
The electric energy produced from the typical renewable
energies, solar, hydraulic, wind, geothermal powers, etc., can be hardly stored
directly. Only capacitors can be used
for the direct storage of electric energy, but a huge system for the society
does not practically make sense. The
conversion from electric energy to chemical energy is indispensable to store
the massive energy for the stable supply and transportation of energy any
places and any time. Hydrogen (H2),
ammonia (NH3), formic acid (HCOOH), and methylcyclohexane (CH3C6H5)
are the strong candidates as an energy carrier.
Replacement of carbon source from fossil resources is also
important. Biomass conversion to
chemicals must be developed in industries.