The intensified use of renewable sources in future energy systems implies the demand for high density storage compounds. Hydrogen, methane, liquid hydrocarbons, methanol, and ethanol are potential candidates for this purpose. Ferdi Schüth, Max-Planck-Institut für Kohlenforschung, Mülheim, Germany, discusses different storage compounds and their advantages and compares drawbacks.

Compounds as hydrogen, methane and liquid hydrocarbons seem to be more suitable as general purpose storage compounds. Ethanol could be an attractive fuel and/or fuel additive for internal combustion engines. It is expected that electromobility will claim an increasing share of individual traffic, but internal combustion engines will probably be used for many more decades to come, even if their fraction will decrease. Dehydration of ethanol is straight forward and leads to ethene, one of the key building blocks for polymers, and thus biomass-based ethanol could be one of the platform molecules for chemical production.

Methanol does not appear to have substantial advantages over other storage compounds. Its storate density is moderate, its synthesis proceeds through hydrogen and requires an additional step compared to that of hydrogen. Methanol as a large-scale infrastructure compound is inferior to the other compounds, and thus the probability for methanol becoming a terawatt-scale product appears rather limited.

• Chemical Compounds for Energy Storage,
  Ferdi Schüth,
  Chem. Ing. Tech. 2011.
  DOI: 10.1002/cite.201100147