What are the challenges in storing hydrogen for fuel cells?

Storing hydrogen for fuel cells is challenging due to its low density, high flammability, and containment difficulties.

Hydrogen, being the lightest element, has a very low density. This means that to store a useful amount of energy, hydrogen must be compressed or liquefied, which requires significant energy input. Compressing hydrogen to a high pressure can make it occupy less space, but the energy required for compression is substantial. Liquefying hydrogen, on the other hand, requires cooling it to extremely low temperatures (around -253 degrees Celsius), which also consumes a lot of energy.

Another challenge is the high flammability of hydrogen. It can ignite very easily, even with a small spark, and burns with a flame that is nearly invisible. This makes handling and storing hydrogen potentially dangerous. Safety measures must be in place to prevent accidental ignition and to detect any leaks quickly.

Lastly, containing hydrogen is difficult due to its small molecular size. Hydrogen molecules can diffuse through many materials, including some types of metal. This can lead to leaks, which not only waste fuel but also pose a safety risk due to hydrogen's flammability. Special materials and designs are needed for hydrogen storage tanks to prevent leakage.

In addition, hydrogen can cause embrittlement in many metals, a process where the metal becomes brittle and can crack. This is another factor that complicates the design of storage tanks and infrastructure for hydrogen fuel.

Despite these challenges, research is ongoing to develop safe, efficient, and cost-effective methods for hydrogen storage. This includes exploring materials that can absorb hydrogen, like metal hydrides, and developing advanced tank designs.