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Design and control of hybrid power and propulsion systems for smart ships: A review of developments

There has been mounting concerns over energy consumption and environmental impacts due to an increase in worldwide shipping activities. The International Maritime Organization has adopted regulations to impose limits on greenhouse gas emissions originated from fuel combustion of marine vessels. Such regulations are introduced in terms of energy efficiency design index and energy efficiency operational indicator. Extensive electrification of ship propulsion and shipboard power systems has been vastly proposed in the literature to make onboard energy systems more efficient. However, energy efficiency in the context of maritime transport is becoming even more stringent. Various technologies and operational practices therefore are being proposed to ensure full compliance with the tightening restrictions. The methods to increase energy efficiency and environmental performance of all-electric ships to satisfy such requirements involve integration of energy storage with a contribution of intelligent power management to optimize power split between various power generation sources; a tendency toward DC power distribution due to eliminating the need of all generators to be synchronized at a specific frequency; installation of unconventional propulsors for greater maneuverability requirements while keeping fuel consumption low; adoption of low carbon content fuel like liquefied natural gas for dual fuel diesel electric propulsion; establishment of onboard renewable energy systems for alternative clean power options; fuel cell integration in complementary operation with conventional diesel generators. This paper identifies promising technologies and practices that are applicable to onboard energy systems of all-electric ships and also reveals energy efficiency sensitivity of all-electric ships to different applications. The proposed strategies should be eventually combined with alternative technology-based and operational-based measures as implemented on conventional propulsion ships in order to realize full potential for energy efficient operation.

Energy efficiency of integrated electric propulsion for ships – A review

Optimization of sizing and frequency control in battery/supercapacitor hybrid energy storage system for fuel cell ship

Ship energy management for hybrid propulsion and power supply with shore charging

In the face of increasingly severe energy shortage and environmental pollution, the use of new forms of energy will become an important direction for the future development of ships. A hybrid power system comprised of various types of energy, such as conventional fossil fuels, renewables, hydrogens, fuel cells and batteries, can ensure a continuous and reliable power source for ships by using different types of energy for various operating conditions. This has become an emerging solution for greener ships and attracted attention from both industry and academia. A state-of-the-art multi-energy hybrid power system for ships is introduced in this paper. The configuration and characteristics of series, parallel and series-parallel hybrid power systems are analyzed and compared. Challenges of multi-energy power system for large-scale ships such as reliability, control and efficiency are discussed, and possible solutions are proposed.

A review of multi-energy hybrid power system for ships

This brief presents an optimal power management scheme for an electromechanical marine vessel’s powertrain. An optimization problem is formulated to optimally split the power supply from engines and battery in response to a load demand, while minimizing the engine fuel consumption and maintaining the battery life, wherein the cost function associates penalties corresponding to the engine fuel consumption, the change in battery’s state of charge (SOC), and the excess power that cannot be regenerated. Utilizing the nonlinear optimization approach, an optimal scheduling for the power output of the engines and optimal charging/discharging rate of the battery is determined while accounting for the constraints due to the rated power limits of engine/battery and battery’s SOC limits. The proposed optimization algorithm can schedule the operation, i.e., starting time and stopping time for a multiengine configuration optimally, which is a key difference from the previously developed optimal power management algorithms for land-based hybrid electric vehicles. Afterward, a novel load prediction scheme that requires only the information regarding the general operational characteristics of the marine vessel that anticipates the load demand at a given time instant from the historical load demand data during that operation is introduced. This prediction scheme schedules the engine and battery operation by solving prediction-based optimizations over consecutive horizons. Numerical illustration is presented on an industry-consulted harbor tugboat model, along with a comparison of the performance of the proposed algorithm with a baseline conventional rule-based controller to demonstrate its feasibility and effectiveness. The simulation results demonstrate that the optimal cost for electric tugboat operation is 9.31% lower than the baseline rule-based controller. In the case of load uncertainty, the prediction-based algorithm yields a cost 8.90% lower than the baseline rule-based controller.

Power Management for Electric Tugboats Through Operating Load Estimation

The strengthening of ship emission controls and expected increase of fuel oil prices in the future have driven the interest in fuel efficient solutions for the maritime industry. Hybrid all-electric tugboat has shown its potential in improving fuel economy. However, using conventional rule-based/heuristic power management strategies relies largely on the experience of the designers and crew operators, which cannot guarantee optimality. Motivated by the optimization-based power management strategies for Hybrid Electric Vehicles (HEVs), this paper investigates the potential benefits of Equivalent Consumption Minimization Strategy (ECMS) in hybrid allelectric tugboats application. The proposed power management strategy promises 17.6% of fuel savings compared to conventional rule-based strategy.

Equivalent Consumption Minimization Strategy for hybrid all-electric tugboats to optimize fuel savings

This paper, inspired by the research on energy management for land-based hybrid electric vehicles (HEVs), presents an optimal power management scheme for electric tugboats that optimally splits the power supply from engines and batteries in response to the load demand, while minimizing the engine fuel consumption and maintaining the battery life. For this purpose, an optimization problem is formulated, in which the cost function consists of power load demand tracking, engine fuel consumption and change in battery state of charge. Utilizing the mixed-integer programming, the optimal power planning for the engines and batteries is determined. The proposed optimal algorithm can control the operation, i.e. starting time and stopping time, for several engines, which is a key difference from several other optimal algorithms developed for land-based HEVs. Since the load demand is unknown, a novel prediction scheme is introduced to anticipate the load demand, allowing the implementation of optimization scheme. Numerical illustration is presented on an industry-consulted harbor tugboat model to show the effectiveness of the proposed schemes. Index Terms—Power management, optimization, marine powertrain systems, hybrid electric vehicles I. INTRODUCTION The tremendous increase in onboard generation and con- sumption of electric power in vehicles in the last two decades as well as in the foreseeable future (1) has called for smart strategies for the generation, storage/ retrieval, distribution, and consumption of electric power in order to limit the associated increase in fuel consumption and exhaust emissions. The hybrid electric vehicle (HEV) technology with the dual onboard power sources and possibility of regen- erative braking has been proposed as a technology for new vehicle configurations capable of developing such strategies. Accordingly, a great amount of research interest has been pursued for the power management and sizing of land-based

Optimal power management for electric tugboats with unknown load demand

Electrification of vessel power and propulsion system has been widely utilized in the shipbuilding industry in recent years. It is expected to be adopted in all marine vessel segments as the increasingly strict marine greenhouse gas (GHG) emissions regulations push the maritime fleet to decrease its reliance on conventional fuels such as marine diesel oil (MDO). With the development of sustainable energy sources and energy storage technologies, such as fuel cells, batteries, and super-capacitors, these renewable energy sources are integrated into the marine electric power system to reduce or even achieve zero-emission operation. A comprehensive shipboard power system model is the crucial foundation for the further research. In this paper, a hybrid shipboard power configuration will be studied and modeled using Matlab/Simulink. The detailed model using average converters’ models for the ship power system will be described. Besides, the simulation results shall be shown and analyzed considering a typical harbor tugboat load profile.

Alf Kare Adnanes

Papers

Power Management for Electric Tugboats Through Operating Load Estimation

Equivalent Consumption Minimization Strategy for hybrid all-electric tugboats to optimize fuel savings

Optimal power management for electric tugboats with unknown load demand

On the Modelling of Fuel Cell-Fed Power System in Electrified Vessels

Control optimization for electric tugboats powertrain with a given load profile