Climate change is a concern. A huge concern.

Let's address one of the quarter of the problem; Transportation.

Transportation is one of those industries that we absolutely require, so the anarcho-primitive idea to solving "climate change" is just out there. Without our robust transportation infrastructure, we'd have mass starvation.

I propose we replace our dependence on oil with two new dependencies; water and energy. When you take energy, in the form of electricity, and apply it to water at a specific voltage, you can actually split the oxygen and hydrogen bond, forming some good old Hydrogen and some pure Oxygen.

Production:

https://art.inl.gov/NGNP/NEAC%202010/INL_NGNP%20References/INL-EXT-10-12967%20PCDR.pdf

Electricity and hydrogen from nuclear.



A renewable way to solve this problem would be huge wind farms and solar panels to convert the local water source into hydrogen. However, it'll take a while to build all the turbines and solar that we'd require to replace gasoline with electric. Not to mention, we're already burning coal to produce energy producing items. In reality, this is where we see diminishing returns on hydrogen.

The energy required depends on the state of the water, when it's in a vapor form, it requires less energy to split, because it already has heat energy.

With that in mind, there's another really, obvious solution. Just rig up a fancy steam engines with a nuclear reactor equipped. Not only do nuclear generators already have the requirement of water, it produces massive amounts of energy. Also, it's output is water vapor, exactly what we need to make a lot of hydrogen.

Ideally, we could bootstrap our hydrogen production infrastructure with nuclear very cost effectively (as in $1.80 / GGE (gas gallon equivalent) in 100% clean fuel).

Logistics
That leaves logistics, how do you transport hydrogen?

Well, there's actually several ways. I'm going to leave out the bootstrapping method, mostly because I lost my train of thought.

The idea way would be to use pipeline. I think it'd be a good idea to retrofit our existing pipeline infrastructure and build out where we can. We can use pipelines and work at phasing out natural gas lines (because hydrogen can be burned for heat, just like your natural gas heat).


Safety is normally highly regulated when it comes to gas lines, I don't see how this would be any different. I think it's safer than many existing pipelines. With your irrational fears annulled, let's continue on.

Vehicles

We already have these. Electric motors are exactly what we need. With a fancy fuel cell stack, hydrogen is converted into electricity. The fuel cell stack does have a byproduct; water vapor. Also, PEM fuel cells aren't perfect, but only because we don't have a perfect catalyst. If our materials scientists and engineers would get off their lazy asses and make a ground breaking breakthrough, we'd see better than our already amazing 50-60% efficiencies with existing materials.

Well, the battery's way more materials costly (even including the fancy hydrogen tank). Also, it's weight is much heavier for less energy, due to batteries very low energy densities. A Honda clarity and Tesla Model S go about the same distance. A clarity has a curb weight of 1,600 kg, a Tesla has a curb weight of between 2000 kg and 2250 kg, depending on how many batteries you add in.

How many losses are generated from having to move that extra 400-600 kg everywhere you go? Not to mention, it's only possible to get only get so many cycles out of the materials heavy battery. With hydrogen tanks, it's feasible to simply reforge them after their service lifetime, given the energy supply.

Boats would utilize the same sort of system, going from diesel generators to hydrogen tanks and PEM fuel cell stacks. However, I have another solution to our boating problem as well.

Now, jets... jets are a different beast. Lockheed CL-400 Suntan exists, where they used liquidized (super-cooled) hydrogen. Program successes included the concept design of a Mach 2.5 aircraft capable of flying at 30,000 meters, and successful conversion of an existing turbojet engine to run on liquid hydrogen, as well as 25+ hours of testing on a customized LH2 engine design. This was back in 1956, if we can't figure out how to retro-fit an airliner with this technology (or compressed hydrogen for that nature), we're doing something wrong as a species.

Missing concepts, filling in the gaps
Please suggest new information here, or ask questions. I'm not really for a social-economic argument. I'd be excited if someone contribute more than "here's how I'd build a commerical airliner powered by hydrogen fuels", but the chances of crypto + hydrogen are slim to none.