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Comment by evandijk70 | Hacker News Reader

The main benefit of hydrogen that it is cheaper to store energy for long periods. When electricity comes mostly from renewables, which is expected to lead to very low, zero or even negative electricity during periods with lots of sun and/or wind, hydrogen could be produced for the cost of capital of electrolyzers + storage, which might tip the scales in favor of hydrogen.

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I thought hydrogen storage was somewhat troublesome because of the cost and lifetime of storage containers.

Compare alternative fuel vehicles and you'll see that hydrogen vehicles are really quite impractical.

Hydrogen vehicles require tanks at extremely high pressure, and they might become fragile from the hydrogen.

Actually, natural gas vehicles (CNG) were more practical and still didn't go that far without subsidies. Note that although natural gas is found natively - in the ground - a significant amount of energy is required to pressurize it to ~3600 psi for transportation.

Now I would agree with you if your statement said diesel instead of hydrogen.

It depends on wether volume matters or not. The comment you are replying to speaks about seasonal storage. You can use caverns for that, like with natural gas. You only need around 3 times the volume to store the same energy as with natural gas.

For vehicles like trains it can still be advantageous compared to batteries if you have very long ranges you have to drive without the possibility to recharge. Batteries simply get too heavy, bulky and expensive then.

CNG vehicles are very common. There are millions of them. It's just the case that in the US, gasoline has been cheap enough to kill off any demand for them. But the US is not the world.

It is. For airplanes it's probably better to lose 30% of the energy and synthesize carbon based fuels.

Hydrogen is still useful as a store of energy to smooth out seasonal variations in solar and wind production though. On a large scale it's more difficult to store than natural gas due to embrittlement but not impractical.

Negative electricity prices only happen due to subsidies.

It's very easy and fast to turn off a solar power plant. Without subsidies, nobody will pay to feed power into the grid.

And that's okay, ~0 is a good enough as a price.

Right now this is the case, but if roof-top solar is used more widely, it can happen even without subsidies. For owners of roof-top solar it should never be beneficial to turn run from the grid if not necessary, so coal and nuclear power plants that take a while to spin down might still produce oversupply, leading to negative prices

You're assuming that rooftop solar receives a fixed power price or is able to do net metering. Both of these are subsidies.

Without subsidies, somebody feeding solar from their rooftop into the grid will need to sell the power on the stock exchange, usually through a power broker company that adds them to their portfolio. (In Germany this is called "Direktvermarktung")

This power broker will remotely curtail (turn off) the solar infeed when the spot prices turn negative.

No, I'm assuming rooftop solar users just use their solar themselves, thus significantly reducing the demand the grid sees. Since there is (and will be) no way to penalize using rooftop power yourself, demand might still be below the generation left even with renewables feeding into the grid turned off. This, of course, assumes widespread rooftop solar usage and a lot of "conventional" slow power generation online (the latter will likely remain the case in France for the next few decades, since they're in no hurry to reduce their nuclear power plant stock).

I'm also don't understand why a fixed feed-in price has to be a subsidy? Is a fixed electricity price or a fixed gas price a subsidy? It could be that home owners are more comfortable selling their electricity for a fixed price and power brokers have determined that accurately measuring feed-in over time and adding remote-curtailment functionality is not worth the cost for small installations. I doubt we will see feed-in prices without any subsidies in the near future, but it could certainly happen.

Okay, if you assume non-renewable generation that cannot be curtailed, then you are right of course.

And your second point is also valid, a small flat rate infeed may be easier to bill for the broker than per-minute pricing with curtailment. But this will only be the case if prices aren't negative for too long.

Austrália has the largest rooftop solar installation in the world and our fixed feed in prices are 100% a subsidy. We have the ability to price energy in half hour intervals for almost every installation in some parts of the country and are on the way to 5 minute intervals.

If it weren’t for the subsidised price and general resistance of consumers to spot pricing we would have someone offering a service offering supply management by rooftop solar installations to increase the spot price, fewer green energy certs being sold, and way fewer installs. We would also see increased battery storage.

In the very long term we would expect electricity generation to become slightly more expensive than free.

People with solar talk a big game but the vast majority of them are thinking about their pocket and just hate our energy industry.

The fact is that if anyone other than a highly niche purely spot pricing business offered a truly fair price for solar the market regulators would be overruled by the government because of the political optics.

And it’s a subsidy that is paid by those who do not have solar.

I just don’t think your comment applies at all here. Perhaps there are other markets and societies but it’s not us. And we have the most rooftop solar per capita on earth.

The issue with this line of thinking is that electrolyzers are very expensive. I've read papers that estimated that using free electricity would only be cheaper than running 100% on the time for normal electricity prices of 8-9 ct/kWh (in germany) if free electricity was available at least 25% of the time. With energy storage for the daily variations already shaving some of the peaks off, I expect this to be surprisingly little energy (not even covering applications where hydrogen usage is pretty certain based on the lack of great alternatives).

This is a very outdated argument. Electrolyzers cost reduce as production capacity expands. All signs suggest that this quickly become a minor source of cost, in the same way PV panels went the same process.

At least historically that hasn't been the case nearly as much as for PV panels.

I unfortunately haven't been able to find great timelines for electrolyzer costs apart from https://www.researchgate.net/figure/Cost-of-electrolyser-tec.... This suggests that costs fell around 50% between 2000 and 2015. Solar panel prices fell around 90% in the same timeframe: https://ourworldindata.org/grapher/solar-pv-prices?time=2000... (and even faster between 2006 and 2021 https://ourworldindata.org/grapher/solar-pv-prices?time=2006...).

Solar cost decreases have been amazing, but for example wind was less impressive and solar thermal didn't scale well.

> The uninstalled capital cost of proton exchange membrane (PEM) electrolyzer systems has been reduced by over 90% since 2001 (and 80% since 2005)

https://www.hydrogen.energy.gov/pdfs/22002-historical-cost-r...

I thought storing hydrogen was extremely difficult? It diffuses through most metals on relatively short time frames (days to weeks), and that's not even getting into embrittlement.

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