Technical developments of the last decades have led to an increase in design space for non-nuclear submarines, especially regarding the increasing amount of feasible power plant configurations. To be able to select the most suitable power plant configuration, it is important to know the effect on the complete submarine design and all systems on board. In the last years, Nevesbu has developed power plant optimization and sizing models to be able to select the best power plant configuration for a certain design. However, these models do not take auxiliary systems into account. The common way used of estimating the main parameters of auxiliary systems in an early design stage, is scaling based on existing submarine designs as reference. When new technologies are applied and alternative power plant configurations are selected, such as totally lithium-ion battery powered designs, reference designs cannot be used any more to make an estimation of the required auxiliary systems. Therefore, new methods have to be developed.
The objective of this thesis is to gain knowledge about, and quantify the direct and indirect consequences for the auxiliary systems when lithium-ion batteries are implemented on a large scale in an entirely battery powered submarine. Design support tools will be developed to support the designer during the design of the battery and auxiliary systems. The associated main research question is:
How can a designer be supported, in an early design stage of an entirely lithium-ion battery powered submarine, when trying to determine the size, weight and energy consumption of systems that, among others, support the safe implementation of the new batteries?
For this thesis, the safe implementation of lithium-ion batteries in an entirely battery powered submarine is studied. This type of battery has the risk of thermal runaway, which is a cascading process in which the battery releases all its stored energy, generating a lot heat and toxic gases, causing an increased risk on an explosion. Research has shown that a foam injection system could be used to mitigate the risk on thermal runaway and such system is also capable of extinguishing other types of fires inside the submarine, creating a safer working environment for the crew members. A foam injection system requires pressurized air, but the amount does not have a significant impact on the pressurized air storage.
The increased endurance of the entirely lithium-ion battery powered submarine requires a reevaluation of the environmental control systems. The amount of chalkholders as CO2 absorbers and oxygen candles to generate oxygen increases due to the increased endurance. The additional weight and volume of these consumables are undesirable. A regenerative CO2 absorption system is introduced which is smaller and lighter, but requires a significant amount of the installed battery capacity, causing a reduction in endurance.
To support a designer in an early design stage, several design support tools are developed: for the lithium-ion battery system, the foam injection system and the pressurized air system. These tools estimate main parameters such as weight, volume and heat load based on system designs and input parameters such as size and weight of components and the pressure hull radius and length. The tools show the designer the consequences of design decisions and provides important information about knock-on effects on other systems. Furthermore, the tools can be used to optimize the weight and volume of the battery system and foam injection system.
A case study, based on a concept design of an entirely battery powered submarine showed the usability of the tools, quantified the effect of these systems on the overall concept design and the importance of the results in an early design stage. The number of crew members had to be reduced with seven to implement the regenerative CO2 absorber and LOX tank. The required pressurized air storage did not change due to the implementation of the foam injection system, but the overall submarine became safer. After changing the concept design, the weight and stability still satisfied all requirements. Taking the output of the tools into account during an early design stage can prevent large design modifications.