Comment by tfourb | Hacker News Reader

Comment by tfourb | Hacker News Reader

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> Strategic mix

Nuclear doesn't vibe well with a grid that is supposed to be dominated by renewable electricity generation. You can't simply increase or decrease nuclear generation and even if you could, it would make the economics even worse, if you wouldn't keep their utilization at maximum capacity.

So if nuclear is supposed to have a "strategic" effect on your electricity mix, you have a substantial (20-40%) block of your electricity generation that is essentially static. That in turn requires you to have static demand. But static demand is poison for a renewable generation. You actually want demand to be highly dynamic via grid-tied batteries and dynamic loads (i.e. electric car charging, scheduled appliances and heating, cost-dependent production) so that it can be tailored to supply and keep the grid stable.

> I'm not saying its a good or bad idea, but nuclear can be used as a tool with batteries to make wind much more reliable.

I doubt that this is a requirement for Denmark. There is tremendous hydro capacity in northern Scandinavia and the country is tied into the EU and UK grid.

> You can't simply increase or decrease nuclear generation and even if you could, it would make the economics even worse, if you wouldn't keep their utilization at maximum capacity.

you totally can, and for keeping the grid stable, they are absolutely grand.

But to your point, pan continental links are not that practical for making up ~30% of a country's peak demand.

> you have a substantial (20-40%) block of your electricity generation that is essentially static. That in turn requires you to have static demand.

If you look at the grid on aggregate, there is always a static demand. If you look at https://grid.iamkate.com/ you'll see the variance in use is 30% over 24 hours.

For denmark (and the UK) wind is a great source of power, but its not always there, even at grid level. Currently the UK uses gas to bridge that demand. The UK is rolling out batteries, and thats going to help with price in the peaks. (currently most of them are used to stabilise rather than "peaking") But _currently_ battery capacity is only really measured in hours. Ideally we'll be measuring capacity in weeks. The hard part there is pricing reserve capacity, especially as it leaks.

Now, where nuclear comes in, is allowing the grid to arbitrage night time production from nuclear, into peak demand or, when wind is short. (in addition to bridging/stabilising) This gives a country more options to

We will see something like this bridging capacity in spain in the next few years. They have a much less well developed battery grid, but have more sun so the generation is a bit more predictable day to day. The problem spain needs to overcome is the morning and evening peaks. From memory its something like 1-2 gigawatts (but it could be more.)

> The problem spain needs to overcome is the morning and evening peaks. From memory it's something like 1-2 gigawatts (but it could be more.)

The EU has collectively added 27 Gwh of battery capacity in 2025 alone. If Spain only needs anything close to 2 GW of load for around 2 hours in the morning and evening each, this seems to be inherently achievable.

> you totally can, and for keeping the grid stable, they are absolutely grand.

Nuclear plants can load follow at about 5% of their rated capacity per minute. This is glacial in the world of electricity.

At the moment, this would theoretically work, because you have gas peaker plants that can adjust much faster and pick up the slack while nuclear plants come up (or down) to speed.

But countries like Spain and Denmark want to have a 100% renewable grid within two decades (much shorter than the typical lifetime of a nuclear reactor). So gas peaker plants are increasingly not an option.

The reality of the grid at that point will be a lot of wind and PV capacity (because it is dirt cheap). Nuclear is not compatible with those on its own, because a cloud passing over a large PV installation will drop power much quicker than nuclear will be able to follow.

Of course you can build a ton of batteries to act as a buffer. And guess what, that's exactly what we are doing right now. But at that point, why do we need nuclear again? Simply building batteries is already much cheaper than building a substantial nuclear generation capacity and while batteries will continue to become cheaper while nuclear won't.

Also, if you require new nuclear plants to load follow on a regular basis, it completely destroys the already bad economics of the technology. You need to run those at capacity continuously to make even remotely sense.

> Nuclear plants can load follow at about 5% of their rated capacity per minute. This is glacial in the world of electricity.

which is why batteries are really great. We have couple of batteries that are 180 and 300gwh, which can turn on frighteningly quick. The iberian market is really young at the moment for batteries, they have a way to go before batteries make a dent in prices (which is great for us)

The spanish grid has about 16% nuclear: https://www.ree.es/en/datos/todate Now spain's grid usually has a whole bunch of solar sites in curtailment, which means they can turn on power fairly quickly. Which is where batteries come in, as the curtailment could be flowing into batteries, and that sweet sweet energy sold at a stonking profit in the evening.

But!

Denmark isn't the spanish grid. They have less predictability, so need bigger storage to account for the variability of wind.

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