicles is still much higher than those of Euro VI diesel buses. In this context, our model helps in identifying ways to minimize infrastructure costs and to efficiently allocate expensive resources such as electric buses to the routes where the maximum environmental benefit can be achieved.
Learning from first experiences of battery-electric bus (E-bus) trials is important to facilitate uptake and develop effective public policy. Here we present initial E-bus trials in Oslo and use the case to 1) model total cost of ownership (TCO) of E-buses vs. diesel buses, and 2) discuss challenges, opportunities, and policy implications. Together, this yields a holistic analysis of requirements for speeding up E-bus adoption, spanning operators and policymakers. Results revealed that rapid E-bus roll-out was achieved through successful contract change order use combined with authority support to reduce operator risk. Challenges were encountered surrounding technical issues, climatization energy use and infrastructure establishment in dense urban areas. In addition, urban E-bus TCO is currently high, and since operation is mostly tender controlled with investment costs covered, higher costs must be covered by public budgets. Despite challenges, operators are positive to further E-bus use, suggesting that companies are willing to support innovation when financial risk is low. We expect E-bus operation to become competitive to diesel buses in Oslo by 2025; to facilitate adoption before economic parity, municipalities and transport authorities must continue to play a large role. Further regulation is also urgently needed to facilitate common infrastructure planning and development.
Electromobility is a vital tool in reducing the environmental impact of transportation. A technologically mature means of public transport is the trolleybus. Based on a case study of the Polish cities of Gdynia and Sopot, this paper explores the factors that influence the development of the trolleybus system. Recent developments of in-motion charging (IMC) technology are analysed what provides a new analytical framework for the trolleybus development, bringing the original path for the expansion of the electromobility in urban areas without overhead lines. The use of an economic model has made it possible to assess the total lifecycle costs of trolleybuses and to specify a threshold that makes it more cost-effective than diesel buses. Operational data allows for a simulation that reveals the minimal rate of catenary coverage of a route in terms of speed and two charging power values. Results indicate that after including external costs into the economic calculation, trolleybus transport is economically efficient, although the energy mix is an important factor. In-motion charging trolleybus can be seen as a compromise solution between capital costs and battery capacity and is recommended for cities already operating this system.
Stabilizing greenhouse gas (GHG) concentrations will require large-scale transformations in human societies, from the way that we produce and consume energy to how we use the land surface. A natural question in this context is what will be the .transformation pathway. towards stabilization; that is, how do we get from here to there? The topic of this chapter is transformation pathways. The chapter is primarily motivated by three questions. First, what are the near-term and future choices that define transformation pathways, including the goal itself, the emissions pathway to the goal, technologies used for and sectors contributing to mitigation, the nature of international coordination, and mitigation policies? Second, what are the key characteristics of different transformation pathways, including the rates of emissions reductions and deployment of low-carbon energy, the magnitude and timing of aggregate economic costs, and the implications for other policy objectives such as those generally associated with sustainable development? Third, how will actions taken today influence the options that might be available in the future? As part of the assessment in this chapter, data from over 1000 new scenarios published since the IPCC Fourth Assessment Report (AR4) were collected from integrated modelling research groups, many from large-scale model intercomparison studies. In comparison to AR4, new scenarios, both in this AR5 dataset and more broadly in the literature assessed in this chapter, consider more ambitious concentration goals, a wider range of assumptions about technology, and more possibilities for delays in additional global
The life cycle cost (LCC) methodology provides understanding of economic aspects of urban buses equipped with different types of propulsion. The LCC analysis delivers the sum of costs related to the acquisition, operation, repair and maintenance disposal as well as the costs for the each bus power train technology. The method allows to take into account all costs for the whole vehicle's life cycle and creates a precondition for precise information database for decision making. In addition to the economic factors LCC can be extended to environmental aspects such as greenhouse gases emissions. The environmental impacts of the vehicle lifetime may be presented in monetary values. The paper presents the Life Cycle Cost analysis undertaken for urban buses fitted with conventional, series hybrid and parallel hybrid drives. Provided LCC analysis includes the economic and environmental aspects. The paper also delivers the evaluation of the total air pollutant emissions for all stages of lifetime of the each analysed urban bus. The results show that the hybrids have slightly lower life cycle cost than conventional bus. Moreover, hybrid buses were found to have lower life cycle environmental impacts.
As a major part of public transportation system, bus transit has been regarded as an effective mode to alleviate the traffic congestion and solve vehicle emission problem. The performance of bus transit system depends largely on its design of proper stop locations. In this research, we proposed a multi-period continuum model (peak hour and off-peak hour) to optimize the design of a bus route for four different vehicle types (i.e., supercharge bus, Compressed Natural Gas (CNG) bus, Lithium-ion battery bus, and diesel bus) considering driving regimes and the pollutant cost. Inter-stop driving regimes, including acceleration, cruising, coasting, and deceleration, are explicitly introduced into the optimization to determine whether and how the coasting regime should be undertaken in the tradeoff between vehicle’s commercial speed and the operating cost. The comparison for the cost effectiveness of each alternative has been investigated in a life span with respect to different vehicle types. The method has been implemented in the real-world bus route 7 in Yaan City (China). The numerical experiments suggest that through optimization, the total system cost has been saved by more than 50%. The results of continuum model are validated by the comparison with the discretized results, and the outcomes are closely located in neighborhood (with error less than 3%). The life-cycle cost of four vehicle types is finally analyzed, and the result indicates that due to the high purchase prices, it’s difficult for clean-energy buses to outperform conventional buses in a life cycle (normally 8 years), unless with subsidies provided.
Uncertainty in operation factors, such as the weather and driving behavior, makes it difficult to accurately predict the energy consumption of electric buses. As the consumption varies, the dimensioning of the battery capacity and charging systems is challenging and requires a dedicated decision-making process. To investigate the impact of uncertainty, six electric buses were measured in three routes with an Internet of Things (IoT) system from February 2016 to December 2017 in southern Finland in real operation conditions. The measurement results were thoroughly analyzed and the operation factors that caused variation in the energy consumption and internal resistance of the battery were studied in detail. The average energy consumption was 0.78 kWh/km and the consumption varied by more than 1 kWh/km between trips. Furthermore, consumption was 15% lower on a suburban route than on city routes. The energy consumption was mostly influenced by the ambient temperature, driving behavior, and route characteristics. The internal resistance varied mainly as a result of changes in the battery temperature and charging current. The energy consumption was predicted with above 75% accuracy with a linear model. The operation factors were correlated and a novel second-order normalization method was introduced to improve the interpretation of the results. The presented models and analyses can be integrated to powertrain and charging system design, as well as schedule planning.
Background: Anthropogenic global warming, interacting with social and other environmental determinants, constitutes a profound health risk. This paper reports a comprehensive literature review for 1989–2013 (inclusive), the first 25 years in which this topic appeared in scientific journals. It explores the extent to which articles have identified potentially catastrophic, civilization-endangering health risks associated with climate change. Methods: PubMed and Google Scholar were primarily used to identify articles which were then ranked on a three-point scale. Each score reflected the extent to which papers discussed global systemic risk. Citations were also analyzed. Results: Of 2143 analyzed papers 1546 (72%) were scored as one. Their citations (165,133) were 82% of the total. The proportion of annual papers scored as three was initially high, as were their citations but declined to almost zero by 1996, before rising slightly from 2006. Conclusions: The enormous expansion of the literature appropriately reflects increased understanding of the importance of climate change to global health. However, recognition of the most severe, existential, health risks from climate change was generally low. Most papers instead focused on infectious diseases, direct heat effects and other disciplinary-bounded phenomena and consequences, even though scientific advances have long called for more inter-disciplinary collaboration.
An increasing number of cities are transitioning from fossil fuel-powered buses for public transport to battery electric buses. Evaluating the energy demand of buses has become an important prerequisite for the planning and deployment of large electric bus fleets and the required charging infrastructure. A number of state-of-the-art approaches to determining the energy requirements of electric buses use individual specific energy demand values or rely on standard driving cycles, though these do not consider local bus route characteristics. Others require high-resolution measurements of the vehicles’ driving profiles, which is impractical for large bus fleets. This paper presents a longitudinal dynamics model to calculate the energy demand for electric buses. The model is designed to be easily applied to large bus networks using real data sources that are commonly available to bus transit operators. This data can be derived from low-resolution data collected from day-to-day operations, where only the arrival and departure time of the buses at each bus stop are available. This approach offers a practical alternative to state-of-the-art methods and requires no high-resolution velocity profiles, which are difficult to obtain, while still taking into account the details of the operational characteristics of the transportation network under consideration. The application of the model is demonstrated in a case study to electrify the complete public bus network in Singapore. The results showed that the heterogeneity of driving conditions observed in a large network leads to a high variance in energy requirements between different bus lines and at different times of day. This confirms the need to take the characteristics of each individual bus route into account. In the case-study, a fully electric public bus fleet would require about 1.4 GWh per day for revenue service, which is about one per cent of Singapore’s daily electricity demand. Another finding is that 50% of the bus lines require less than 40 kWh per terminus-to-terminus journey, which indicates a good potential for fast opportunity charging during layover time. The results of the model should serve as the basis for further studies into battery sizes, charging strategies and charging infrastructure requirements.
Many public transport authorities have a great interest in introducing zero-emission electric buses. However, the transformation process from diesel to electric bus systems opens up a vast design space which seems prohibitive for a systematic decision making process. We present a holistic design methodology to identify the ‘most suitable system solution’ under given strategic and operational requirements. The relevant vehicle technologies and charging systems are analysed and structured using a morphological matrix. A modular simulation model is introduced which takes technical and operational aspects into account. The model can be used to determine a feasible electric bus system. The technology selection is based on a detailed economic analysis which is conducted by means of a total cost of ownership (TCO) model. To cope with uncertainties in forecasting, a stochastic modelling of critical input parameters is applied and three different future scenarios are evaluated. The applicability of the model was verified in a pilot project in Berlin and the methodology was applied to a realistic operational scenario. Our results indicate that electric bus systems are technically feasible and can become economically competitive from the year 2025 under the conditions examined.
Transport is almost entirely powered by internal combustion engines (ICEs) burning petroleum-derived liquid fuels and the global demand for transport energy is large and is increasing. Available battery capacity will have to increase by several hundred fold for even light duty vehicles (LDVs), which account for less than half of the global transport energy demand, to be run on electricity alone. However the greenhouse gas (GHG) impact of battery electric vehicles (BEVs) would be worse than that of conventional vehicles if electricity generation and the energy used for battery production are not sufficiently decarbonized. If coal continues to be a part of the energy mix, as it will in China and India, and if power generation is near urban centers, even local urban air quality in terms of particulates, nitrogen oxides and sulfur dioxide would get worse. The human toxicity impacts associated with the mining of metals needed for batteries are very serious and will have to be addressed. Large prior investments in charging infrastructure and electricity generation will be needed for widespread forced adoption of BEVs to occur. There will be additional costs in the short term associated with various subsidies required to promote such a change and in the longer term, the loss of revenue from fuel taxes which contribute significantly to public finances in most countries. ICEs will continue to power transport, particularly commercial transport, to a large extent for decades to come and will continue to improve. There will also be a role for low-carbon and other alternative fuels where they make sense. However such alternatives also start from a low base and face constraints on rapid and unlimited growth so that they are unlikely to make up much more than 10% of the total transport energy demand by 2040. As the energy system is decarbonized and battery technology improves there will be an increasing role for BEVs and hydrogen which could replace liquid hydrocarbons in transport and the required infrastructure will evolve. Meanwhile, there will certainly be increasing electrification, particularly of LDVs in the form of hybridization to improve ICEs.
The development of a systematic framework to support the design of transit bus fleets is justified by the significant and long-lasting implications associated with decisions to purchase transit vehicles, as well as by developments in fuel propulsion and battery technologies over the last 2 decades that have increased the options available to transit operators, and, in turn, the complexity of assessing the corresponding tradeoffs. The need to evaluate these tradeoffs is, in part, driven by the emergence of environmental impact mitigation, i.e., emissions reductions, as a critical concern of transit operators and governments around the world.
The deployment of battery-powered electric bus systems within the public transportation sector plays an important role to increase energy efficiency and to abate emissions. Rising attention is given to bus systems using fast charging technology. This concept requires a comprehensive infrastructure to equip bus routes with charging stations. The combination of charging infrastructure and bus batteries needs a reliable energy supply to maintain a stable bus operation even under demanding conditions. An efficient layout of the charging infrastructure and an appropriate dimensioning of battery capacity are crucial to minimize the total cost of ownership and to enable an energetically feasible bus operation. In this work, the central issue of jointly optimizing the charging infrastructure and battery capacity is described by a capacitated set covering problem. A mixed-integer linear optimization model is developed to determine the minimum number and location of required charging stations for a bus network as well as the adequate battery capacity for each bus line. The bus energy consumption for each route segment is determined based on individual route, bus type, traffic and other information. Different scenarios are examined in order to assess the influence of charging power, climate and changing operating conditions. The findings reveal significant differences in terms of required infrastructure. Moreover, the results highlight a trade-off between battery capacity and charging infrastructure under different operational and infrastructure conditions. The paper addresses upcoming challenges for transport authorities during the electrification process of the bus fleets and sharpens the focus on infrastructural issues related to the fast charging concept.
This paper evaluates the energy consumption and battery performance of city transit electric buses operating on real day-to-day routes and standardized bus drive cycles, based on a developed framework tool that links bus electrification feasibility with real-world vehicle performance, city transit bus service reliability, battery sizing and charging infrastructure. The impacts of battery capacity combined with regular and ultrafast charging over different routes have been analyzed in terms of the ability to maintain city transit bus service reliability like conventional buses. The results show that ultrafast charging via frequent short-time boost charging events, for example at a designated bus stop after completing each circuit of an assigned route, can play a significant role in reducing the battery size and can eliminate the need for longer duration charging events that would cause schedule delays. The analysis presented shows that significant benefits can be realized by employing multiple battery configurations and flexible battery swapping practices in electric buses. These flexible design and use options will allow electric buses to service routes of varying city driving patterns and can therefore enable meaningful reductions to the cost of the vehicle and battery while ensuring service that is as reliable as conventional buses.
This paper presents a twofold modelling exercise to investigate the implementation of battery electric buses (BEBs) in a full transit network. First, using three BEB concepts: flash, opportunity, and overnight, a real-time simulation model is developed for a full transit BEBs operation in order to (1) quantify the energy demands, (2) design the required infrastructure of the charging station, (3) test the transit operation feasibility, and (4) generate the charging load profile. Simulation results show that flash and opportunity BEBs are more feasible for full transit BEBs operation, however they suffer from high and intermittent power demands. Second, the generated charging load profile for each BEB operation is utilized to study its impact on the utilization and lifetime of the transformers, and the operation of the local distribution grid. Results indicate that the operation of overnight electric buses is more feasible as it relates to their impacts on the substation transformer and distribution feeders overloading, voltage regulation and quality aspects, and operation of voltage control devices. Collectively, findings from this study highlight that the selection of BEBs in a full network transit operation hinges on achieving feasible operation while reducing impacts on utility grid. Insights derived from this work can help optimize the implementation of BEBs in transit context.
Evidence suggests that the role of electric buses in public transit is important if we are to take steps to reduce climate change and the environmental impacts of fossil fuels. Several electric alternatives are currently operationalized, and the debate about which is most suitable is attracting considerable attention. This article provides a detailed review of various performance features for three categories of electric buses: hybrid, fuel cell, and battery. Economic, operational, energy, and environmental characteristics of each technology are reviewed in detail based on simulation models and operational data presented by various scholars in different contexts. The study develops a holistic assessment of electric buses based on side-by-side comparison of 16 features that best inform the decision making process. The review indicates that the selection process of electric technology is highly sensitive to operational context and energy profile. In addition, it highlights that hybrid buses will not provide a significant reduction in GHG and would be suitable only for short-term objectives as a stepping-stone towards full electrification of transit. Battery and fuel cell buses are arguably capable of satisfying the current operational requirements, yet initial investment remains a major barrier. Overnight battery electric bus is advocated as the most suitable alternative for bus transit contexts given the expected improvements in battery technology and the trend to utilise sustainable sources in electricity generation.
Public transport is an especially promising sector for full electric vehicles due to the high amount of cycles and predictable workload. This leads to a high amount of different vehicle concepts ranging from large batteries, designed for a full day of operation without charging, to fast-charging systems with charging power up to a few hundred kilowatts. Hence, many different issues have to be addressed in the whole design and production process regarding high-voltage (HV) batteries for buses. In this work, the design process for electric public buses is analyzed in detail, based on two systems developed by the research projects Smart Wheels/econnect and SEB eÖPNV. The complete development process starting, with the demand analysis and the operating scenario, including the charging routine, is discussed. This paper also features details on cell selection and cost estimations as well as technical details on the system layout, such as the management system and passive components as well as thermal management.
Purpose
Alternative fuel options are gaining popularity in the vehicle market. Adopting alternative fuel options for public transportation compared to passenger vehicles contributes exponentially to reductions in transportation-related environmental impacts. Therefore, this study aims to present total air pollutant emissions and water withdrawal impacts through the lifetime of a transit bus with different fuel options.
Methods
In consideration of market share and future development trends, diesel, biodiesel, compressed natural gas (CNG), liquefied natural gas (LNG), hybrid (diesel-electric), and battery electric (BE) transit buses are analyzed with an input-output (IO)-based hybrid life cycle assessment (LCA) model. In order to accommodate the sensitivity of total impacts to fuel economy, three commonly used driving cycles are considered: Manhattan, Central Business District (CBD), and Orange County Transit Authority (OCTA). Fuel economy for each of these driving cycles varies over the year with other impacts, so a normal distribution of fuel economy is developed with a Monte Carlo simulation model for each driving cycle and corresponding fuel type.
Results and discussion
Impacts from a solar panel (photovoltaic, PV) charging scenario and different grid mix scenarios are evaluated and compared to the nation’s average grid mix impacts from energy generation to accommodate the lifetime electricity needs for the BE transit bus. From these results, it was found that the BE transit bus causes significantly low CO2 emissions than diesel and other alternative fuel options, while some of the driving cycles of the hybrid-powered transit bus cause comparable emissions to BE transit bus. On the other hand, lifetime water withdrawal impacts of the diesel and hybrid options are more feasible compared to other options, since electricity generation and natural gas manufacturing are both heavily dependent on water withdrawal. In addition, the North American Electricity Reliability Corporation’s (NERC) regional electricity grid mix impacts on CO2 emissions and water withdrawal are presented for the BE transit bus.
Conclusions
As an addition of current literature, LCA of alternative fuel options was performed in this paper for transit buses with the consideration of a wide variety of environmental indicators. Although the results indicate that BE and hybrid-powered buses have less environmental emissions, the US’s dependency on fossil fuel for electricity generation continues to yield significant lifetime impacts on BE transit bus operation. With respect to water withdrawal impacts, we believe that the adoption of BE transit buses will be faster and more environmentally feasible for some NREC regions than for others.
United States in 2017 emitted about 14.36% of the total global Greenhouse Gas (GHG), 27% of which comes from the transportation sector. In order to address some of these emission sources, alternative fuel technology vehicles are becoming more progressive and market ready. Transit agencies are making an effort to reduce their carbon footprint by adopting these technologies. The overarching objective of this paper is to aid transit agencies make more informed decisions regarding the process of replacing a diesel fleet with alternative-technology buses to minimize GHG emissions. This study investigates the complete course of fleet replacement using a deterministic mixed integer programming. Bus fleet replacement is optimized by minimizing the Life Cycle Cost (LCC) of owning and operating a fleet of buses and required infrastructures while reducing GHG emission simultaneously. Buses operated by Connecticut Department of Transportation (CTDOT) were used as a case-study. Results also show a significant reduction in both cost and emission for optimized replacement schedule vs the unoptimized one. Results also show that a fleet consisting of 79% Battery Electric Bus and 21% Diesel Hybrid Bus yields the least cost solution which conforms to the other operational and environmental constraints. This study also includes various sensitivity tests, that illustrates that although the magnitude of the results may vary depending on the input data, the direction remains the same. The problem formulated in this study can help any transit agencies determine the most optimized solution to their fleet replacement problem under customizable constraints or desired set of outcomes.
There is a great deal of evidence that climate change affects socioeconomic systems. The social cost of carbon (SCC) is calculated by scientists to monetarize the incremental unit of carbon emission and is used to assess climate policies. This study begins with a review of current research on the SCC, followed by a discussion of the choice of models for the SCC. We give a list of advantages of disadvantages of each model and finally use a meta-analysis to evaluate the SCC from published research. The main findings were as follows. (i) Integrated assessment models (IAMs) are often employed to assess the SCC, research on IAMs was started booming in the 1990s and slightly decreased after 2012. (ii) The estimated SCC ranges from −50 to 8752/tCO2), with a mean value of 200.57/tCO2) and it equals to 112.86/tCO2) with a PRTP at 3% in peer-reviewed studies. (iii) The estimated SCC is higher in newer publication year and in peer-reviewed studies, the same trend happens with a higher climatic sensitivity and employing DICE/RICE and PAGE. (iv) The pure rate of time preference (PRTP) is tightly associated with the estimated SCC, and a higher PRTP has a lower estimated SCC. (v) The outliers often appear without realistic scenario setting and in studies have not peer-reviewed.
This paper focuses on the potential impact of various options for decarbonization of public bus transport in Stockholm, with particular attention to electrification. An optimization model is used to locate electric bus chargers and to estimate the associated carbon emissions, using a life cycle perspective and various implementation scenarios. Emissions associated with fuels and batteries of electric powertrains are considered to be the two main factors affecting carbon emissions. The results show that, although higher battery capacities could help electrify more routes of the city's bus network, this does not necessarily lead to a reduction of the total emissions. The results show the lowest life cycle emissions occurring when electric buses use batteries with a capacity of 120 kWh. The fuel choices significantly influence the environmental impact of a bus network. For example, the use of electricity is a better choice than first generation biofuels from a carbon emission perspective. However, the use of second-generation biofuels, such as Hydrotreated Vegetable Oil (HVO), can directly compete with the Nordic electricity mix. Among all fuel options, certified renewable electricity has the lowest impact. The analysis also shows that electrification could be beneficial for reduction of local pollutants in the Stockholm inner city; however, the local emissions of public transport are much lower than emissions from private transport.
Low-emission alternative bus technologies are of increasing interest to bus fleet operators due to the reduced environmental impact and potential for lower operating costs. However, with uncertainty regarding the total cost of ownership of new technologies and life cycle impacts beyond the typical well-to-wheel boundary, stakeholders may not have the necessary specific tools or evidence to evaluate life cycle impacts. The aim of this paper is to develop a novel framework to assist decision-makers in assessing the uncertainty of the life cycle impacts of alternative bus technologies. The Technology Impact Forecasting methodology was employed, integrating a life cycle model, to investigate whole life cycle impacts in an exploratory assessment environment, allowing for the analysis and trade-off evaluations of alternative drivetrain technologies and operational scenarios. This research provides a comprehensive novel framework for addressing uncertainty in whole life cycle costs and GHG emissions for the manufacture, use, maintenance and infrastructure phases of diesel and battery electric buses. Eleven scenarios are assessed in the framework, evaluating combinations of battery technologies, well-to-tank pathways, charging infrastructure and auxiliary demands. For every battery electric bus scenario, there is an 80% confidence that life cycle GHG emissions are mitigated by 10–58% compared to the baseline diesel bus, but life cycle costs are 129–247% higher. Opportunity charged electric buses employing a lithium-titanate battery are the most effective scenario for mitigating GHG emissions per additional cost of the new technology to the operator. The framework highlights a key trade-off between dependence on battery capacity and high-power charging infrastructure for battery electric bus technologies. The framework enables stakeholders to make technology adoption and resource allocation decisions based on the risk of a scenario and provides a level of confidence in a technologies’ ability to mitigate whole life cycle impacts.
Deploying large-scale wireless charging infrastructure at bus stops to charge electric transit buses when loading and unloading passengers requires significant capital investment and brings environmental and energy burdens due to charger production and deployment. Optimal siting of wireless charging bus stops is key to reducing these burdens and enhancing the sustainability performance of a wireless charging bus fleet. This paper presents a novel multi-objective optimization model framework based on life cycle assessment (LCA) for siting wireless chargers in a multi-route electric bus system. Compared to previous studies, this multi-objective optimization framework evaluates not only the minimization of system-level costs, but also newly incorporates the objectives of minimizing life cycle greenhouse gas (GHG) emissions and energy consumption during the entire lifetime of a wireless charging bus system. The LCA-based optimization framework is more comprehensive than previous studies in that it encompasses not only the burdens associated with wireless charging infrastructure deployment, but also the benefits of electric bus battery downsizing and use-phase vehicle energy consumption reduction due to vehicle lightweighting, which are directly related to charger siting. The impact of charger siting at bus stops with different route utility and bus dwell time on battery life is also considered. To demonstrate the model application, the route information of the University of Michigan bus routes is used as a case study. Results from the baseline scenario show that the optimal siting strategies can help reduce life cycle costs, GHG, and energy by up to 13%, 8%, and 8%, respectively, compared to extreme cases of “no charger at any bus stop” and “chargers at every stop”. Further sensitivity analyses indicate that the optimization results are sensitive to the initial battery unit price ($/kWh), charging power rate (kW), charging infrastructure costs, and battery life estimation methods.
This study estimates Well-to-Wheel (WTW) fossil energy use and greenhouse gas (GHG) emissions for six types of city buses with conventional, hybrid-electric and plug-in hybrid-electric powertrains, including two-axle, articulated and bi-articulated chassis in the BRT (Bus Rapid Transit) system in Curitiba, Brazil. Particular emphasis is put on the operation phase (Tank-to-Wheel, TTW) of the city buses using the Advanced Vehicle Simulator (ADVISOR). The simulations are based on real-world driving patterns collected from Curitiba, comprising 42 driving cycles that represent city bus operation on seven BRT routes with six operation times for each.
Hybrid-electric and plug-in hybrid-electric two-axle city buses use 30% and 75% less WTW fossil energy per distance compared to a conventional two-axle city bus (19.46 MJfossil,WTW/km). This gives an absolute reduction of 1115 gCO2e,WTW/km in WTW GHG emissions when operating a plug-in hybrid-electric city bus instead of a conventional two-axle city bus (1539 gCO2e,WTW/km). However, a conventional bi-articulated city bus can be environment-friendlier than hybrid-electric city buses in terms of WTW fossil energy use and WTW GHG emissions per passenger-distance, if its passenger capacity is sufficiently utilised. Nonetheless, the plug-in hybrid-electric city bus remains the most energy-efficient and less polluting option. Hybrid-electric and plug-in hybrid-electric powertrains offer the possibility to achieve much higher levels of decarbonisation in the BRT system in Curitiba than the blending mandate of 7%vol biodiesel into diesel implemented in Brazil in 2016. In addition, the simulations show that TTW energy use can considerably vary by up to 77% between different operation times, BRT routes and types of city buses.
In conclusion, advanced powertrains and large passenger capacity utilisation can promote sustainability in Curitiba’s BRT system. The results of this analysis provide important insights for decision makers both in Curitiba and other cities with similar conditions.
New powertrain technologies, such as Hybrid Electric Vehicles, have a price premium which can often be offset by lower running costs. Total Cost of Ownership combines these purchase and operating expenses to identify the most economical choice of vehicle. This is a valuable assessment for private and fleet purchasers alike. Studies to date have not compared Total Cost of Ownership across more than two vehicle markets or analysed historic costs. To address this gap, this research provides a more extensive Total Cost of Ownership assessment of conventional, Hybrid, Plug-in Hybrid and Battery Electric Vehicles in three industrialized countries – the UK, USA (using California and Texas as case studies) and Japan – for the time period 1997–2015. Finally, the link between Hybrid Electric Vehicle Total Cost of Ownership and market share is analysed with a panel regression model.
In all regions the incremental Total Cost of Ownership of hybrid and electric vehicles compared to conventional vehicles has reduced from the year of introduction and 2015. Year on year Hybrid Electric Vehicles Total Cost of Ownership was found to vary least in the UK due to the absence of subsidies. Market share was found to be strongly linked to Hybrid Electric Vehicle Total Cost of Ownership through a panel regression analysis. Financial subsidies have enabled Battery Electric Vehicles to reach cost parity in the UK, California and Texas, but this is not the case for Plug-in Hybrid Electric Vehicles which haven’t received as much financial backing. This research has implications for fleet purchasers and private owners who are considering switching to a low-emission vehicle. The findings are also of interest to policymakers that are keen to develop effective measures to stimulate decarbonisation of the fleet and improve air quality.
Battery electric buses are seen as a well-suited technology for the electrification of road-based public transport. However, the transition process from conventional diesel to electric buses faces major hurdles caused by range limitations and required charging times of battery buses. This work addresses these constraints and provides a methodology for the cost-optimized planning of depot charging battery bus fleets and their corresponding charging infrastructure. The defined problem covers the scheduling of battery buses, the fleet composition, and the optimization of charging infrastructure in a joint process. Vehicle schedule adjustments are monetized and evaluated together with the investment and operational costs of the bus system. The resulting total cost of ownership enables a comparison of technical alternatives on a system level, which makes this approach especially promising for feasibility studies comprising a wide range of technical concepts. Two scenarios of European cities are analyzed and discussed in a case study, revealing that the cost structure is influenced significantly by the considered bus type and its technical specifications. For example, the total energy consumption of the considered lightweight bus is up to 32% lower than the total consumption of the high range bus, although the deadheading mileage increases. However, the total costs of ownership for operating both bus types are relatively close, due to the increased fleet size and driver expenses required for the lightweight bus system. The case study furthermore reveals that a mixed fleet of different bus types could be advantageous depending on the operational characteristics of the bus route.
Electric city buses and high power charging systems have been rapidly developed in recent years. Battery electric buses are energy efficient and emission free but due to the expensive technology, lifecycle costs can be much higher in comparison to diesel or hybrid buses. This research presents a lifecycle cost analysis for a fleet operation of electric city buses in different operating routes. The objective is to define charging power and battery requirements as well as energy consumption and lifecycle costs. A specific simulation tool was developed to comprehensively evaluate electric buses in different operating conditions. The tool allows to systematically generate and simulate different operating scenarios with a chosen bus configuration, charging method and operating route. Based on the simulation results and predefined cost parameters, lifecycle costs are calculated for each operating scenario. The considered charging methods include overnight, end station and opportunity charging. Simulation results are presented for four operating routes which were measured from existing bus lines in Finland and California, USA. The results show that high energy capacity of the battery system is crucial for the overnight charging buses to achieve adequate daily operation whereas the battery size has a minor impact on the energy consumption and lifecycle costs of the fast charging buses. The lifecycle costs of electric buses are heavily impacted by capital costs including purchase costs of the buses and charging devices. When considering 12 years of service life, the end station charging electric buses can have slightly lower lifecycle costs than diesel buses but on average they have 7% higher lifecycle costs. The overnight charging buses have on average 26% and opportunity charging buses 35% higher lifecycle costs than diesel buses.
Low emission alternative driveline technologies are of increasing interest for bus fleet operators due to evidence of reduced environmental impact and potential for lower operating costs. However, with uncertainty regarding the total cost of ownership of new technologies and life cycle impacts beyond the typical well-to-wheel boundary, bus operators and manufacturers may not have the necessary specific tools or evidence to evaluate whole life cycle impacts. This paper evaluates the Technology Impact Forecasting methodology as one such technique for assessing whole life cycle impacts in an exploratory assessment environment. The assessment of ten technology scenarios within a life cycle framework has demonstrated that the method is applicable for evaluating contrasting drivetrain technologies and combinations of technology and operational conditions. High levels of uncertainty within the framework have highlighted the need for increased fidelity in the life cycle model and appropriate application of shape functions.
Reductions of fuel consumption and gas emissions count among the main advantages of hybrid electric vehicles (HEV). It is well known that the level of hybridisation has a large influence on the fuel consumption, the manufacturing cost and the battery lifetime. Therefore, a proper selection of the size of components could be the result of a trade-off between them. This paper provides models and a methodology to address the sizing of components of a HEV. Specifically the work is focused on the series architecture with internal combustion engine and battery. The sizing criteria are oriented to reduce the operating costs, in which are included the
fuel consumption and the battery-life consumption. Finally, the methodology proposed is applied in a case study. It corresponds to a real hybrid electric bus operating under urban driving conditions. Simulation results show that the best solutions are obtained by oversizing the battery with respect to power requirements.
Alternative vehicle propulsion technologies are being promoted to reduce energy consumption and environmental impacts in transportation. Life-cycle assessment (LCA) is often used to assess and compare the environmental impacts of these technologies, but, in its traditional form, it lacks the ability to capture the transient effects as new vehicles displace older vehicles in the fleet. Fleet-based life-cycle (LC) approaches – which combine the LCA methodology with fleet models that describe the stocks and flows associated with a class of products over time – have been proposed to circumvent this issue. This article presents a critical review of the literature addressing fleet-based LC approaches by providing an overview of modeling approaches, its main applications, and an analysis of the key aspects underlying environmental and energy impacts of vehicle fleets (focusing on electrification pathways).
This paper adopts the contingent valuation method to study people’s willingness to pay for the adoption of new energy buses in the four most developed cities of China: Beijing, Shanghai, Guangzhou and Shenzhen. An interval regression model is employed to analyze the influencing factors of people’s willingness to pay and estimate the exact amount of extra money people would pay per fare. The results show that approximately eighty percent of the respondents in the four cities would like to pay extra fare to support the adoption of new energy buses and the specific amount is 0.653 RMB/fare among all the respondents. Those with higher household income, who are younger, who think the adoption can significantly improve air quality and who deem that they live in a place with good air quality are willing to pay higher. But public concern about energy security issue in China does not have significant impact on the willingness to pay. It is therefore recommended that setting a higher price for new energy bus fare is reasonable and more knowledge of new energy buses should be conveyed to the public, especially its purpose of improving air quality and alleviating the high pressure of energy security.
In this paper a dynamic, modular, 1-D vehicle model architecture is presented which seeks to enhance modelling flexibility and can be rapidly adapted to new vehicle concepts, including hybrid configurations. Interdependencies between model sub-systems are minimized. Each subsystem of the vehicle model follows a standardized signal architecture allowing subsystems to be developed, tested and validated separately from the main model and easily reintegrated. Standard dynamic equations are used to calculate the rotational speed of the desired driveline component within each subsystem i.e. dynamic calculations are carried out with respect to the component of interest. Sample simulations are presented for isolated and integrated components to demonstrate flexibility. Two vehicle test cases are presented. The application to a conventional heavy-duty vehicle demonstrates the operational capabilities of the modelling methodology, while the inclusion of electrical components to form a mild-hybrid heavy-duty vehicle demonstrates the model’s potential for predicting improvements in fuel economy and performance over a specified drive cycle. Qualitative validation characteristics are presented, highlighting the ability of the model to accurately capture dynamic events and fuel consumption profiles.
Monitoring the service quality of high-frequency bus transit is important both to agencies running their own operations and those contracting out, where performance measures can be used to assess contract penalties or bonuses. The availability of automatically collected vehicle movement and demand data enables detecting changes in running times and demand, which may present opportunities to improve service quality and fleet utilization. This research develops a framework to maximize service performance in a set of high-frequency bus routes, given their planned headways and a total fleet size constraint. Using automatically collected data and simulation modelling to evaluate the performance of each route with varying fleet sizes, a greedy algorithm adjusts allocation toward optimality. A simplified case study involving morning peak service on nine bus routes in Boston demonstrates the feasibility and potential benefits of the approach. A potential application is automated detection of routes operating with insufficient or excessive resources.
The transit authority in Perth, Western Australia, has put several alternative fuel buses, including diesel-electric hybrid and hydrogen fuel cell buses, into revenue service over the years alongside conventional diesel and natural gas buses. Primary data from this fleet is used to construct a Life Cycle Cost (LCC) model, providing an empirical LCC result. The model is then used to forecast possible scenarios using cost estimates for next generation technologies. The methodology follows the Australian/New Zealand Standard for Life Cycle Costing, AS/NZS 4536:1999. The model outputs a dollar value in real terms that represents the LCC of each bus transportation technology. The study finds that Diesel buses deliver the lowest Total Cost of Ownership (TCO). The diesel-electric hybrid bus was found to have a TCO that is about 10% higher than conventional diesel. The premium to implement and operate a hydrogen bus, even if industry targets are attained, is still substantially greater than the TCO of a conventional diesel bus, unless a very large increase in the diesel fuel price occurs. However, the hybrid and hydrogen technologies are still very young in comparison to diesel and economies of scale are yet to be realised.
This paper evaluates the lifecycle costs and carbon dioxide emissions of different types of city buses. The simulation models of the different powertrains were developed in the Autonomie vehicle simulation software. The carbon dioxide emissions were calculated both for the bus operation and for the fuel and energy pathways from well to tank. Two different operating environment case scenarios were used for the primary energy sources, which were Finland and California (USA). The fuel and energy pathways were selected appropriately in relation to the operating environment. The lifecycle costs take into account the purchase, operating, maintenance, and possible carbon emission costs. Based on the simulation results, the energy efficiency of city buses can be significantly improved by the alternative powertrain technologies. Hybrid buses have moderately lower carbon dioxide emissions during the service life than diesel buses whereas fully-electric buses have potential to significantly reduce carbon dioxide emissions, by up to 75%. The lifecycle cost analysis indicates that diesel hybrid buses are already competitive with diesel and natural gas buses. The high costs of fuel cell and battery systems are the major challenges for the fuel cell hybrid buses in order to reduce lifecycle costs to more competitive levels.
Simulation is a well-established and effective approach to the development of fuel-efficient and low-emissions vehicles in both on-highway and off-highway applications.
The simulation of on-highway automotive vehicles is widely reported in literature, whereas research relating to non-automotive and off-highway vehicles is relatively sparse. This review paper focuses on the challenges of simulating such vehicles and discusses the differences in the approach to drive cycle testing and experimental validation of vehicle simulations. In particular, an inner-city diesel-electric hybrid bus and an ICE (Internal Combustion Engine) powered forklift truck will be used as case studies.
Computer prediction of fuel consumption and emissions of automotive vehicles on standardised drive cycles is well-established and commercial software packages such as AVL CRUISE have been specifically developed for this purpose. The vehicles considered in this review paper present new challenges from both the simulation and drive-cycle testing perspectives. For example, in the case of the forklift truck, the drive cycles involve reversing elements, variable mass, lifting operations, and do not specify a precise velocity-time profile. In particular, the difficulties associated with the prediction of productivity, i.e. the maximum rate of completing a series of defined operations, are discussed. In the case of the hybrid bus, the standardised drive cycles are unrepresentative of real-life use and alternative approaches are required in the development of efficient and low-emission vehicles.
Two simulation approaches are reviewed: the adaptation of a standard automotive vehicle simulation package, and the development of bespoke models using packages such as MATLAB/Simulink.
Battery electric buses can reduce energy use and carbon dioxide (CO2) emissions in China's transportation system. On-road testing is necessary to evaluate these benefits compared to their diesel counterparts through life-cycle assessment for both the upstream fuel production and operation stages. Three electric buses from China are operated and charged in Macao under different air-conditioning, load, and speed settings. In the minimum load scenario, the two 12-m buses achieve 138–175 kWh/100 km, and the 8-m bus achieves 79 kWh/100 km (system charging loss included). When air-conditioning and load are at their maximum values, the energy consumption increases by 21–27%; however, air-conditioning usage exerts a greater impact than passenger load. The diesel bus on-road performance increases more significantly than the electric bus performance under low speeds, higher load, and air-conditioning use, while the electric bus energy and CO2 emission benefits increase. Across a wide range of conditions, the electric bus reduces petroleum use by 85–87% compared to a diesel bus and achieves a 32–46% reduction in fossil fuel use and 19–35% in CO2 emissions from a life-cycle perspective. A cleaner power grid and an increase in system charging efficiency (if better than 60–84%) would enhance the future benefits of electric buses.
Abstract The electrification of road vehicles was introduced as a way to significantly reduce oil dependence, increase efficiency, and reduce pollutant emissions, especially in urban areas. The goal of this paper is to find the best alternative vehicle to replace a conventional diesel bus operating in urban environments, aiming to reduce the carbon footprint and still being financially advantageous. The multi-objective nondominated sorting genetic algorithm is used to perform the vehicle optimization, covering pure electric and fuel cell hybrid possibilities (with and without plug-in capability). The used multi-objective genetic algorithm optimizes the powertrain components (type and size) and the energy management strategy. Although multiple optimal solutions were successfully achieved, a decision method is implemented to select one unique solution. A global criterion approach, a pseudo-weight vector approach, and a new multiple criteria score approach are considered to choose a preferred optimal vehicle. Real and synthetic driving cycles are used to compare the optimized buses concerning their powertrain components, efficiency and life cycle of fuel and vehicle materials. The conflict between objectives and the importance of the decision considerations in the final solutions are discussed. Passengers load and air conditioning system influence in the solutions and its life cycle is addressed.
There is a huge uncertainty in the GHG emissions reduction potential with transport electrification. The typical Life Cycle Assessment (LCA) practice of modeling a pathway by reducing what is known about a model parameter to a single value to produce a single-point GHG emissions estimate has led to reports in literature on the GHG emissions differences between Electric Vehicles (EV) and conventional Internal Combustion Engines (ICE) to range significantly from below 10% to above 60%. In this study we performed a LCA, combined with a Monte Carlo stochastic simulation, to determine the uncertainty in GHG emission differences between EVs and gasoline ICEs, by taking into account of all the possible variations that may affect the lifecycle GHG emissions estimates for EVs and ICEs based on the technologies already available in the market today. This study provides insights into the relative importance of the factors driving the lifecycle GHG emissions difference between the EVs and ICEs, and a measure of the probability for EVs providing benefits over ICEs globally today and projected to 2040. This paper offers critical perspective to inform the global debates on the role of transport electrification as means to a low carbon mobility future, and the implications for policy makers.
In today's atmosphere of constrained defense spending and reduced research budgets, determining how to allocate resources for research and design has become a critical and challenging task. In the area of aircraft design, there are many promising technologies to be explored, yet limited funds with which to explore them. In addition, issues concerning the uncertainty in technology readiness, as well as the quantification of the impact of a technology (or combinations of technologies), are of key importance during the design process. This paper presents a methodology that details a comprehensive and structured process in which to quantitatively explore the effects of technology for a given baseline aircraft. This process, called technology impact forecasting, involves the creation of an assessment environment for use in conjunction with defined technology scenarios, and it will have a significant impact on the resource allocation strategies for defense acquisition. The advantages and limitations of the method are discussed. In addition, an example of a technology impact forecasting application, an uninhabited combat aerial vehicle, is presented and serves to illustrate the applicability of this methodology to a military system.
China is facing serious issues involving energy sufficiency, greenhouse gas (GHG) emissions and air pollution caused partly by the rapid growth of vehicles. In order to relieve those problems, new energy vehicles are introduced into the bus and car market. We adopt life cycle analysis to evaluate the well-to-wheels (WTW) energy consumption, CO2 emissions and pollutant emissions from the traditional diesel bus and new energy buses, including diesel hybrid electric vehicles (HEVs), compressed natural gas vehicles (CNGVs) and battery electric vehicles (BEVs). This study reports the current situation and projects future scenarios for the BEV bus for several regions in China due to significant regional differences in the power generation mix. Compared to the diesel bus, the HEV bus can reduce petroleum, fossil fuel use and CO2 emissions by about 20%, and, at the same time, produce stable reduction benefits for all air pollutants. The CNG bus achieves reductions of WTW primary PM2.5 emissions by 70% over its diesel counterpart and, of course, uses little petroleum; but increases fossil fuel consumption moderately and has no benefit in GHG emissions. The BEV bus can deliver a substantial petroleum consumption advantage and greatly reduce the WTW NOX, VOC and CO emissions; but, if the electricity is generated from burning coal, the BEV bus has no PM2.5 emission benefit compared to the conventional diesel bus. Currently, the BEV bus increases fossil energy use and CO2 emissions in the coal-dominated regions; but, in the future, it can achieve substantially lower fossil energy use and CO2 emissions with more penetration of clean electric energy. To reach the win–win strategy, a city’s initial reliance on diesel buses for the public fleet has to give way to a mixture of these new energy buses; and the fleet mix should be diversified over the region and modified over time to accommodate changes in these energy and environmental parameters.
Wireless charging, as opposed to plug-in charging, is an alternative charging method for electric vehicles (EVs) with rechargeable batteries and can be applicable to EVs with fixed routes, such as transit buses. This study adds to the current research of EV wireless charging by utilizing the Life Cycle Assessment (LCA) to provide a comprehensive framework for comparing the life cycle energy demand and greenhouse gas emissions associated with a stationary wireless charging all-electric bus system to a plug-in charging all-electric bus system. Life cycle inventory analysis of both plug-in and wireless charging hardware was conducted, and battery downsizing, vehicle lightweighting and use-phase energy consumption were modeled. A bus system in Ann Arbor and Ypsilanti area in Michigan is used as the basis for bus system modeling. Results show that the wirelessly charged battery can be downsized to 27–44% of a plug-in charged battery. The associated reduction of 12–16% in bus weight for the wireless buses can induce a reduction of 5.4–7.0% in battery-to-wheel energy consumption. In the base case, the wireless charging system consumes 0.3% less energy and emits 0.5% less greenhouse gases than the plug-in charging system in the total life cycle. To further improve the energy and environmental performance of a wireless charging electric bus system, it is important to focus on key parameters including carbon intensity of the electric grid and wireless charging efficiency. If the wireless charging efficiency is improved to the same level as the assumed plug-in charging efficiency (90%), the difference of life cycle greenhouse gas emissions between the two systems can increase to 6.3%.
Military decision makers need to understand and assess the benefits and consequences of their decisions in order to make cost efficient, timely, and successful choices. Technology selection is one such critical decision, especially when considering the design or retrofit of a complex system, such as an aircraft. An integrated and systematic methodology that will support decision making between technology alternatives and options while assessing the consequences of such decisions is a key enabler. This paper demonstrates, through application to a notional medium-range short takeoff and landing aircraft, one such enabler: the Technology Impact Forecasting (TIF) method. The goal of the TIF process is to explore both generic, undefined areas of technology, as well as specific technologies, and assess their potential impacts. This is actualized through the development and use of technology scenarios, and allows the designer to determine where to allocate resources for further technology definition and refinement, as well as provide useful design information. The paper particularly discusses the use of technology scenarios and demonstrates their use in the exploration of seven technologies of varying Technology Readiness Levels.
The Clean Air Act in the United States identifies diesel-powered motor vehicles, including transit buses, as significant sources of several criteria pollutants that contribute to ground-level ozone formation or smog. The effects of air pollution in urban areas are often more significant due to congestion and can lead to respiratory and cardiovascular health impacts. Life cycle assessment (LCA) has been utilized in the literature to compare conventional gasoline-powered passenger cars with various types of electric and hybrid-powered alternatives, however, no similarly detailed studies exist for mass transit buses.
LCA results from this study indicate that the use phase, consisting of diesel production/combustion for the conventional bus and electricity generation for the electric bus, dominates most impact categories; however, the effects of battery production are significant for global warming, carcinogens, ozone depletion, and eco-toxicity. There is a clear connection between the mix of power-generation technologies and the preference for the diesel or electric bus. With the existing U.S. average grid, there is a strong preference for the conventional diesel bus over the electric bus when considering global warming impacts alone. Policy makers must consider regional variations in the electricity grid prior to recommending the use of battery electric buses to reduce carbon dioxide (CO2) emissions. This study found that the electric bus was preferable in only eight states, including Washington and Oregon. Improvements in battery technology reduce the life cycle impacts from the electric bus, but the electricity grid makeup is the dominant variable.
Vehicle scheduling is a crucial step of the public transport planning process because it results in the number of vehicles required, thus it is directly related to fixed cost and labor cost. It is desirable, therefore, to minimize the number of vehicles used and operational cost. This paper proposes a new methodology for the multiple vehicle types vehicle scheduling problem (MVT-VSP). The methodology is based on a minimum-cost network flow model utilizing sets of Pareto-optimal timetables for individual bus lines. Given a fixed fleet size the suggested methodology also allows a selection of the optimal timetable. The method developed enables to stipulate the use of a particular vehicle type for a trip or to allow for a substitution either by a larger vehicle or a combination of smaller vehicles with the same or higher total capacity. Moreover, a variation of the method portrayed makes it possible to construct sub-optimal timetables given a reduction of the vehicle-scheduling cost. It is demonstrated that a substitution of vehicles is beneficial and can lead to significant cost reductions in the range of more than 27%. The suggested methodology is applied to a real-life case study in Auckland, New Zealand, and the results show improvements of greater than 15% in terms of the cost of fleet compared with vehicle schedules that are provided by standard models.
Abstract Fuel cell powered hybrid electric vehicles (FC-HEV) and plug-in hybrid electric vehicles (FC-PHEV) are being addressed by the automotive industry as improved and more sustainable alternative technologies relatively to conventional vehicles. Nevertheless, hybrid propulsion raises new challenges in designing the vehicle powertrain. This study highlights the significance of the driving conditions and the conflict between the optimization of investment cost, efficiency and life cycle impact (LCA) in powertrain design optimization of these kinds of vehicles. A single-objective (minimization of cost, fuel or LCA CO2eq) and multi-objective genetic algorithms (minimization of the couples cost and fuel, cost and LCA CO2eq, fuel and LCA CO2eq), linked with the vehicle simulation software ADVISOR, are used to optimize the design of powertrain components. The main outcomes of the research are as follows. The optimization of LCA CO2eq emissions and cost are conflicting as well as cost and energy use, what can be observed in the Pareto solutions. The fuel and LCA CO2eq emissions optimization are coupled for pure hybrids but not for plug-in hybrid configurations, due to the electricity consumption. Fuel cell buses can reduce the energy consumption by 58%, and emit 67% less LCA CO2eq than the conventional diesel bus, and achieve compensatory payback of 0.620 $/km (depending on the hydrogen price). The FC-PHEV configuration shows more potential for achieving higher operation efficiencies, but the FC-HEV shows to have lower life cycle impact and lower cost in general.