My $.02, for what it's worth. At face value, I like the idea of HFC powered, well, anything. After all, H2 + atmospheric gases usually yield water, unless the reaction conditions vary significantly from STP (Standard Temperature (25C), and Pressure (1 atm) for the Chemistry challenged
).
But, then I started to think about the source H2. While there is some "free" H2 in our atmosphere, you can't really use it for this purpose. That being said, where will it come from?
There are 2 major sources for H2; seawater and methane (ethane/ethanol can be used but methane is more abundant and cheaper). The seawater solution is, to me, retarded. It takes electricity to split H2O into H2 and O2 then mechanical energy to compress the H2 and more mechanical and thermal energy to transport the compressed/liquified H2 to a filling station. Then more electricity is used to pump or flow regulate the H2 as it enters my car just so I can turn it into electricity to operate the vehicle. In summary, it takes electricity to make H2 plus a ton of other energy sources to transport it so my car can convert with heat loss to electricity. Am I the only one that sees this as a bit stupid?
OK, so forget about seawater. Let's get those hydrogens from CH4 (methane or natural gas). This is a fairly simple and actually considerably more efficient. But, there's a catch. The byproducts of CH4 + atmosphere include CO2 and some nasty NOx molecules (acid rain) so it's not a clean solution. In fact, since the energy density of H2 is so low, a currently operating vehicle of the same weight class as an H2 powered vehicle that used LPG as its fuel is cleaner, cheaper, and no one has to wait 10 years for a roll out. They've been in operation for decades.
For the reasons listed I don't see H2 going anywhere. It's expensive, it's not clean, and it's a fuel transportation nightmare. What exactly is there to like?