Hydrogen as a Clean Fuel: Challenges in Chemical Storage and Energy Conversion Efficiency in Internal Combustion and Fuel Cell Systems

Hydrogen is regarded as a leading candidate for clean energy due to its high gravimetric energy density and emission-free combustion. Despite this promise, real-world implementation is largely restricted by two primary challenges: efficient storage and effective energy conversion. This paper examines the chemical storage of hydrogen—particularly via metal hydrides—and assesses the efficiency of hydrogen use in both internal combustion engines (ICEs) and fuel cell systems. An interdisciplinary approach is applied, bridging thermodynamic and electrochemical properties from chemistry with performance and integration considerations from mechanical engineering. We simulate storage thermodynamics, PEM fuel cell reactions, and mechanical energy conversion systems to provide a comprehensive analysis of current capabilities and future directions. Results indicate that metal hydrides offer compact and safe hydrogen storage, but system efficiency and viability improve significantly when fuel cells are used in place of ICEs. The paper concludes by proposing an integrated mechanical-chemical system architecture optimised for hydrogen utilisation.