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gerkletoss t1_j5qfn0i wrote

How much of energy that it took to make the hydrogen is recovered when it's used in a fuel cell?

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mhornberger t1_j5qgd3f wrote

I don't think efficiency matters as much when we're talking about sunlight. The sun was going to shine anyway. When burning fuel efficiency matters more, since you're consuming a resource that you had to extract and refine. Not saying efficiency means nothing here, just that it might take a backseat to the importance of reducing the burning of fossil fuels.

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wwarnout t1_j5qijjz wrote

Here's a thought:

Using solar directly is more efficient that using it to extract H2, which is subsequently used for essentially the same purposes.

However, there are times when solar or wind have to be turned off, because they are producing more energy than can be used at the time, and storage is still not well developed.

So, rather than turning the renewables off, they could redirect the energy to extracting H2. This would make much more sense than using solar for H2 extraction instead of using it on the grid.

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Surur t1_j5qrvic wrote

That logic especially holds when you overbuilt solar and have masses of excess solar that would otherwise go to waste.

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Nah-vi t1_j5qy4y0 wrote

Couldn't you collect the water after using the fuel to drink or at the very least water plants also? Meaning even if it isn't efficient ad a fuel source it has other valuable benefits.

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Ps1on t1_j5so25a wrote

Yes, but then you have to be able to have sufficient storage of H2. I'm not sure if that's there yet. It's a highly flammable, very light gas that needs to be stored in obscene quantities over a period of months.

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cybercuzco t1_j5qozy4 wrote

Sure but if you are going to convert that H2 back into electricity you will get more electricity back if you store it in batteries.

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killcat t1_j5r64k6 wrote

As a percentage, yes, but it comes down to energy density per dollar of storage cost, and there are applications for Hydrogen gas that raw electricity can't do.

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cybercuzco t1_j5qokoj wrote

It does matter because if this is just being used as an energy storage mechanism there are probably more efficient means of storing that electricity (batteries). If they are making process hydrogen that is replacing a natural gas source then you’re right efficiency doesn’t matter.

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martinstoeckli t1_j5qt3wz wrote

Converting electricity to hydrogen and back to electricity is one of the cleanest ways to store energy, this has the potential to reduce the summer/winter differences.

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johnpseudo t1_j5tzkj4 wrote

Batteries are only more "efficient" than hydrogen when their duty cycle is relatively high. For seasonal balancing (with a duty cycle of ~1/year), hydrogen is significantly cheaper because of the lower storage costs.

For example this study:

>For storage durations longer than approximately 36 h, technologies with very low storage costs, such as geologic hydrogen storage and natural gas with CCS, offer the least-cost options for LDES and low-emission power generation capacity.

>These results share some similarities with those of previous studies while also offering unique insights. Schmidt et al.11 similarly demonstrated that hydrogen storage and CAES have the lowest costs for seasonal storage in the near term, with hydrogen becoming the least-cost technology for seasonal storage in the future. The present analysis, however, introduces a lower-cost HDV-PEM fuel cell system compared with the stationary fuel cell system considered in Schmidt et al.11 The HDV-PEM system in this analysis provides both a lower power capital cost by using the HDV-PEM fuel cell as well as a lower energy storage capital cost by using a salt cavern. These cost reductions are slightly offset by the lower capacity factor modeled for HDV-PEM systems because of their lower round-trip efficiency, but the results still indicate that HDV-PEM|Salt systems achieve the lowest LCOE at durations as low as 36 h in the future scenario, much lower than the duration estimated by Schmidt et al.11 when including all technologies.

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cybercuzco t1_j5u7epc wrote

Right but what that study fails to mention is that we don’t need seasonal storage if we are using combined wind and solar, because wind produces more in the winter and solar produces more in the summer. source

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johnpseudo t1_j5uids4 wrote

Obviously it'll depend a lot on location and availability of long-distance transmission.

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gerkletoss t1_j5qgr4c wrote

It would certainly affect whether it's preferable to biofuels

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mhornberger t1_j5qh99h wrote

Plant-based biofuels are land- and water-intensive. Putting aside recent rains, CA has been facing serious drought issues. Plant-based biofuels are just not that great.

If we scaled algae-based biofuels that picture might be different.

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gerkletoss t1_j5qijno wrote

Solar power is land-intensive.

Hence why a trade study is needed.

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mhornberger t1_j5qixij wrote

Solar can coexist with agriculture on the same land via agrivoltaics, and also with wind turbines. PV can also go on rooftops, over reservoirs, etc. Studies have already been done showing that, per acre, PV generates more energy than plant-based biofuels. "But they both use land" doesn't make them equal.

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gerkletoss t1_j5qlgv7 wrote

May I see some of these studies?

Regardless, when it comes to load-following power plants or airplanes, the balance does shift.

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expertestateattorney t1_j5qtokg wrote

I have been through that area. There are immense tracts of unused desert land.

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gerkletoss t1_j5r03w5 wrote

A) deserts have important ecology

B) we're not just talking about this one site

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SandAndAlum t1_j5sc769 wrote

The worst areas are within easy transmission range of somewhere with a winter capacity factor over 8%.

Power density is around 1MW/ha nameplate when land optimized. This is under 70m^2 (8m x 8m) per person to provide world final energy of around 10TW. This land can coexist with many other uses (such as roofs, car parking, and agrivoltaics)

The fact that you're pearl clutching over this, but not over the average 8 car parks per person at 40m^2 each or the land required to support eating beef makes your motivations fairly clear.

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gerkletoss t1_j5skjo1 wrote

I don't need a lecture from someone who can't even keep track of what I'm talking about trading.

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SandAndAlum t1_j5smffo wrote

You only dog whistled it but it's obvious nonetheless.

You're talking about more land, more pollution and more long term costin the form of gas.

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gerkletoss t1_j5smw7i wrote

I could make up far worse lies about you but it would only make me look like more of a moron than you and I'd probably get banned for it.

Maybe if you pull you head out of your ass you'll figure out that deserts are real places with real environmental impact and while they're certainly not bad places for solar installation care must be taken to avoid erosion problems due to construction and lack of plants.

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SandAndAlum t1_j5sbjym wrote

Solar uses less land than coal extraction or the largest uranium mines per unit power. There is no choice with lower impact.

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gerkletoss t1_j5skgn8 wrote

If you look back three comments you'll see that I wasn't comparing to any of those.

>There is no choice with lower impact.

For many applications there are. For instance, it's better to run my blender off the grid than to use solar hydrogen.

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[deleted] t1_j5sky5m wrote

[removed]

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[deleted] t1_j5smloa wrote

[removed]

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SandAndAlum t1_j5smwv0 wrote

No. You were repeating fossil fuel propaganda unrelated to the issue at hand.

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gerkletoss t1_j5sn5my wrote

They use real concerns in their propaganda because it's effective

But you'll note that I only mentioned carbon-neutral alternative technologies here, which terrifies the fossil fuel industry. Or maybe not. My hopes aren't high.

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SandAndAlum t1_j5sniku wrote

Except it's not a real concern when its less bad than any other option. By all means push for less land use, but pick the low hanging fruit first.

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gerkletoss t1_j5snsqw wrote

The other carbon-neutral options are what I was talking about you reactionary hero

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SandAndAlum t1_j5snx6r wrote

You continue to dog whistle gas with carbon capture (which is fictional) whilst not being brave enough to say it out loud.

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gerkletoss t1_j5so2bi wrote

Yes, carbon capture is on the list of things I didn't say.

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SandAndAlum t1_j5so76s wrote

Which continues to be fossil fuel propaganda.

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gerkletoss t1_j5sohfm wrote

Fossil fuel propaganda would be accusing everyone who asks questions about hydrogen generation compared to other carbon-neutral technologies of being shills regardless of whether they're suggesting that it's probably great for certain applications in other contexts and were doing so before you made your accusation.

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SandAndAlum t1_j5sp0hl wrote

You're attacking solar derived energy and dog whistling fossil fuel hydrogen. The motivation is obvious. This 'just asking questions' act fools nobody.

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Jorbam t1_j5qi5nk wrote

Electrolysis ranges in efficiency from about 65% to 75% depending on the equipment used. Then a fuel cell is about 40% to 60% efficient.

So with green energy cars its pick your poison. Expensive ass batteries that take ages to charge or expensive ass fuel with very few filling stations.

We need to build the infrastructure for one or both of them.

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cybercuzco t1_j5qp3pl wrote

We need more ass fuel rather than expensive ass fuel.

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mhornberger t1_j5qino3 wrote

I'm honestly more interested in hydrogen as a feedstock to make ammonia, for seasonal storage. BEVs are moving quickly, both in market share and also the technology moving forward. I'm not opposed to fuel-cell cars, but I don't see a robust network of filling stations being built out. Not where it could compete with the charging network+home charging.

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gerkletoss t1_j5qlxcw wrote

Cars aren't the only possible application for hydrogen fuel. Aircraft are going to have a very difficult time using batteries.

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mhornberger t1_j5qneix wrote

There's also synfuel, also called electrofuel. Prometheus Fuels and multiple other companies are working on synthesizing jet fuel (and diesel, and everything else we get from fossil fuels now) from air-captured CO2. It won't be as efficient or cheap as electrified planes, but as you say, electrifying aviation won't be easy.

I have more confidence in this synthetic jet fuel, mainly because it works in planes we already have now. Not hypothetical future designs that use only hydrogen.

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gerkletoss t1_j5qnp8m wrote

You also have efficiency gains from not having to carry a heavy battery through the air though lift induced drag is way worse than rolling resistance. And that could potentially be the best way to do it indefinitely as long as we get carbon neutral, especially for military applications.

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bubba-yo t1_j5rne8a wrote

With the most efficient fuel cells and electrolysis processes, about 75%.

But that misses the point. California is currently working to address some of the problems associated with large scale solar production. Because demand for power doesn't move in alignment with production, each additional megawatt of generation you add reduces its efficiency because you are also adding production at times when there's no demand. There's a few ways of mitigating this, such as batteries, but also by adding demand. As such, in a configuration like this, the hydrogen is a battery, and how efficient of a battery depends on how this plant is being operated. Without mechanisms to either add demand during peak power times, or mechanisms to bank it, the efficiency of the solar infrastructure will continue to decline as it builds out.

CA is currently curtailing about 2TWh of renewable power annually. That's solar/wind that has an efficiency rating of 0%. Using it for literally anything is an improvement.

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gerkletoss t1_j5rtodz wrote

>But that misses the point.

Does it? 75% is already much better than iron-air batteries, so that's pretty good before even considering this other stuff.

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bubba-yo t1_j5s6wsg wrote

The problem with batteries is that their capacity and throughput are basically the same thing. Capacity is VERY expensive with batteries.

With hydrogen it's different - throughput is the cost of the fuel cell, but capacity is just the tank you store the hydrogen in. You can grow capacity for a LOT less money than throughput. So for short term storage, battery is great. For longer term storage, it falls off.

Iron air is designed to fill that gap a bit - really cheap, but pretty shit efficiency. But you can package them up, slap one under every solar panel, and get a huge gain. Hydrogen still needs distribution, and all that, or getting a reversible fuel cell down in cost enough to compete so you can slap them down as frequently. That's probably not going to happen.

But in both cases, these things are trying to convert a 0% efficiency due to oversupply into something positive. Almost anything is a gain.

FWIW, some breakthroughs in iron air has gotten their efficiencies up over 65%, so given their costs, they're pretty viable. Not useful for transportation applications though, where hydrogen is. Solid state hydrogen energy density is upwards of double that of lithium ion.

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