As a part of ongoing research into the use of fuel cells to power underwater platforms, studies have been conducted to investigate the effect of change in oxygen flow through the proton exchange membrane fuel cell (PEM-FC) cathode channel, to develop a method for controlling this flow. Due to the lack of specific information or studies on the effect of pure oxygen flow through the PEM-FCs cathode channel on the correctness of its work, a series of experiments have been carried out within the framework of in-house research to determine this dependence. The experiment was conducted in series, during which the only change in the operating parameter of the PEM-FC stack was the stoichiometric flow rate of oxygen supplied to the cathode channel of the fuel cells' stack. The research shows that for the PEM-FCs stack fed with pure oxygen, the cathode stoichiometry can be kept at a much lower level comparing to the systems supplied with air. It has been found that the fuel cells' stack fed with pure oxygen will perform well in steady state while reducing the cathode stoichiometry by as much as 40% compared to systems utilising oxidant from atmospheric air.

Lead-acid batteries are still being used in conventional submarines as the primary source of power. Due to their properties, lead-acid batteries require a lot of attention during their operation, including charging according to fairly rigorous rules. Because of their special operating conditions in submarines, it is not possible to maintain optimal conditions for such batteries. The battery's integrated management system allows for remote and online monitoring. However, it gives only general information about how much energy remains in the battery for use in operating conditions. The submarine's operational capabilities, such as range and operation time, depend to a great extent on battery capacity, so information of its condition and status is very important. The proposed method of evaluating the capacity of lead-acid batteries allows them to be processed during their exploitation, without the need for a time-consuming and expensive capacity test. The measurements needed to implement the proposed algorithm are already implemented in the existing battery monitoring system-no additional equipment is required. Based on the results of the proposed method, it will be possible to easily determine how much energy is available to the submarine, which is crucial in planning combat missions at the sea.

For ships, the total loss of electrical power, 'blackout', is a critical failure. The failure of the marine power supply system not only results in loss of ability to perform tasks, but also poses a threat to human life and often to the environment. No less serious emergency is 'partial blackout', i.e. the loss of electricity in parts of the electrical system. Designers are introducing technical and system solutions to minimise the likelihood of power failure and to support its recovery in a timely manner. One of the methods to minimise the likelihood of power failure is to identify and then monitor diagnostic symptoms that are susceptible to approaching the failure of key components of the power system. This article discusses the use of recording and analysis of changes in voltages and excitation currents in parallel synchronous generators to determine the threshold above which their parallel operation can lead to an emergency power failure.