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Isn't one of the other problems of a hydrogen system safely storing the stuff?

Icon: What happens when you don't store the stuff properly.

Yep, and even ignoring safety concerns hydrogen is a bit of a faff to store, transport and transfer.

Some folk are looking at using amonia (one nitrogen and three hydrogen atoms) as an energy dense fuel - again using catalysts and renewable power sources:

https://www.sciencemag.org/news/2018/07/ammonia-renewable-fuel-made-sun-air-and-water-could-power-globe-without-carbon

Since it is obvious that the energy required to split water is always going to be more than what you gain from recombining it then this technique can be best used instead of storage.

Trouble with ammonia is that it is toxic.

at least you can smell when it leaks.

Good thing gasoline isn't toxic

You could say exactly the same about petrol too. It's been said that if petrol was proposed today as a new fuel, it would not get approved due to the same safety concerns.

Not quite. Hydrogen gas only has a molecular weight of 2. It's practically the smallest thing that exists naturally. Think about how tough it is to reliably store helium (atomic weight 4) because of its tendency to seep through even the tiniest holes; hydrogen is even worse than that. Containment and leaking have always been the biggest problems with hydrogen gas.

Such Hydrogen leakage is too small to pose any serious risk in most applications. And if there is a major leak, gasoline is far more likely to pose a problem than Hydrogen. It's actually not that easy to get Hydrogen to burn or explode, gasoline on the other hand is easy, and it burns for much longer

https://www.youtube.com/watch?v=7bFJK5kU_UQ&feature=emb_err_woyt

The real issue with Hydrogen is storage density. There are number of proposed solutions, but we're still waiting for one to take off.

Safely isnt really that much of an issue from a technology standard.

Engineers are already looking at converting wind power to hydrogen (it was via electrolysis) as a more efficient method of transferring energy from offshore to land as the %of electricity lost to power transmission can be upwards of 6% - even at very high voltages (where windfarms use step up transformers to send the power). This would open up large shallow areas of sea which are not close to land, but have more consistent wind - such as Dogger Bank and potentially floating (rather than anchored) wave and wind power. Tankers or pipelines then 'tap off' hydrogen and return it to land.

One of the problems with gaseous hydrogen is that to have decent quantities of it, it needs to be rather compressed..... and compressed Hydrogen is perhaps the molecule most prone to leaking through other materials - as well as making others brittle. Steel is one of the worst to get brittle damage - though copper pipes are almost immune, they cant handle sustained pressures and is fairly porus, so complex material engineering is going to be required....

Another problem with storing compressed hydrogen is the weight of containers that can store it safely at the sort of pressure needed to match the energy stored in a similarly sized tank of petrol or diesel. The catch is that the weight of these containers is enough that, although the energy content per litre of hydrocarbon fuel can be matched easily enough by compressing the hydrogen, the total weight of the hydrogen tankful will almost certainly be much higher than that of the same sized tank of petrol or diesel.

Result: inferior performance and load-carrying capacity of the hydrogen fuelled vehicle when compared with its diesel or petrol equivalent.

But MUCH lighter than the batteries of a tesla: 480 kg

"Result: inferior performance and load-carrying capacity of the hydrogen fuelled vehicle when compared with its diesel or petrol equivalent."

No. One of my customers has just started testing a heavy vehicle for demanding applications which is powered by hydrogen fuel cells. They (v serious and competent engineers) expect it do deliver the same performance as the diesel vehicles they also build. They're developing it because their industrial customers are asking for options to reduce their carbon footprint.

If only we could use composite overwrap vessels, shame no-one is developing those to withstand very high pressures at extremely low mass.

And no, low temperature isn't an issue for them, given that their current applications tend to be cryogenic.

Another problem with storing compressed hydrogen is the weight of containers

Isn't that a problem of scale? It would be silly to power something small like an electric bike with hydrogen because the weight of the container and fuel cell will dwarf the small quantity of hydrogen it requires. But for something like a train it should have a much better power to weight ratio than batteries of equivalent energy. The crossover is likely somewhere between "passenger car" and "semi tractor".

Is it worse than the fuel we currently put in cars?

I think you have hit on the main reason why there is so much research in recombining recovered CO2 with hydrogen back into fuel: you end up with something that comfortably sits inside the established supply chain of tank wagons and pump stations, you end up with a more regular kaboom risk and from what I remember it didn't require much adaptation of existing combustion engines.

If I recall correctly there's even a form of storage-in-fluid for cell use which renders it kaboom free and usable in electric cars, but with a need to collect the waste product to "recharge" it - again, not hard for established infrastructure but it's more involved than just re-creating fuel.

I see this as a more promising approach to electric cars - batteries has a FAR lower energy density, yet take a long time to recharge. That last fuel cell approach would basically amount to emptying a tank and refuelling, as quick as a fossile fule powered vehicle, with FAR lower risk of it self-igniting or expose fire brigade crew to dangerous events in case of an accident. Lithium fires are not fun.

I loved the comment from Malte Janssen of Imperial college.

I bet he would have been with the ' Too fast to breathe' crowd at the advent of the railways.

Fine, continue with developing proven technologies but don't sweep something new and innovative under the carpet because you didn't think of it.

Valencia is my local uni and they do some good outside the box thinking.

Not really: Hydrogen is not what you want for storing energy. You might use it in a fuel cell to drive something but otherwise for transport and storage virtually anything else is preferable. But the chemistry and physics of electrolysis are also disadvantageous because breaking the O-H bond requires so much energy all at once. Other multiple step processes don't need as much for each step, which offers more scope for catalysts.

But it is still good research.

"It has nearly three times the energy density of petrol ".

Is that comparing liquid H2 with Petrol? Or Molar H2 with Molar petrol/ethanol (petrol being a mixture of molecule types).

Making and storing liquid H2 is non trivial so that's a fairly significant point to brush over and a Mole of gasious H2 is going to need a lot more space than a mole of liquid petrol even at high pressure

Yeah, hydrocarbons for storage make more sense and probably have a better energy path: CO 2 + H 2 O -> hydrocarbon can already done at slightly over cost and has had far less spent on it that some of the marginal improvements to Lithium batteries.

Yup, making Hydrogen could be free, but you still have the issue of liquifying it and keeping it that way. That takes plenty of energy that needs to be accounted for.

In terms of energy per kg it doesn't really matter what form the hydrogen is in, but for energy per litre, which is important for transport(*), hydrogen is at best one third of the energy density (LOx).

[1]Convenient table on Wikipedia .

(*) Unless you don't mind your car/lorry being 90% tankage.

[1] https://en.wikipedia.org/wiki/Energy_density#Tables_of_energy_content

Energy density in MJ/kg, yes.

Energy density in MJ/l, not so much.

There are three ways to store hydrogen: compressed, liquefied or bound to e.g. nickel. Each of these methods suck in its own special ways.

The problems with liquefying hydrogen are that it takes a lot of energy to get it this cold, keeping it cold and finding a safe place where it can reliably remain cold. Not ideal for most situations.

Binding hydrogen to usually some metal molecule has the advantage that this is very stable and thus quite safe. The major disadvantage is that since it's a stable connection, it's hard and thus very slow to get the hydrogen to become unbound again. The other major disadvantage is that this storage method is very bulky and heavy, making it only suitable for situations where you need stationary storage and aren't too worried about how fast you can get hydrogen back out.

Finally, the most common method of storage and what is generally used for transport applications is to compress the gas and storing it in super-thick walled (composite) tanks. This has to occur at very high pressures as hydrogen has a stupidly unreasonable power-to-volume ratio. These hydrogen tanks have a very limited lifespan and need to be regularly inspected for safety reasons.

In industrial applications, the preferred method is to produce needed hydrogen on the spot, in limited quantities for immediate use. See the issues with storage for why.

As far as general safety goes, hydrogen is a fairly unique gas in that it is highly inflammable, more than anything else. If mixed with an oxygen ratio between almost nothing and close to saturation, it'll happily and violently detonate. Over the past years there have been multiple explosions at hydrogen refueling stations and production facilities, including an accident last year in California that show just how much of a liability H2 is in general use: https://www.cnet.com/roadshow/news/hydrogen-fuel-cell-car-california-explosion/

As mentioned by others, the amazing thing about hydrocarbons is that they are very stable, very dense and easy to store. Hydrogen without the carbon is essentially the opposite. Hydrogen reacts with everything (which causes the metal embrittlement and violent reaction with oxygen), is the exact opposite of dense and is very hard to store (see above).

Current suggestions for hydrogen in the fuel mix is to add hydrogen to the natural gas pipelines, but as we'll one day want to stop using natural gas, we'll lose the one easy(-ish) way to transport hydrogen that way. Maybe a methane-based economy makes more sense than a hydrogen-based one? Can still use steam-reformation with the methane to get hydrogen where it's needed, but avoid the headaches of storing and transporting of hydrogen.

You *could* bind it to carbon also.

Or -even better- to TWO Carbon and a single Oxygen, like this

3H-C-C2H-OH

Isn't that what they do in those recombined fuel trials? Combine recovered carbon dioxide with hydrogen to make "regular" fuel?

Key to all of this is availability of cheap electricity (as you're basically looking at ways to store electric energy in a form you can transport easily) and I think this will really take off once we have green and nuclear* energy to a point where their price point matches fossil fuel.

I must admit I have always considered battery stored power a bit of a stopgap until we had something with a far higher energy density.

* I'm thinking the newer LIFTR Thorium reactors here, which also could be operated directly at the temperature required for the most efficient way to produce hydrogen (thermochemical, which needs some 950ºC to work).

On the basis that existing vehicles use hydrogen (albeit not particularly cheaply) and get 300 odd miles from a 70kPa tank in a reasonably sized tank.

For the energy revolution the hydrogen will need to be turned into methane. This makes the hydrogen easily storeable and transportable. Furthermore, Methanation uses CO2 to turn hydrogen into methane. Thus, you can plumb the exhaust stream of something you can not avoid, e.g. garbage incineration, into the loop and avoid emissions.

Isn't methane one of the more dangerous greenhouse gasses?

Isn't the thawing tundra rin danger of eleasing gigatonnes of the stuff?

AFAIK, that's about the last thing we want to create.

Yes it is, You're actually better off capturing the methane and burning it than letting the methane go into the atmosphere, the net impact of the CO2 from burning it is less than that of the Methane itself. And in the process you can generate electricity. It's not at all carbon neutral, but if you've got the methane you might as well use it rather than let it escape.

And it's not just the thawing tundra that is a potential source. We have lots of it under the oceans and those deposits are becoming unstable

https://en.wikipedia.org/wiki/Methane_clathrate#Methane_clathrates_and_climate_change

"technologies that are relatively mature"

Algae, water, carbon dioxide and sunlight to produce carbohydrates.

Carbohydrates plus yeast to produce alcohol.

Alcohol or maybe some derivative such as biodiesel plus ICE produces water and carbon dioxide as by-products.

Fuel is distributed through the existing system.

Some very ancient technology and nothing that's immature.

not a problem but several

1 the explosive range is about 5% to 75% oh H2 in air, so it goes bang very easily and often when and where you don't want it. methane has a range of 8% to 18%

2 it is almost impossible to store, steel is right out of the question, but nickel is used in some short exposure environments, so instead of $600 for your material its $20k and then you have to replace it regularly. Use ammonia instead.

3 and H2 you spill is lost permanently, it goes to the top of the atmosphere and drifts off into the deep cosmos, but there is a lot of it on Earth.

4 H2 has been an industrial hazard for a long time (centuries), thus it is well characterised and electrolysis a text book example for 150 years. So this may make this step cheaper, making H2 is not the problem, it is storing it, not losing it and not blowing yourself or your customer up in using it.

5 H2 can be a liquid, but at boiling point of 20K, the economics look bad so use ammonia

written by an engineer with two degrees and 20+ years in the fuel and fuel storage industry

Thank you for these. Instead of ammonia (NH3), what about the Sabatier reaction and methane (CH4) or even methanol (CH3OH). I am sure burning ammonia produces nitrogen oxides. Methanol has the decency to be a liquid at room temp and pressure. Probably as hazardous to humans as drinking petrol (or sniffing petrol) which we aware not to do.

By the same reasoning why not store it as ethanol (less toxic, can be quite enjoyable) or propanol, butanol or pentanol?

"any H2 you spill is lost permanently" - if you're lucky; if you're unlucky it finds friends in the ozone layer.

> blasting microwave radiation at a watery chemical soup

It's good to know that someone has found a use for supermarket Caldo

What's the recipe? 5 minutes at maximum power.

This is actually IMO the key feature - by turning a dissolved chemical into a catalyst using microwaves, they have avoided all the usual difficulties of trying to maximise a (the) catalyst's surface area (e.g. the "a lot of two-dimensional cells that are stacked together" comment in the article).

You'd hope that this would be what appears in vehicles. The ability to turn this goop into H2 on demand in situ. Rather than having it produced in bulk elsewhere and transported / stored,

"However, if we are to meet 2050 targets, we are probably well advised to use technologies that are relatively mature and can be manufactured at a larger scale right now," Jansen said.

But, given that present 'mature' technology is massively capital intensive, would you invest in any if you'd just read this article? That's a big problem in many areas. A technology is developed that works, but someone already has something in the lab that will be simpler, cleaner, 50% faster, and 90% cheaper. Granted it will take 2-3 years to fully develop, but it means anyone investing now have to recoup all their capital costs in that 2-3 years before they become redundant, instead of over 10-20 years that the plant could probably run for. Which seriously increases prices for users, who won't switch.

See "Cost of EVs and problems charging them" as an example

You wouldn't want to buy a second-hand one

There will never be any cheap old used ones (at least none with old storage tanks and piping)

maintenance costs at a main dealer will make even current audi or even Maserati owners wince