Innovative, non-nuclear Power Plant Concepts for modern Submarines with very low Indiscretion Ratio

Disruptive technologies exponentially increase the number of conceptual designs to be considered for non-nuclear power plants on board submarines. Not only are there more options nowadays, like Li-ion battery technology, fuel cell technology and permanent magnet electric machines; furthermore, one must realise that the power / energy rating of these different power plant components may vary almost continuously, and significantly, during concept design. For long-range expeditionary submarines for instance, given the constraint of a non-nuclear submarine, it is interesting to combine these new disruptive technologies in an optimally balanced power plant that utilizes diesel engine-generator sets as range extender at or near the surface, fuel cells as submerged range extender and a battery as an energy storage and peak load shaver required for e.g. submerged sprints; a “trihybrid” system concept for submarines. The optimal power split between these components will greatly depend on the operational requirements of a navy, such as required range and (submerged) mission profiles. Should a limited range be acceptable for instance, then an all-battery power plant concept may be considered for which the power rating of the diesel-generator sets or fuel cells on board of the submarine is zero. The impact of these very different power plant concepts on the overall submarine design is significant. Selecting the right components of the power plant at an early design stage is therefore key to a successful submarine design. In recent years, Nevesbu and TU Delft have developed, through a number of MSc graduation studies (of 9 months), mean-value first-principle tools that determine the mass, volume, power rating and energy rating of different optimally balanced submarine power plants based on parameterized mission profiles (and vice versa). Together, these design studies provide an interesting non-nuclear submarine concept exploration effort that demonstrates the impact of integrating disruptive technologies on overall submarine design. Combined, the studies provide an excellent opportunity to reflect on the design methods used and the importance of the starting point of a design study. This paper presents and discusses the results of the different design studies that were performed, i.e. the above-described submarine power plant concepts and their impact on overall submarine design, and concludes which power plants concepts are best suited for different design requirements.