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Comment by kepler1 | Hacker News Reader

My understanding is that the cost of producing hydrogen is not one of the major bottlenecks about why those vehicles are slow to be adopted?

I mean, good to have such breakthroughs, but this is not (right now) a huge limiting factor on why we don't drive more H vehicles, is that right? It's more the storage of it? And specialty fuel cells needed to power the cars?

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There are many, many uses for green hydrogen unrelated to road vehicles. Long-term power storage (use cheap summertime solar to bank hydrogen for utility power in the winter), ammonia synthesis for fertilizer, replacing fossil fuels for high-temperature heat to drive industrial processes such as steel and cement production, possibly as fuel for long-haul shipping and aviation (either directly as hydrogen, or after conversion to other forms such as ammonia or hydrocarbons), etc.

Reduction of iron ore to metallic iron (DRI, "direct reduced iron").

> replacing fossil fuels for high-temperature heat to drive industrial processes such as steel and cement production

IIUC, 1 kg of hydrogen has close to the same energy as 1 gallon of gasoline - which has 120k btu.

It takes ~39 kWh with perfect efficiency to produce 1 kg of hydrogen (120k btu).

1 kWh = 3412 btu

39 kWh = 133k btu

Wouldn't you always be better off converting kWh to heat than kWh to hydrogen and then burning hydrogen?

I think the key word here is high heat, I'm not sure electrical heating can be used in the same places?

I believe the hydrogen is actually part of the chemical process for steel production, not just a source of heat.

For steel making, hydrogen is used as a reducing agent to reduce iron oxide to iron. I think arc furnaces are the usual heat sources if you're not using coal or natural gas.

I work in the steel industry so I can provide some background.

An Electric Arc Furnace (EAF) uses electricity and solid feed such as scrap metal and/or DRI (Directly Reduced Iron Briquettes) to produce Steel. The electrical arcs basically melt the solid feed producing liquid steel.

Note that an Arc Furnace needs highly metallic feed, Iron Ore which you dig up from the ground is an oxide (i.e. it is not metallic) it needs to be chemically reduced. You cannot feed ore directly into an Arc Furnace to produce steel. Arc Furnaces can recycle steel scrap into new steel but they are not suited to making virgin steel.

The most common way of producing virgin steel from Iron Ore is through what is known as an integrated steel plant which combines two processes

1. A Blast Furnace - which uses chemical reduction to produce molten liquid Iron.

2. A Basic Oxygen Furnace (also known as an LD converter) which injects oxygen at supersonic speed into the liquid Blast Furnace iron to remove impurities such as Carbon and Phosphorus. This produces liquid steel at the end of the process

Blast Furnaces use Carbon (Typically the carbon comes in form of coke, which is basically highly refined coal) for the chemical reduction of iron ore. CO2 is a byproduct of this reaction.

There are some alternates to a Blast Furnace Such as DRI (which uses a gas such as Natural Gas rather than Coke).

It is possible to chemically reduce Iron Ore using Hydrogen rather than Carbon (Thus avoiding CO2 as a byproduct) but for a variety of complicated technical reasons it is not as simple as just swapping the coke in a blast furnace one for one with hydrogen.

Hydrogen is widely seen within the industry as being the future of steelmaking, there is massive ongoing effort currently underway to develop capability etc the industry is very much going through a transitional period at the moment. I know of one plant in Sweden which is doing some pretty cutting edge work in this area currently.

Thanks for the detailed reply! Is hydrogen being used as the heat source and the reducing agent, or is it exclusively for reduction?

Inefficiency of producing hydrogen relative to storing energy in batteries is one of the major points that detractors of hydrogen cite.

yes but it is not and has never been an "EITHER / OR" scenario.

be wary of others that claim it is.

Grossly higher capital cost of batteries per kWh of storage capacity is one of the major points that defenders of hydrogen respond with.

You're having a dig at someone who's on your side! His point was that this improvement helps negate that criticism.

Appreciate you sticking up for me, but I didn't interpret the parent's comment as a dig. Just an attempt to add some additional context to the "debate", which is always welcome.

As for what side I am on - you're right that I am excited about hydrogen as an energy storage medium due to its high energy density, and am in favor of developing the technology further. The challenges are real, and I don't know if it will ever be practical for powering personal transportation (though I wouldn't rule it out either), but there are many other applications beyond just cars where that energy density could prove useful.

I do find it disheartening that battery vs. hydrogen has become some sort of holy war instead of viewing them as two complementary technologies.

Indeed. They are complementary. Batteries for rapidly cycling storage where efficiency is important, hydrogen for long term or rarely used storage where efficiency is less important than minimizing capital cost.

Yes but in a lot of instances the cost of the batteries will be greater than the cost of the electricity you store in them.

Isn't the issue with hydrogen more storage/transportation than production?

The production of hydrogen is already 70-80% efficient. The conversion back to electricity seems like a bigger bottleneck for vehicles at ~40-60%.

Wikipedia claims that fuel cells can hit 85% efficiency by using cogeneration to repurpose the waste heat, so to me it would seem that hydrogen is more interesting at grid scale.

With hydrogen, you're just trading the problem of storing energy for the problem of storing hydrogen, which always leaks and can penetrate and weaken metal storage containers, valves and so on.

The big industry aim is to cheaply produce hydrogen, transport and store as ammonia, convert back and use in large scale regional baseload power stations to buffer wind and solar.

ie. Still an electric car renewable future, but one with a more reliable supply of less fossil fuel baseload generation, less battery farms.

The future is mixed hybrid.

Storage, transport, and fueling are all big problems for personal vehicles.

It may still be useful for energy storage and industrial processes (see sibling comments). Better storage for excess solar/wind generation would be very helpful.

Perhaps it would also be useful for limited range applications where you wouldn’t need lots of spread out stations like for vehicles at a port that do a lot of work but never get very far from home.

Hydrogen and electric are complementary strategies, not competitors.

I think Toyota is working on a hydrogen combustion engine. Maybe this plus that could be interesting

There's potentially some merit there, since the expense of the catalyst (and its decontamination process) is a significant barrier to the use of hydrogen fuel cells. That said, I'd expect it to be dramatically less efficient than a fuel cell system.

One of the things I've seen Tata Motors talking about re: Hydrogen ICE as an intermediate technology is that the fuel purity requirements are much lower for an ICE than for a fuel cell.

I have my doubts that hydrogen combustion will ever be viable for consumer vehicles. The energy output is far too low, and storage is vastly too problematic.

They have a fuel cell vehicle - https://www.toyota.com/mirai/

Toyota (in collaboration with Yamaha) is developing a V8 hydrogen combustion engine [1]. BMW also developed a V12 hydrogen combustion engine back in 2005 [2].

"Engineering Explained" has put out videos on both, and neither of them sound very appealing to me. [3][4]

[1] https://www.topgear.com/car-news/future-tech/toyota-and-yama...

[2] https://en.wikipedia.org/wiki/BMW_Hydrogen_7

[3] https://www.youtube.com/watch?v=vJjKwSF9gT8

[4] https://www.youtube.com/watch?v=AouW9_jyZck

(a) There aren't enough hydrogen charging stations, even in California.

(b) I'd rather drive around with a Lithium battery than a pressurized tank of hydrogen.

(b) you don't seem to understand how hydrogen functions as a fuel. It can be burned but it can also be used to make electricity. "it depends"

(d) sintered metal storage of hydrogen for ..

(e) electric motors where the regen of electricity from H2 produces water as a byproduct of electricity from H2

(a) who cares about ordering?

(f) yes there is hydrogen combustion outcomes for H2 powered cars too and yes early demonstrators do H2 in tanks but the scale industry here isn't targetting Gaseous H2 tanked vehicles AFAIK.

If there's a pressurized tank of hydrogen and something pierces the car, it's kaboom.

If something pierces a lithium battery you at least have a few seconds to get out.

If there's a pressurised tank and something pierces the car. its not necessarily kaboom. H2 is lighter than air. It disperses. Its burn patterns are different. I don't doubt its scary but the assumption it's worse than other fuels is an open question. It might be better than LNG in some circumstances.

As I said, the goal is not H2 tanks. Did you read that? do you understand how sintered metal H2 storage works? or NH storage? (NH is btw, also scary bad. people used to die when ammonium refrigerators leak)

Here's a video released by Toyota where they shot a hydrogen tank used in the Mirai with a 50-caliber bullet [1]. The bullet pierced the tank, but it didn't go kaboom. The hydrogen just leaked out.

Now personally I think that a hydrogen leak could also be very dangerous. But so can a gasoline leak or a lithium ion battery if exposed to the air.

[1] https://www.youtube.com/watch?v=jVeagFmmwA0

In a car crash, there are frequently showers of sparks from metal bits grinding against pavement. I'd like to see that test performed with an ignition source near the tank.

Here's a video from 2003 where BMW stuck a hydrogen tank and a gasoline tank in a fire and compared the results [1]. Not exactly what you were asking for - but demonstrates hydrogen being released at high pressure and ignited.

The caption from BMW is:

> Fire behaviour test, comparing a petrol tank and a tank filled with liquefied hydrogen. The heat from outside causes a rise of pressure inside the hydrogen tank. The hydrogen gasifies and emerges through a safety valve into the air, where it burns off. From the fuel tank liquid petrol emerges and causes a surface fire. Statements by Dr. Joachim Wolf, Linde AG "What that means for the car manufacturer – or for cars in general – when we transfer this hypothetical situation into reality: an accident happens, petrol runs out, and a car drives into the flames. It’s not very nice when a car is on fire and people have to be rescued. That’s the case with petrol. With hydrogen, if the fuel escapes then it disperses upwards. That probably offers much better options for rescuing people who may be trapped in the vehicles.""Hydrogen is no more dangerous than petrol: I think this test shows that. We see a clear blue flame that doesn’t produce as much heat as burning petrol. Hydrogen is not more dangerous, but it’s also no less dangerous than petrol. It simply poses different potential hazards."

I more or less agree with the statement that Hydrogen is not necessarily any more dangerous than the cars we are already driving around, but poses a different a different set of potential hazards. That being said - I don't think I would like to be an early adopter of hydrogen cars.

[1] https://www.press.bmwgroup.com/embed/Ufc3E4x91b

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