Toyota hydrogen testing

I think there is a misconception about how Hydrogen vehicles would function. No one is talking about having a pressurized tank of hydrogen gas in the vehicle. That obviously won't work as you need to contain leaks of the leakiest gas in the universe (smallest atom size) and you are driving around with a bomb that is sensitive to impacts.

Modern hydrogen vehicles use Hydrogen Fuel Cells where the hydrogen is stored in a solid form as a Metal Hydride. The reactive metal, metal hydride, and hydrogen gas exist in an equilibrium and we can shift that equilibrium to either make hydrogen gas and free metal or solid metal hydride. The "tank" would contain the solid metal hydride which would release hydrogen gas in small quantities on demand to run the engine. Once the metal hydride has released a certain amount of hydrogen gas the remaining free metal is in large quantity so the equilibrium reaction really really wants to make more metal hydride so when hydrogen gas or liquid is reintroduced it immediately converts it into the solid metal hydride. The metal hydride doesn't have the issue with gas leaks or being a time bomb.

Materials chemists and physicists are constantly improving the safety and efficiency of solid state hydrogen fuel cell technology. However, to really make this an improvement over oil, solar efficiency has to increase as well so that the energy required to split water molecules to generate hydrogen is not a problem.

 

It's dead because there is no efficient way to acquire hydrogen. Hydrolysis uses too much power and reforming from natural gas defeats the purpose of getting away from fossil fuels..

 

Thanks for the update!

 

There’s lots of people that would be much better off with an EV instead of an ICE vehicle. But not everyone

I’m seeing more fleets opting for EV’s, but in IMO fleets would be better off using hydrogen vehicles instead. Unfortunately, they don’t have much choices available. And If we all go gung-ho for the EV’s, the grid won’t be able to handle it.

When I looked into the viability of getting one (EV), I knew I’d have to get an independent way of charging at home and powering the home off the grid because it’s just not ready, and not the best choice for me.
The government is trying to throw billion to make the grid better, but I have a feeling at least half those funds will disappear into the black hole and we’ll all still be left in the dark.

IMO gas is cheaper in comparison to other things and if it gets too high they'll be punished or be taken over by the governments, so they produce less, as the risk/reward ratio is not in their favor. The cure for high gas prices is higher prices IMO.

 

I'd still rather burn natural gas (to make either electricity or hydrogen) than coal (which is how we still make a big chunk of our electricity here).

 

Love the chemistry and agree that the hydrogen power plants use fuel cells as described. Less expensive modular electrolysis units to generate H2 can bring the capital expense down. These can use solar for a power source rather than using the grid and retail price for electricity. There are also ways to store and distribute H2 via low pressure methods that begin to address the distribution network issue and reduce risk.
The red hydrogen post from @Taco X needs to be viewed.

 

But but but... Red hydrogen isn't green!

 

Yeah, and there’s been solid data on electric cars being ‘cleaner’ overall for nearly two-thirds of a decade. People just need to bother to look.

 

Hydrogen + spark = boom

 

That's not what happens in a car.

 

That only applies to German made zeppelin’s.

Oh, the humanity!

 

The flammability of hydrogen is also an issue. Hydrogen has a flammability range between 4% to 75% in air, which is very wide compared with other fuels (gasoline is to 7.6%). Under the optimal combustion condition (a 29% hydrogen-to-air volume ratio), the energy required to initiate hydrogen combustion is much lower than that required for other common fuels (for example, a small spark will ignite it). However, hydrogen is about 57 times lighter than gasoline vapour and 14 times lighter than air. This means that if it is released in an open environment, it will typically rise and disperse rapidly. This is a safety advantage in an outside environment. Hydrogen also burns with an almost invisible flame, making it less noticeable and harder to firefight.

So leakage of hydrogen can be a concern, especially when vehicles are stored in enclosed spaces as hydrogen can build up in roof spaces. Due to its small molecular size, hydrogen disperses quickly at normal atmospheric pressure. Therefore it needs to be maintained at higher pressures (up to 10,000 pounds of force per square inch). The rupture of a pressure tank can cause high concentrations of hydrogen to form in the vicinity of the vehicle, as the turbulent flow rate of hydrogen is extremely high. Even though hydrogen disperses quickly, this emission will cause a combustible mix to form for a short period in the open.

 

True, but it wont explode. The tanks have been subjected to gun fire, placed in bonfires, dropped, crushed etc. with no explosions. Gasoline cars are still much more dangerous than hydrogen cars in an accident.

 

hydrogen cars don’t use pressurized tanks of hydrogen gas. It is a hydrogen fuel cell where the hydrogen is stored as a solid metal hydride and hydrogen gas is released on demand in small amounts by the fuel system for combustion.

 

This is a fallacy. Any solar power diverted or installed to make hydrogen is unavailable to power the grid. It is a zero sum game and there isn't any excess that is "free" to make hydrogen.

 

this is true for now but solar cell technology is still in its infancy, I have spoken to quite a few inorganic/materials/physical chemists who would bet their life savings (and actually have by forming companies and investing into their own research) that solar efficiency will increase by 5-10 times over the next 25 years while prices per panel fall. We will eventually reach a point where day time energy generation in sunny areas is nearly free which leaves plenty of excess room for hydrogen generation by electrolysis of water. Hydrogen fuel cell tech doesn’t bother me like electric vehicles because it’s still a powerful internal combustion engine with deep exhaust sound and range/power that can match gasoline. But still I agree with you that currently it is not viable - I’m just optimistic about its future.

 

I believe that this is overly optimistic. I love the tech and these things will certainly improve over time. But however optimistic one is one has to acknowledge that there will be some hard coded physical limits and gains of this magnitude may not be physically possible. IMO these sorts of projections fall into 2 camps. First are the advocates who supply a bit of well intentioned disinformation. Then there are the more diabolical uses by, say, big oil who will use this supposed coming windfall of essentially free energy to encourage wanton waste of our remaining fossil fuels.

 

There are onboard pressurized tanks with H2 @ 300-700 bar and sent to the fuel cell where intake oxygen is also used. That's how a fuel cell works. There is no combustion in a fuel cell.

 

the combination of hydrogen and oxygen to produce water (and energy) is combustion, it is burning hydrogen aka combustion (reacting with oxygen which produces heat and other forms of energy)

you are right that it’s not the gas expansion driving the engine though it’s the electricity generation

but there are full Hydrogen ICE engine setups being developed that use metal hydride storage rather than metal hydride low level combustion seen in fuel cells - https://www.sae.org/publications/technical-papers/content/2004-01-0699/

 

You're thinking hydrogen BMWs from the '90s. There's no combustion with fuel cells. Hydrogen passes through the fuel cell's proton exchange membrane to separate the proton and electron. The electron flow is electricity. By avoiding combustion, the process exceeds theoretical efficiency limits imposed by thermodynamics with burning a fuel.

Fuel cells in vehicle applications aren't sized for peak power demands, so the electricity generated still gets stored in small battery pack in cars like the Mirai.