An interesting document that Energy Storage Technologies

I would like to see more emphasis on the solar chemical storage systems... eg the methane and ammonia reforming systems. The ammonia system I would have thought attractive as the required catalysts should just be a transplant from the ammonia synthesis industry. In fact most of the technology should be well understood.

See the bottom of page 20
One advantage of this kind of storage is that it is essentially 100% "efficient" after the reactants are separated, unlike heat which will always have losses.

see page 25-26 where both graphite and ammonia storage systems are described as being at incubation - early commercialisation compared to hydrogen which is still at R&D stage.

ANUs solar chemical storage page
A more recent report for NSW and Vic Govs