That's not the elephant in the room at all.Ehhh said:Which leaves the question of where the energy to create the hydrogen will come from. That's the elephant in the room with regard to 'the hydrogen economy'.
The elephant is the infrastructure needed to support a hydrogen economy as well as the comparative efficiencies.
The "power-source to end-use" efficiency of hydrogen using (say) a fuel-cell is in the region of 25%. That means that for every 1 unit of energy your car (as an example) uses, 4 need to be generated. "So what", say the advocates here. "With free generation, its all gravy". Well, yes, except that other, non-hydrogen-centric approaches (e.g. Li-ion batteries) offer efficiencies miore like 1 unit of power requiring 1.1 units of generated power.
Transport of hydrogen is also problematic. Cryogenic storage, pressure-based storage...whatever...its all expensive, energy-hungry stuff.
Ah, the advocates say, you're still thinking old-school. The new hydrogen economy will have micro-generators everywhere, and hydrogen will be made where its needed, thus removing the need to transport it at all, which in turn removes much of the inefficiency from the equation.
They have a point...in the sense that in order for a hydrogen economy to work, a distributed network is what is needed rather than a distribution network like we have at present.
Which brings us back to the elephant in the room.
If you want to go for a drive in your car today, and don't just consider the convenietn cases like small islands in Western Europe, then you need to be able to sit in and go for hours...potentially for a couple of thousand km. You want to be able to refuel at will, quickly and cleanly.
If you want to set up a petrol station today, you need some petrol tanks. OK..they're not free, but they're far from rocket science.
If you want to replace these with hydrogen refuelling stations, then you've got a problem. A decentralised network will mean that each station will need its own generating capacity (which should be free energy), its own localised storage facility, the ability to 'fill' fuel-cells (if we go that way instead of storing hydrogen under pressure in tanks in the boot of our cars).....and you need it over a large area.
That is the elephant in the room.
One can forsee, in the short-to-medium term, increased use of hydrogen for things like airport ground-fleet vehicles, or maybe even public transport fleets, where a single or small number of refuelling stations can serve a significant number of vehicles. But it'll be a long, long time before we start seeing anything like a hydrogen economy.