OT - Hydrogen economy - please explain

Just for readers in the US, when I write 'gas' I mean it as a state of matter, not shorthand for gasoline

I don't understand the logic of a hydrogen economy, maybe I am missing something. I use 'natural gas' (it is mostly methane) to heat my home because it was 1/6 of the price of electricity, though that has now changed to 1/3. If hydrogen is made by using electricity from solar cells then hydrogen will be at least twice the price of electricity. Let me explain, the conversion process of splitting water in to oxygen and hydrogen is at best 50% efficient, so hydrogen will always then have to be more than twice the price of the electricity used to make it. So why would I continue to use use a gas to heat my home if electricity is cheaper?

Then, in a wider context, there will always be gasses lost in production and transport, hydrogen is a very small atom, and will be very searching in finding ways to escape. Hydrogen that escapes doesn't just hand around at low level waiting to be reunited with oxygen, it rises and escapes the atmosphere. So there are two problems, we are splitting water to make hydrogen, and then loosing some of that hydrogen, which means we loose a little water. Water is rather important to life on earth. Second problem is that in loosing hydrogen we will end up with an excess of oxygen, and oxygen is a poison, it is essential to life, but it is a powerful oxidising agent and I don't want to be oxidised. We will end up having to find a way to get rid of excess oxygen, and I guess that burning coal will be out of the question
I know that there are some industrial processes that work much better when heated with a gas flame, so maybe for those, we make hydrogen, but for most we can convert to using electricity.
For cars and trucks, why would you use hydrogen at twice the price of electricity, especially when you add in the problems of a hydrogen leak causing explosions.

So can somebody show me where my logic is wrong, and a hydrogen economy is a good idea! Maybe I am biased, as an electrical engineer.

I see hydrogen as a 'convenient' way of storing energy. You can electrolyse it during periods of excess production from renewal energy sources and use it produce electricity in a conventional way to account to dips in production, similar to how hydroelectric pumped storage stations currently operate. You can set up a gas turbine to burn hydrogen, or you can use it to directly fire a boiler in a coal or biomass site to generate steam.

For transportation, until better and lighter batteries are available you'll be able to get a much higher range out of a vehicle and it can refill in a similar time to a vehicle using liquid fuel, rather than the extra time needed for an electric vehicle.

Safety is a big concern though. It's been a while since I did anything with combustibility, but I think hydrogen is the most flammable substance on a chemical level.

https://www.volkswagenag.com/en/new...the hydrogen,to 20 percent overall efficiency.

TLDR:

This means that the hydrogen-powered electric car only achieves an efficiency of between 25 to 35 percent, depending on the model. For the sake of completeness: when alternative fuels are burned, the efficiency is even worse: only 10 to 20 percent overall efficiency.

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So hydrogen is overall approximately twice as efficient as gasoline.

Oh, I realize that BryanG compares Hydrogen with Methane, not Hydrogen vs. Gasoline.
I think that Methane is up to 65% efficient vs. Hydrogen which is up to 72% efficent.
So there is a small gain with hydrogen vs. methane. But the downside is that a vehicle can carry less Hydrogen, so the range is less.

edit: And if someone wonders about the difference between the two values (72% and 25-35%), then the first is the production of Hydrogen whereas the latter is the total efficiency of production, distribution and combustion in the vehicle.

BryanG said:

I don't understand the logic of a hydrogen economy, maybe I am missing something.

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The proponents of hydrogen pre-suppose electricity sources will be 100% all-solar (i.e. wind; photovoltaic; hydro). The conversion from water to hydrogen is near 100% (80% in that VWag post).

Whether that is a valid presupposition is separate discussion, but it is certainly a possible weak link in the chain of the case for hydrogen.

Thanks for the link to the VW information, though my question wasn't so much about transport and more about energy use in the home/office/factory. I am feeling like a smarty pants because it backs up my scepticism about hydrogen. And not just for motor vehicles.

I don't have a full story, because efficiency calculations should take in to account the full journey, from the mine to an energy storage system ready to use. I don't have information on the difference between making and delivering a battery, compared with making and delivering a fuel cell system and hydrogen production and storage, compared with making and delivering a conventional internal combustion engine with a hydrogen production and storage. The VW information gives a chart with overall efficiency, though I would always take promotional material with a pinch of salt. Their numbers give a hydrogen system as 30% efficient and a battery system as 76% efficient.

I see hydrogen as a 'convenient' way of storing energy.

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It may be 'convenient' but it is very inefficient. You would be better with a gravity battery. I found this on the various storage methods efficiencies:
https://kosatka.media/en/category/blog/news/5-sposobov-hraneniya-energii-i-naskolko-oni-effektivny

We have lots of hills up here in the north of the UK

So I still have the question, what use is the hydrogen economy, and maybe I should be asking who is promoting it as a good idea.

The conversion from water to hydrogen is near 100% (80% in that VWag post).

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Not sure where VW get their data. That well known source of good information Wikipedia puts it at 60% to 70% in the introduction, but less than 50% in their comparison table:
https://en.wikipedia.org/wiki/Water_splitting
I did find an article that said they could improve that by 50 times more efficient, but don't hold your breath. Even if the conversion was 100%, you still loose out converting it back in to electrical energy. Fuel cells seem to be about 50% efficient, which can only be bettered by a Combined Heat and Power machine giving up to 60%, that is if you can use the heat.

BryanG said:

If hydrogen is made by using electricity from solar cells then hydrogen will be at least twice the price of electricity.

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If it is made using solar cells that were purchased and the cost of them budgeted already then the cost of making hydrogen using them is maintenance on the system and the cost of the water. [Twice $0.00 electricity is $0.00]

BryanG said:

Not sure where VW get their data. That well known source of good information Wikipedia puts it at 60% to 70% in the introduction, but less than 50% in their comparison table:
https://en.wikipedia.org/wiki/Water_splitting
I did find an article that said they could improve that by 50 times more efficient, but don't hold your breath. Even if the conversion was 100%, you still loose out converting it back in to electrical energy. Fuel cells seem to be about 50% efficient, which can only be bettered by a Combined Heat and Power machine giving up to 60%, that is if you can use the heat.

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All true, but doing the same comparison for gasoline, you will find that gasoline has an appalling efficiency. Not only energy is lost, but CO2 being released directly to the atmosphere at the refineries.
And there is also the issue with other harmful particles emitted to the atmosphere, where hydrogen is very close to zero emission.

Like BryanG, I am very skeptical.
My attitude is make it work without know nothing politicians interfering and then I will evaluate.


Toyota claims they have gas engines that are almost 40% efficient. Their hybrid cars are amazing. I was skeptical about these too because they look complicated and then I saw a video on how they can keep the car engineer running in its optimal power range.


I am interested in solar power. When I go camping I run off of solar panels. I can go days without using my propane generator. In fact, in 3 years now I have only 2.5 hours of my generator and a lot of that is just turning it over to make sure it still runs.


I have bought a 200W Renergy solar panel kit that I use to charge the old lead acid batteries that were in my camper. This is just to see what my solar setup does. Right now it isn't practical but I could used in an emergency to power something. My camper now has Battle Born liFePO4 batteries.



There is a forum for the greenies here

https://www.eng-tips.com/threadminder.cfm?pid=1618


Storing power is dangerous. We seem to accept the problems with having a small bomb in our gas tanks. The hydrogen people claim the H2 will dissipate and not explode. We'll see.



I object to know nothing politicians forcing us to do something. Right now my heating is done with natural gas. Our city council is being lobbied to prohibit the use of natural gas in new constructions. In Eugene OR they want to force current users to switch. That will be expensive. Who pays for that?


Hydrogen gas will seep through just about anything. I was once at a place where 1 and 2 liter plastic soft drink bottles were tested. They used hydrogen gas because it would seep through the plastic bottle. The hope was that the much bigger CO2 molecules would not.

Peter Nachtwey said:

Hydrogen gas will seep through just about anything. I was once at a place where 1 and 2 liter plastic soft drink bottles were tested. They used hydrogen gas because it would seep through the plastic bottle. The hope was that the much bigger CO2 molecules would not.

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I worked at a refinery that had a catalytic reforming unit with a gas stream that was 60-70% Hydrogen. The standard method around the rest of the refinery was to use rubber bladders to take gas samples to the lab to do chromatography to get composition (H2, methane, ethane, water vapor, etc.). But for this stream we used polyethylene bladders because by the time the rubber bladders got to the lab the hydrogen concentration in the bladder would have dropped a few percent due to differential diffusion rates.


Everything leaks, the question is how fast and how much.

Here is a perspective of Hydrogen in transportation:
https://arstechnica.com/cars/2022/0...heres-where-hydrogen-make-sense-in-transport/



ANd from the comments using Toyota's long-term experiments with Passenger cars motivated via Hydrogen:

Lithium-ion batteries are around 100-225Wh per kg. Hydrogen is 33,000Wh per kg.

Diesel is 12,500Wh per kg. Worse than hydrogen.

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Once you count the tankage for H2 like you're counting the battery structure for batteries, Hydrogen takes quite a few steps back on energy density. Hydrogen with high-pressure tankage that can survive collisions without violently exploding does much, much worse on per-kg than its nominal lab value.

Ex: The Mirai's tank is 87.5kg, and holds 5kg of H2. So you're already down to 1885Wh per kg of tank+fuel. But for a vehicle application, the electricity needs to be put into another heavy traction battery (in the Mirai: ~50kg) to avoid load spikes on the fuel cell. The H2 + tankage + traction battery are going to take your spectacular 33,000Wh per kg and bring it down to not much better than a simple battery.

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There are several things to consider here.

1) Like Peter, I don't think the "Hindenburg Effect" should be completely discounted. The experts figured that was safe too.

2) There are other ways besides electrolysis to generate hydrogen. https://afdc.energy.gov/fuels/hydrogen_production.html The Dept. of Energy site indicates reforming is more common than electrolysis.

3) No matter what method is used, getting hydrogen is energy intensive. Saying the energy will be 100% green sounds good, but it is yet to be proven economically or technologically feasible. Material and product sourcing for solar, for example, could become a major problem with international political ramifications.

4) Nothing is free. There may be no charge for the sunshine or the wind, but the systems to capture them are large capital expenses that must be paid for and amortized. There are also social and environmental side effects that the cheerleaders tend to ignore. For example, what is the impact of taking good midwestern farmland out of production to create wind farms? What effect does a massive solar installation have on the local ecology?

5) Government incentives distort the cost/benefit evaluation, making it impossible to make a rational decision. For example, if the government pays for a system it doesn't become free. It just means that the cost is hidden and you and I pay it in tax dollars.

batteries have two orders of magnitude lower energy density than petrochemical. I wonder if wood is better than batteries.

If it is made using solar cells that were purchased and the cost of them budgeted already then the cost of making hydrogen using them is maintenance on the system and the cost of the water. [Twice $0.00 electricity is $0.00]

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I think an accountant might find the maths a bit off You could write off the price of the solar cells in the first year of use, but the electricity that year would be so expensive that nobody would buy it. As with everything, you write off the cost of something for how long you expect it to last. Then you also have to allow for the cost of the system to convert the hydrogen back in to electricity or heat.