Comment by Accujack | Hacker News Reader

Comment by Accujack | Hacker News Reader

This is interesting for cleaning up internal combustion engine use, but it's not so useful for climate change because although burning hydrogen doesn't produce carbon dioxide or methane, it does produce water vapor. See this page for info on that:

https://www.acs.org/content/acs/en/climatescience/climatesci...

Also, the big issue with hydrogen as a fuel is that while it has a high energy density per unit mass, it has a very low energy density per unit volume... IE, from an engineering point of view you have to carry a large volume of the stuff to have a vehicle with any significant range.

Discussion of how that could potentially be done here:

https://www.energy.gov/eere/fuelcells/hydrogen-storage

In a way, this sort of research addresses the same problem as improved battery technology - we need mobile energy sources for moving things.

I think a major reason we haven't gotten where we need to go with this problem is that researchers tend to look for a way to replace gasoline - to find another fuel that can simply be used in place of gas/diesel using the same engine technology (and associated control, fuel handling, and other tech).

That's very, very difficult to do, because gasoline is uniquely suited to what we use it for - it has high energy density per unit volume and mass, it's moderately volatile at standard temperature and pressure, and most interestingly we don't have to expend much energy to produce it, because all that energy was stored aeons ago. We just have to get it out of the ground and separate it into usable fractions. It's essentially a "free ride" as far as energy sources go.

It's too bad continual use will destroy us.

505,000 cubic kilometres of water falls from the sky every year as rain across 510.1 million km² of surface area. Directly adding water vapor like this would have an impact so small as to be undetectable change in the global average humidity.

What that link is talking about is changing systems that operate at a scale it’s hard to fathom.

I think you misunderstand the cited article on water vapor.

The water cycle is self regulating, unlike other green house gases.

>> "However, water vapor does not control the Earth’s temperature, but is instead controlled by the temperature. This is because the temperature of the surrounding atmosphere limits the maximum amount of water vapor the atmosphere can contain."

The other non condensing gases, largely from man made sources, contribute to global warming and elevate the amount of water that can be vaporized per unit volume of air.

Cutting down on emissions by replacing oil based vehicles with electric/hydrogen fuel cell powered vehicles absolutely helps the environment. Cutting emission sources makes job of scrubbing the atmosphere of the green houses gases already present more achievable.

Okay, exhaust water from engines does not add greenhouse gases to the atmosphere in significant quantity to increase the rate of climate change - that happens naturally according to the temperature of the atmosphere. Not sure what I was thinking exactly when I wrote that.

However, there are other reasons not to use hydrogen powered IC engines instead of electric engines, like the efficiency of electric motors vs. IC engines, the need to transport hydrogen fuel in greater volume than gasoline for the same range and power, potential issues with corrosion due to immediate condensation, safety issues in cold climates with exhaust immediately freezing on road surfaces, and others.

If someone had a way to create liquid hydrogen with little energy, store it safely in a vehicle, and have an engine able to use it, that might change the game. Gaseous hydrogen, not so much.

Hydrogen fuel from seawater is a neat idea compared to gasoline, but the chances of wide deployment of hydrogen fuels being a significant contribution to saving ourselves from climate change are minimal, in my opinion.

Water vapour is pretty easily re-condensed, though, no? Cars emit their waste products into the air because it’s kind of hard to capture gaseous waste (you would need a compressor, which would use almost as much energy as the car itself.) But if your waste was water vapour, you could just route your gas waste through a condenser column, and then dump it into a storage tank.

And, since the waste product is literally just water, that tank could be emptied pretty frequently—any time you’re near a municipal storm drain, in fact. So you wouldn’t need to worry about your car taking on that much mass.

A condenser column would need to be cooled. Even a passive radiator adds weight.

Another step in the engine cycle can cool and condense the water vapor to liquid, and extract additional energy from the exhaust. The weight of the required additional engine parts, and the cooler in particular, tends to erase all the actual benefit in an automobile. Cargo ships and train locomotives could do it.

> This is interesting for cleaning up internal combustion engine use, but it's not so useful for climate change because although burning hydrogen doesn't produce carbon dioxide or methane, it does produce water vapor.

Water vapour is exactly something we want from sea water, in addition to the hydrogen we can use as fuel. It's easily condensed into fresh water, which will likely become increasingly scarce over the next century. Looks like a win-win.

There's also the fact that metals become brittle when exposed to hydrogen. Hydrogen seeps through the crystal/atomic lattice and combines with oxygen or carbon, and tears the metal apart.

https://en.wikipedia.org/wiki/Hydrogen_embrittlement

The high pressure containers are made from composites though. Are they susceptible to embrittlement as well?

I thought hydrogen embrittlement only effects mainly steel that under go high temperature. That's why the rebake stuff in inert environments that was forged like screws.

With regards to fuel cells for transportation, wouldn't it be easier to generate electricity from the hydrogen and use that to charge EVs?

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