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Making hydrogen from water and solar light is certainly better than using nuclear energy for that.

There is no reason for consuming valuable nuclear fuel, for which better uses exist, instead of using free solar light.

The efficiency of converting solar energy into hydrogen is already acceptable. The same is true for the efficiency of converting hydrogen and concentrated carbon dioxide into synthetic hydrocarbons, which are the best means for long term energy storage, and also for applications like aircraft and spacecraft.

The least efficient step remains concentrating the diluted carbon dioxide from air.

While the efficiency of converting solar energy and water into hydrogen by artificial means is already better than that of living beings, the living beings are still much more efficient in converting H2 and CO2 from air into organic substances.

Besides improving the efficiency of the existing techniques, an alternative method of CO2 capture would be the genetic engineering of a bacterium that would produce some usable oil from H2 and air, with an improved productivity over the existing bacteria, which use most of the captured energy to make substances useful for them, not for us, so unmodified bacteria would not have a high enough useful output.

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> Making hydrogen from water and solar light is certainly better than using nuclear energy for that.

Using heat is the most efficient and if you use nuclear heat directly, and you don't have to go to the step of converting to electricity, you get huge efficiency.

> There is no reason for consuming valuable nuclear fuel

Nuclear fuel is not valuable once you have a closed cycle. Fuel cost are already only a few % of total nuclear cost and in a closed cycle would be almost nothing. As soon as you breed fuel from fertile material the cost is basically 0.

> The efficiency of converting solar energy into hydrogen is already acceptable.

It requires a very large plant to do in many small batches and cost 20x what hydrogen costs from natural gas. Its not efficient and will not be for the next 20+ years at least.

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IIRC nuclear doesn't really work well as the last 5-10%. Start-up and shut-down for nuclear reactors is a slow process. When it's generating, it needs to just keep on generating. Not so quick to dial down or up just because the wind is(n't) blowing.
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It's not that slow. They can ramp up and down over hours, and those demand patterns are known in advance. Combine with battery, pumped storage, or synfuel generation to soak up excess power during low demand times, and use that to provide peaker capacity during high demand times.
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Demand following for nuclear is possible (after all, if you produce 10X but the demand suddenly drops to 7X, what you can always do is to "dump" 3X worth of steam instead of injecting it in the turbine), but because the cost of nuclear is mainly upfront, it is not cost efficient at all.

If it costs 10X dollars upfront to build a nuclear central that can produce 10X energy, then if you run it at 100%, it will cost 1 dollar per 1 unit of energy. If you follow the demand, you will not produce 10X, but let's say to illustrate maybe 5X, and it will cost 2 dollars per 1 unit of energy.

You are right about storage as a way to help with demand following, but if you build enough storage capacity, then you basically have solved "for free" a big part of the problem linked to the intermittence of renewables. In this case, you have the choice between building an expensive nuclear central and a distributed cheaper renewable generation.

I'm not saying it demonstrate renewables are better, but that it is true that nuclear is not the obvious winner it looks like before we look into the practical details.

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No, nuclear storage needs to be optimized for 1-2h peaks, if you build a renewable system you need, much, much more. And you have much more localized peaks and valleys depending on weather and such.

So basically, you can put some battery next to every nuclear plant and otherwise use the same grid.

For renewable you need a much more complex grid with much more battery.

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The problem is the economics. They’re just horrifyingly expensive to build. The equivalent to each new large scale reactor in GWe requires tens of billions in subsidies.

The next problem comes from incentives. Why should anyone with solar or storage buy this expensive grid based nuclear electricity?

Why should their neighbors not buy surplus renewables and instead pay out of their nose for expensive nuclear powered electricity?

EDF is already crying about renewables cratering the earning potential and increasing maintenance costs for the existing french nuclear fleet. Let alone the horrifyingly expensive new builds.

And that is France which has been actively shielding its inflexible aging nuclear fleet from renewable competition, and it still leaks in on pure economics.

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The French have used their nuclear system for 20+ years as a giving tree.

The forced EDF to sell nuclear at very cheap prices to fossil fuel companies and then buy it back at much higher price.

The French forced EDF to give subsides to solar even when that actually hurts their economics.

The French randomly in the 2010s decided to replace nuclear in a short time-frame (completely 100% unrealistic) but it sounds good to politicians. And they decided to delay all maintenance and didn't do any of the upgrades many other nations did.

Once of the secrets of French nuclear is, that their grandfather were so good in providing them these nuclear plants, the french absolutely suck at running them. Other countries like the US and ironically Germany managed to run their reactors at higher factors.

The problem is the solar is cheap when its being produced and makes the economics of base lose worse, without actually solving base load. Solar has been cross subsidized this way for a long time. And has been more explicitly subsidized. But its a private good, it helps only private people, it is negative on a system level.

Once you think on a systemic level, how to provide reliable energy for a whole country, nuclear is not more expensive and France saved a huge amount of money buy doing what they did.

> Why should anyone with solar or storage buy this expensive grid based nuclear electricity?

If somebody privately wants to build solar/storage that's fine, but they should get no support. Also prices should be adjust to actually reflect peak demand. Historically the way the system operated is with much simpler pricing models because it was understood that everybody shares in this infrastructure. In such a situation, the majority of people wouldn't build solar and batteries.

But really, the question we should ask, what the best thing to run a modern economy on and the German solution of 'lets build a massive electricity pipeline to solar farms in Greece' isn't a great model.

All this new energy transfer infrastructure is incredibly expensive. It cost at least as much as the generation itself, and sometimes more.

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People disliking renewables always say this.

Then when asked what method to price in the Swedish nuclear fleet having ~50% of capacity offline multiple times last year and France famously having 50% of the capacity offline during the energy crisis I always get crickets for answers.

It’s apparently fine when nuclear plants doesn’t deliver, but not renewables.

The difference with renewables is that it’s even easier to manage. Their intermittency is entirely expected and the law of large numbers ensure we never have half the capacity offline due to technical issues at the same time.

> Once you think on a systemic level, how to provide reliable energy for a whole country, nuclear is not more expensive and France saved a huge amount of money buy doing what they did.

Given that new built nuclear power costs 18-24 cents per kWh and won’t come online until the 2040s what you’re trying to tell me is that multiplying the current electricity cost 3-4x and creating a self made energy crisis isn’t so bad.

The French made a good choice half a century ago. The equivalent choice in 2026 are renewables and storage.

Just look at the proposed EPR2 fleet. A 11 cent per kWh CFD and interest free loans. Summing up to over 20 cents per kWh for the electricity. With the first reactor coming online at the earliest in 2038.

It’s just complete insanity at this point.

> All this new energy transfer infrastructure is incredibly expensive. It cost at least as much as the generation itself, and sometimes more.

The 10 GW HVDC links being built costs €20B. That’s equivalent to the subsidies needed for one new large scale reactor. Then you have the market price of electricity on top of that.

Are you starting to realize the conundrum?

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The problem isn't technical dispatchability, it's economic dispatchability. A nuclear plant operated at 5-10% capacity factor would be ludicrously uneconomical, even to just operate.
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First of all its not that slow, and when you know when you need it, at what point in the day, so you can ramp up in anticipation.

Also, the claim that nuclear is slow to change is a limitation of current nuclear plants, more modern plants could be far better. Some designs are very much load following.

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It's not a technical limitation, it's economic. The cost of nuclear is almost all in building (and decommissioning) the plant, the fuel is almost free. So you want to produce flat out as long as you can get almost any positive price for the output.
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Nuclear reactors make awful targets in a conflict, not sure having many around is generally a good idea if conflict is a risk and there are alternatives.
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For many nations that is really not the primary reason to choose infrastructure. And even if that is your goal. Then building a 500MW reactor you can drop in the ground is likely a pretty decent solution.
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> and there are alternatives

That's a big if, though. Solar and batteries require globalisation, based on fossil fuels.

I feel like nuclear reactors are a better choice.

> in a conflict, not sure having many around is generally a good idea

On the other hand, blowing nuclear reactors could be considered a big escalation. We see with Iran and Ukraine that it's not exactly the first thing one wants to target.

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For shipping?

Wind, Tidal or geothermal are also around, for example.

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My point was that photovoltaic is "an alternative" to nuclear reactors, but an alternative that relies on globalisation. Nuclear reactors... much less.
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> The only thing that's actually tricky is synfuels and solar/battery doesn't solve that. High temperature reactors using heat to create hydrogen is arguable the better path to synfuels then electrolysis.

Found this interesting: https://phys.org/news/2026-02-microbial-eco-friendly-butanol.

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