From the post I was replying to: "In my opinion, the most significant argument against hydrogen fuel cell vehicles involves the safety risks from hydrogen explosions. This is far beyond the potential consequences of gasoline, diesel, or battery fires in personal vehicles."
As for the safety of air travel, I don't think it is good that people are so afraid of it, irrational fears lead to irrational decisions which lead to worse outcomes. Some people are afraid of flying to the point that they will take a road trip when a flight would be better, risking their lives more than necessary.
I want to move to more rational decisions where possible, and that means acknowledging that we don't know exactly how frequent or severe hydrogen accidents will be in comparison to gas. We have an unknown, likely very high danger, a known high danger, and a known low danger. Going overboard against the unknown danger is not particularly helpful.
With all due respect, waiting until we have enough data to determine "exactly how frequent or severe hydrogen accidents will be" with H2 FCVs and their fueling infrastructure is not rational and is not the way modern safety engineering is done, not for any potentially very high consequence risk. If that was the way we operated in industry, we'd be killing people on the job a couple of orders of magnitude more often than actually occurs.
To illustrate with a real example, almost 20 years ago I was part of a multidisciplinary team in my company that spent months studying a specific risk scenario and developing mitigations for a potential catastrophic event that had never happened to anyone, anywhere in the world. We studied near misses, used human factors analysis, the probabilities and consequences of flammable material release fires and explosions, and component and system failure probabilities. We developed a dynamic event model using known reaction kinetics and materials science. This was all input for a risk assessment. Bottom line, we estimated that the worst case scenario would occur about once every hundred years, two orders of magnitude more often than the mitigation threshold for consequences of that nature. We spent millions of dollars implementing systems across the company to reduce that specific risk below the threshold. This was not based on an irrational fear. It's our jobs to keep people safe.
I was driving home from work one night when I saw the night sky lit up in flames at a competitor's facility. The worst case scenario that had never happened anywhere before had happened to them. A man was dead and dozens were injured. It happened much as our dynamic model predicted. It almost certainly would not have happened if they'd had the mitigations in place that we implemented.
It's not necessary to wait for excessive risks to be taken and for people to be needlessly hurt, and to accumulate statistically significant fatality numbers in order to rationally assess and mitigate risks. Studying and mitigating "what if" potential safety incidents is a lot of what many of us do in our work. When dealing with high pressure flammable material releases, worst case scenarios that are rare often turn out to be the failure mode that dominates the risk score and determines the necessary mitigations, more so than higher probability, lower consequence scenarios.
There is enough data on component and systems failure probabilities and enough understood about vehicle accidents, compressed gas behavior, and the science of hydrogen fires and explosions to do risk assessments for H2 FCV cars and H2 fueling stations. Like all risk assessments, these studies are evergreen as new data and scenarios become better understood.
If H2 FCVs were a necessary mitigation to prevent predicted AGW then I would say we need to move as quickly as possible toward switching the vehicle fleet to H2 FCVs and do it as safely as possible. However, neither of these is the case. The siting of H2 fueling stations has not been as safe as reasonably possible. H2 FCVs are not a necessary mitigation for AGW because they have a larger carbon footprint than BEVs and are no better than HEVs in that regard. The most efficient FCV tested by NREL has a carbon footprint no lower than a Prius. Compared to a FCV, a Prius costs less to purchase, costs less to fuel, does not require a new multibillion dollar fueling infrastructure, and does not incur the potential safety consequences of 10,000 psig H2.
