The argument for hydrogen generally revolves around the fact that it's only waste product is literally H2O. So by using an FCV, you only really emit water as a byproduct, which in general is not of a global cooling chemical than a global warming chemical; though, I don't mean to suggest, in any way, shape, or form that FCVs have any impact at all in reversing global warming.

I would argue that efficiency isn't necessarily the most critical point in regards to "Green" technology. It's an important factor, true, especially when dealing with portable or vehicular energy, since storing a large amount of fuel/energy/power to do a task is generally considered to be a bad idea, mainly due to the size and weight of such storage. I would argue that the efficiency in a less size/weight constrained system, such as a depot or facility, is less of a problem. For example, let's say we're getting 30+ % efficiency solar panels and generating... say, 10kW from the array on average for 5 hours, a total of 50kWh. There's already losses from the solar, but we'll discount that since there's no competing technology to generate power from sunlight which has anywhere near as much efficiency.

From there, we lose maybe 30% from water electrolysis to generate hydrogen. We will lose an additional 40% when that is converted back to electricity for use in FCVs.

The output power will be ~21 kWh.

This is equivalent to a solar array of ~4.5 kW in the same situation, using BEV.

My argument here, against the efficiency matter is: the BEV array is approximately half as large or using panels that are half as efficient, this is going to be located at a facility or location where the hydrogen is stored, which will likely have room for a larger solar array than 10kW. So the only sacrifice made in the scenario is to allocate a larger space and some additional panels to a static location where the hydrolysis is being performed.... Big deal. It's entirely green energy with immense storage capacity (even just as a pressurized gas), and incredible energy density.

Obviously there are still risks with it being literally an explosive, though it can be argued that gasoline also carries that risk and it's literally everywhere. Albeit not as extreme of a risk, but bluntly, gasoline sticks around. Hydrogen generally screws off. Once it's released into atmosphere, yes it's incredibly dangerous and explosive in the presence of oxygen, but it will quickly rise and clear out from ground level where all the spark hazards are... While gasoline releases vapor continually and any ignition of the vaporized gasoline will likely find it's way back to the source of those vapors and ignite them. Hydrogen is a flash and it's gone. It's a trade off of risks either way.

I hear what you're saying, I just don't necessarily agree that it's as bad as it would initially seem.

In the other hand, I've seen the dumb shit people do with anything flammable or explosive and I'd rather not put something so energetic into the hands of the general public. So there's that as well.

I also want to address the matter of urgency. It's not critical that we convert all of the cars to EVs. Personally owned vehicle emissions are not the greenhouse gasses that cause the most significant problem. What most graphs show are intra-country emissions, which either lump all "transportation" emissions into one category, or categorize mostly land-based transport methods. In more global charts they generalize "transportation" as one thing, not defining what each transportation type is contributing. There's a few graphs that are out there, if you dig for them, which show that global transportation is ~75% of emissions, but break it down by purpose/type of transit, and if you really dig into the data, personally owned vehicles are something less than 10% of overall emissions. The rest goes to shipping, like boats, transport planes, trucks etc. large tank liners or cargo vessels are a huge portion of the emissions. There has been zero push to have those converted to electrical options. Whether fuel cell or battery, it's not something that's even discussed. The fact is, those boats are running basically 24/7, consuming more fuel daily than even a mid-sized town of consumer vehicles, and homes combined. And that's just one ship. There are hundreds of them on the water. So having the public convert to EVs, is a literal drop in the bucket of CO2 emissions.

So the question is, why aren't we talking about it? I think the answer is clear. Ships are the bread and butter for oil conglomerates. They need fuel, usually diesel, to get anything anywhere. The global demand for energy to simply move shit around is massive. Nobody wants you looking at it and complaining. Even if the consumer vehicles were all converted to some form of EV overnight, oil companies would still make money hand over fist.

None of this should be taken as "fuck it, let's just keep going with ICE cars". Absofuckinglutely not. Consumers still need to convert to EVs. There is no "but what about" going on here. But having perspective on the issue is essential. We all need to do our part. Right now, everyone seems happy to stay focused on consumer vehicles and the drive towards personal responsibility of carbon emissions, but that's only focusing on consumer emissions. Industrial emissions from shipping and energy production, even just getting the energy products to where they need to go, should also be something that is a part of the discussion because they are far and above more egregious in their carbon footprint than the consumers are. IMO, they've set the pubic against itself to distract from the fact that we're not the biggest problem. There's now a war of sorts happening between "tree hugging" EV advocates and "dinosaur burning" ICE enthusiasts. It's worked and we need to realise that we are all on the same side, and we need to recognize that the real problem isn't us, it's the companies who would rather ruin the planet than ruin their bottom line. Yes, that includes oil companies, but also shipping companies. Other industries are also guilty of massive ecological destruction too.

IMO, this is yet another example of the "elite" driving a narrative that benefits them. That somehow because reasons we should all feel bad about driving our cars to the places we need to go, burning mere gallons of fuel daily for everything we do, while they burn barrels of fuel hourly so they can line their pockets with our money.

Personally, I don't think we should give up on fuel cells or green hydrogen, because there's literal acres of land that can be used for solar to generate the power to produce hydrogen, and use that hydrogen to power fuel cell based electric vessels for transport. They have a virtually inexhaustible supply of water right next to where these docks exist, and plenty of land for solar which can be used for the process. It makes sense; and with a fuel cell vessel the hydrogen can be stored in large pressurized containers that are regularly tested and validated to be safe, with extended safety mechanisms in place that we basically can't do with consumer goods. Weight is also less of a concern, and they already allocate a nontrivial amount of space on the ship to storing fuel for the journey. It would make such a significant impact to overall emissions that the consumer EV thing would be little more than a footnote, rather than the headline news it is right now.

But I don't see anyone even remotely discussing it. Maybe they should.