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Comment by CGamesPlay | Hacker News Reader

So it's more of a battery rather than a fuel. I wonder what the energy density and longevity is compared to other industrial batteries. On a side note, what's the point of a brewery (single business) using it? Do they have some unique energy requirements?

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As I understood the article, the brewery is not using the process to generate electricity, but to heat fluids (water and wort).

In essence brewing process is a hell of a lot about moving heat around: You heat water to mash the grain to make wort, you boil the wort, then you remove the heat (via heat exchanger) as quickly as possible to get the wort down to where the yeast is happy. What are you going to do with all that energy you've pumped in to the fluid in the first place and have just pumped out again? If you're clever (energy conscious) you find a way to cycle that back into the process. There are lots of opportunities to optimise and conserve the energy that gets shunted back and forth in a brewery and it's a whole art/science in itself.

> On a side note, what's the point of a brewery (single business) using it? Do they have some unique energy requirements?

It's a collaboration with a local university to test the technique on industrial scale. According to the researchers there the goal is to grow to grid-scale and convert coal-fired power plans in the coming decade.

The brewery is not using the process to generate electricity, but to heat fluids (water and wort). The research team behind it hope to scale it up to electricity generation in the future.

Iron has a specific energy of 4.9 MJ/kg (for comparison: wood 18, coal 26-33, natural gas 53.6, jet fuel 43, diesel 45.6, gasoline 46.4).

So having ships, planes or even cars powered by burning iron seems to be unfeasible (at least from energy production standpoint). Albeit iron has much higher density, so if weight is not a problem then it may work. Iron has energy density of about 40 MJ/liter which is comparable with coal, diesel, petrol, which have ~34-40 MJ/liter.

That's still 5-10 times higher than lithium based batteries (0.3-1MJ/kg) and those are being used in cars and almost good enough for some airplane use cases. Heat engine efficiency isn't as good as electric motors, but it isn't bellow 20%. Downside is that recharging by converting back to iron probably can't be done within device. While pouring in metal powder in for fast refilling might be doable getting it out is probably messier.

You would need a steam engine to convert heat into work, which is clearly out of the question for planes, and might make cars and trucks impractical. Maybe rail and boats though ?

Yes, but even best combustion engines have at very best 50% efficiency using direct transformation of thermal energy through gas expansion into mechanical energy. This involves numerous technologies, which better mix fuel and air, inject fuel directly, adjust timing of injection and exhaust following the RPMs, etc. Cars don't generate steam or use any other indirect method of transformation of thermal energy into mechanical energy, due to losses and impracticality (otherwise we would see other types of combustion engines). Burning of powder iron would not work with normal ICEs since powders are not liquids, they are abrasive and burn residuals are not gaseous (rust dust, which is even more abrasive). At very least this is non trivial engineering challenge. So 5-10 times lower specific energy of lithium batteries wins because of simplicity (and lower weight) of whole power-train (inverters, engines) and their high overall efficiency (90-95%). But indeed, on big ships (e.g. tankers), which can have a steam turbines, iron might be a feasible fuel (especially if using onboard solar power while cruising it is possible to recover part of it as a fuel again).

I this is is largely on point - this should work for larger ships that have steam turbines. Also, said turbines have better efficiency than an ICE engine.

They don't, actually. Steam turbines are less, not more efficient than marine diesel engines. In modern marine propulsion, turbines are used pretty much only on gas and coal carriers.

Ships get well north of 70% efficiency on the same cycle: technically, the Diesel cycle. (It is named after the person, not the fuel.)

Most cars run on the Otto cycle, less efficiently. (It is named after the person, not the vehicle.:-)

>So having ships, planes or even cars powered by burning iron seems to be unfeasible

aluminum of course. It is cheap too and has higher specific energy than iron. Using aluminum-air fuel cell instead of burning makes the efficiency about 2 times higher. The actual cars powered by aluminum have range up to 2000km per refueling.

It us perfectly feasible on ships, they are not restricted on mass very much and their fuel is dirty and not very efficient.

Although we could have really fast nuclear powered container ships and the whole problem goes away

One nice thing is that in brewing it can be used to generate heat for boiling during brewing rather than converting to electricity first. They mention a furnace but not a generator. 81% of Dutch power is fossil fuel based, if you have an environmental concern about that and it's good press why not.

Not unique, but the twist is that they need heat, not electricity. I thought it interesting.

Edit: Made me day dream about Iceland exporting iron powder for burning, electrolysed with their geothermal energy.

I suspect the primary point is marketing. But that is fine, new tech needs early adopters to speed up development. For whatever reasons.

Iron is much durable than a battery.

The brewery is like lots of other industrial processes. They need a lot of heath which typically coal produce today. Metal powder can replace coal in all these industrial settings.

Iron can be produced from electricity as the article mentions, but most iron today is produced with coal, since its far cheaper.

This is just a way for the brewery to get cheap heat, with a level of indirection from the source coal so it can be advertised as green.

It's a shame the journalist that did this article didn't think to research how iron is typically made...

Once made and stuffed into this system, the iron can be used in an infite loop of combustion and restore using electricity when it's available.

The Oxygen too could be in the same infinite loop if there is some kind of storage large enough. (Salt mine?)

Then there would be NOx pollutants either.

Indeed, but the iron oxide powder resulting from this process would be cheaper to turn back into iron metal using coal in a regular blast furnace.

We'll they are trying to make it green as possible so coal if out of game. At least locally for one device.

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