Marine propulsion using battery power

Abstract: The global demand to reduce CO2 emissions requires effort from the shipping industry which currently emits about 2% of anthropogenic global Greenhouse Gases (GHGs) and which is predicted to increase due to growth of world trade. Therefore, it is important to find new ways to reduce CO2 emissions from shipping using new operational strategies, improved ship designs and new technologies. Battery technologies have been developing rapidly leading the road transport industry into a greener future with hybrid and electric vehicles but such a change is not so apparent in the shipping industry. This paper provides an overview of the state of the art battery technology and important future developments that may potentially exploit batteries in future ship’s power and propulsion systems. Through case studies, the paper assesses the applicability of battery power to ships, more specifically small ones. Approximately 14,000 ships, 22% of the global commercial fleet are below 400 gross tonnes, most of which are small coastal ships, e.g. tugs and passenger ships/ferries. Existing battery-powered ship system configurations are summarised; battery developments are considered, impacts of battery application on ship performance are discussed in the paper supported by a case study

An analysis of the energy flow and energy potential from human energy harvesting with a focus on walking

This paper aims to determine the limitations for electrical energy generation from harvesting mechanical work during walking. The assessment was considered from the point of chemical energy ingested in food, through the development of mechanical work, to the conversion into useful electrical energy from the perspective of the conversion efficiencies. An average person was considered, with four mechanical to electrical energy conversion technologies assessed. It was found that for an individual walking on level ground a potential of up to 5 J/step of electrical energy is available. Stair use impacts this, where stair ascent decreased and descent increased the potential. It was concluded that, although the energy outputs are small, they scale with the number of people, where an estimated potential of 900 MWh/day is calculated in the UK. Harvesting even a fraction of this available potential would appear worthwhile, however, it is unclear if this potential can be practically utilised

Loss Performance Evaluation of Ferrite-Cored Wireless Power System with Conductive and Magnetic Shields

This paper presents a loss evaluation of ferrite-cored wireless power transfer (WPT) systems using conductive and magnetic shield materials. The modelling and analyses of the coil systems were implemented using the finite element method. Three coil systems were modelled-circular coils, rectangular coils and flux-pipe coil system using magnetic shields (Mumetal and electrical steel) and conductive shields (aluminum and copper). From the results presented in the analyses, it was noted that ohmic losses and core losses in the WPT system are independent of the type of conductive shield used. Similarly, it was noted that the self-inductance, coupling coefficient and losses in the system is affected by the type of magnetic shield used. For the flux-pipe resonant coil system, high power losses were recorded when a magnetic shield was used as the shielding topology while low power losses were recorded in the circular coil and rectangular coil resonant systems when the magnetic shield was used as the shielding material. For optimal WPT system requiring low eddy current losses, it was established that copper shield is the appropriate choice for flux-pipe resonant coils while electrical steel is the suitable shield material for the circular resonant coil and rectangular resonant coil systems

Impact of Coil Turns on Losses, Output power and Efficiency Performance of Flux-Pipe Resonant Coils

This paper presents a finite element analysis of five different sizes of flux-pipe resonant coil design with a different number of coils turns but having the identical length of litz copper wire and aluminum shield. The analysis was undertaken to establish the impact of the number of coil turns on the losses, magnetic flux distribution, power output, and power transfer efficiency of flux-pipe resonant coils. From the results presented, it was noted at a constant frequency, an increase in the excitation current causes a significant increase in the ohmic, core, and eddy current losses for each of the coil model designs. Similarly, at constant excitation current, it was observed that the eddy current losses increase significantly with an increase in resonant frequency. In contrast, the ohmic and core losses are relatively constant over the range of resonant frequencies used in the analysis. It was also noted that term k√Qps (where k is the coupling coefficient and Q ps is the product of the quality factor of the primary and secondary coils) has a significant influence on the input power, output power and coil-to-coil efficiency of a particular flux-pipe resonant coil design. Increasing the value of k√Qps increases the value of output power, input power, and coil-to-coil efficiency. Similarly, the lower the coupling coefficient, the higher the required optimum resonant frequency for optimum coil-to-coil efficiency and output power

Fuel Economy of a Current Hybrid London Bus and Fuel Cell Bus Application Evaluation

London has over 8,500 buses in operation, carrying six million passengers on 700 routes each day. In central London the majority of the bus fleet has been replaced by diesel-electric hybrid buses. In this study, we will investigate the degree of energy efficiency via practical on-road bus performance recordings, forming a foundation for future improvements to diesel and fuel cell hybrid bus design. Research at UCL has investigated the design and performance of the ENVIRO 400H model bus on various different routes in London, obtaining a wide range of data for real world performance. This data includes information on routes, usage, energy consumption and passenger count profiling. Analysis has been conducted on the efficiency of the propulsion system over all the data sets. This knowledge can be used as the basis for developing computer modelling capabilities to in the future to optimize the system performance. The key components in the propulsion system are the diesel engine, generator, converter, battery bank, and traction motor. The energy management strategy has been analysed for different operating conditions and will be discussed in this paper. It was concluded that the system performance varied, with a number of patterns emerging with regards to the engine load and battery State of Charge for providing the propulsion power requirements. The operation strategies employed have been analysed to give a detailed understanding of the operation of the diesel-electric hybrid propulsion system under real-world operation

Conceptual Evaluation of a Fuel-Cell-Hybrid Powered Bus

This paper considers the conceptual design of a fuel-cell-hybrid engine to replace the conventional diesel internal combustion engine for use in London buses. Fuel cells are expensive power units costing in the region of £2.50/W compared to the conventional diesel-engine at 5p/W. A fuel-cell-hybrid solution is proposed to minimize initial costs whilst achieving good operational performance and specifically reducing greenhouse gas emissions for future `zero-emission zones'. Different London bus types and their routes have been reviewed with route 226 (from Ealing Broadway Station to Golders Green Station) and the Alexander Dennis Enviro 200 Dart bus being selected for detailed study. Considering factors such as number of stops, route length, public demand, bus dimensions and weight a series fuel-cell-hybrid power plant using 20 kW polymer electrolyte membrane (PEM) fuel cells with a nano-phosphate Lithium-ion battery providing power to four AC three-phase induction propulsion motors is proposed. The fuel-cell-hybrid engine has been designed with re-engineering of the bus in mind to layout level and performance analysis has been undertaken using computer based simulation

Simulation of a stabilised control strategy for PEM fuel cell and supercapacitor hybrid propulsion system for a city bus

Fuel Cells (FC) are a clean energy source capable of powering a bus electrically with zero operating emissions. This research investigates the potential of FC and Supercapacitor (SC) hybrid buses for clean city transportation. To investigate the FC/SC hybridisation strategy, a scaled FC/SC hybrid drivetrain has been developed to provide the power system of a scaled bus model. The scaled model was developed as a MATLAB Simulink computer model and cross referenced against the constructed laboratory test rig for validation. A novel control strategy focusing on power balancing between the FC, the SC and the load has been developed and validated in the computer model. It has been demonstrated in both the test rig and computer simulation that the proposed control strategy is capable of maintaining a controlled and stable FC output while meeting different bus load regimes. The validated computer model can provide a reliably representative, convenient and low cost platform for further performance investigation and component optimisation of FC/SC hybrid drivetrains. The control strategy has also been demonstrated to be function as expected after scaling up the developed scaled model to a full scale model which can be used for simulation of practical bus performance

Development and Modelling of a Lab Scaled PEM Fuel Cell Drive System for City Driving Application

This paper details a study carried out by UCL to explore potential improvements to the Fuel Cell (FC) bus propulsion system specifically designed for the city driving environment. In this paper, a 1:10 scaled lab based FC bus drive train has been developed to study the performance of a FC directly driving an AC induction motor. The PEMFC is the main power source for the drive train while a boost converter will work as the power conditioning system to control the FC output voltage. The AC motor will work as the bus prime mover. The system has been built in the Electrical Laboratory to evaluate the performance of a FC driving a motor. MATLAB Simulink has been used to simulate the system and has been validated against the lab based system. A number of tests have been carried out in terms of efficiency and transit change response with both the lab and simulated models. The results showed that the FC is capable of directly powering the motor in general bus driving conditions, but it is not well suited for quick transient changes. This study provides an important contribution to further improve the FC bus with hybrid propulsion systems and validates the computer model to allow faster analysis of proposed system improvements. The next step of this study is to use an energy storage system to aid the FC to cover quick transient power demand and validate it against a representative load system

Autonomous navigation system for unmanned surface vehicles

This paper presents work on the development of a real-time autonomous navigation system for Unmanned Surface Vehicles (USVs). The navigation system being developed is using an embedded hosting platform consisting of navigational data fusion processes together with algorithms used for path planning and collision avoidance when the USV is operating alone or in cooperation. An improved A* path planning algorithm based on rasterized map is developed for single USV operation; whereas the fast marching square algorithm is implemented for multiple USVs. Both algorithms have been tested using a practical simulation environment. The resulting trajectories are guaranteed to be the shortest collision-free path

Stabilised control strategy for PEM fuel cell and supercapacitor propulsion system for a city bus

Fuel Cell (FC) buses have been developed as a long term zero emission solution for city transportation and have reached levels of maturity to supplement the coming London 2020 Ultra low emission zone implementation. This research developed a scaled laboratory Fuel Cell/Supercapacitor hybrid drivetrain implementing DC/DC converters to maintain the common busbar voltage and control the balance of power. A novel and simple hybrid control strategy based on balancing the currents on the common busbar whilst maintaining a stable FC output has been developed. It has been demonstrated that the FC power output can be controlled at a user defined value for both steady state and transient load conditions. The proposed control strategy holds the promise of extending FC life, downsizing power systems and improving the FC operating efficiency