Diesel Buses Research Articles

Charging infrastructure and charging methods for electric buses

The movement towards a sustainable and greener future aims to transform the transport sector. Therefore, the public transportation sector is currently undergoing a major transition. In comparison to diesel buses, electric buses have a limited driving range and the charging process takes longer. However, they offer an improved environmental balance. Cities like Shenzhen provide an example on how to transform public transport with a fully electric bus fleet in operation.

Life Cycle Energy Consumption and Air Emissions Comparison of Alternative and Conventional Bus Fleets in Vietnam

The study (a) assesses the life cycle energy consumption and air emissions impacts of battery electric buses (e-buses) and conventional buses operated in Vietnam, and (b) compares them with those of hydrogen buses. The results indicate that e-buses and hydrogen buses are preferred options compared to conventional buses in terms of energy consumption, GHG emissions and other air quality impacts over their whole life cycle. Life cycle energy consumption of diesel buses is triple that of e-buses, and is significantly higher than that of hydrogen buses. Replacing conventional buses with e-buses can reduce energy consumption by 50%. For GHG emissions and air quality impacts, the adoption of electric and hydrogen mobility in replacement of conventional buses will reduce GHG emissions by 39%, and other impacts related to air quality by 13% to 90%.

Comprehensive Total Cost of Ownership Framework for Alternative Fuel Public Transportation Buses

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.

Exploring Low-Carbon Bus Options for Urban BRT Systems: The Case of Amman

Being able to provide high-quality, metro-like transit service at a fraction of the cost of other options, bus rapid transit (BRT) has been viewed as one of the most cost-effective public mass transport systems suitable for urban areas. Since significant amounts of greenhouse gas (GHG) and air pollutant emissions are attributed to the transport sector, deploying low-carbon buses for BRT systems should be of high priority. With a view to promoting low-carbon buses instead of diesel buses for a BRT system currently being planned in Amman, Jordan, this paper evaluates several low-carbon bus options—hybrid, plug-in hybrid, opportunity charging, trolleybus, and battery electric bus—against the baseline case of diesel buses. While low-carbon buses reduce GHG and air pollutant emissions often considerably, they usually require higher upfront capital costs and additional infrastructure investments. On the other hand, they tend to incur lower energy and maintenance costs and have a longer lifetime, particularly battery electric buses. All these advantages and disadvantages are included in the assessment of low-carbon bus options relative to diesel buses. For the trunk routes of the Amman BRT, the analysis shows that the opportunity charging bus can be the most appealing option, having a positive internal rate of return (IRR) for the incremental investment costs. For the feeder routes, both low-carbon bus options considered, hybrid and battery electric, do not result in a positive IRR. Nevertheless, the battery electric bus is found to be a comparatively better option than the hybrid bus. A sensitivity analysis was conducted for both trunk and feeder routes to examine the variability of several parameters used in the study, such as capital expenditures, electricity price, and diesel price. The results show that IRR could increase favorably under certain conditions.

Rethinking mobility strategies for mega-sporting events: A global multiregional input-output-based hybrid life cycle sustainability assessment of alternative fuel bus technologies

Sustainability has been enshrined in the official claims of mega sporting events, and scholarly debates persist on how to achieve environmental stewardship and a prolonged legacy. Revitalizing the public transportation system with alternative fuel bus technologies has speculated significant environmental and socio-economic benefits to the host nation. This paper thus attempts to quantify and analyze the environmental, social, and economic impacts of alternative fuel buses throughout their entire life cycle stages to support the thought process of sustainable mobility practices in hosting mega-events. A hybrid, multi-regional Input-Output (MRIO) based life cycle sustainability assessment (LCSA) model is developed to assess three bus types: compressed natural gas (CNG), electric buses (EBs), and diesel buses (DBs). The results are investigated in terms of a combination of various manufacturing and end-of-life scenarios by encompassing impacts embedded in the global supply chains. A scenario-based analysis is then conducted to assess the impacts and associated benefits of EB compared to alternative bus technologies in host nations, during and post-event, taking the upcoming FIFA World Cup Qatar 2022™ as a case. The results for the MRIO analysis demonstrate the impacts embedded in the global supply chains and on-site benefits of adopting alternative fuel buses may compromise each other, as impacts might be shifted towards other countries (through manufacturing and end-of-life, in exporting countries) while minimizing the operation phase impacts in the importing country, Qatar. Even though the economic benefits of EBs are higher than the CNG buses, and with almost similar social benefits, the environmental impact of the CNG buses inside the host nation is much less than the DBs. This would thus make CNG buses a more balanced alternative than the DBs and EBs. The outcome of this research stays as an eye-opener to the local organizing committee of mega-events to rethink the current sough alternatives for the use of electric transit with more balanced alternatives as proposed in the study, to achieve the mandated carbon neutrality and environmental footprint mitigation goals.

Big Data and Discrete Optimization for Electric Urban Bus Operations

The electrification of urban bus fleets is a challenging task, especially for smaller public transport operators. The main challenge lies in the uncertainty about many technical aspects, like range of vehicles under different circumstances or charging times, that are new for the operators. The purpose of this research is to introduce an approach to solve this problem by incorporating all available data from an existing bus fleet and finding an optimal solution with discrete mathematical optimization. Extensive data logging in the project enabled us to leverage tracking data from the whole bus network including trajectories, powertrain data, and operational data. This enabled us to validate assumptions about the energy demand, waiting times, and different traffic situations during the day. To get better insights into the requirements of an urban bus fleet, we simulated the potential electric buses in detail and extracted other necessary data like actual dwell times. Based on the simulation results and processed data, we implemented a linear programming model to search for a cost-optimal configuration of vehicles and charging infrastructure. We tested the framework with a scenario in which we analyzed the solutions with different numbers of diesel buses in the fleet. The application of our algorithm shows that it can produce optimal results in a short amount of time, for a medium-sized city in Germany. We also demonstrate that the flexible and constraint-based formulation of this approach allows it to be incorporated in the planning process of most public transport operators.

Multiobjective and social cost-benefit optimisation for a sustainable hydrogen supply chain: Application to Hungary

This article presents a comprehensive approach to design hydrogen supply chains (HSCs) targeting industrial and mobility markets. Even if the inclusion of sustainability criteria is paramount, only a few studies simultaneously consider economic, environmental, and social aspects - the most difficult to measure. In this paper, the safety risk and the social cost-benefit (SCB) have been identified as quantifiable social criteria that would affect society and the end-users. The objectives of this research are (1) to design a sustainable HSC by using four objective functions, i.e., levelized cost of hydrogen, global warming potential, safety risk and social cost-benefit through a mixed-integer linear programming model; (2) to compare results from SCB and multiobjective optimisation. The integration of the SCB criterion at the optimisation stage is not a trivial task and is one of the main contributions of this work. It implies the minimisation of the total cost of ownership (TCO) for buses and trucks. The evolution of the HSC from 2030 to 2050 is studied through a multiobjective and multiperiod optimisation framework using the ε-constraint method. The methodology has been applied to a case study for Hungary with several scenarios to test the sensitivity of demand type and volume as well as the production technology. The results analysis highlights that (1) it is beneficial to have mixed demand (industry and mobility) and a gradual introduction/migration to electrolysis technology and fuel cell vehicles (FCVs) for a smooth transition. Liquid hydrogen produced via water electrolysis powered by nuclear and wind energy can result in an average levelized cost of $4.78 and 3.14 kg CO2-eq per kg H2; (2) the frameworks for multiobjective optimisation and SCB maximisation are complementary because they prioritise different aspects to design the HSC. Taxes and surcharges for H2 fuel will impact its final price at the refuelling station resulting in a higher TCO for FCVs compared to diesel buses and trucks in 2030 but the TCO becomes almost competitive for hydrogen trucks from 2035 when SCB is maximised. The SCB function can be refined and easily adapted to include additional externalities.

On the economics of a hydrogen bus fleet powered by a wind park – A case study for Austria

This paper investigates the economics of a fuel cell bus fleet powered by hydrogen produced from electricity generated by a wind park in Austria. The main research question is to simultaneously identify the most economical hydrogen generation business model for the electric utility owning wind power plants and to evaluate the economics of operating a fuel cell bus fleet, with the core objective to minimize the total costs of the overall fuel supply (hydrogen production) and use (bus and operation) system. For that, three possible operation modes of the electrolyzer have been identified and the resulting hydrogen production costs calculated. Furthermore, an in-depth economic analysis of the fuel cell buses as well as the electrolyzer technology has been conducted. Results show that investment costs are the largest cost factor for both technologies. Thus, continuous hydrogen production with the smallest possible electrolyzer is the economically most favorable option. In such an operation mode (power grid), the costs of production per kg/H2 were the lowest. However, this means that the electrolyzer cannot be solely operated with electricity from the wind park, but is also dependent on the electricity mix from the grid. For fuel cell buses, the future cost development will depend very much on the respective policies and funding programs for the market uptake, as to date, the total cost of use for the fuel cell bus is more than two times higher than the diesel bus. The major final conclusion of this paper is that to make fuel cell electric busses competitive in the next years today severe policy interferences, such as subsidies for these busses as well as electrolyzers and bans for fossil energy, along with investments in the setup of a hydrogen infrastructure, are necessary.

Charging Infrastructure and Schedule Planning for a Public Transit Network with a Mixed Fleet of Electric and Diesel Buses

Promoting battery electric buses (BEBs) can reduce fuel consumption and air pollution from the transit system. A complete transition from the current diesel fleet to BEBs is costly and time-consuming. Thus, the intermediate solution is a combination of diesel, hybrid, and BEBs. Therefore, a planning framework is required that simultaneously tackles three contiguous aspects of transit electrification and their interconnections, namely charging infrastructure, fleet configuration, and scheduling. Accordingly, this study considers a mixed fleet of diesel and BEBs. It aims to concurrently find (i) the optimal location and capacity of charging infrastructure, considering micro-grid specifications, the impact of distributed energy resources, and time-of-use electricity rates and (ii) optimum operation and refueling strategies. Another objective of this study is to capture the impacts of adverse weather conditions on transit electrification. A mixed-integer problem is proposed and solved using a metaheuristic algorithm based on simulated annealing to minimize system costs, including infrastructure, fleet, and operation costs. A subnetwork of transit in Worcester, Massachusetts, is selected as a case study, including three routes, five candidate charging locations, and three bus types. Findings suggest that BEBs can operate and serve the passenger demand with sufficient charging infrastructure. Sensitivity analyses show that even though high-power chargers are more expensive per piece, they reduce the overall cost as fewer chargers are required. The cost rises for chargers with power of 350 kW or more. It is worth noting that the benefits of BEBs are more significant in smaller buses and are heavily affected by adverse weather conditions.

Introducing Electric Bus Fleets in Rio de Janeiro City Methodology and Analysis

This paper describes the establishment of a methodology aimed at planning the electrification of public urban bus fleets in order to characterize the operational requirements of the battery recharge process. Specifically, it deals with obtaining the behavior of demand and the necessary electrical energy for battery recharging. The effects on the electrical system peak and the resulting environmental benefits are also evaluated by comparing with current internal combustion fleets. An innovative method is applied to a fleet in the city of Rio de Janeiro. The motivation for this work is due to the characteristics of the Brazilian energy mix that is highly favorable to the electrification of urban transport with greater energy efficiency, with a view to reducing the impacts of internal combustion drive and the respective atmospheric emissions that are harmful to the environment. Also, this work offers the steps to establish essential elements, as daily, month and year energy consumption in order to recharge an electric bus fleet and data for the transportation bus company contracts an electric power distribution utility in Brazil. In spite conservative premises were considered, the calculations show electric bus option attractive. The operational energy consumption of diesel bus fleet is 19.10 MJ/km more than three times the consumption of electric bus fleet, this is 6.10 MJ/km. Additionally, 153 ton of fossil CO2 atmospheric monthly emissions are avoided. The results obtained indicate the need for public policies in favor of electric power and the environmental benefits of adopting electric buses.

Real-Time Charging Scheduling and Optimization of Electric Buses in a Depot

To improve the air quality in urban areas, diesel buses are getting replaced by battery electric buses (BEBs). This conversion introduces several challenges, such as the proper control of the charging process and a reduction in the operational costs, which can be addressed by introducing smart charging concepts for BEB fleets. Therefore, this paper proposes a real-time scheduling and optimization (RTSO) algorithm for the charging of multiple BEBs in a depot. The algorithm assigns a variable charging current to the different time slots the charging process of each BEB is divided to provide an optimal charging schedule that minimizes the charging cost, while satisfying the power limitations of the distribution network and maintaining the operation schedule of the BEBs. A genetic algorithm is used to solve the formulated cost function in real time. Several charging scenarios are tested in simulation, which show that a reduction in the charging cost up to 10% can be obtained under a dynamic electricity price scheme. Furthermore, the RTSO is implemented in a high-level charging management system, a new feature required to enable smart charging in practice, to test the developed algorithm with existing charging infrastructure. The experimental validation of the RTSO algorithm has proven the proper operation of the entire system.

Exhaust and non-exhaust airborne particles from diesel and electric buses in Xi'an: A comparative analysis

Switching diesel buses (DBs) to electric buses (EBs) has been a global trend to reduce the use of fossil fuels and improve air quality. However, buses electrification may lead to additional vehicle weight, which may emit more non-exhaust particulate matter (PM) emissions. It remains debatable whether buses' electrification will successfully improve air quality as excepted. To assess the effect of the buses' electrification on the levels of PM emissions, PM emission factors (EFs) were evaluated from EBs and equivalent DBs. In addition, the total mass of PM emissions from EBs and equivalent DBs in 2021 was calculated in Xi'an using the real-world number and mileage of EBs. The non-exhaust PM EFs from EBs were larger than total exhaust and non-exhaust PM EFs from DBs, indicating that the electrification of buses would cause an increase in the level of PM emissions. The total annual mass of PM emissions from EBs was apparently higher than that from DBs. Moreover, a sensitivity analysis showed that tire wear, brake wear, and road wear PM emissions were more reliant on vehicle mileage, whereas resuspension of road dust was more dependent on vehicle weight. This finding can serve as a guideline for policymakers to design mitigation strategies for reducing extra PM emissions due to the electrification of buses by reasonably reducing vehicle weight and annual mileage.

ON THE QUESTION OF CREATING A TRAILER BUS TRAIN

Hinged buses and bus trains are usually operated in large cities with heavy traffic. Therefore, the traction and speed properties of bus trains should be at the level of single buses. Among the 13 indicators of traction and speed properties that assess the dynamics of the road train, the most important are maximum speed, acceleration during acceleration, time and path of acceleration to maximum speed, acceleration time on the path of 400 and 1000 m. road trains. The A70132 diesel bus and the A701 electric bus were selected as the object of the study when working with the trailer. A comparative assessment of these buses on the indicators of traction and speed properties. It was found that the use of electric buses to create a bus train is problematic in view of the lack of traction in the area of high loads due to the acceleration of the bus. However, for a bus with diesel there is a significant reserve of traction in lower gears, due to the operation of the torque converter. The efficiency of using such a bus train when working on urban routes, where there is a limit on the maximum speed at 50 km / h. If the speed increases to 70 km / h, the use of a bus train consisting of a bus A70132 and a trailer with a total weight of 16,000 kg becomes inefficient. To increase the speed, it is necessary to either increase the power of the bus engine or activate the trailer.

Assessing Feasibility of overnight-charging electric bus in a real-world BRT system in the context of a developing country

Air pollution, as a major urban problem in metropolises, has harmful impacts on societies in many aspects. According to the worn-out fleet of diesel buses and fossil fuel dependencies in Tehran, alternative fuels have become more popular in sustainable public transportation. Although battery electric buses (BEBs) provide many benefits, their purchase price and required infrastructure are the main challenges for decision-makers. This paper provides a systematic approach to examine the environmental, traffic and economic efficiency of overnight-charging electric buses (OCEBs) in Tehran, Iran. Environmental analysis shows that Carbon Oxide and Nitrogen Oxide will reduce to zero, and eliminate dependence on fossil fuels. The payback period predicted to be 7 years. Due to the better acceleration of OCEBs, the travel time, delay and stop time reduce about 4%, 10.67%, and 5.15% on average, respectively which leads to a better experience of passengers and an increase in public transportation utility that cause more people attract to OCEBs. The present results indicate the feasibility of OCEBs implementation as a sustainable transportation mode and can be useful in decision-making of policymakers and planning for future public transport system.

The Comprehensive Automobile Research System (CARS) – a Python-based automobile emissions inventory model

Abstract. The Comprehensive Automobile Research System (CARS) is an open-source Python-based automobile emissions inventory model designed to efficiently estimate high-quality emissions from motor vehicle emission sources. It can estimate air pollutant, greenhouse gas, and air toxin criteria at any spatial resolution based on the spatiotemporal resolutions of input datasets. The CARS is designed to utilize local vehicle activity data, such as vehicle travel distance, road-link-level network geographic information system (GIS) information, and vehicle-specific average speed by road type, to generate an automobile emissions inventory for policymakers, stakeholders, and the air quality modeling community. The CARS model adopted the European Environment Agency's on-road automobile emissions calculation methodologies to estimate the hot exhaust, cold start, and evaporative emissions from on-road automobile sources. It can optionally utilize average speed distribution (ASD) of all road types to reflect more realistic vehicle speed variations. In addition, through utilizing high-resolution road GIS data, the CARS can estimate the road-link-level emissions to improve the inventory's spatial resolution. When we compared the official 2015 national mobile emissions from Korea's Clean Air Policy Support System (CAPSS) against the ones estimated by the CARS, there is a significant increase in volatile organic compounds (VOCs) (33 %) and carbon monoxide (CO) (52 %) measured, with a slight increase in fine particulate matter (PM2.5) (15 %) emissions. Nitrogen oxide (NOx) and sulfur oxide (SOx) measurements are reduced by 24 % and 17 %, respectively, in the CARS estimates. The main differences are driven by different vehicle activities and the incorporation of road-specific ASD, which plays a critical role in hot exhaust emission estimates but was not implemented in Korea's CAPSS mobile emissions inventory. While 52 % of vehicles use gasoline fuel and 35 % use diesel, gasoline vehicles only contribute 7.7 % of total NOx emissions, whereas diesel vehicles contribute 85.3 %. However, for VOC emissions, gasoline vehicles contribute 52.1 %, whereas diesel vehicles are limited to 23 %. Diesel buses comprise only 0.3 % of vehicles and have the largest contribution to NOx emissions (8.51 % of NOx total) per vehicle due to having longest daily vehicle kilometer travel (VKT). For VOC emissions, compressed natural gas (CNG) buses are the largest contributor at 19.5 % of total VOC emissions. For primary PM2.5, more than 98.5 % is from diesel vehicles. The CARS model's in-depth analysis feature can assist government policymakers and stakeholders in developing the best emission abatement strategies.

Towards the Hydrogen Economy in Paraguay: Green hydrogen production potential and end-uses

This study was conducted to estimate the potential for green H2 in Paraguay. A total production potential of 22.5 × 106 tons/year was obtained with a main contribution (93.34%) from solar photovoltaic. The greatest potential for producing H2 from solar and wind resources is in the Western region, and from hydro resources is in the Eastern region of the country. Two end-uses of green H2 were assessed: (1) automotive transportation, replacing gasoline and diesel; and (2) residential energy, replacing firewood and LPG for cooking in households across the country. In 16 of the 17 departments, green H2 is able to replace the overall consumption of gasoline and diesel, as well as firewood and LPG. Finally, energy service cost (mobility), environmental aspects and CO2 emissions were considered for three urban mobility technologies for the Metropolitan Area of Asunción. Results show that the mobility cost of fuel cell hybrid electric buses is still very high in comparison to diesel buses and battery electric buses. However, when a longer driving range is required, fuel cell hybrid electric buses could become a viable alternative in the long term. From an environmental point of view, green H2 used in fuel cell hybrid electric buses has the potential to save about 96% of CO2 emissions in comparison to diesel buses. It is concluded that the estimated green H2 production potential favors the incorporation of the Hydrogen Economy in Paraguay.

A joint optimisation model for charger locating and electric bus charging scheduling considering opportunity fast charging and uncertainties

The continuous improvement of charging technologies makes fast charging applicable to overcoming the limited driving range of electric vehicles by providing en-route opportunity charging. Fast chargers can be deployed at bus stops to top up the battery for an electric bus during its dwelling time when passengers board and alight, which allows the usage of small size battery and avoids deadheading trips to depot or charging station for recharging. This paper examines the joint optimisation problem of locating fast chargers at selected bus stops and developing charging schedule to support electric bus operation considering time-varying electricity price and penalty cost if passengers’ extra waiting time, the delay time of starting a trip or the excessive travel time of completing a trip is caused by charging activities. To handle the uncertainties associated with the travel time and passenger demand, a robust model is proposed and formulated. The proposed methods are applied to multiple bus routes in Sydney in the numerical studies. The numerical results show that frequent charging activities occur at both intermediate and last stops during bus service trips, indicating that it is beneficial for buses to utilise passengers’ boarding and alighting time at intermediate stops and resting time at the last stop between two adjacent trips to top up battery. Sensitivity analysis on a series of system parameters, such as the acquisition cost of chargers, amortized battery price and charging power, is conducted. The numerical results verify the feasibility of deployment of fast chargers and corresponding top-up charging activities at both intermediate and last stops. Electric buses outperform the conventional diesel buses regarding energy consumption cost, especially considering the increasing diesel fuel price and its costly environmental impacts. Moreover, charging activities at intermediate stops will become more common when passenger demand (the volume of boarding and alighting passengers) increases at intermediate stops.

Optimizing mix of heterogeneous buses and chargers in electric bus scheduling problems

Many bus operators are planning to replace or have replaced diesel buses with electric buses in public transportation. However, the scheduling of electric buses is more complex than that of diesel buses in various aspects, including battery recharging, compatibility between batteries and chargers, and dispatching and recharging strategies. The problem of electric bus scheduling is often studied using mathematical programming approaches. However, the operation rules are usually simplified to solve the problem in a reasonable time. A simulation model and a heuristic algorithm are proposed to deal with the complicated electric bus scheduling problem without considerable simplification. The scheduling problem aims to minimize the total cost, including bus, charger, and electricity costs. The model outputs include the required numbers and types of buses and chargers and the bus dispatching and recharging schedules. A case study of a bus company is conducted to demonstrate the application of the proposed method and its potential to improve the operations of electric buses. The novelty of the proposed method lies in its ability to optimize heuristically the mix of heterogeneous buses and chargers while considering their compatibility. The factors critical in electric bus operations, such as bus dispatching and recharging strategies, are explicitly considered.

Heavy-Duty Battery Electric Buses’ Integration in Cities Based on Superfast Charging Technologies: Impact on the Urban Life

As part of this work, several Battery Electric Buses (BEBs) of 9 m, 12 m, and 18 m lengths and superfast chargers based on a pantograph of up to 600 kW were developed and demonstrated in selected European cities. In Osnabrück (OSN), Germany, superfast charging technologies based on BEBs were demonstrated, and numerous measurement campaigns were conducted. Within the scope of this work, two measurement campaigns are presented, which are related to the impact of BEBs on the urban life, i.e., people’s safety, environment, and users’ comfort. People’s safety was investigated in terms of the electromagnetic emissions emanating from two superfast chargers of 350 kW and 300 kW, as such high charging power during the charging process could be a risk to people’s health and electronics inside and outside the bus. The results showed that the magnetic and electrical emissions are far below the safety standard limits. This confirms that the developed vehicles and chargers in the ASSURED project operate under safe conditions for people in the vicinity of the charging station. Environmental impact and users’ comfort were studied in terms of electric motor noises (compared to diesel engines), power electronic devices and their cooling, contact noises of the pantograph, and vibration inside the BEBs compared to diesel buses. It was found that, in most cases, the outside noise emission of BEBs are significantly lower than the noise emissions emitted by diesel buses. Considering the inside noise emissions in the passenger’s section, all BEBs showed lower Sound Pressure Levels (SPLs) in comparison to the diesel busses. As a second part of the ride comfort, vibrations inside BEBs are on the same level as some diesel buses but are mostly significantly lower. All charging processes (pantograph operation and charging process) have a slight noise emission, with 64.6 dB(A) and 52.3 dB(A), respectively, when comparing the engine noise at the departure of the tested diesel buses with 70.8 dB(A) to 80.4 dB(A). Overall, a reduction in noise emissions and an improvement in the ride comfort were observed for the BEBs compared to diesel busses. The objective of this brief study is to provide bus operators, decision-makers, urban planners, and authorities with an overview of the benefits of BEBs for cities and to help them understand the various infrastructural impacts on urban areas and improve the quality of services.

Modelling synthetic methane production for decarbonising public transport buses: A techno-economic assessment of an integrated power-to-gas concept for urban biogas plants

The integration of power-to-gas (PtG) technology into existing urban anaerobic digestion (AD) plants could be an interesting concept to recycle biogenic CO2 and increase CH4 production as renewable fuel to further decarbonize public transport buses (PTB). However, such implementation is challenging for several reasons, including power restrictions during peak load, physical and temporal availability of CO2 from AD plants, and the need for expensive intermediate gas storages to avoid mismatch between the constrained synthetic CH4 production and the variable fuel demand. To investigate whether synthetic CH4 could be a feasible alternative for buses currently powered by fossil fuels, a dynamic model was built for discrete-event simulations of PtG technology integrated into an urban AD plant designed to supply biomethane as fuel for bus fleets. Different scenarios were assessed, including variations in power availability to run a proton exchange membrane electrolyser as well as variations in the production scale of synthetic CH4 based on ex-situ biological methanation. The results show that a constrained power utilization (maximum of 12 h per day) increased the production cost of synthetic CH4 by 20%. In contrast, an increase in PtG production capacity from 0.75 MWth to 2.25 MWth decreased costs by 16%. From the PTB operators’ perspective, the total cost of ownership (TCO) increased in all analysed scenarios when replacing diesel buses by gas buses powered by synthetic CH4. However, when using synthetic CH4 as drop-in fuel to replace natural gas in existing gas bus fleets, the TCO could be reduced up to 4.4% depending on the PtG plant configuration and the assumed fossil fuel price. Furthermore, our results show that a carbon tax on fossil fuels has only a limited effect on promoting synthetic CH4 as alternative fuel for PTB, and additional incentives should be put in place to prioritize a fuel switch, especially for existing gas bus fleets.