Probably just as dangerous as driving with a tank of pressurized natural gas, which is already very common (for instance, where I live, nearly all taxis are converted to run on pressurized natural gas, since it's cheaper than gasoline).
I shouldn’t think it’s much more dangerous than other pressurized flammable gases. Those pressure vessels are designed for safety contrary to what you see in movies. I’d be about as concerned as I am driving around with a tank of highly flammable gasoline.
Hydrogen forms explosive mixtures with air at a much wider range of concentrations than typical hydrocarbons and has a nasty tendency to permeate straight through a lot of materials.
It’s lighter than air though so it won’t pool in low areas and if a pressure vessel won’t contain it it probably diffuses through car interiors / dry wall and vapor barrier pretty quickly. What’s the rate at which it escapes? Probably pretty slow.
It can be very safe if using hydride tanks. I think there are some international arms controls related to hydrogen bombs that makes hydride tanks difficult to produce.
Yes. Gasoline has a relatively narrow ignition range, it has much less rigorous sealing requirements, and it burns with a flame that's visible in daylight.
The problem is that we can't easily make gasoline with solar panels and water.
Actually it is possible to make gasoline with solar panels, water and carbon dioxide from the air.
Making synthetic gasoline was already possible before WWII and that was used a lot by Germany.
It is true that making hydrogen is easier, because making gasoline requires additional steps and equipment, but due to the large disadvantages of storing and handling hydrogen, making gasoline is nonetheless preferable and it does not require any infrastructure change.
While hydrogen is preferred currently for room-temperature fuel cells, for the moment that seems like a dead end, because the current catalysts are much too expensive.
High-temperature fuel cells can use gasoline, so hydrogen no longer has advantages.
Even if one would not choose gasoline, there are still other much better ways to chemically store solar energy than hydrogen, e.g. ammonia or methanol.
Wasn't Germany's synthetic gasoline derived from coal?
Fun fact: methanol has a similar "invisible fire" risk, which is the origin of the "Don't let the invisible fire burn my friend" joke in Talladega Nights.
For short-term storage a rechargeable battery is certainly preferable.
For long-term storage, the battery auto-discharges, so the efficiency drops quickly with the storage time, until it becomes much less than for storing the energy by synthesizing some appropriate chemical compound.
For storing solar energy, both short-term storage (e.g. for a day or a week), like rechargeable batteries, and long-term storage (e.g. for a year or more), like synthetic gasoline, are needed.
Lithium self discharges at 1-2% per month, not an issue in most circumstances, not sure where it would be an issue, if it was just have a maintaining solar panel nearby.
