Are hydrogen tanks superior to batteries?

Of COURSE I am claiming it doesn't eliminate the need to provide the energy! Only a complete cretin would imagine I ever did! I never even mentioned energy on the basis that it was so self-evident that energy IS needed to compress gas however it is done, and also because it was not relevant to the point I was making.

I can't be bothered with addressing the rest of your post, sorry.

 

As to fuel cell durability it has improved considerably according to this:

https://www.nrel.gov/hydrogen/highlight-fcev.html.

If it's correct I think 120,000 miles with a 10% degredation would be very tolerable. That corresponds to about six or seven years of use in my case. I have never kept a car from new for longer than five by which time they begin to show their age, develop rattles, the shock absorbers need replacement etc. etc. and its time to get rid. There is more work being done to extend life too. Here's news of another advance from the University of Delaware.

https://www.sciencedaily.com/releases/2017/09/170905134458.htm

I will, as ever, believe it when I see it deployed, but it certainly looks as if some progress is being achieved in the area. I guess they will cotinue to improve at a decreasing rate for ages, but in my opinion they are already good enough to make a practical car.

 

I imagine home hydrogen systems are like hens teeth at the moment, so I will defer looking for ten years or so in the hope that there are more about.

I don't believe Honda's pilot plant was ever intended for home use. Their approach was to make a compact system that could be 100% made in the factory and delivered to site quickly and inexpensively. How it got its electricity was not really their concern although their pilot plant used solar. It was, I think, only designed to supply one car. You have to register with Honda to read their technical journal and it is well worth doing. It is free and I think open to anyone and there are a lots of papers on automotive matters which I think may be of general interest.

 

Having a physics degree myself I respect his scientific knowledge. However I was not criticising this. I was not even criticising his defence of his business, indeed I applaud it. As a salesman and a businessman it is his job.

I was, in fact, criticising those people stupid enough to take his opinions about the relative merits of his, versus a competitor's product at face value and believe them.

Again, you are apparently failing to understand plain English. Do try to keep up Pushmi!

 

I received this from iluvscuba. Apparently it was to this thread but seems to have vanished

"Martin said: "As to the production of hydrogen, I suspect that given time it will all come from electrolysis, not methane. Why? Because it is a convenient way of putting excess renewable power to use. In order to get most of your electricity from - say - wind, you have to over-provide in terms of peak power. Basically, you get about 40% of whats on the nameplate so if you aim to get 50% of a years electricity from wind, you will have to install 50% more than you need. This means periods when you have far more power than you need, and the result is wind farms are often shut down in windy conditions. The electricity they provide could be usefully put to work in electrolysing tapwater. "

You are joking right? Do you know how much clean water you need to create enough hydrogen to power all the cars in the world if what you propose happens? Fresh water is an extremely scarce and finite resource on earth, with climate change, there are already prediction from scientist that the plain states and Sask/Man turning into desert within 100 years. The Colorado river is already running dry, millions of people does not have clean drinking water already and yet people like you is still pushing hydrogen that waste water and electricity instead of using renewable energy like wind and solar. Isn't it better to use our resources to provide wind turbine and solar panel to every household instead? "

He can be reassured that every drop of hydrogen produced from water is returned to the environment as water. The whole process is 100% energy neutral.

 

Thanks for your support Don. Its good to know that there are people here who prefer debate to cheerleading.

101101 has asked a good question. The answer to it involves mainly cost. Batteries are expensive. Probably, if one is storing energy for general use later, Lead acid would be a better choice - weight and bulk are not important in a fixed installation. A hydrogen installation - particularly if a compressor is not needed - would be less expensive. The cost - per unit of stored energy - of tanks falls with size. It's round-trip efficiency is low of course.

Overall efficiency for a battery solution would be higher, but with the caveat that if you are intending to charge your car from a storage battery, you are losing energy rather faster than you might think. Batteries (Lithium ion phosphate batteries - the most efficient solution for a stationary installation) have a round trip efficiency of about 90%. The inverter to supply it would manage about 95%. You will need a DC-DC converter or something similar to charge your car which will have an efficiency again of 95%. Thus the best you can manage is .95 x 0.9 x 0.95 = 81% In other words, you are losing nearly 20% of the energy.

If you use a lower cost lead acid battery system, then the best you can manage is .95 x .7 x .95 = 63%. You lose 37% of the energy.

It is not often mentioned, but 'fast charging' is very energy inefficient and once you abandon slow constant-current charging for speed, the round trip efficiency plunged dramatically.

However, I make the point once again that if the energy is essentially free, then efficiency may be less important than capital cost.

 

Very interesting. I find Llewellyn rather irritating. He seems to have no scientific knowledge whatsoever which means he can't ask any searching questions and accepts what he's told. Often, this comes from people who have 'skin in the game' and the result is heavily skewed. He is, I understand, heavily subsidised by the EV business, and relentlessly pushes battery cars which probably further explains why awkward questions are rare.

I'm not sure I agree with your conclusion that hydrogen is 'too inefficient' to replace the ferry. What they said was that they were preparing for it when it is time to replace the ship, by training seamen sufficiently knowledgeable about it to handle it safely. I'd imagine it perfectly feasible to look at a hydrogen fuel cell ship. If it can be done for trains, I see no obstacle for ships. I'd be surprised if the ferry were not diesel electric anyway, so half the technology exists!

Orkney is hardly typical of the mass of us who live in a more urban environment, though, so much knowledge gained from trials like this will not be applicable. An example is the wide use of battery cars. On a small island where long journeys are not possible, a decent range is not necessary, and they suit the lifestyle of the inhabitants.

 

My reasons for not inventing silly names for people whose ideas I disagree with are that it is a childish thing to do.

Awfully simple really.

 

Lead acid cells can be stuck in an unheated well-ventilated outhouse and will tolerate a wide range of temperatures quite well. You can't do that with any lithium batteries, and this is what makes the big difference. Lithium ion cells are not the right cells to use for domestic storage anyway. Lithium ion phosphate are better as they have the best round-trip efficiency. Poorer energy density, but that's not very important in a static application. I expect Musk has foisted lithium ion cells on his powerwall customers simply because he makes them, and they are more compact and therefore saleable, although he may have done the right thing.

Lead acid cells don't require much in the way of natural resources either. they have an excellent recycling infrastructure and almost 100% of the lead is used time after time after time. Horses for courses. The right way to go for domestic storage is undoubtedly lead acid, just as it is for conventional ICEs, submarines and most aircraft.

Actually, you CAN get away without the need for a compressor by using an electrolyser that will tolerate a high pressure between the anode and the cathode. Honda has such a device and I expect so have other companies. In a domestic system, not intended to fill cars, you don't need to worry about maintaining a high pressure. You can let it go up and down according to generation and use.

If you want to charge your car, you need pressure higher than the 70Mpa it is designed for and a tank that is more voluminous than that of the car, but that is something you design for. The electrolyser raises the pressure in your storage tank to maybe 100Mpa and connecting it to the car's tank until it reaches 70Mpa is all that is required. No compressor anywhere in either case.

I can't see how this simple arrangement can, in mass production, work out more expensive than a massive set of batteries (Big enough to store all your car needs as well as your house) kept in about room temperature plus all the high power inverters and dc-dc converters required!

Finally, I repeat that nobody is claiming that the high differential pressure electrolyser doesn't involve energy to effect the compression. It does. In fact it does the job quite a bit more efficiently than a mechanical compressor, but that is not its main advantage. It's biggest advantage is in the elimination of a noisy and expensive component and the system simplicity this offers.