• Energy Research
• 2021-2025close

The energy transition and the decarbonization of transport dictate a switch towards electrification in the naval sector. Ferries, among the different types of ships, are those most suited for a full electrification, consisting in the replacement of engines with electric motor drives and fuel tanks with electrochemical energy storage systems. However, some cost issues and energy storage technological limitations still hamper full electrification, making partial electrification more practical, which can still be effective in reducing pollutant emissions in ports and surrounding areas. The aim of this work is to investigate some issues related to onboard energy storage systems needed for electric ferries. The Ro-Ro Elio ferry, operating in the Strait of Messina is considered as a case study. Some different solutions are investigated, in terms of economic/enviromental efficiency, which is the cost of preventing the emission of a kg of CO2.

The electrification of ferries requires efficient shore infrastructures that include energy supply grids, communication networks, charging systems, energy storage systems, interfacing and monitoring devices. In this context, a lot of research and development efforts have been made in the last decade that are reviewed in this paper. Energy storage technologies, battery charging requirements and their safety parameters are first analyzed. A comprehensive review on shore side infrastructure design and power system architecture are then provided. Different shore to ship interfaces are finally presented along with, some alternative solutions to battery charging stations.

A three-phase multi-level multi-input power converter topology is presented for grid-connected applications. It encompasses a three-phase transformer that is operated on the primary side in an open-end winding configuration. Thus, the primary winding is supplied on one side by a three-phase N-level neutral point clamped inverter and, on the other side, by an auxiliary two-level inverter. A key feature of the proposed approach is that the N-level inverter is able to perform independent management of N − 1 input power sources, thus avoiding the need for additional dc/dc power converters in hybrid multi-source systems. Moreover, it can manage an energy storage system connected to the dc-bus of the two-level inverter. The N-level inverter operates at a low switching frequency and can be equipped with very low on-state voltage drop Insulated-Gate Bipolar Transistor (IGBT) devices, while the auxiliary inverter is instead operated at low voltage according to a conventional high-frequency two-level Pulse Width Modulation (PWM) technique and can be equipped with very low on-state resistance Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) devices. Simulations and experimental results confirm the effectiveness of the proposed approach and its good performance in terms of grid current harmonic content and overall efficiency.

Capacity loss over time is a critical issue for lithium-ion batteries powering battery electric vehicles (BEVs) because it affects vehicle range and performance. Driving cycles have a major impact on the ageing of these devices because they are subjected to high stresses in certain uses that cause degradation phenomena directly related to vehicle use. Calendar capacity also impacts the battery pack for most of its lifetime with a capacity degradation. The manuscript describes experimental tests on a lithium-ion battery for electric vehicles with up to 10% capacity loss in the WLTP CLASS 3B driving cycle. The lithium-ion battery considered consists of an LMO-NMC cathode and a graphite anode with a capacity of 63 Ah for automotive applications. An internal impedance variation was observed compared to the typical full charge/discharge profile. Incremental capacitance (IC) and differential voltage (DV) analysis were performed in different states of cell health. A lifetime model is described to compute the total capacity loss for cycling and calendar ageing exploiting real data under some different scenarios of vehicle usage.

A technique to improve the performance of grid-connected induction motors by exploiting an auxiliary winding set is proposed in this paper. This auxiliary winding features the same distribution of the main winding, although with a reduced number of turns and it is fed by an inverter a fraction of the power in comparison with the rated size of the induction motor. As shown in the paper, through the auxiliary winding, it is possible to set the machine power factor, increasing the efficiency of the power conversion system and mitigating speed oscillations due to torque disturbances. A mitigation of the grid current peaks due to motor start-up is obtainable. First, the proposed technique is theoretically introduced, then a feasibility assessment is accomplished by simulations.

Environmental climate change has encouraged countries across the world to develop policies aimed to the reduction in energy consumption and greenhouse gas emissions. The introduction of Zero-Emission Vehicles based on electrical powertrains, could reduce the emission of environmental pollutants, the noise levels and could increase the liveability of urban areas. Although in recent years research on batteries has brought several benefits to electric vehicle performance, key barriers to their adoption are still high cost, reduced autonomy, long charging times and the leak of a suitable network of charging stations. Substantial improvements in electric vehicles performance are expected with the development of new Li-ion batteries, thanks to some notable advantages over other types of batteries, such as: high energy density, high power density, long cycle life and long calendar life. This paper is aimed to present a reliability assessment procedure based on an ageing model able to estimate from datasheet information the lifetime of Lithium-ion batteries for electric vehicles, the residual capacity and reliability margins under different driving cycles, taking also into account the battery calendar ageing.

An Open-End Winding system is proposed able to manage the electric generator and the battery energy storage system in a wind power plant with integrated energy storage. The proposed system is formed by connecting a T-Type rectifier and a two-level inverter/rectifier equipped with fast GaN devices through the open stator winding of the AC generator. The T-Type rectifier feeds power to the dc bus of the grid inverter, while the energy storage system is managed by the inverter/rectifier, which acts also as an active power filter to sinusoidally shape the generator phase currents, and as a voltage equalizer to balance the voltage of the output capacitors. A three-port power conversion system with almost negligible switching power losses is obtained, because the T-Type rectifier is operated at very low switching frequency, while low inverter switching power losses are achieved thanks to the GaN devices. Purposely developed modulation and control techniques are exploited to cope with the specific features of the proposed Open-End Winding system. Simulation results confirm the consistence of the proposed system in managing with high efficiency a wind power plant with an integrated battery energy storage system.