Introduction to the hydrogen energy transition
Hydrogen is considered as a renewable energy source for the future, it is environmentally friendly and is present abundantly in water as a combined molecule. The usage of hydrogen in transportation and other sectors as fuel would save fossil fuels and reduces pollution. However, storage and supply of hydrogen to a small-scale vehicle requires higher precision and capability to withstand its pressure. Failure of this storage or supply leads to accidents and destroys that vehicle. From this perspective, every physical, chemical, mechanical, and tribological aspect of that storage and supply system should be studied .
Fig-1 Green hydrogen supply schematic diagram 
Tribological challenges in the hydrogen energy transition
The hydrogen energy system is a complicated structure that involves many machine elements operating within hydrogen gases. The tribological behaviors of such systems especially in bearings and seals are affected by the hydrogen environment. The interactions between these materials and the gaseous hydrogen which involves in physisorption of hydrogen molecules and the chemisorption of dissociated atoms on metal surfaces cause the formation of metal hydrides causes the damage. Hence it is important to study the tribological properties of the materials used in these applications to provide a proper design guideline .
Fig-2 Schematic representation of hydrogen fuel cell 
There are various challenges with hydrogen storage, the problems include the embrittlement of the materials when the hydrogen is dissolved in them. Hydrogen is stored under high pressure to achieve high specific energy which enhances the uptake of hydrogen in metals causing its failure. Hydrogen permeation in rubbers and polymer seals is another issue that leads to their failure. These problems should be addressed in the case of the components involved in the hydrogen storage system. The components such as piston rings and seal bearings should be studied carefully in a pure medium for their tribological behavior in order to provide better solutions. Their properties are mainly affected by the gas environment and tribochemical interactions with hydrogen on the contacting surfaces.
Storage challenges in hydrogen energy
The product released from the hydrogen combustion is water, the formation of water means mixing two atoms of hydrogen with one atom of oxygen which requires a lot of energy. This causes the high temperature to raise in the combustion chamber leading to increased time for cooling down. If the temperature remains higher in the combustion chamber it leads to water condensation on the walls of the chamber. This in turn causes the oxidative wear of the combustion chamber walls leading to damage. Considering all the pros and cons of hydrogen storage systems it is very important for this technology to be researched extensively for a future energy source.
Fig-3 Illustration of green hydrogen economy 
Hydrogen fuels are the future fuels for automobiles and hence the tribological aspects of these components involved in this hydrogen storage system have to be studied. The use of electric battery fuels and other green sources of energy seems to be effective, whereas the hydrogen fuel source will re-innovate and change this energy sector into a zero-emission medium for future usage.
I am currently working as a Postgraduate Researcher at the University of Leeds. Previously I completed my master's under the prestigious Erasmus Mundus joint master's degree program (Master's in Tribology). I have also completed my bachelor's in Mechanical engineering from VTU, Belgaum, India. I am working as the social media manager for Tribnet and also I have my youtube channel Tribo Geek.