Methods and systems of providing a source of hydrogen and oxygen with high volumetric energy density, as well as a power systems useful in non-air breathing engines such as those in, for example, submersible vehicles, is disclosed. A hydride reactor may be utilized in forming hydrogen from a metal hydride and a peroxide reactor may be utilized in forming oxygen from hydrogen peroxide. The high temperature hydrogen and oxygen may be converted to water using a solid oxide fuel cell, which serves as a power source. The power generation system may have an increased energy density in comparison to conventional batteries. Heat produced by exothermic reactions in the hydride reactor and the peroxide reactor may be transferred and utilized in other aspects of the power generation system. High temperature water produced during by the peroxide reactor may be used to fuel the hydride reactor.