In addition to the other objection, "low level heat" is a useful commodity. Why not use it rather than throwing it away.

Actually, what will happen is that people will move away from places that do this, or they will continue to drive, but more slowly, or they will ignore the speed limits and pay the tickets.

The only way to shorten trips is to increase density, and that can't just magically happen.

Walking and biking are fine if you are only a couple of blocks away from where you are going. They don't work for long distances. So they don't solve the problem, either.

You either have urban density or you don't. If you do, then cars don't work very well. If you don't, then alternatives don't work very well. There's a grey area in between where neither one works very well.

I'm thinking about my rural hometown in west Tennessee, and imagining middle school kids biking to school for up to an hour each way while carrying books, musical instruments, gym clothes, etc., and I'm laughing at how well your "magic cure" would work. It's the sort of thinking I'd expect from someone who has never lived somewhere with fewer than half a million people.

+1. As soon as you get out of the core of Paris and its inner suburbs (Hauts-de-Seine), a lot of metro Paris is suburbia with zero-lot-line single-family houses.

Mind you, it's not "a hundred houses all alike" suburbia, because it was built up before folks started doing that sort of mass development, but it's still suburbs.

I think you missed the joke, which was that you can delete two words from the quote and get "I believe you are a racist."

Bets about whether they stop working with HomeKit in February of 2026?

Waste from a molten salt reactor should be fairly stable. Put it in the center of a glass brick and use it as a low level heat source. (Actually, that's what I think they ought to do with most reactor waste except the stuff that's too hot for glass to hold. And you might need a couple of barriers within the glass. Glass would stop alpha and beta cold, but some gamma might need a lead foil screen.)

Yes, there's a paper saying that given enough centuries the waste will slowly leach out. But the level of the radiation emitted would be less than the rock it was concentrated from. The only problem is the rate of release, and if you dilute it enough the problem disappears. (Either that, or nobody should live much above sea level.)

Scale *will* have its own challenges. So will maintenance. This is an "always true". They may well but soluble, but that sure isn't guaranteed.

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.

IIUC, they're talking about turbines, so probably not fuel cells. (And fuel cells have their own problems, which is why they aren't more popular.)

Not really. It might not be technologically apt, but if you think of the gas as a "battery that can hold a charge for a really long time" it makes sense. The question is more "is this a reasonable approach with our current technologies?", and I don't know the answer to that.

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.