Optimization of Marine Energy Storage Systems for Desired Lifetime, Energy Saving and Safety

The project has addressed the task of optimizing the power and energy rating, as well as the task of optimizing the operation of energy storages in hybrid electrical power and propulsion systems in ships with diesel generator sets and energy storage. Hybrid systems had at project start already been shown to give significant reduced fuel consumption as well as reduced emissions for several kinds of vessels and operations. However, back in year 2015, the industry project partner Rolls Royce Singapore, experienced that the knowledge and experience on how to select the best combination and size of energy storages within the required constraints was not in the public domain. They therefore initiated this joint research effort with research and industry partners from Singapore and Norway aiming to make new knowledge on design and optimization of marine energy systems available to a wider industry. The defined primary objective of the project was to develop methodology for optimized sizing of energy storage in hybrid ship power and propulsion systems. The project is one of the projects that received funding under the Joint Call for Proposal in Maritime Research between Singapore and Norway. The call asked for collaborative projects involving research groups (universities, university colleges and research institutions) from Singapore and Norway. The partners of this project have been Nanyang Technological University (NTU), Singapore, Rolls Royce Singapore Pte. Ltd, SINTEF Energi, Norway and since 2019, Kongsberg Maritime, Norway after their acquisition of the initial project partner Rolls Royce Marine, Power Electric systems. Results of the activities carried out in Norway includes methodology for using load duration curves rather than time series of predicted load to estimated expected fuel saving from using batteries for spinning reserve and strategic loading of engines on hybrid vessels; methodology for design of minimum fuel consumption energy management strategy for hybrid marine vessels with multiple diesel engine generators and energy storage; simple procedures for favourable trade-off between fuel saving and storage lifetime; methods to consider the battery degradation in the optimization of storage size and storage usage; methodology for the design and tuning of real-time power and energy management systems for plug-in marine vessels for optimal use of energy charged from shore and tool for estimation of battery system degradation utilizing the scarce degradation data that realistically will be available for ship system designers. Results from the activities in Singapore includes among others, optimization formulation and tool implementation of battery sizing using Particle Swarm Optimization (PSO) to solve the optimal sizing problem taking into account load profile, operation constraints and battery system lifetime; control, and fault detection methods for use of multi-level modular converters with distributed energy storages to address the voltage matching issue of low voltage (LV) energy storage modules and high voltage ship power systems. The project has produced results that have the potential of reducing the cost related to the use of battery systems in ships since results can be used for more optimal sizing of battery storage, as well as more optimal usage of the battery storage in operation in order to maximize the value of the installed storage. This will in the long term contribute to reduced fuel usage and reduced emissions from the type of vessels considered in this work.

The project has produced results that have the potential of reducing the cost related to the use of battery systems in ships since results can be used for more optimal sizing of battery storage, as well as more optimal usage of the battery storage in operation. This will in the long term contribute to reduced fuel usage and reduced emissions from the type of vessels considered in this work. Key project results have already been published in scientific publications and are now available for use by industry and further use in related research. The project has for the Norwegian research given significant increased competence on the use of batteries. Competence, experience, and methods from the project have already been found valuable in other projects and is also planned used in projects that are under development. The project has also given contacts with relevant Norwegian industry partners beyond the project industry partner and has contributed to other battery related projects.

The primary objective of this project is to develop a methodology for optimized selection of energy storage solutions in hybrid ship power and propulsion systems. An energy storage system on a vessel can have several advantages and can be utilized for several different purposes depending on the onboard power system configuration. The intended use, as well as class society requirements for safety and power availability has to be accounted for when optimizing the sizing of such energy storage systems. The knowledge and experience of how to select the best combination and size of energy storage within the required constraints for safety and power availability is not in the public domain, and practical system designs depend on recommendations from specialized consultancy services or battery manufacturers. Thus, the project aims to make knowledge on design and optimization of marine energy systems available to the wider industry. This will be obtained through the development of a generalized methodology for selecting and sizing the energy storage for a given vessel, considering applicable class rules, a given operating profile and required energy storage lifetime. The methodology will towards the end of the project be implemented in a tool for demonstration and testing and to facilitate rapid vessel design development. The project is targeting the topic of Green Shipping, subtopic Energy Efficiency, in the Joint Call for Proposals in Maritime Research between Singapore and Norway. Knowledge relevant for reducing the cost and risk of a shift towards greener and more efficient vessel power systems with reduced fuel consumption fits well within the ambitions of reducing the emissions from the maritime transportation. Norway and Singapore have both maritime industries that include yards, ship designers and equipment manufacturers that can benefit from such knowledge.