Hydrogen

[Macaque]

Hi I also post as Dog on HPC

 

Hydrogen is touted around as the wonder fuel of the future. I have serious doubts about this for two reasons.

 

Firstly, very heavy pressure vessels have to be used for storing hydrogen in useful quantities.

 

When hydrogen is handled outside, it is a very forgiving gas. It has a low combustion temperature and rapidly disperses into the atmosphere. Inside buildings however it is a very different story. It has a very low ignition energy (which means that the tiniest spark can cause a flammable hydrogen mixture to ignite). It has a very wide flammability range (which means that small concentrations (4%) of hydrogen mixed with air can ignite). It is a very light gas and easily accumulates in overhead pockets within buildings. It also has a very high combustion velocity which is a particularly nasty characteristic. Hydrogen deflagration within a confined space can rapidly progress into a detonation. Detonations tend to rip buildings to pieces. Hydorgen powered machines would be very difficult to store or use within enclosed spaces. Hydrogen powered cars for example could be extremely dangerous if parked in a garage or multi story carpark.

 

So we have a wonder fuel which is too heavy to move around easily and is too dangerous to use or store inside buildings.

[malco]

I share your doubts. Another point is that H2 has to be made in some way. At present it is mostly made from nat gas, not a lot of use in the long term. You can make it from electrolysis, but this is inefficient. It's better just to send the electricity down lines to electric cars - which as you have pointed out elsewhere have their problems. Maybe we'll find a way of improving on photosynthesis. Maybe...

 

There are currently some heavy vehicles that are powered by methane under high pressure (600 bars). The installation is extremely strong within a vehicle that is massively built, so the road safety issue is quite different from what it would be in cars. Also, the vehicles are used in specific projects where there is a known route and a steady market set by long term contract. Vehicle capital recovery is thus very high. The operation can be run by a select team of well-trained operatives. Plus, the nat gas distribution infrastructure is already there. The weakness is of course that nat gas is a fossil fuel and it will deplete.

 

It might be the case that H2 would be used for municipal vehicles in some places where electricity is cheap and the distances are too great to consider direct electrical distribution. This is doubtless why Iceland has a few buses and garbage trucks run on H2.

 

I see H2 as a bit of a dabble at a time when many folk think there is no pressing crisis and there is lots of time to day-dream about the post-oil future, without really being pressed hard up against the realities of whether it is actually scalable or useful.

[Macaque]

The main value of hydrogen (within the alternative fuel market) is to give scientists an opportunity to pillage research budgets. It is the modern equivalent of a quack medicine.

[spline]

Hi Dog – I think I agree with malco, H2 is really a container of energy and has to be “made” somewhere. I guess it’s main advantage would be no CO2 emissions at the point of use, but obviously plenty at the point of manufacture, and, quite important for urban use, there is no trace sulphur in the fuel, so that’s an huge reduction in SOX as well. But I think it’s also quite bulky per unit of energy delivered and that would impact the range or likely size of the vehicles – aeroplanes would come out looking very fat.

[DontPanic]

H2 can be made in high temperature gas reactors which form part of the research going into "Generation 4"

http://en.wikipedia.org/wiki/Generation_IV_reactor

[malco]

H2 can be made in high temperature gas reactors which form part of the research going into "Generation 4"

http://en.wikipedia.org/wiki/Generation_IV_reactor

 

No it can't. All of those designs are prospective and not expected to be in commercial use for another 25 years. The use of waste heat from a few of these designs is only described as "potential". That does not mean very much. Potentially the poor sods on the Titanic could have made lifeboats by ripping up the deck planking, but that does not mean they actually did it. Time is the crucial element of a crisis.

 

I remain exceedingly sceptical of the H2 economy. I work in the gas industry, that gives me a healthy respect for the precautions that have to be taken in handling methane. H2 is an awful lot more hazardous than methane.