The sustainability policy requires the Netherlands Ministry of Defense (MoD) to become largely independent of fossil fuels in the coming decades, while at the same time the geopolitical situation requires the Armed Forces to operate globally. Therefore, the Royal Netherlands Navy needs to reconsider its fuel strategy, to gradually change to energy carriers from renewable sources, and to redesign its power and propulsion system, both to improve efficiency and to reduce its emissions and signatures. The aim of this chapter is to provide a critical review of the challenges and opportunities of the transition to alternative energy carriers and energy systems and to provide a direction for the required research and development towards the future Navy fleet that can operate independently of fossil fuels and with minimal signature. First, the chapter reviews production, expected availability and projected development of cost of the various alternative fuels, with a specific focus on hydrogen, methanol, and renewable drop-in alternatives for naval distillate fuels, according to NATO F-76 spec- ifications. Subsequently, the chapter will discuss the impact of these three fuels on three differently sized navy vessels, that are currently considered for replacement: diving vessels, seagoing support vessels, and future surface combatants. For these three use cases, the chapter also discusses the potential power and propulsion system configurations and the opportunities to reduce signatures by alternative power supplies, such as fuel cells and batteries. Based on this analysis, the chapter will propose a fuel selection strategy for future navy vessels and will discuss the required research and development that is required to achieve the identified opportunities. The chapter closes with conclusions and recommendations on the route towards a future fleet that can operate globally independent of fossil fuels.

Extractable deposits of silver, gold, copper, zinc, lead, gas hydrates and other valuable materials can be found at the ocean floor. The most valuable minerals are found at large depths, starting from 1000 m and deeper. Therefore, the leading offshore companies are currently designing systems and tools for deep sea mining. The mining at the desired depth of a few kilometers is a great challenge though as it has never been attempted before at the commercial scale. One of the fundamental design challenges lays in the understanding of and preventing from the problems associated with the dynamics of a subsea Vertical Transport System (VTS). The function of the VTS is to transport slurry (a thin mixture of water and finely divided minerals) from the seafloor to the mining support vessel. The VTS consists of a vertically hanging submerged pipe through which the slurry is transported upwards and a number of booster stations which maintain the pressure in the pipe that enables the desired slurry flow. The VTS system is subject to a number of the dynamic excitations such as the vessel motion, the slurry flow in the pipe, the sea current and a propulsion device that is envisaged to control the position of the lower end of the pipe at the desired location. To design a reliable VTS system the effect of all the above-mentioned excitation mechanisms has to be accounted for.