Hydrogen rich substances as ammonia and hydrazine are great for storing hydrogen. This is due to their energy density, for ammonia at least 1.3 times that of liquid hydrogen. Hydrazine is almost twice as dense in energy compared to liquid hydrogen, however a downside is that dilution is required in the use of direct hydrazine fuel cells, which lowers the overall power one can get from this fuel cell. Besides the high volumetric density, ammonia and hydrous hydrazine have a low flammability, which makes it superior to hydrogen by lowering the storage and transportation costs.