In article , Nightjar wrote:
If you use the electricity from variable and unreliable sources, like
wind farms, the fuel is, effectively, a way to store that energy for
later use. Perhaps not the most efficient way to do it, but possibly the
most useful.

Which is exactly why Audi say they are working on it:

http://arstechnica.com/science/2015/...arbon-dioxide/
'Currently, Germany's vast expansion of photovoltaic power has largely been
able to eliminate the peak of demand for traditional generation that occurs
at mid-day. However, as the country continues to expand the installation of
renewable power, it's quite possible that there will be periods of
over-production. As such, Audi is promoting the technology as a means to
"stabilize the grid when production of green power peaks."'

The US Navy are also working on it. Having a nuclear powered aircraft carrier
being able to create fuel for aircraft and escort ships is potentially useful
even if it costs more than having fossil fuel delivered in a tanker. Long term,
they are aiming for "in the range of $3 to $6 per gallon to produce":
http://www.nrl.navy.mil/media/news-r...ks-to-the-seas