Energy & Green Tech

Hydrogen: Handle with care

When produced and used properly, hydrogen can potentially play many roles in the transition toward clean energy and industrial systems. Hydrogen can directly replace natural gas and coal in industrial and manufacturing processes ...

Energy & Green Tech

Green ammonia for the hydrogen economy

Research in the International Journal of Exergy has looked at how a novel small-scale power-to-ammonia (P2A) system might be a useful tool in the move to a hydrogen economy. The work considers the energy efficiency and cost-effectiveness ...

Energy & Green Tech

A baking soda solution for clean hydrogen storage

In a world of continuously warmer temperatures, a growing consensus demands that energy sources have zero, or next-to-zero, carbon emissions. That means growing beyond coal, oil, and natural gas by getting more energy from ...

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Hydrogen storage

Hydrogen storage describes the methodologies for storing H2 for subsequent use. The methodologies span many approaches, including high pressures and cryogenics, but usually focus on chemical compounds that reversibly release H2 upon heating. Hydrogen storage is a topical goal in the development of a hydrogen economy. Most research into hydrogen storage is focused on storing hydrogen in a lightweight, compact manner for mobile applications.

Some attention has been given to the role of underground hydrogen storage to provide grid energy storage for unpredictable energy sources, like wind power.

Hydrocarbons are stored extensively at the point of use, be it in the gasoline tanks of automobiles or propane tanks hung on the side of barbecue grills. Hydrogen, in comparison, is quite difficult to store or transport with current technology. Hydrogen gas has good energy density by weight, but poor energy density by volume versus hydrocarbons, hence it requires a larger tank to store. A large hydrogen tank will be heavier than the small hydrocarbon tank used to store the same amount of energy, all other factors remaining equal. Increasing gas pressure would improve the energy density by volume, making for smaller, but not lighter container tanks (see pressure vessel). Compressed hydrogen will require energy to power the compressor. Higher compression will mean more energy lost to the compression step.

Alternatively, higher volumetric energy density liquid hydrogen or slush hydrogen may be used (as in the Space Shuttle). However liquid hydrogen requires cryogenic storage and boils around 20.268 K (–252.882 °C or -423.188 °F). Hence, its liquefaction imposes a large energy loss (as energy is needed to cool it down to that temperature). The tanks must also be well insulated to prevent boil off. Insulation for liquid hydrogen tanks is usually expensive and delicate. Assuming all of that is solvable, the density problem remains. Liquid hydrogen has worse energy density by volume than hydrocarbon fuels such as gasoline by approximately a factor of four. This highlights the density problem for pure hydrogen: there is actually about 64% more hydrogen in a liter of gasoline (116 grams hydrogen) than there is in a liter of pure liquid hydrogen (71 grams hydrogen). The carbon in the gasoline also contributes to the energy of combustion.

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