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The advent of space exploration missions, especially those aimed at establishing a sustainable presence on the Moon and beyond, necessitates the development of efficient propulsion and mission planning techniques. This study presents a comprehensive analysis of chemical and electric propulsion systems for spacecraft, focusing on optimizing propellant distribution for missions involving transfers from Low-Earth Orbit (LEO) to Geostationary Orbit (GEO) and the Lunar surface. Using mathematical modeling and optimization algorithms, we calculate the delta-v requirements for key mission segments and determine the propellant mass required for each propulsion method. The results highlight the trade-offs between the high thrust of chemical propulsion and the high specific impulse of electric propulsion. An optimization model is developed to minimize the total propellant mass, considering a hybrid approach that leverages the advantages of both propulsion types. This research contributes to the field of aerospace engineering by providing insights into propulsion system selection and mission planning for future exploration missions to the Moon, Mars, and Venus. [ABSTRACT FROM AUTHOR]

The driving characteristics of a hybrid propulsion system (HPS) depend on operational management strategies. However, the differences in output and response of various types of power sources make real-time management of operating conditions complex. In this study, an operational management strategy, which combines adaptive equivalent consumption minimization strategy (AECMS) and general regression neural network (GRNN), is proposed for optimizing power controls within hybrid power sources. Under this strategy, the optimal function of the AECMS is adaptively calculated by the load profile changes based on GRNN’s prediction results, and it is more suitable for the HPS. Furthermore, the proposed GRNN-AECMS method can minimize fuel consumption and meet requirements for power tracking. From simulation results, fuel consumption under GRNN-AECMS method can be reduced by 2.715 kg, or 31.8%.

The advent of space exploration missions, especially those aimed at establishing a sustainable presence on the Moon and beyond, necessitates the development of efficient propulsion and mission planning techniques. This study presents a comprehensive analysis of chemical and electric propulsion systems for spacecraft, focusing on optimizing propellant distribution for missions involving transfers from Low-Earth Orbit (LEO) to Geostationary Orbit (GEO) and the Lunar surface. Using mathematical modeling and optimization algorithms, we calculate the delta-v requirements for key mission segments and determine the propellant mass required for each propulsion method. The results highlight the trade-offs between the high thrust of chemical propulsion and the high specific impulse of electric propulsion. An optimization model is developed to minimize the total propellant mass, considering a hybrid approach that leverages the advantages of both propulsion types. This research contributes to the field of aerospace engineering by providing insights into propulsion system selection and mission planning for future exploration missions to the Moon, Mars, and Venus.

The application of newly available technologies in the green maritime sector is difficult due to conflicting requirements and the inter-relation of different ecological, technological and economical parameters. The governments incentivize radical reductions in harmful emissions as an overall priority. If the politics do not change, the continuous implementation of stricter government regulations for reducing emissions will eventually result in the mandatory use of, what we currently consider, alternative fuels. Immediate application of radically different strategies would significantly increase the economic costs of maritime transport, thus jeopardizing its greatest benefit: the transport of massive quantities of freight at the lowest cost. Increased maritime transport costs would immediately disrupt the global economy, as seen recently during the COVID-19 pandemic. For this reason, the industry has shifted towards a gradual decrease in emissions through the implementation of "better" transitional solutions until alternative fuels eventually become low-cost fuels. Since this topic is very broad and interdisciplinary, our systematic overview gives insight into the state-of-the-art available technologies in green maritime transport with a focus on the following subjects: (i) alternative fuels; (ii) hybrid propulsion systems and hydrogen technologies; (iii) the benefits of digitalization in the maritime sector aimed at increasing vessel efficiency; (iv) hull drag reduction technologies; and (v) carbon capture technologies. This paper outlines the challenges, advantages and disadvantages of their implementation. The results of this analysis elucidate the current technologies' readiness levels and their expected development over the coming years. [ABSTRACT FROM AUTHOR]

Climate protection goals and the transformation of the mobility sector are pushing the shipping industry to develop new propulsion systems emitting fewer or no greenhouse gases. One promising approach to eliminate greenhouse gas emissions from ships is a hybrid propulsion system powered by fuel cells and batteries. A high-temperature solid oxide fuel cell (SOFC) can supply heat and the electrical power demand in combination with a battery. Due to the low dynamic performance of the SOFC when faced with sudden load changes, a battery is responsible for providing the power for the dynamic load components. To ensure the resource-efficient operation of the propulsion components, intelligent energy management methods are required for power distribution control. Implementing a machine-learning-based energy management method based on twin-delayed deep deterministic policy gradient (TD3) improves the overall system efficiency, lifetime, and fuel economy compared to conventional energy management methods. To verify the technical feasibility of the propulsion system including its controls, the system is tested in a hardware-in-the-loop (HIL) environment. By implementing the TD3-based algorithm within the energy management used on the test bench, hydrogen consumption was reduced by approximately 10% and the remaining battery capacity after five years was 6% higher in comparison to conventional energy management methods. [Display omitted] • Hybrid electric propulsion system for a marine application. • Development of machine-learning-based energy management algorithms. • Validation measurements with propulsion components. • Assessment of the economic performance for a large cruise ship application. [ABSTRACT FROM AUTHOR]

The application of newly available technologies in the green maritime sector is difficult due to conflicting requirements and the inter-relation of different ecological, technological and economical parameters. The governments incentivize radical reductions in harmful emissions as an overall priority. If the politics do not change, the continuous implementation of stricter government regulations for reducing emissions will eventually result in the mandatory use of, what we currently consider, alternative fuels. Immediate application of radically different strategies would significantly increase the economic costs of maritime transport, thus jeopardizing its greatest benefit: the transport of massive quantities of freight at the lowest cost. Increased maritime transport costs would immediately disrupt the global economy, as seen recently during the COVID-19 pandemic. For this reason, the industry has shifted towards a gradual decrease in emissions through the implementation of “better” transitional solutions until alternative fuels eventually become low-cost fuels. Since this topic is very broad and interdisciplinary, our systematic overview gives insight into the state-of-the-art available technologies in green maritime transport with a focus on the following subjects: (i) alternative fuels; (ii) hybrid propulsion systems and hydrogen technologies; (iii) the benefits of digitalization in the maritime sector aimed at increasing vessel efficiency; (iv) hull drag reduction technologies; and (v) carbon capture technologies. This paper outlines the challenges, advantages and disadvantages of their implementation. The results of this analysis elucidate the current technologies’ readiness levels and their expected development over the coming years.

Following the climatic changes, there is a universal commitment to reduce greenhouse gas emissions, especially those due to mobility. A particular interest is addressed to hybrid propulsion systems, which are currently considered as viable candidates for a sustainable mobility. Within this commitment, the study proposes an approach to improve the cost‐effectiveness, compactness and reliability of the electric drive unit of hybrid propulsion systems. This is achieved thanks to different associations of brushless DC motors (BDCMs) and reduced topologies of DC/AC converters such as the four switch inverter and three switch inverter. A special attention is focused upon the analysis of the sequences and commutations characterising the six‐phase and three‐phase BDCM drive operation. Implementation schemes of dedicated control strategies are given. Moreover, a comparison of selected features related to the ratings of the investigated BDCM drives is carried out and commented. Experimental results are provided to validate the performances of a reduced structure inverter fed three‐phase BDCM under the dedicated control strategy. [ABSTRACT FROM AUTHOR]

This paper presents a simulation-based analysis of hybrid and plug-in hybrid propulsion system concepts for diesel-electric multiple unit regional railway vehicles. These alternative concepts primarily aim to remove emissions in terminal stops with longer stabling periods, with additional benefits reflected in the reduction of overall fuel consumption, produced emissions, and monetary costs. The alternative systems behavior is modeled using a backward-looking quasi-static simulation approach, with the implemented energy management strategy based on a finite state machine control. A comparative assessment of alternative propulsion systems is carried out in a case study of a selected regional railway line operated by Arriva, the largest regional railway undertaking in the Netherlands. The conversion of a standard diesel-electric multiple unit vehicle, currently operating on the network, demonstrated a potential GHG reduction of 9.43–56.92% and an energy cost reduction of 9.69–55.46%, depending on the type of service (express or stopping), energy storage technology selection (lithium-ion battery or double-layer capacitor), electricity production (green or grey electricity), and charging facilities configuration (charging in terminal stations with or without additional charging possibility during short intermediate stops) used. As part of a bigger project aiming to identify optimal transitional solutions towards emissions-free trains, the outcomes of this study will help in the future fleet planning.

• Methodologies for preliminary co-design of hybrid regional aircraft electric components and control strategies. • Energy benefits and mass and volumetric impacts of regional aircraft fuel cell hybridization. • Real mission profiles exploited to derive the blended control strategy for the electrified turboprop section. • High-potential of hydrogen and PEM fuel cell technology to mitigate the mass impact of aircraft electrification. • Exploitation of versatile control rules to support the preliminary design of hybrid aircrafts. The growing demand for air travel in the commercial sector leads to an increase in global emissions, whose mitigation entails transitioning from the current fossil-fuel based generation of aircrafts to a cleaner one within a short timeframe. The use of hydrogen and fuel cells has the potential to reach zero emissions in the aerospace sector, provided that required innovation and research efforts are substantially accomplished. Development programs, investments and new regulations are needed for this technology to be safe and economical. In this context, it makes sense to develop a model-based preliminary design methodology for a hybrid regional aircraft assisted by a battery hybridized fuel cell powertrain. The technological assumptions underlying the study refer to both current and expected data for 2035. The major contribution of the proposed methodology is to provide a mathematical tool that considers the interactions between the choice of components in terms of installed power and energy management. This simultaneous study is done because of the availability of versatile control maps. The tool was then deployed to define current and future technological scenarios for fuel cell, battery and hydrogen storage systems, by quickly adapting control strategies to different sizing criteria and technical specifications. In this way, it is possible to facilitate the estimation of the impact of different sizing criteria and technological features, at the aircraft level, on the onboard electrical system, the management of in-flight power, the propulsion methods, the impact of the masses on consumption and operational characteristics in a typical flight mission. The proposed combination of advanced sizing and energy management strategies allowed meeting mass and volume constraints with state-of-the-art PEM fuel cell and Li-ion battery specifications. Such a solution corresponds to a high degree of hybridization between the fuel cell system and battery pack (i.e., 300 kW and 750 kWh), whereas projected 2035 specs were demonstrated to help reduce mass and volume by 23 % and 40 %, respectively. [ABSTRACT FROM AUTHOR]

The operational management of vehicular hybrid propulsion systems (HPSs) is critical to its fuel consumption, overall efficiency, and life-cycle cost. With the help from hybrid energy storage systems (HESS), the conventional problem associated with the fluctuating load profile of vehicular system can be addressed. However, the diverse power/energy/efficiency characteristics of different energy sources leads to complex operational management strategies that coordinate them under different operational scenarios. In this paper, a two-layer hierarchal optimization framework is proposed to improve the performance of vehicular HPSs. In the first layer, the fuel consumption of the system is focused and the coordination strategy between power generation and energy storage is optimized by adopting adaptive neural fuzzy inference system based on the dynamic programming (ANFIS-DP) strategy. Further, the operational loss of the HPSs is considered as the secondary optimization target, the coordination strategy of HESS is optimized by adaptive low-pass filtering (ALPF) strategy. To demonstrate the advantage of the proposal, a shipboard HPS is involved as the benchmark study case, a hardware-in-the-loop test is conducted. The results show that the ANFIS-DP strategy reduces fuel consumption by 14.3%, and the suggested ALPF strategy may minimize system loss by up to 11%, when compared with more conventional methodologies. • A DG/Battery/SC vehicular HPSs is proposed to separate load fluctuations from the vehicle system. • A real-time ANIFS-DP strategy is developed to reduce fuel consumption. • An ALPF strategy is developed to improve the overall efficiency and life-cycle of HESS. • A two-layer hierarchical optimization framework is proposed to coordinate two OMS. • The proposed framework of OMS is validated in a hardware in the loop experiment. [ABSTRACT FROM AUTHOR]

The paper deals with the direct torque control (DTC) of brushless DC (BLDC) motor drives fed by four-switch inverters (also known as B4-inverters) rather than six-switch inverters (also known as B6-inverters) in conventional drives. The B4-inverter could be regarded as a reconfigured topology of the B6-inverter in case of a switch/leg failure which represents a crucial reliability benefit for many applications especially in electric and hybrid propulsion systems. The principle of operation of the BLDC motor is firstly recalled considering both cases of B6- and B4-inverters in the armature, with emphasis on the two- and three-phase conduction modes. Then, the DTC of B4-inverter-fed BLDC motor drives is treated considering three strategies, such as: 1) DTC-1: a strategy inspired from the one intended to B6-inverter-fed BLDC motor drives; 2) DTC-2: a strategy that considers a dedicated vector selection subtable in order to independently control the torques developed by the phases connected to the B4-inverter legs during their simultaneous conduction; and 3) DTC-3: a proposed strategy that eliminates the torque dips penalizing DTC-2 during sector-to-sector commutations. Following the design of the corresponding vector selection tables and subtables (if any), an experimentally based comparative study of the three DTC strategies is carried out considering, in the first step, the BLDC motor steady-state operation under DTC-1 and DTC-3. Then, the comparison is extended to the BLDC motor features during sector-to-sector commutations, under DTC-2 and DTC-3. The experimental results clearly validate the predicted performance of the proposed DTC strategy. [ABSTRACT FROM AUTHOR]

This paper presents a simulation-based analysis of hybrid and plug-in hybrid propulsion system concepts for diesel-electric multiple unit regional railway vehicles. These alternative concepts primarily aim to remove emissions in terminal stops with longer stabling periods, with additional benefits reflected in the reduction of overall fuel consumption, produced emissions, and monetary costs. The alternative systems behavior is modeled using a backward-looking quasi-static simulation approach, with the implemented energy management strategy based on a finite state machine control. A comparative assessment of alternative propulsion systems is carried out in a case study of a selected regional railway line operated by Arriva, the largest regional railway undertaking in the Netherlands. The conversion of a standard diesel-electric multiple unit vehicle, currently operating on the network, demonstrated a potential GHG reduction of 9.43–56.92% and an energy cost reduction of 9.69–55.46%, depending on the type of service (express or stopping), energy storage technology selection (lithium-ion battery or double-layer capacitor), electricity production (green or grey electricity), and charging facilities configuration (charging in terminal stations with or without additional charging possibility during short intermediate stops) used. As part of a bigger project aiming to identify optimal transitional solutions towards emissions-free trains, the outcomes of this study will help in the future fleet planning. [ABSTRACT FROM AUTHOR]

Recent developments in fuel cell (FC) technologies show great potential to increase flight duration of unmanned aerial vehicles (UAVs) with satisfactory fuel economy. The three most common FCs used to power UAVs are: 1) polymer electrolyte membrane FC, 2) direct methanol FC, and 3) solid oxide FC. Because of the power performance limitation of pure FC propulsion systems, hybrid propulsion systems that integrate FCs with other power sources such as batteries, supercapacitors, solar cells, and conventional internal combustion engines are recommended for UAVs. This paper reviews the current developments in FC hybrid propulsion systems applied to UAVs. The topics covered include the operating principles and characteristics of three typical FCs, issues faced by FC-powered UAVs, specific roles of other electric power sources, pure electric hybrid constructions of FC hybrid propulsion systems, hybrid engine-electric FC hybrid propulsion systems, potential impacts of various flight factors, energy management strategies of FC hybrid propulsion systems, and similarities/differences of FC hybrid propulsion systems in other vehicle applications. Finally, future trends and challenges of FC hybrid propulsion systems are discussed, which could be valuable for the development of next-generation UAVs. [ABSTRACT FROM AUTHOR]