In practice, storing energy for a longer period of time is basically never done, with the only real exception I can think of being space travel. And it's not how long the storage period is that matters. It's how quickly you need to get the energy when you're done. Sure, if you store a year worth of energy in a day and dribble it out over a year, a tiny fuel cell and a huge tank is great for cost. But literally space travel is the only practical application of that. For every real-world application other than space travel, you need to be able to dump the entire contents of the fuel cell in at most maybe five to ten times the period of time over which it was built up, if not less. That means either big fuel cells or a lot of fuel cells.

See above. And to that, I would add that converting electricity to hydrogen with electrolysis of water and back is likely to result in a loss of somewhere around 60% to 70% of the energy that you put in. So even if you somehow manage to find some rare edge case (e.g. trying to do solar in Alaska or something similarly nuts) where you really do want to store power long-term and spread it out over a long period of time, the loss of energy is still going to be around 5x as high from fuel cells as lithium ion batteries even factoring in the self-discharge rate over several months.

And that's before you factor in the additional losses from having to pressurize the hydrogen, which adds further the losses. In fact, you'd actually be better off building air tanks and pressurizing them and using the air pressure to turn turbines than doing electrolysis, pressurizing hydrogen, and dumping it into a fuel cell. That will give you a loss of only 25% to 50% of the energy that goes in. Sure, it will take up more space, but you won't have hydrogen making the metal brittle after a few years, requiring you to replace the whole system over and over again, so it makes *way* more sense.

When I say that IMO, there is literally no case where hydrogen fuel cells make sense other than space travel, I mean that. It is utterly terrible efficiency-wise, so much so that almost anything is better, including things that are way simpler and cheaper than hydrogen, like a giant air tank and an air turbine.

I would still expect it to be less efficient than electric arc furnaces, but maybe not, so I'll grant you that this might be a very narrow use case, solely because burning the fuel source is actually important for that. :-)

Fuel cell efficiency is at best about 60%. So no, you do NOT have 80% round-trip efficiency, unless you've found a way to violate the first law of thermodynamics.

60% efficiency times 68% is 40.8% efficiency. Yeah, that's slightly better than 34%, but in much the same way that a s**t sandwich is slightly better than s**t. :-)

And this will still be capable of running on natural gas, which probably means it won't be optimal efficiency-wise for either fuel.

The losses from electrolysis alone make it a bad idea, even if the next step were 100% efficient. It just gets worse from there.

For the general population yes. For Amazon's use probably not. Since Amazon paid for the whole thing, it might be easier/faster to connect directly from Amazon data enter in Maryland to Amazon data center in Ireland than to Nova Scotia, Newfoundland, or New England and then switch to another optical line for land based traversal.

I do not understand. Private companies have been laying undersea cables since Morse code was the default communications protocol. Your objection is over a hundred years too late. Second, while the summary does not detail what Amazon plans to do with the cable, the primary use will be to connect Amazon's internal systems first. The excess capacity might be leased. So this cable may not really connect to Europe at all for you or the general population.

A battery for a small amount of power is not hard to make. A battery large enough to power a city overnight does not exist. The alternative is a very large bank of batteries. While working with hydrogen has problems, there is a great deal more experience with large scale hydrogen use like in refineries today.

The main obstacle I see is you need to build large banks of batteries. There would be less infrastructure involved with storing a large amount of gas. Also this plan retrofits an existing gas turbine so it is being repurposed.

The number one objection that opponents have against solar or wind power is that it is not always available. Storing excess electrical power has been a goal. Large banks of batteries is a possible solution. Or pressurized caves. Or molten salt. This proposes using hydrogen. The main advantage is that burning hydrogen can use existing infrastructure if it is modified.

So you admit the article identifies a source; you simply dismissed it because you think it will not work.

I see there is another person who did not read the whole summary.

Only if you did not read the next paragraph of the summary.

You forgot that this is about gas turbines. They're going to BURN the hydrogen. Divide that 68% number by two, and that's still probably wildly optimistic. More realistic numbers are probably more like 20%.

Not really, no.

If you're rolling it around on wheels, maybe. For a fixed installation, weight has exactly zero relevance. You're putting it on top of a concrete slab on top of dirt. Who cares how much it weighs?

Volumetric density might matter sometimes. Typical density for hydrogen peaks at about 40 kg per cubic meter (assuming Google search isn't lying to me). With a fuel cell, this will maybe give you 1320 kWh. But then you need additional space for the fuel cell itself, plus compressors to compress the hydrogen on the way in.

Batteries give you half the energy density, but that's all you have to have. Electricity in, electricity out.

Which one is more dense depends entirely on A. how quickly you need to store the incoming hydrogen (size/number of compressors) and B. how quickly you need to be able to turn the hydrogen in your tanks into electricity. Because the batteries will be instant. The power is just there. Whereas with fuel cells you need more/bigger fuel cells depending on how high your kW output needs to be. So storing huge amounts of power is more dense with hydrogen if you only need to dribble it out, but massively less dense if you need to dump all of the stored energy in an hour or two.

And realistically, for grid-tied energy storage, that second case is more common than the first. You aren't going to store energy for a year unless you're in Alaska had have all-day twilight for several months. No, you're going to store the energy during the day and use the vast majority of it between the middle of the afternoon to the early evening. It's probably a three or four hour window in which you will be dumping all the energy that you stored, give or take.

But to make matters worse for hydrogen, they're talking about burning it, not using it in a fuel cell. The efficiency there is maybe half the efficiency of a fuel cell. So when used in that way, batteries are more efficient in terms of volumetric density than hydrogen even BEFORE you factor in all the space for the turbines to burn it and turn it into electricity! This is absolutely *insanely* space-inefficient.

Add to that the problem of hydrogen embrittlement, where you have to keep replacing those storage tanks every few years, not to mention the pipes, turbines, etc., and it quickly becomes obvious that this project is a giant money pit in which Southern California will burn dollars and turn them into a negligible amount of temporary power storage.

There's no way in this world that burning hydrogen from electrolysis at somewhere in the neighborhood of 20% round-trip efficiency makes sense. This is quite possibly the single most clueless idea ever to come out of California's government in the history of California's government. The only people this makes sense for are the ones who are bilking the taxpayers by building out this infrastructure. Because it will never be useful. It will always be more efficient to use the incoming energy to charge batteries, or to do something else. Even when you're talking about things like nuclear power and using waste heat to crack water into hydrogen, you'd still be more efficient with any number of other thermoelectric energy capture systems going straight to electricity and storing it in a battery.

Hydrogen is not the answer. Hydrogen is the question. No is the answer. Always. For literally any purpose you could possibly come up with other than fusion.

Fuel cell efficiency sucks, too. Sure, maybe it's half again more efficient or even twice as efficient, but a battery would be more like 5x as efficient.