Fuel cells and the hydrogen economy 3

[GregLocock]

While I'm still unconvinced that green hydrogen is going to be a thing (I know two people working in the field) this looks rather jolly.

Alkaline fuel cells enable the use of earth-abundant elements to replace Pt but are hindered by the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline media. Precious metal–free HOR electrocatalysts need to overcome two major challenges: their low intrinsic activity from too strong a hydrogen-binding energy and poor durability due to rapid passivation from metal oxide formation. Here, we designed a Ni-based electrocatalyst with a 2-nm nitrogen-doped carbon shell (Ni@CNx) that serves as a protection layer and significantly enhances HOR kinetics. A Ni@CNx anode, paired with a Co−Mn spinel cathode, exhibited a record peak power density of over 200 mW/cm2 in a completely precious metal–free alkaline membrane fuel cell. Ni@CNx exhibited superior durability when compared to a Ni nanoparticle catalyst due to the enhanced oxidation resistance provided by the CNx layer. Density functional theory calculations suggest that graphitic carbon layers on the surface of the Ni nanoparticles lower the H binding energy to Ni, bringing it closer to the previously predicted value for optimal HOR activity, and single Ni atoms anchored to pyridinic or pyrrolic N defects of graphene can serve as the HOR active sites. The strategy described here marks a milestone in electrocatalyst design for low-cost hydrogen fuel cells and other energy technologies with completely precious metal–free electrocatalysts.

https://www.pnas.org/doi/suppl/10.1073/pnas.2119883119

Big shout to pnas as well, imagine being able to read stuff for free.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[TugboatEng]

I'd like to see more emphasis on fuel cells for the future. They may not eliminate carbon emissions but they can absolutely reduce pollutant emissions. The hybrid technology of today is a perfect pairing with fuel cells.

 

[dik]

as long as it doesn't take twice the energy to charge them...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

The hydrogen economy as imagined by entrepreneurs (those folks with apps who are saving the world through created needs and self-interest) will not happen. However, hype about the hydrogen economy is in full swing, and probably attracting investment.

Hydrogen will be a useful piece of the puzzle with several significant niches, but not more than that.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[moltenmetal]

Green hydrogen's highest merit order use is for replacing the BLACK hydrogen we depend on to keep living.

90 million tonnes of the stuff will be needed post decarbonization- 30 of the 120 million or so we use yearly will go away when we stop burning fossils as fuels, but the rest is important to us- for things like making ammonia, which feeds literally half the human population and represents fully 1/2 of the nitrogen cycle on earth right now. ALL of that ammonia production is from BLACK hydrogen, made from fossils without carbon capture, which is barest minimum 30% blacker per joule than the natural gas it is made from.

Fuelcells are a nice way to react hydrogen to make electricity without making NOx. But their efficiency is no better than that of large engines. Combine that with the inherent, permanent loss of 6.1 kWh per kg in the form of the heat of condensation of the product water, which the fuelcell cannot convert into electricity, the other (ohmic/polarization, 2nd law etc) losses in the electrolyzer and in whatever hydrogen storage method you use, and you end up with hydrogen being irretrievably a really terrible battery. Best case cycle efficiencies are on the order of 37% from electricity back to electricity again. You can make the "kit" cheaper, but you'll never make that cycle efficiency better than 50%.

Hydrogen's just a bad way to store energy. It's neither efficient nor effective as a fuel.

(

http://www.spitfireresearch.com)

 

Green hydrogen's highest merit order use is for replacing the BLACK hydrogen we depend on to keep living.

Last time I checked, the only things we depend on to keep living are food, water, and shelter.

Perhaps you meant 'in the manner in which we have become accustomed'.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[TugboatEng]

The life expectancy of humans living hunter-gatherer lifestyles was 21-37 years with an average of 31. I think we need a bit more than food, water, and shelter.

 

[GregLocock]

Cycle efficiency is slightly less important when the input energy is 'free' or would be unused otherwise. So a plan is big sloar farms in the outback, make hydrogen, turn it into smething transportable, then reform it to hydrogen at point of use or use the intermediate form directly. The UK faces the same problem where a 600% overbuild of renewables is needed, and so when the sun shines and the wind blows they have a lot of excess electricity. The advantage of non battery energy storage is that it makes sense for 6 month storage, batteries are too expensive and self discharge.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[LionelHutz]

600% overbuild of renewables is needed

The possible on a perfect day renewable output is 600% of the UK required energy, right? I don't think it's possible to get to 100% with existing technology.

 

[dik]

In addition to other things, maybe they didn't have enough proper food, water and/or shelter? Shelter being synonymous with safety...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[TugboatEng]

Plastics have greatly improved life on this planet. How we recycle/dispose of them is where our error is.

Anyways, who knows about hydrogen batteries? Maybe lithium is the wrong tech. There are nickel hydrogen batteries that have ideal characteristics for day/night storage/discharge profiles. However, they use a lot of rare materials including nickel and platinum.

Something to ponder, hydrogen is directly above lithium in the periodic table. That means it has similar characteristics. At low enough temperatures, hydrogen has been observed to behave as a metal. Maybe plentiful hydrogen could substitute for lithium in a supercooled battery.

 

Plastics have greatly improved life on this planet.

If you consider the entire life cycle of the planet, not so much. Hint: the really expensive externalized costs are the ones borne by the environment.

How we recycle/dispose of them is where our error is.

Hypothetical: recyclable and recycled are separated by many percentage points. My conclusion is that for all practical purposes plastics cannot be recycled. And when microplastics are deliberately injected into things like cosmetics and clothing, it is as close to impossible as makes no difference.

I prefer evidence to cliché based hypotheticals.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[dik]

Using too many of them and using them too often, may have contributed a bit, I suspect... It's a matter of recycling as well as reducing the consumption.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[TugboatEng]

My conclusion is that for all practical purposes plastics cannot be recycled.

That is only because you choose to ignore the only practical method of recycling plastics and that's power generation.

 

Burn, baby burn is your solution?

I'll repeat it slowly:

How do you gather up all the gazillions of particles of microplastics from hard to extract locations?
I won't even mention the fillers that leach out over time.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[TugboatEng]

Burning macroplastics will help a great deal of them from becoming microplastics. By using them as fuel you give waste plastics value which incentivizes their collection vs disposal. No, it doesn't fix problems such as plastics from paint on ships or fibers from your clothes in the washing machine but it will certainly put a big dent in the problem while also reducing our carbon foot print (the current methods of plastic recycling require lots of energy input).

 

Oh dear, Tug, you just keep shifting the questions sideways to avoid confronting the information presented.

FYI this is not a competitive debate where points are made and trophies handed out. You seem absolutely determined to stick to your positions, without seriously considering contrary evidence. That's how science works, and we need to be open to revising or even giving up our views, without personal attacks or mischaracterizations. I hope that I would do the same. What I am not responsible is your self-education. I'm speaking to a few others here as well.

As I said before, nature doesn't care what happens on Eng-tips. Or Fox news, or CNN, or FB, or twitter (remember that 'twitter' starts with 'twit'). The Climate Crisis is not talk, it's reality, and an existential threat all of us need to figure out, in a very short time. The solutions will need to be more drastic than anyone on these threads imagines. Old belief systems are failing and clichés will not save us. We are seeing all the classic symptoms of failing empires, which always involve environmental collapse, only this time the consequences will be total and catastrophic.

As I've also said before, I'm just the messenger, so don't shoot (or demonize, or mischaracterize) me. Go ahead and dismiss me, but it's not about me so I never take it personally. I know what I know, and if I don't know I don't speak without qualifying the statement. I do the same at work, as a fundamental matter of professional ethics.



"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[JoshPlumSE]

Getting back to the original discussion of Fuel Cells....

I did some engineering work for a company called Fuel Cell Energy about 20 years ago.

Essentially, they use natural gas to produce electricity using fuel cell technology (i.e. a electro chemical process). Producing much LESS CO2 than would be produced to generate the power by burning fossil fuels.

They have an interesting niche. At the time, they had a lot of 250kW plants operating. Often for industrial clients (water treatment facilities or such) or hospitals which require backup power for emergencies where the entire grid goes down. This is a huge benefit to clients like waste water treatment facilities that produce their own natural gas. Rather than burning this off and releasing it into the atmosphere, they use it to power their facility. Pretty cool concept.

They were trying to expand up to about 3.0 MW plants, but it was a challenge. I'm on the structural side, not the process side, so I don't know all the details (other than that their construction management team was a pain in my ass). But, my impression was that the fuel cell technology worked great on the small scale (i.e. the 250 kW mini plants), but that it was not possible for large scale power production (100+ MW) like we get at major power plants.

Technology like this can be VERY useful in the fight against AGW, but has trouble expanding out of its niche market. It's not a magic solution, but it can be one piece to a very large puzzle.

In my opinion, it should be championed for use in large facilities that need back-up power. Facilities that produce their own gas and wish to generate their own power and contributed (in a small degree) to the overall power on the grid. Or, small communities that don't want to rely on a grid where the power is produced hundreds of miles away.

 

[TugboatEng]

You seem absolutely determined to stick to your positions, without seriously considering contrary evidence.

I am trying to propose solutions. You have done nothing but say the world is ending, we must stop using all plastic, white people are bad, capitalism sucks.

I say burn plastics to remove them from the environment. What reasonable solution do you have?

 

[JoshPlumSE]

Generally speaking, plastics are pretty good at being "down cycled".

By this, I mean that they're different than glass or aluminum. When you recycle glass and aluminum bottles, then those bottles are used to create the same type of bottles that you originally had.... a nearly infinite loop of material.

That's just not true with plastics. When you recycle you plastic bottles, that might be used to produce plastic grocery bags or such. It's still a form of recycling. But, must less environmentally friendly.

That being said, I'm not sure that plastics are a inherently bad for our environment as some other people think. Certainly, they do take up a lot of space in our land fill and they take years to degrade / decompose. It's also possible that they'll leak various chemicals into our water supply. But, at least to me, this is not the environmental crises that AGW is. I have to see better studies that demonstrate the harm they cause.... besides just being an eyesore on the beach, in the ocean or in our landfills.