Hydrogen is so hard to handle that NASA never really figured it out; hydrogen leaks just delayed Artemis 2 last week. There's been about 70 years of trying to solve these issues for space launch and very little progress. It doesn't seem like it'll be easier trying to do this as the scale of every gas station?
The article skips that i think most realistic and plausible option - fuel cell using hydrogen extracted from the standard hydrocarbon fuel right on the truck. Thus hydrogen would be present only in the short path - from fuel splitter to the fuel call. The fuel cell has higher efficiency than ICE and having electrical engine works better for trucks than ICE too. Such setup is overkill, at least for near future, for regular cars, while for trucks it seems worth the investment.
Short answer, it takes more energy to generate than the energy it produces.
You can do things like only producing electrical power from the alternator when decelerating, ensuring no load comes off the engine, but that would require accumulation as you're not actually burning fuel then either.
But running the numbers on the power requirements, I reviewed one commercially available system (at 12v 14A) and calculated that the HHO they are able to produce is 0.037% by energy going into the engine vs regular fuel.
When presented with 0.037% of the fuel substituted, their 10-15% claim on fuel savings becomes a bit of a red flag.
Surely that's a thermodynamic waste? Use the energy in the fuel to extract hydrogen from the fuel to them use the energy in the hydrogen to generate electricity to turn the wheels.
Is there a chemical process that achieves this with a better efficiency than just using the fuel to turn the wheels?
Onboard reforming has been explored and it's not great. The end-to-end efficiency is poor (<50%). It adds a ton of complexity. It requires having a reactor running at over 700°C. It takes time to warm up. It's not cleaner. Impurities like sulfur kill it.
In the end it's only about as efficient as just using a regular diesel engine, much harder to service, more expensive to maintain, and doesn't improve your carbon footprint at all. What's the point?
