Energy generation from Aluminium and Water: Feasible or snake oil?

[Cunjo Carl]

Swinging back around to the Aluminum and water thing, I figured I'd chime in about an interesting wrinkle. I helped a neighboring lab develop this chemistry a while back for the purpose of very (very) very high purity Hydrogen production which is necessary for some fancy business in electronics fabrication. Unfortunately it would be very tricky to develop it for use in a battery though. Our desired reaction looks like this, all nice and clean...

2 Al + 3 H₂O -> 3 H₂ + Al₂O₃

But it's unfortunately pretty tricky to make work well in the real world, because also:

2 Al + 6 H₂O -> 3 H₂ + 2 Al(OH)₃                 (and a host of other related hydroxides)

Now from one point of view this is no trouble because we make the same amount of Hydrogen with either reaction. But, unfortunately for a battery, Al(OH)₃ is a terribly gloopy gel in these conditions. It pushes the Gallium away from the Aluminum surfaces, prevents stirring (important for mid-sized batteries because the reaction gets very hot), makes a spattery mess with the Hydrogen bubbles, and generally does all sorts of things that are obnoxious to deal with for a battery. In a lab or factory setting no troubles, but for a standalone battery it'd be a big pain!

 

[sevenperforce]

2 hours ago, Cunjo Carl said:

Swinging back around to the Aluminum and water thing, I figured I'd chime in about an interesting wrinkle. I helped a neighboring lab develop this chemistry a while back for the purpose of very (very) very high purity Hydrogen production which is necessary for some fancy business in electronics fabrication. Unfortunately it would be very tricky to develop it for use in a battery though. Our desired reaction looks like this, all nice and clean...

2 Al + 3 H₂O -> 3 H₂ + Al₂O₃

But it's unfortunately pretty tricky to make work well in the real world, because also:

2 Al + 6 H₂O -> 3 H₂ + 2 Al(OH)₃                 (and a host of other related hydroxides)

Now from one point of view this is no trouble because we make the same amount of Hydrogen with either reaction. But, unfortunately for a battery, Al(OH)₃ is a terribly gloopy gel in these conditions. It pushes the Gallium away from the Aluminum surfaces, prevents stirring (important for mid-sized batteries because the reaction gets very hot), makes a spattery mess with the Hydrogen bubbles, and generally does all sorts of things that are obnoxious to deal with for a battery. In a lab or factory setting no troubles, but for a standalone battery it'd be a big pain!

 

I wonder if any catalytic salts could arrest the production of Al(OH)₃.

[Cunjo Carl]

1 hour ago, sevenperforce said:

I wonder if any catalytic salts could arrest the production of Al(OH)₃.

That'd be nice!

There may well be one, but catalysts for dehydration reactions of metal salts are unfortunately a little rare. I gave it a quick check, but all I could find for turning the hydroxide into alumina was the thermal decomposition. The reaction of Aluminum with water is very aggressive, so it would be hard to find a catalyst active enough to stop the initial production as well.

As the standard solution, Aluminum Hydroxide can be neutralized using various acids, which would remove the gelling issue but add some new ones from the complexity. As an alternative, the medical industry seems to be leaning towards using surfactants (like soap) to help with similar issues in Aluminum Hydroxide gels, so those might be a way forward- though given our gas generation surfactants might even make more of a mess! Finally, the first option that popped into my head was something mechanical like sonication (using high frequency sound waves to stir). Aluminum Hydroxide is shear thinning, so if it can be kept constantly stirred, its viscosity can be kept lower. This would also help release the Hydrogen gas and break down the Aluminum chunks.

 

[kerbiloid]

Al+H2O cells will power the trucks to get the Al(OH)3 away from the city.

[sevenperforce]

4 hours ago, Cunjo Carl said:

That'd be nice!

There may well be one, but catalysts for dehydration reactions of metal salts are unfortunately a little rare. I gave it a quick check, but all I could find for turning the hydroxide into alumina was the thermal decomposition. The reaction of Aluminum with water is very aggressive, so it would be hard to find a catalyst active enough to stop the initial production as well.

Yeah, nothing's going to stop the initial progression, but a catalyst that would render the reaction more complete while also making it controllable is what I was thinking of. The Al + water = alumina reaction is of course very exothermic so perhaps that waste heat can be used to induce thermal decomposition of the hydroxide.

[Cunjo Carl]

I looked around for a while and found some people who were able to roll with the punches, including this amazing work by Ryuhei Mori. Mori actually manages to make a rechargeable Aluminum-Air battery, completely bypassing the obnoxious Hydrogen gas production step we've been talking about. This battery sucks Oxygen right out of the air and ultimately combines it with Aluminum to make Al₂O₃ + Electricity. Then, if you push power back into the battery it reverses the reaction to recharge the battery. To put icing on the cake, Mori manages this with only simple, common materials. If I didn't see his results, I'd have called it impossible- it's really spectacular!

https://pubs.rsc.org/en/content/getauthorversionpdf/C4RA02165G

Of particular interest to us space-y people, Most of the mass involved in this battery can be sourced from the Moon. It's mostly just Aluminum, Aluminum Oxide and Water. It has some salt, some metal and some plastic binders as well, but they're a minority of the mass. I really love Mori's material choices, and production-wise it's all industrially feasible. All this said, we probably won't be seeing many of these batteries, at least for a while. The Aluminum battery's not without its drawbacks, and here on Earth there's little commercial drive for it. Electric cars and storage facilities are served almost as well by Lithium batteries, which are extremely well suited to their task and becoming cheaper by the day. Of particular note for Lithium is the roll-to-roll drycells recently developed by Maxwell, which are poised to make Lithium batteries even cheaper, lighter and more energetic. It's a very hard bar to beat.

For sourcing on the Moon though, Aluminum-Oxygen, Aluminum-Glass and Aluminum flywheels are kinda the only three options that don't require a ton of refining. So for there, this is very interesting!

Ryohei Mori's Aluminum Battery, ALFA, can store electricity by reversibly oxidizing Aluminum using only common materials.

[lajoswinkler]

On 2/24/2019 at 3:37 PM, Nivee~ said:

I found this article about generating hydrogen by treating water with aluminium. Can anyone here prove if it's really feasible in the long term?

https://timesofindia.indiatimes.com/people/this-delhi-boy-is-trying-to-disrupt-the-energy-industry/articleshow/67923808.cms

Absolutely not feasible. The whole article is a typical "local man outsmarts experts" and national pandering pamphlet that fails at its premises.

This is not an energy source. It's storage, and a very inefficient one. It's so inefficient it's hilarious. No wonder no one is contacting him. Nobody serious would actually devote resources to it.

Even the idea to use discarded aluminium is ridiculous because recycling already metallic aluminium is so much more beneficial for the environment as you don't need to use Hall-Héroult process again (and BTW, someone said that carbon rods used in this process is carbon sink - it's not, as they sublimate and form carbon oxides that leave the cell together with hydrogen fluoride in a nasty flue gas).

[Nivee~]

16 minutes ago, lajoswinkler said:

Nobody serious would actually devote resources to it.

I have been reading about the 'Theranos' fiasco, and this guy's approach is almost the same... befuddle the layman, and try to scoop all the funding.. Seriously, calling him a 'disruptor' is just going overboard...

[DDE]

2 hours ago, Nivee~ said:

I have been reading about the 'Theranos' fiasco, and this guy's approach is almost the same... befuddle the layman, and try to scoop all the funding.. Seriously, calling him a 'disruptor' is just going overboard...

He, however, lacks a critical advantage:

I’m not sure who was pulling the strings behind the scenes (major snake oil salesmen always seem to have major backers), but she was obviously very easy to market to the public as an innovator.

Edited March 17, 2019 by DDE

[Nivee~]

8 hours ago, DDE said:

He, however, lacks a critical advantage

A Steve Jobs turtleneck? 

[kerbiloid]

12 hours ago, Nivee~ said:

'Theranos' fiasco

Like they are asking: "R U sure?"

Spoiler

 

[mikegarrison]

This whole topic reminds me of a time someone called in to "Car Guys" and was excited to report that they could charge their electric devices by using the charging port in their car. They thought this was free electricity. The caller was sad to find out that the electricity in the car is not free, but rather comes from burning gasoline in the engine.

[magnemoe]

4 hours ago, mikegarrison said:

This whole topic reminds me of a time someone called in to "Car Guys" and was excited to report that they could charge their electric devices by using the charging port in their car. They thought this was free electricity. The caller was sad to find out that the electricity in the car is not free, but rather comes from burning gasoline in the engine.

And you could discharge the battery in the car if using lots of power while car is parked. More modern cars will probably cut power. 

And yes its a bit funny if they thought it was free power. On the other hand some people has found a way to use hybrid cars as generators.
And yes this is smart if you need power off the grind and something the  military is into. Lots of their cars are used as command centers or have weapons or sensors. 
Also very relevant for stuff like self powered artillery who mostly just are at standby. 

[kerbiloid]

2 hours ago, magnemoe said:

And you could discharge the battery in the car if using lots of power while car is parked.

A lifehack: you can charge several cars with just one Tesla.

[Cunjo Carl]

Man, I'm painfully slow at writing now. This took almost a week!

I finally read the article posted by @Nivee~ and it's pretty uncanny- This exact project has actually come across my desk. I guess I should give some context. I was previously a  process development engineer for an academic institution which heavily promoted commercial development (though now I'm much happier just being a physics researcher). I gained a reputation for being able to unstick stuck projects, so people would often bring me problems for unofficial consulting. This project came to me about a year before I got sick, so maybe 2 years ago? I should also preface that I'm not a proponent (I think it's destined to not quite work), but this particular project has people acting in good faith. There are MANY projects presented very similarly which are just scams. It's also possible development's stopped and it's since become a scam, but anyways, on with the story.

This was one of two applications for a shoe-string budget project on H2 production, and it actually does have merits. Like everyone else has said, unlike in the article, it's not one weird trick that power companies hate him for , but it does have locations where it's viable. There are, I was told, isolated small communities where Aluminum cans are used in volume (thanks to pepsi co's legendary distribution network), but it's not practical or politically viable to have a sorting/recycling service. In these places, the Al is literally just being tossed into the garbage heaps. There's apparently a lot of places like this.

In order to be viable they'd need to crack 3 small breakthroughs. The first being closing the loop on Gallium which is used to 'soften up' the Al, but which is expensive and largely consumed in the process. I ran the numbers back then and showed they'd need at least ~~90% recycling of Gallium to become economically feasible relative to petrol power. Fortunately there's a couple techniques that could conceivably make this possible, including a simple insitu electrochemical cell to recover Gallium within the process directly on to fresh shredded Aluminum presented as the cathode. It's plausible, but would need significant development. Next, I thought fuel cells wouldn't be economically viable given the size scale of their intended application. Keeping those things hot is a pain. It looks like the gentleman in the article is trying to solve the problem with an internal combustion cycle... There's a lot of difficulties to this with Hydrogen. It resists ignition better than gasoline, has a very complicated combustion rate-vs-concentration profile (kinetics), it slowly embrittles steel, and has a nastily negative Joule-Thompson coefficient all of which are kinda unpleasant. Anyways, if some handy engineer figured it out, I'm happy. I'd definitely want to see it running in person, 'cause the devils in the details for a design like that. Lastly is what to do with the waste streams which will be a terrible grey sludge full of old soda, beer and inks. I'm still a fan of @kerbiloid's suggestion!

For all the trouble we'd get about a C-cell's worth of power out of each can. Not bad! Also not good. I mentally put the project about on par with grass-roots campaigns to recoup power from compostables outgassing (like here in California), or power generation from burning flammable trash (like in Japan). It's much more difficult than these, but could serve a similar roll specifically for communities where proper recycling infrastructure isn't feasible.

Edited March 27, 2019 by Cunjo Carl

[Shpaget]

On 3/24/2019 at 7:23 PM, Cunjo Carl said:

There are, I was told, isolated small communities where Aluminum cans are used in volume (thanks to pepsi co's legendary distribution network), but it's not practical or politically viable to have a sorting/recycling service. In these places, the Al is literally just being tossed into the garbage heaps. There's apparently a lot of places like this.

Croatia had similar issues.

While recycling bins were available in every neighborhood, they were not really used by general public. In 2005 a system of recycling was introduced where most of the products sold in plastic bottle or aluminium cans had a small surcharge (roughly $0,07) which was refunded to the customer when they brought back the bottle or the can.

The system is still in place and I find the results great. Where it was not uncommon to see discarded bottles and cans thrown aside in nature, now you can not find any. It really made a difference, and it took only a few months for the change to become noticeable.

Edited March 27, 2019 by Shpaget