The transportation sector uses around 25\% of the worldwide commercial energy and its emissions are constantly growing. Environmental concern has increased and legislation is forcing technology to develop new solutions for this global challenge. Hybrid, electric and fuel cell vehicles appeared as one of the most promising technologies to reduce emissions and fuel consumption. There are already plenty of models in the market and these technologies, boosted by legislation and current investments, may achieve mass-market penetration in the next decades. However, more research is needed, especially to extend these technologies beyond road vehicles. In this thesis is performed a study, design, and implementation of a hybrid and a fuel cell powertrain for two projects in the marine sector.