Alternative Propulsion Technologies Research Articles

Improving Short-Haul Intermodal Transit Times on Low-Density Rail Corridors with Platoons of Self-Propelled Autonomous Railcars

U.S. freight railroads consume in excess of 13 billion liters of diesel fuel yearly. Although efforts to improve energy efficiency and reduce emissions have made substantial progress in the last decades, the benefits are relatively incremental and will not be sufficient to realize full decarbonization. Several independent efforts are underway to develop alternative locomotive fuels and propulsion technologies designed to fit within the typical locomotive envelope. In addition to these more conventional efforts, multiple startup companies are working to develop self-propelled autonomous railcars (SPARCs) that can achieve targeted decarbonization levels while also disrupting the traditional railroad operating paradigm. SPARC operations with multiple platoon lengths, as well as a control scenario with a conventional train length of 110 railcars, were simulated on an example corridor linking a port with an inland intermodal terminal. This line was single track with short sidings on inconsistent intervals, which is typical of U.S. branch lines serving few local customers without heavy through traffic. For all traffic levels simulated, SPARCs had a much lower transit time than the conventional trains. Optimal platoon length varied between 15- and 38-vehicles per platoon depending on the traffic demand, well under North American standards of over 100 railcars per train.

Efforts to Improve Ship Main Engine Efficiency and Ensure Its Safety

Efforts to improve ship main engine efficiency and ensure its safety have been ongoing endeavors in the maritime industry, driven by the dual imperatives of economic competitiveness and environmental sustainability. The main engine of a ship serves as its heart, propelling it through the vast expanses of the world's oceans while consuming significant quantities of fuel. Therefore, enhancing its efficiency directly impacts operational costs and reduces the environmental footprint associated with maritime transport. One primary focus of improving main engine efficiency lies in the advancement of engine design and technology. Over the years, there has been a concerted effort to develop engines that offer higher power output while consuming less fuel. This has led to the emergence of more efficient engine designs, such as slow-speed two-stroke engines and high-pressure, common-rail fuel injection systems. These innovations optimize fuel combustion, minimize energy losses, and enhance overall propulsion efficiency. Moreover, ongoing research and development efforts are aimed at harnessing alternative fuels and propulsion technologies to further enhance efficiency and reduce environmental impact. LNG (liquefied natural gas) has gained traction as a cleaner-burning fuel alternative, offering significant reductions in sulfur oxides (SOx) and nitrogen oxides (NOx) emissions compared to traditional marine fuels. Additionally, the exploration of hybrid and electric propulsion systems holds promise for reducing greenhouse gas emissions and improving overall energy efficiency. Ensuring the safety of ship main engines is paramount to the reliability and operability of vessels at sea. A robust maintenance regimen is essential to identify and address potential issues before they escalate into costly failures or pose safety hazards. Routine inspections, preventive maintenance, and condition monitoring play crucial roles in detecting abnormalities, wear, and tear, allowing for timely interventions and repairs. Furthermore, advancements in predictive maintenance technologies, such as remote monitoring systems and data analytics, enable real-time assessment of engine performance and early detection of potential malfunctions. The ARAS method lacks the capability to handle ambiguity, subjective judgments, and coping with incomplete information. It relies on unbiased good judgment to address uncertainty, particularly in unknown and complex conditions, making it a valuable approach. The method provides options for sequencing and analysis based on facts and special cases, allowing selectors to express both optimistic and rational attitudes. While it appears numerical on paper, it offers the flexibility to create e-learning pathways tailored to individual needs, emphasizing the importance of mastery. The proposed integrated software for this method is both cost-effective and validated for suitability, ensuring its practical application. Advanced Engine Designs, Improved Monitoring and Maintenance, Enhanced Fuel Management, Innovative Propulsion Technologies, Automation and Remote Monitoring and Advanced Materials and Coatings. the Rank Efforts to improve ship Main Engine efficiency and Ensure its safety for Additive Ratio Assessment method. Advanced Materials and Coatings is showing the highest rank and Advanced Engine Designs is showing the lowest rank. Fuel Efficiency Improvement, Emissions Reduction, Reliability and Maintenance Costs and Safety Performance.

Reverse engineering of stakeholder preferences – A multi-criteria assessment of the German passenger car sector

Germany is a frontrunner in setting frameworks for the transition to a low-carbon system. The mobility sector plays a significant role in this shift, affecting different people and groups on multiple levels. Without acceptance from these stakeholders, emission targets are out of reach. This research analyzes how the heterogeneous preferences of various stakeholders align with the transformation of the mobility sector, looking at the extent to which the German transformation paths are supported and where stakeholders are located.Under the research objective of comparing stakeholders' preferences to identify which car segments require additional support for a successful climate transition, a status quo of stakeholders and car performance criteria is the foundation for the analysis. Stakeholders' hidden preferences hinder the derivation of criteria weightings from stakeholders; therefore, a ranking from observed preferences is used. This study's inverse multi-criteria decision analysis means that weightings can be predicted and used together with a recalibrated performance matrix to explore future preferences toward car segments.Results show that stakeholders prefer medium-sized cars, with the trend pointing towards the increased potential for alternative propulsion technologies and electrified vehicles. These insights can guide the improved targeting of policy supporting the energy and mobility transformation. Additionally, the method proposed in this work can fully handle subjective approaches while incorporating a priori information. A software implementation of the proposed method completes this work and is made publicly available.

Energy assessment of the ageing phenomenon in Li-Ion batteries and its impact on the vehicle range efficiency

The 2035 European Union ban on internal combustion engines pushes the transport industry toward alternative propulsion technologies. One of the most potent alternatives to the 250 million passenger automobiles in Europe is the use of electric vehicles with lithium-ion batteries as a special energy storage system. To develop a sustainable, money-saving, and mature technology like today's internal combustion engines, however, issues including battery deterioration, charging times, and safety must be addressed. In this study, Lithium Ferrum Phosphate and Nickel Manganese Cobalt, two distinct cathode chemistries indicative of transport solutions, are compared for cell performance and ageing. It is possible to improve battery design to increase capacity and lower the risk of thermal runaway by using experimental and numerical methods to evaluate and predict the battery ageing effect. The calibrated ageing model may also forecast battery life and its effect on the vehicle's driving range. The findings indicate that the Lithium Ferrum Phosphate cathode chemistry has a lower energy density and ages more quickly than the Nickel Manganese Cobalt, resulting in a shorter driving range. In specifically, a brand-new Nickel Manganese Cobalt battery provides 84 km of additional city driving range and 50 km of highway driving range over a Lithium Ferrum Phosphate battery. The Nickel Manganese Cobalt battery offers 53 km more driving range on the interstate and 91 km more in urban driving at the end of its useful life (20 % capacity loss).

Fire tests with lithium-ion battery electric vehicles in road tunnels

Alternative propulsion technologies, including battery-electric vehicles, are becoming increasingly prevalent. Whilst such vehicles remain a small overall proportion of the vehicle fleet, the combined impact of government policy and technological advances in alternative fuels is expected to accelerate the increase in their numbers in coming years.As a result of these changes, the nature of tunnel safety risk (including the risk of fire) is expected to change over time. The risk implications associated with such vehicles thus requires more detailed consideration. This entails evaluation of incident consequences with particular attention being paid to the impact of fire characteristics and toxic emissions on tunnel users and to the need for specific emergency intervention strategies.In the past, concerns were voiced with respect to the fire safety of the new energy storage device (battery) and the possibility of more difficult firefighting conditions. This resulted in a series of investigations concerning the safety aspects of batteries and battery electric vehicles. However, most of the tests performed merely dealt with battery cells or battery packs. To date, publicly available tests involving actual vehicles remain relatively rare. In 2018, the Austrian Government commissioned a research project concerning the effect of incidents with battery electric vehicles on tunnel safety. This project encompassed fire tests of passenger cars, simulations for heavy duty vehicles, and the impact of incidents with such vehicles on the safety of tunnel users and the tunnel structure.In a series of fire tests, the heat-release and production of (toxic) substances has been evaluated. The burning behaviour of vehicles with different energy storage technologies (i.e. Li-ion batteries, Diesel) was monitored and compared to each other. The heat-release rate and emission of (toxic) substances was measured, and different fire-fighting methods were applied during each test.This paper will focus on the aspect of full-scale fire tests of passenger cars performed in a road tunnel. It should be emphasized that the battery-electric vehicle fire tests presented here were the first of their kind under real road tunnel conditions. This concerns the fire behaviour, but also some new approaches to fighting a BEV fire. All previous tests reported in journals were either carried out in fire halls or only concerned individual battery modules.

Techno–Economic and Risk Evaluation of Combined Cycle Propulsion Systems in Large Container Ships

Owing to the stringent regulations on pollutant emissions that are imposed by the International Maritime Organization and increasing fuel prices, there has been significant research on developing cleaner fuels and novel propulsion systems. This study presents a techno-economical and risk assessment method for evaluating alternative propulsion technologies and cleaner fuels as substitutes for heavy fuel oil and two-stroke diesel engines in marine transportation. This analysis was carried out for two different journeys. Accordingly, we evaluated the economic benefits of using an enhanced intercooler/reheat combined gas and steam cycle or simple and intercooler/reheat combined gas and steam cycles that were fueled by marine diesel oil or liquified natural gas instead of a two-stroke diesel engine that was fueled by MDO as the propulsion system in a large container ship, considering different shipping routes. The results highlighted the advantages of implementing the simple, intercooler/reheat, and enhanced combined gas and steam cycles as propulsion systems. A sensitivity analysis was performed to investigate the effects of the fuel cost, capital cost, and hull fouling resistance on the economic analysis. For the routes that were considered herein, compared to a two-stroke diesel engine that was fueled by MDO, the simple, intercooler/reheat, and enhanced gas and steam combined cycles that were fueled by LNG increased the net present value by 78.3%, 78.5%, and 76.4%, respectively, and reduced the payback period by 38.8%, 38.9%, and 35%, respectively. Furthermore, the fuel and capital costs had a significant influence on the overall economic profit.

Environmental sustainability of alternative marine propulsion technologies powered by hydrogen - a life cycle assessment approach

Shipping is a very important source of pollution worldwide. In recent years, numerous actions and measures have been developed trying to reduce the levels of greenhouse gases (GHG) from the marine exhaust emissions in the fight against climate change, boosting the Sustainable Development Goal 13. Following this target, the action of hydrogen as energy vector makes it a suitable alternative to be used as fuel, constituting a very promising energy carrier for energy transition and decarbonization in maritime transport. The objective of this study is to develop an ex-ante environmental evaluation of two promising technologies for vessels propulsion, a H2 Polymeric Electrolytic Membrane Fuel Cell (PEMFC), and a H2 Internal Combustion Engine (ICE), in order to determine their viability and eligibility compared to the traditional one, a diesel ICE. The applied methodology follows the Life Cycle Assessment (LCA) guidelines, considering a functional unit of 1 kWh of energy produced. LCA results reveal that both alternatives have great potential to promote the energy transition, particularly the H2 ICE. However, as technologies readiness level is quite low, it was concluded that the assessment has been conducted at a very early stage, so their sustainability and environmental performance may change as they become more widely developed and deployed, which can be only achieved with political and stakeholder's involvement and collaboration.

A Comparative Review of Alternative Fuels for the Maritime Sector: Economic, Technology, and Policy Challenges for Clean Energy Implementation

Global maritime transportation is responsible for around 3% of total anthropogenic greenhouse gas emissions and significant proportions of SOx, NOx, and PM emissions. Considering the predicted growth in shipping volumes to 2050, greenhouse gas emissions from ships must be cut by 75–85% per ton-mile to meet Paris Agreement goals. This study reviews the potential of a range of alternative fuels for decarbonisation in maritime. A systematic literature review and information synthesis method was applied to evaluate fuel characteristics, production pathways, utilization technologies, energy efficiency, lifecycle environmental performance, economic viability, and current applicable policies. Alternative fuels are essential to decarbonisation in international shipping. However, findings suggest there is no single route to deliver the required greenhouse gas emissions reductions. Emissions reductions vary widely depending on the production pathways of the fuel. Alternative fuels utilising a carbon-intensive production pathway will not provide decarbonisation, instead shifting emissions elsewhere in the supply chain. Ultimately, a system-wide perspective to creating an effective policy framework is required in order to promote the adoption of alternative propulsion technologies.

Assessment and Recommendations for a Fossil Free Future for Track Work Machinery

Current railway track work machinery is mainly operated with diesel fuel. As a result, track maintenance of Austrian Federal Railways (OeBB) amounts to nearly 9000 t CO2 equivalent per year according to calculations from Graz University of Technology. OeBB’s total length of railway lines only accounts for 0.56% of the world’s length of lines. This indicates huge potential for mitigating greenhouse gas emissions considering the need for track maintenance worldwide. Environmental concerns have led to the introduction of alternative drives in the transport sector. Until now, R&D (Research & Development) of alternative propulsion technologies for track work machinery has been widely neglected. This paper examines the possibility of achieving zero direct emissions during maintenance and construction work in railways by switching to alternative drives. The goal is to analyze alternative propulsion solutions arising from the transport sector and to assess their applicability to track work machinery. Research results, together with a calculation tool, show that available battery technology is recommendable for energy demands lower than 300 kWh per construction shift. Hydrogen fuel cell technology is an alternative for energy demands higher than 800 kWh. For machinery with energy requirements in between, enhancements in battery technology are necessary and desirable for the coming years.

Environmental performance of four different heavy-duty propulsion technologies using Life Cycle Assessment

The goal of this study is to perform an environmental analysis using the Life Cycle Assessment methodology to compare different technologies for heavy-duty trucks: Diesel, Diesel Hybrid, Spark-Ignited Natural Gas, High-Pressure Direct Injection Natural Gas. The analysis considers five impact categories: climate change, particulate matter, ozone photochemical formation, terrestrial eutrophication and acidification. This paper also contains a Total Cost of Ownership analysis.The main results reveal a reduction between 5 and 6% of Greenhouse Gases for alternative propulsion technologies. Natural gas trucks show a considerable reduction (40–50%) compared to conventional diesel in terms of terrestrial eutrophication and acidification, besides, for particulate matter and photochemical ozone formation, there are also minor reductions (10%).The economic analysis indicates that diesel is an attractive alternative, despite its poor environmental behaviour, and natural gas trucks do not seem to be as economically competitive as diesel. Diesel hybrid results show a not good option neither economically nor environmentally.

The trajectory of hybrid and hydrogen technologies in North American heavy haul operations

The central aim of this paper is to provide an up-to-date snapshot of hybrid and hydrogen technology-related developments and activities in the North American heavy haul railway setting, placed in the context of the transportation industry more broadly. An overview of relevant alternative propulsion technologies is provided, including a discussion of applicability to the transportation sector in general and heavy haul freight rail specifically. This is followed by a discussion of current developments and research in alternative and blended fuels, discussed again in both general and specific settings. Key factors and technical considerations for heavy haul applications are reviewed, followed by a discussion of non-technical and human factors that motivate a move toward clean energy in North American Heavy Haul systems. Finally, current project activities are described to provide a clear understanding of both the status and trajectory of hybrid and hydrogen technologies in the established context.

Innovative and Highly Integrated Modular Electric Drivetrain

A highly integrated electric drivetrain module with 157 kW peak power is presented, which incorporates novel technologies in the field of electric machines, power electronics and transmissions: 1. High-speed electric machine with six phases and injection mould polymer-bonded magnets; 2. High-ratio dual-speed transmission with double planetary gear set (Ravigneaux gear set); 3. Gallium nitride (GaN) power electronics with winding reconfiguration feature.The combination of these components in one single housing makes the drive module flexible to integrate and to combine with conventional or alternative propulsion technologies, thus allowing various hybrid and electric drivetrain topologies. All technologies are selected in accordance with mass production potential and can therefore have a high impact on the automotive market in the future. Currently, the drive module is under development; the first models will be assembled in winter 2019. The integration into a demonstrator vehicle in 2020 will prove the potential of many new technologies and the suitability for the automotive market.

How much energy does a car need on the road?

A car often requires more energy when driven in daily operation than indicated by the manufacturer. This paper presents a model to derive this real-world energy demand for a passenger car, based on a few widely available input data on vehicle operation. The approach works for conventional and alternative propulsion technologies. The underlying data stem from an extensive Swiss chassis dynamometer and on-road measurement campaign, which lasted for more than a year. The test fleet consisted of a compressed natural gas, gasoline hybrid, gasoline plug-in hybrid, fuel cell electric, and a battery-electric vehicle. The derived model adjusts the propulsive power demand within the legislative WLTP cycle for class 3b vehicles to a road mission by incorporating effects of traffic, driving styles, and topography. It additionally accounts for load from auxiliary devices. The approach works with input data from a household travel survey or traffic flow simulation and can serve as a tool to everyone who needs to estimate the average on-road energy demand of any passenger car or a fleet of them, rather than their type-approval values. Tested on a compact-sized vehicle, the approach estimates a mean discrepancy in real-world energy demand to WLTP type-approval values for Switzerland of about 22% for conventional cars. Furthermore, we can show similar gaps for hybrid technologies of around 30% and for battery-electric cars of 25%.

Modeling and Investigation of a Turboprop Hybrid Electric Propulsion System

Hybrid electric propulsion in the aviation field is becoming an effective alternative propulsion technology with potential advantages, including fuel savings, lower pollution, and reduced noise emission. On the one hand, the aeroengine manufacturers are working to improve fuel consumption and reduce pollutant emissions with new combustion systems; on the other hand, much attention is given to reducing the weight of the batteries increasing the energy density. Hybrid electric propulsion systems (HEPS) can take advantage of the synergy between two technologies by utilizing both internal combustion engines (ICEs) and electric motors (EMs) together, each operating at their respective optimum conditions. In the present work, some numerical investigations were carried out by using a zero-dimensional code able to simulate the flight mission of a turboprop aircraft, comparing fuel consumption and pollutant emissions of the original engine with other two smaller gas turbines working in hybrid configuration. An algorithm has been implemented to calculate the weight of the batteries for the different configurations examined, evaluating the feasibility of the hybrid propulsion system in terms of number of non-revenue passengers.

Sectoral dynamics and technological convergence: an evolutionary analysis of eco-innovation in the automotive sector

We know from evolutionary theory that sectoral characteristics are important to innovation. This paper investigates if sectoral characteristics also are important to eco-innovation, a hitherto under-researched theme. We argue that research into possible sectoral patterns in eco-innovation is key to understanding green industrial dynamics and the greening of the economy. This paper investigates to what degree the economy is greening horizontally (sector-wise). Starting with a sectoral case study, we undertake a longitudinal analysis of the breath and strength of the greening of the automotive sector from 1965 to 2012, focusing on powertrain technologies. The empirical analysis is based on patent data amongst big car producers and focuses on identifying changes in two main aspects: (1) the convergence/divergence of firms’ green strategies and technologies within the automotive sector; and (2) the contribution of alternative key green technological trajectories relative to the dominant design. Our findings indicate that the evolution of relative green patenting has followed a positive, linear growth over the last decades with increasing participation of alternative propulsion technologies and increasing convergence of automakers’ strategies towards a diversified portfolio.

Cost benefit analysis of three different urban bus drive systems using real driving data

One of the CIVITAS-ELAN project measures in Ljubljana, Slovenia, was the introduction of alternative city bus propulsion systems (CNG, hydraulic hybrid buses) into the public transport and comparison of their performance in terms of costs and benefits with conventional (diesel) buses. A cost-benefit analysis was conducted to provide a model for identifying the most attractive alternative, with aim of aiding the decision making process for future rational up-scaling of the alternative propulsion technologies in PT fleet in Ljubljana. This paper focuses on presenting the key findings of this CBA, using real driving data, while demonstrating the sensitivity/variance of different parameters of a CBA, as well as the differentiation between uncertainties of parameters in an ex-ante analysis versus an ex-post analysis.

Hybrid-electric propulsion for automotive and aviation applications

In parallel with the automotive industry, hybrid-electric propulsion is becoming a viable alternative propulsion technology for the aviation sector and reveals potential advantages including fuel savings, lower pollution, and reduced noise emission. Hybrid-electric propulsion systems can take advantage of the synergy between two technologies by utilizing both internal combustion engines and electric motors together, each operating at their respective optimum conditions. However, there can also be disadvantages to hybrid propulsion. We are conducting an analysis of hybrid-electric propulsion for aircraft, which is looking at modelling systems over a range of aircraft scale, from small UAVs to inter-city airliners. To support the theoretical models, a mid-scale hybrid-electric propulsion system for a single-seat manned aircraft is being designed, built, and tested to generate data for validation and development of the simulation models. This paper draws parallels between the synergy of hybrid-electric propulsion for automotive and aviation applications, and presents an innovative theoretical approach integrating several desktop PC software packages to analyse and optimize hybrid-electric technology for aircraft. Our findings to date indicate that hybrid-electric propulsion can have a significant impact in the small- and mid-scale sectors, but only a minor impact in the large-scale sector assuming battery energy densities predicted for the next decade. Fuel savings of up to 50 and 10 % have been calculated for a microlight aircraft and inter-city airliner, respectively, over the mission profiles considered.

Air Quality and Climate Impacts of Alternative Bus Technologies in Greater London

The environmental impact of diesel-fueled buses can potentially be reduced by the adoption of alternative propulsion technologies such as lean-burn compressed natural gas (LB-CNG) or hybrid electric buses (HEB), and emissions control strategies such as a continuously regenerating trap (CRT), exhaust gas recirculation (EGR), or selective catalytic reduction with trap (SCRT). This study assessed the environmental costs and benefits of these bus technologies in Greater London relative to the existing fleet and characterized emissions changes due to alternative technologies. We found a >30% increase in CO2 equivalent (CO2e) emissions for CNG buses, a <5% change for exhaust treatment scenarios, and a 13% (90% confidence interval 3.8-20.9%) reduction for HEB relative to baseline CO2e emissions. A multiscale regional chemistry-transport model quantified the impact of alternative bus technologies on air quality, which was then related to premature mortality risk. We found the largest decrease in population exposure (about 83%) to particulate matter (PM2.5) occurred with LB-CNG buses. Monetized environmental and investment costs relative to the baseline gave estimated net present cost of LB-CNG or HEB conversion to be $187 million ($73 million to $301 million) or $36 million ($-25 million to $102 million), respectively, while EGR or SCRT estimated net present costs were $19 million ($7 million to $32 million) or $15 million ($8 million to $23 million), respectively.

Individual characteristics and stated preferences for alternative energy sources and propulsion technologies in vehicles: A discrete choice analysis for Germany

With respect to the German goal of a transition to a lead market for electromobility within a short time period, this paper empirically examines the preferences for alternative energy sources or propulsion technologies in vehicles and particularly for electric vehicles. The data stem from a stated preference discrete choice experiment with 598 potential German car buyers. In order to simulate a realistic future purchase situation, seven vehicle types were incorporated in each of the six choice sets, i.e. hybrid, gas, biofuel, hydrogen, and electric vehicles besides common gasoline and diesel vehicles. The econometric analysis with flexible multinomial probit models reveals that potential car buyers in Germany currently have a low stated preference for electric, hydrogen, and hybrid vehicles. While our paper also discusses the impact of common vehicle attributes such as purchase price or service station availability, it particularly considers the effect of socio-demographic and environmental awareness variables. The estimation results reveal that younger potential car buyers have a higher stated preference for hydrogen and electric vehicles, males have a higher stated choice of hydrogen vehicles, and environmentally aware potential car buyers have a higher stated preference for hydrogen and electric vehicles. These results suggest that common policy instruments such as the promotion of research and development, taxation, or subsidization in the field of electromobility could be supplemented by strategies to increase the social acceptance of alternative vehicle types that are directly oriented to these population groups. Methodologically, our study highlights the importance of the inclusion of taste persistence across the choice sets and a high number of random draws in the Geweke–Hajivassiliou–Keane simulator in the simulated maximum likelihood estimation of the multinomial probit models.

Conventional helicopters: an adaptiveness study for more electric and alternative propulsion technologies

The power plant and drive systems in a conventional helicopter cause high development and operating costs, compromise safety, and introduce performance limitations. Even though much effort is devoted to mechanical transmission systems, the use of electric components promises a higher reliability. Magnetic gearboxes address many of the problems in mechanical transmissions, but proved to be too heavy at this time. However, since this technology has not achieved its full potential, improvements are imminent and could allow its implementation in the near future. Several combinations with energy sources, amongst which liquid hydrogen (LH2), showed a turboshaft with kerosene to offer the lightest configuration. For the lower required power range, Avgas piston engines should at least be replaced with more efficient diesel engines. The possibility of using electric motors, such as the switched reluctance motor, to drive the tail rotor is possible at the expense of weight. The use of LH2, which has a threefold higher energy density than kerosene, in a helicopter seems feasible; though heavier due to an increased helicopter volume and tank weight, it offers a free cold source for high-performing high-temperature superconductive devices.