That is true when the market price is fairly static and doesn't change much. This is how it used to be when fossil fueled power dominated the grid, since the biggest cost is the fuel and that could scale based on demand.

For EU this is no longer the case. The difference in market price between low and high can be above 100x. In theory a power plant could earn as much in 4 days as an other plant earn in a year worth of power generation. This is why all those nations started to bailout the power bills of businesses and citizens last winter. A single month for some people costed more than a years worth of power. For companies with contract obligations, paying what ever the market demanded was the lesser evil.

The US is not in the same situation, but the energy grid there is still a market based one. There is also other technologies that could in theory compete in such volatile market.

Those high points are better addressed by such things as hydrogen-burning turbines. Hydrogen produced from excess renewables during the price troughs, stored underground, then burned at the peaks. Because the capacity factor of these turbines would be low the cost of fuel would be acceptable, and their capital cost would be an order of magnitude below what a nuclear plant would cost, per unit of power output.

Europe has enough salt formations to store many petawatt hours of hydrogen, far far more than would be needed.

People are naturally allowed to invest in what ever technology they think will fit the role best, such as green hydrogen. No one is investing in that, there exist no hydrogen-burning turbines that burn green hydrogen, but someone could become the first and do that.

Producers of green hydrogen are currently more interested in delivering green steel, which pays much better than hydrogen-burning turbines. The general idea is that this will in the future reduce prices down to energy grid levels, and a researcher here in Sweden working on such project estimated prices to drop to those levels around ~2060-2080.

This could happen much earlier if prices continue to increase as they do, but who knows. It would make for a good A/B testing to produce both and see which one was the cheaper option, and if the green hydrogen power plant fail they can always just produce more hydrogen for steel production.

Plenty of investment is going into green hydrogen, to mature the remaining technologies (such as electrolysers and hydrogen combustors) and drive their costs down learning curves.

Note, however, that as long as your grid is still burning natural gas for power, it doesn't make much sense to burn green hydrogen on it too. Eventually the natural gas will get very expensive (CO2 charges if nothing else), but for now price spikes are short term because LNG can be brought in (this is what Europe has done after Russia shut off the gas.)

Green hydrogen is going to have to be something that is produced, because the world uses about 100 million tonnes of hydrogen a year. Ammonia is an essential commodity chemical made from hydrogen. Some 6% of current world natural gas consumption goes to making hydrogen. These markets can and will be served by green hydrogen even before hydrogen is used for grid generation, and this will serve as dispatchable demand to help smooth renewable intermittency even without hydrogen being burned for power generation. And once there are large stockpiles of green hydrogen, it will be a small step to divert some of it for backup generation.

The ACES project for green hydrogen and electricity production is currently under construction in Utah:

https://www.deseret.com/2022/5/9/23046910/green-hydrogen-ene...

The project will take that excess solar and wind capacity and through a process called alkaline electrolysis it will separate oxygen and hydrogen from water through 220 megawatt electrolyzers, producing up to 110 tons of hydrogen a day.

It is called green hydrogen because it is derived from renewable power source.

...

The other “wow” factor of the project is the salt cavern storage reservoirs.

“Those salt caverns will be the largest single storage site for hydrogen, globally,” Ducker said.

He pointed out that the battery storage capacity across the United States sits at two gigawatt hours via lithium ion batteries. The Utah project will have storage for 300 gigawatt hours of energy.

...

The salt domes for storing the hydrogen will be 3,500 feet underground and will be as deep as the Empire State building is tall — about 1,500 feet.

Ducker said the caverns will enable long duration storage of energy and prevent monthly curtailments of solar and wind energy.

Mitsubishi delivered the gas turbines for the project a few days ago:

https://power.mhi.com/regions/amer/news/20230727

And note that these storage caverns are only a small fraction of the potential of that salt formation.

Whats the energy->hydrogen conversion efficiency these days of processes that don't dump CO2? (aka ones that are using Natural gas as the feedstock).

This is such an incredible misrepresentation. The only thing nuclear can't do is respond to sudden demand surges. But that's what batteries can do (it's also the only thing they can do well).

This[1] is the Australian energy market operator dashboard. Note the demand curve. It is not sudden in anyway - it is highly, highly predictable. Nuclear reactors can handle that sort of curve just fine - you roll the control rods in when it's low, pull them out when it's high.

The "inability" of nuclear reactors to handle variable loads is to do with the thermal mass of the reactor pile which can't be changed rapidly, but electrical load generally doesn't change rapidly - it changes very, very predictably at large scale.

Nuclear reactors can handle normal electrical demand flows just fine.

[1] https://aemo.com.au/en/energy-systems/electricity/national-e...

Your counterargument there betrays a complete misunderstanding of the point I was making.

I wasn't claiming that nuclear power plants couldn't technically ramp up and down. I will happily stipulate that they could. I was arguing it was economically ludicrous to do so. That's because most of the costs of nuclear are fixed: capital cost, financing costs, fixed manpower costs. If you operate the power plant at low capacity factor, the cost per unit of energy produced increases inversely, just because these fixed costs are being spread over less output.

Nuclear either makes sense for baseload or it doesn't make sense at all. Trying to retreat to an application for which it isn't suited, like covering for intermittent renewables, is a losing game. There are any number of alternatives that would be much cheaper.

Take a real close look at the scale on that dashboard. While peak power is about 9Gw, sometimes up to 12GW, the lowest power output overnight is 6GW and that's the absolute bottom.

So in a standard 24 hour day, there is at minimum 6GW of capacity which is always available and always demanded. And for most of year that's 2/3rds of the total demand which ever applies.

The question you are not answering is whether the cost of building a proportionally larger nuclear plant - i.e. one which can meet the upper ends of this scale - is substantially more expensive then a smaller one.

The answer is pretty obviously no: nuclear plants are front-loaded in capital and construction costs, but their relative size has very little impact on the cost of building them, or their maintenance needs, or even fueling costs.

The reality is renewables haven't got anything on that except from an electricity market which mostly doesn't care about them. Start asking renewable generators to well you guaranteed kilowatt-hours throughout the year and watch the "cheap" power skyrocket in cost.

If your argument there was correct, people would be building ginormous nuclear plants and not focusing on SMRs.

But many components of a nuclear plant have size that scales with power. There are some economies of scale, but they're fairly marginal. It's mostly to amortize fixed operating costs (like personnel) over more output.

you can nuclear in load following mode (France does)

but it hurts the economic efficiency massively, as costs for nuclear are almost entirely fixed at construction time