Hydrogen recently has been touted by various political leaders around the world as a clean panacea to the problem of energy storage or heat or electricity. Hydrocarbons traditionally have served that role and have been stored in above-ground tanks and below-ground caverns or geologic formations. Future use of hydrocarbons, however, in some jurisdictions is not politically favored. Electric batteries are an energy storage alternative, but they are limited in capacity, are costly and eventually must be replaced. What about hydrogen? Hydrogen also can serve as an energy-storage mechanism in the form of a gas, as a liquid formed cryogenically, or within a liquid compound, such as in ammonia. There are, however, technological and economic drawbacks.
Hydrogen does not exist naturally on earth, so it must be manufactured, as opposed to natural gas, for example, which is found naturally. Manufacturing adds a cost component which makes hydrogen more expensive than conventional alternatives such as oil products or natural gases or natural gas liquids.
Further, hydrogen has serious physical drawbacks due to its very nature. It is an extremely small molecule, and as a gas, it can penetrate containers that are not molecularly tight. The metallurgy of such containers is vitally important because hydrogen can cause metal embrittlement and subsequent failure. Any escaping hydrogen molecules are unstable and prone to ignition and explosion.
Hydrogen can be stored as a gas underground, much like natural gas. But hydrogen quickly forms compounds with other minerals that may be present underground, causing unpredictable results. Also, in an underground environment, hydrogen becomes a favored source of food for certain types of microbes which may result in the loss of hydrogen or the creation of hazardous substances.
Hydrogen can be cryogenically liquified, but this adds yet another cost on top of the manufacturing cost. Storing liquid hydrogen is exponentially more difficult than storing it as a gas. If the hydrogen is not kept cooled below the vapor point, the pressure in the storage container will increase to the point where the vessel fails and explodes.
Hydrogen also can be stored in a liquid compound at near-ambient temperatures, but there is the problem and expense of separating the hydrogen from compound before it can be used as a stored fuel.
There are other forms of hydrogen storage, but they remain at a theoretical level. There will be years of research and experiments before they can be technologically and economically feasible.
The world’s current hydrocarbon storage infrastructure was designed and built to utilize hydrocarbon products. Although this infrastructure theoretically may be used to store hydrogen, hydrogen’s unique properties must be considered. In summary, hydrogen can be used as a storage alternative, but there are drawbacks that policy makers may not generally comprehend.
*Special thanks to Zimei Fan for his valuable assistance in preparing this blog post.