Hydrogen as part is totally reasonable. It gives us hydrocarbon density without us needing to add to the CO2 in the atmosphere. The important thing to remember when discussing it is that it's an energy storage medium, not an energy generation medium. Most of the time I get irritated is when people treat hydrogen as the latter. But if our culture is just too damn wedded to cars for now, and battery tech just isn't there yet, then using hydrogen as a stopgap--provided the hydrogen is made from renewable energy--seems fine to me.
It doesn't cause metals to become brittle. Its relatively stable. It doesn't require as low temperature or as high pressure to liquidize. It also stores ~50% more hydrogen per volume, as each ammonia has 3 hydrogen, unlike elemental hydrogen with just 2.
But we have handled ammonia on an industrial scale for more than a century and are really good at it. Any safety concerns about ammonia are ridiculous when compared with some of the other substances we handle and live around on a daily basis.
A a John Deere employee I can tell you that several very much wanted products have failed to be developed because someone put their safety black-hat on and came up with a to abuse that product the release ammonia into the air. Once an evil person figures out how to control our system it is trivial for them to figure out many terrorist attacks involving ammonia releases.
Yes the world deals with ammonia all the time. However we have special training for anyone who handles it. Even the most caution to the wind types wear full respirators and thick gloves when handling it.
When you buy ammonia at walmart what you get is 1% ammonia, 99% water. Then you are instructed to dilute it with more water 16:1, Even at that ratio it is nasty enough that those who use it have windows open.
Please be specific. Liquid anhydrous ammonia is a common fertilizer. John Deere still sells e.g. the 2430 and the 2510. How did the hypothetical "very much wanted" products differ from those applicators? Are we talking about a handheld model? (That might have been a bad idea!) One suspects the hypothetical "evil persons" whose threat delayed product development were more interested in cooking meth than in terrorist attacks...
John Deere is to be commended, one supposes, for being much more concerned about blackhat terrorists than e.g. Siemens with all their internet-accessible SCADA installations, but neither ISIS nor Putin care about killing a couple of farmers in western Iowa. Thread parent was about automobiles, and while maybe professionally-operated vehicles like semi trucks or buses would be better with which to start using ammonia on a large scale, vehicles are unlike applicator implements in that they aren't actually designed to release ammonia into the environment. Conceivably a car could be hacked to lock the brakes at high speed, but there's just no mechanism to pour out its fuel tank.
Ammonia is less flammable and explosive than gasoline, which is commonly found in currently-engineered and currently-existing fuel tanks. They are both much less flammable and explosive than hydrogen, which is the other fuel under discussion in this thread. Ammonia tanks would be pressurized, which is different than gasoline, but lots of tanks are pressurized.
Hydrogen is not toxic by inhalation, but it's a much worse explosion/fire risk.
Hydrogen is flammable when mixed with air between 4% and 75%, and it takes a minimum energy of 0.016 millijoules to ignite. Ammonia is flammable between 15% and 28% and takes 680 millijoules to ignite. It takes much more energy to ignite ammonia and there's a much narrower range of mixtures with air where it can support combustion.
Yep, and that's a very legitimate concern and why I'm certainly not bullish about hydrogen. I just don't want to reflexively throw it out; sufficient energy production from clean sources would make electrolysis quite reasonable, even if it's not ideal, and there are approaches to handling the storage, too, if that ends up being the last bit. I suspect, based on current trends and sciences, that we'll see better batteries instead, but I don't see harm in continuing to look at hydrogen for now.
Hydrogen vehicles will never become popular. There are several reasons for this:
- To be carbon-neutral, the hydrogen must come from splitting water.[1] Currently hydrogen comes from steam reforming of methane (which releases lots of carbon).[2]
- Hydrogen is a very pernicious molecule. It will slowly leak through metal and weaken it.[3]
- Hydrogen vehicles must be refueled at special fueling stations. Electric vehicles can be charged anywhere there is electricity (such as at home).
- Hydrogen fuel cell vehicles are more expensive than battery electric vehicles. Toyota sells the Mirai for $57,500 and loses money on each one.
- Storage and transportation of hydrogen is very difficult. It must either be stored in gaseous form at very high pressure, or in liquid form at 20 degrees above absolute zero. Current vehicles use high pressure tanks, which also require high pressure pumps. Many hydrogen stations can only provide 5,000psi pumps, which means you'll only get half a tank (and half of your expected range).[4]
- Hydrogen is more flammable than gasoline (it will ignite in a much wider range of mixtures with oxygen).[5] Unlike gasoline, the flame is invisible in daytime. Unlike gasoline, hydrogen is invisible and has no smell, making leaks undetectable without special equipment. If an odorant is added to the hydrogen, it will likely damage the fuel cell.
- Hydrogen is more expensive than gasoline and far more expensive than electricity. Even with subsidies, refilling a Toyota Mirai costs over $80.[4] That gives you just over 300 miles of range. My Tesla Model 3 has the same range and a full charge costs me $6 at home. Supercharging is also cheaper, at around $25.
- Batteries got cheap faster than anyone predicted (except Tesla). In 2015, a study looked at past estimates of battery prices versus observed prices. They found that analysts were consistently pessimistic about cost reductions. Correcting for this, they noted that cost per kWh, "...could reach $200 by 2020." Actual cost in 2020 was $123.[6]
Given all of these disadvantages, I don't see how hydrogen vehicles could be considered reasonable. The economics, physics, safety, and convenience simply don't work out.
