How is nuclear a good complementary source to renewables? You complement renewables with a source of flexibility, not another source of inflexibility.
"Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope." from https://en.m.wikipedia.org/wiki/Load_following_power_plant
There are some differences between BWRs and PWRs, but the figures are not hugely different.
Economically, partnering renewables and nuclear doesn't work well. Nuclear does a very poor job covering for renewables intermittency, and renewables crowd out nuclear during the times they're churning out the power.
And in general, renewables do need a flexible supplement. So what would you suggest? More pumped hydro is impossible to build due to environmental regs, NIMBY and geography. Coal and lignite isn't flexible at all, and it is coal. Gas is extremely expensive to run, so expensive that there are gas peaker plants on idle for years in Germany. Also, they are burning gas. Bio gas is not available in sufficient capacity. Battery storage might be an option 30 years from now when enough old EV batteries are available on the cheap. But that will prevent recycling them into new EV batteries and need even more resources like lithium and cobalt. So the alternatives to nuclear like coal and gas are worse, and only still in use because they don't pay fair a price on their carbon emissions.
This also happens in unplanned grids where market forces are being allowed to operate. Renewables, if they are cheaper per kWh than nuclear, drive down the price sufficiently often that nuclear struggles (and with production subsidies, they can drive prices negative, but never mind that). Today, even existing nuclear plants are struggling to make an operating profit in the US.
> And in general, renewables do need a flexible supplement. So what would you suggest?
For the moment, this would be natural gas. If you object to the CO2 from this, consider that to compete against NG CC for BASELOAD in the US, new nuclear would need a CO2 tax of $300/ton or more (see below for quote and link). For new nuclear to compete against NG to cover renewable intermittency, the CO2 tax would have to be much higher, perhaps $1000/ton or more, depending on the fraction of time the NG generators are needed. This is a ludicrously high CO2 tax, and shows how far out of contention new nuclear plants would be.
In the future, this last resort generation could be replaced with something like hydrogen (either produced from NG by SMR with CO2 capture, or from renewable energy by electrolysis.) And it would still be cheaper than new nuclear.
> Gas is extremely expensive to run,
No. Quote from Physics Today (Crane was the president of Exelon):
https://physicstoday.scitation.org/doi/10.1063/PT.3.4088
“The cost of new nuclear is prohibitive for us to be investing in,” says Crane. Exelon considered building two new reactors in Texas in 2005, he says, when gas prices were $8/MMBtu and were projected to rise to $13/MMBtu. At that price, the project would have been viable with a CO2 tax of $25 per ton. “We’re sitting here trading 2019 gas at $2.90 per MMBtu,” he says; for new nuclear power to be competitive at that price, a CO2 tax “would be $300–$400.” Exelon currently is placing its bets instead on advances in energy storage and carbon sequestration technologies.
(Since then, Exelon has announced they want to spin off all their nuclear generating assets.)
> More pumped hydro is impossible to build due to environmental regs, NIMBY and geography.
More pumped hydro ON EXISTING RIVERS is geographically constrained, but off-river PHES much less so. It has vast potential in most parts of the world, especially when coupled with long distance transmission.
How to get rid of excess complexity in regulations while still retaining good safety... I have some ideas.
If new nuclear is going to ever be plausible, it has to be some fundamentally new (like reactors with molten salts) that don't need massive containment buildings that can safely contain large volumes of steam in accidents. Such reactors will not be commercially viable soon.
I was referring to the expense introduced due to regulations. Or are you saying that one could make a much cheaper pressure vessel without those pesky regulators?
Gen IV reactors have the property that they aren't available now, and won't be available and matured anytime soon. Many also have aggressive operating profiles that will stress materials. No one is going to want to buy a MSR only to discover corrosion limits its lifespan to 20 years. So, getting them to a state that customers would be comfortable with will take a long time.
That stress will limit the lifetime of a reactor is true for any reactor. Any BWR or PWR has a maximum lifetime set by the pressure vessel, because that is the one single component you can neither fix nor exchange. As soon as mechanical stress, neutron embrittlement and temperature gradients have done a certain amount of damage, the plant is finished. But even for currently operating reactors, we are still exploring how long that will take exactly, by regularly checking the materials in the running reactors, because no one ran a prototype for 40 or 60 years. And you cannot compare with other models of reactors, because they are usually very different in operating parameters, materials and design.
We currently do not know what a few decades of operation will do to a MSR vessel, but the point is that trying it out has been hindered for a long time by regulations that are not fit for that type of reactor. So you arrive at a costly chicken and egg problem, where a regulator asks for a proof (ideally a proof by pointing at a working prototype with a few decades of maturity) just to allow you building a prototype.
Yes they are not available now but they could be available in this decade and by the 2040 you can build 100s if you really actually put some resources behind it.
These designs are infinity easier to scale then what France did.
Of course that kind of planning is not really how the US does things but at least they could seriously get behind a few prove of concept projects. Currently its not even possible to get a non PWR reactor regulated at all.
There is no inherent reason why a small reactor couldn't be mass produced. In a perfect world you would have a factory spitting out finished nuclear reactor every day.
Transport it to a site, drop it into a concrete hole, connect the salt loop and plug in the refiling pipe.
It really shouldn't need much operation other then planning how much to refuel.
We have gotten used to thinking of nuclear reactors as these civil engineering projects with large costume one of designs, but there is no inherent reason why you can't produce them at comparable to speeds other items of that size are built. Really once you have the material qualified a nuclear reactor is in some ways simple then a rocket engine or an airplane.
The problem in days world is that you need to get threw regulation (in the US factually not possible, and requires complex engagement with every countries regulatory scheme) and then you need enough costumers that you can actually invest in the assembly line.
Safety could be actually improved by doing more efficient regulation.
If you are building a new nuclear plant to target the Rankine steam cycle at a lousy ~140°C inside an enourmous concrete bomb, you are doing it wrong.
The cool kids are targeting the Brayton cycle at ~700°C and atmospheric pressure.
However if there was serious commitment to nuclear, these things would be sensible to develop also.
Your overall point is well taken, nuclear is better when running at full capacity, even if I would argue that with a modern reactor with less operational cost this would be less of an issue.
That however is exactly why many nuclear plants in planning today will actually heat up molten salt and use that to drive the turbine. So there is basically a built in flexible heat battery.
The idea of most modern approaches is actually to have more generation power then the reactor actually provides, and have a heat battery containing in between. This makes sense as you have to have a salt loop anyways, so adding a larger tank isn't really a big extra cost.
Additionally it means that the nuclear build of your project is actually a smaller % of the cost with everything outside of the nuclear boundary being pretty standard salt loops and turbines. So you might build a 500MW nuclear plant with 1.5GW turbines plus a big tank full of salt. All the turbines and the salt tank have essentially nothing to do with nuclear or nuclear regulation.
However if we had started to seriously consider this in the 60s/70s/80s, establishing wind and solar would never even have made any sense outside of some niches. You build nuclear plants that can load follow without issue and accept the capacity problem. Clever engineers and business people would have soon realized that the salt loop can double as a heat battery.
The problem is simply that all these issues were not seriously considered in the past. Basically the Navy wanted PWR for submarines, because those got so much development the largest contractors and the government picked it up for civilian power. Once all the large nuclear companies had bought in to that, they no longer want lots of research on other types of reactors, so not even the nuclear industry advocated for such projects. Combine that with the general turning against nuclear and you basically get massive stagnation.
Unfortunately all the Molten Salt based nuclear work was done in Tennessee, a place that was not very relevant politically. There is even a famous call where Nixon basically says, moves all that potential money to projects in California.
Wind and solar were already a lot cheaper than Hickley C a couple of years ago, so that question is not about costs.
I don't think anyone (on this thread) is suggesting that we phase out already built nuclear capacity before it's planned lifetime.
That means the winter renewable production troughs on dark, windless days become more shallow. Since the requirement on installed wind and solar capacity is driven by how many Watt-hours you need to overproduce so that they can be stored for sunless, windless days, that ends up drastically reducing how many solar panels and wind turbines you need.
You can test this in the model.energy simulator that you linked by simply subtracting a value from "constant electricity demand". I just did that using realistic values for Germany - reducing the constant electricity demand by 20GW from 66 to 46 GW (roughly the peak capacity of nuclear plants in their heyday) leads to a reduction of peak renewable capacity from 537 to 358 GW, basically exactly a factor of 1.5.
You'll still need a flexible source of course to get rid of the oscillations over the minimum demand.
But, qualitatively, it sounds like the step-like behavior you describe simply reflects whether LCOE(nuclear) > LCOE(renewable+storage)?
That wouldn't tell the whole story though, since you might still want to keep the number of nuclear plants low, or you might simply be thinking about whether to keep operating existing plants, rather than building new ones.
And yes, this modeling site is about designing an energy system from scratch, not operating existing plants.
2) there are always going to be Capex-dominated industries running full-bore 24/7 that need base power with the same power gen profile. Nuclear is perfect for this.
You exactly want to complement renewables with inflexible. You want 100% of your "DC component" of your load profile handled by base load power plants, and maximizing the utilization of power storage by variables.
Even consumers that have their own baseload requirements and are not on the grid don't necessarily want baseload sources. An example is mines in Australia, which are installing batteries to work with solar and combustion turbines (for the latter, they allow the turbines to run at full load for a while, then turn off, which is more efficient than operating at partial load.)