The role of hydrogen cars
The role of hydrogen cars will be a lott more than transportation only.
The main drawback of some renewable energy is the fluctuation of the production. Windmills and PV-panels only produce if wind and sun are available. The consumers might not require the energy at these moment, and this is where the hydrogen infrastructure come in.
When there is an overproduction of electricity by windmills and/or PV-panels, all batteries of cars who are connected to the grid will be charged. If the production still exceed consumption hydrogen can be produced (with descending prices).
and here comes the best part:
When there is a short in production of electricity by windmills and/or pv-panels, cars who are connected to the grid can produce power. All cars become local and small scale energy plants.
(as long as there is enough power in the battery and H2 in the tanks to get too the nearest station.)
This infrastructure make hydrogen the battery which stores the overproduction of energy by windmills and PV-panels every now and than.