https://www.oecd-nea.org/upload/docs/application/pdf/2021-12...
... most of the modern light water nuclear reactors are capable (by design)
to operate in a load following mode, i.e. to change their power level once
or twice per day in the range of 100% to 50% (or even lower) of the rated
power, with a ramp rate of up to 5% (or even more) of rated power per minute.
You could just keep it spinning nonstop without a load I suppose, but for anything but nuclear it's not gonna be economical.
The thing is, they don't really want to do it if they can save fuel by shutting down.
You'll soon end up with a burning/melted generator.
> "pump some water in a loop"
OK, but you're going to need huge pumps (1000+ MW!). Expensive.
> "or discharge through some resistors"
Again, you'll need extremely large resistors, and a way to dissipate an awful lot of heat. We're talking about a huge amount of energy here!
Could try also melting some salt on the side.
But operating a nuclear plant in this fashion pushes up the price per MWh considerably given their very high cap-ex and op-ex. And while fuel cost is negligible for nuclear, creating more nuclear waste per useful MWh generated is a further drag on costs.
So as a solution, it "works" if the nuclear plant does not have to compete in terms of price with other sources of electricity. But nuclear fails to compete on cost even if operated continuously - it's uncompetitive with cheap, quick to deploy, low op-ex, modern tech like CC gas turbines or renewables in most western electricity markets and can only survive with government subsidy[2].
[1] https://www.nrc.gov/docs/ML0703/ML070380209.pdf [2] https://www.washingtonpost.com/business/2022/04/19/biden-adm...
There's good reason why they are hard to throttle. For starters thermal contraction shortened lifespan; but also because the nuclear cycle itself doesn't lend itself to throttling safely - nuclear products create "retarded (?) neutrons" which are the cornerstone of a stable control system (as opposed to prompt neutrons) and also significant amounts of neutrons poisons which are normally "burned" at equilibrium steady state power levels but which accumulate if you throttle down (therefore be needing even more prompt neutrons).
My understanding is that the more you need to rely on prompt neutrons for your neutron balance the more unstable your reactor (starting them up, therefore, is delicate). Throttling the power upsets this balance by at least two different mechanism.
First, reactors are in a stable equilibrium when operating, so one will actually increase their power by increasing the rate at which heat is removed (and v.v.). Alas, that's workable only within some small range.
A reason[1] load-following with PWRs was originally difficult is that traditionally PWRs use boron concentration in primary loop to regulate power and that can be decreased only slowly. The reason it's done that way is that it's the easiest way to ensure that power is adjusted uniformly throughout the core; if instead some control rods were partially inserted, the top part of the core would operate at lower power (and thus lower fuel burn-up) than the bottom part, which would cause compounding control issues later on.
France is using their PWRs in load-following mode by (a) having additional less absorptive control rods ("gray rods") that can be inserted fully to adjust power by smaller increments (b) more complicated schemes to decide which combination of available actuations to use to change power. See https://hal.science/hal-01496376/document for a paper that tries to optimize control designs so that power changes are more possible (and describes how the control schemes work).
Note that the total heat capacity of even just the primary loop in usual reactors is quite large: in PWRs it usually requires ~0.5s of full power output of the reactor to warm it by 1degC, so this can easily cover, say, ~5% variations for something like a minute.
[1] Another is that reactors are not stateless due to xenon poisoning.
The big problem is that energy prices are set based on the most expensive unit that needs to be turned on to meet demand. Renewables do not tend to be that during periods of low supply, as low supply of energy in the eu market generally means sub-optimal weather conditions for renewables. It is going to be either fossil fuels, nuclear, or battery. If we take out fossil fuels then that leaves battery or nuclear. Neither is very economical without subsidies. Governments (and tax paying citizens) are however very keen on grid stability and thus willing to spend a lot of money to keep it running.
This is all predicated on the market operator actually having the systems in place to signal the need for curtailment effectively, of course. That’s a whole different question.
That is not a problem, it is the incentive to have supplies available so they can be turned on.
I therefore wonder if the market couldn't be structured in a better way which would still ensure that the fossil backup generators are adequately compensated but smoothes the extra cost over the remaining cheap GWh. Something like a meditating party which is aware of the production costs and buys up the daily power and sells it on at an averaged price. There are probably good reasons why this wouldn't work, but I am too stupid to figure them out.
It's worth noting there are some demand response initiatives and the like that are approaching this from the other side - they will pay a user to not use power at particular times of high load. If you don't want to pay a premium on power, I suspect there will be providers happy to oblige, so long as you are willing to forgo the 100% service guarantee.
At this point there isn't really any part of the energy grid that governments do not subsidize. They subsidize companies that provide grid stability. They subsidize renewables that provide capacity. They subsidize the customer who buy energy. They subsidize the grid infrastructure that transports the energy. They subsidize the interconnection between countries that enables trade between countries. They subsidize the cleaning up and associated costs from pollution.
It's called pumped storage.
We dont need as much storage as people think. Solar and wind anti correlate and a vast amount of demand can be time shifted.
Alas, in the real world because of public opinion and political pressure, it's almost impossible to build new nuclear power plants. And those that get build are crazy expensive and overengineered, and invariable overrun their schedule and budget.
Could you at least mine bitcoin or something like that?
It's because of this that there's a lot of talk about wild ideas like pressurizing abandoned mines and so on - there are a lot of mines around. But then we're back to the "proven technology" sticking point.
Nowhere is currently "well" provisioned for pumped hydro given a solar and wind grid coz while they existed for over a hundred years they have never had to store that much energy. Newer, larger ones are being built around the world. Australia will be well provisioned soon.
Go back in time 10 years when solar and wind first became economic and people made similar comments about how little of it there was (1% of total power!), ignoring the unit economics completely. We are at that exact same inflexion point with pumped hydro.
What's the longest period without wind and sun you're willing to provision for before you give up and tell the population they'll have to do without electricity for a bit? A day, a week, a month? Numerically, how much storage would that actually need? How many stations, how big? You'd need over a hundred Fengnings to power the UK for a week. Where would they go? I'm all for renewables + storage but you can't handwave these questions as FUD, it's a serious problem.
I suspect that if we committed to categorically eliminating fossil fuels, including peaker plants, the first time the lights went out because the weather was bad you'd have people clamoring to build nuclear power plants. Statistically, it'll happen at some point no matter how much storage you provision.
6.5 Fengnings or equivalent should be enough for a 94% renewable grid in the UK.
It is well within the same order of magnitude.
>the first time the lights went out because the weather was bad you'd have people clamoring to build nuclear power plants
because why build a solar or wind farm this year when you can instead wait 20 years for hinkley c to be finished at FIVE times the LCOE cost?
it's absurd. the people dont clamor for nuclear power. only the military industrial complex does.
That doesn't follow at all from your article, which is about the US. You can't just extrapolate from a different country at a lower latitude with different weather patterns and vastly more space to put things like onshore wind/solar farms without running into NIMBYIsm, not to mention more hours of sunlight just from spanning 4 timezones. 6 hours of storage is not even close to enough for reliable renewable power in the UK. It wouldn't even cover a single windless winter night.
And even if we take it at face value, the scenario you linked involves masses of overbuild, over the course of nearly 30 years ("by 2050"), and still leaves 6% of energy coming from carbon combustion. If we start building nuclear plants now, even if we accept your premise that they take 20 years to build (they needn't, especially with scale), then we can get to zero carbon almost a decade earlier - and with minimal land use.
It's not like it's impossible - France went all in on a nuclear grid.
This is FUD.
You absolutely can if you are discussing orders of magnitude which we were.
Our fundamental disagreement wasnt about whether it was 8x fengnings or 6.5x but rather whether it was of the order of 65 or 6.5.
>It's not like it's impossible - France went all in on a nuclear grid.
Not impossible, just at great expense and it wasnt worth it. In 5 years less of France's electricity will be nuclear than it is now while still spending vast sums on new plants. They're officially hoping renewables will make up the difference.