The main reason that (new) nuclear doesn't combine well with renewables: nuclear kWh's become even more expensive in a system with a high share of wind and solar (and hydro). Threadlet.
When there's lots of wind and sun, wind and solar power would start to push out nuclear, since their marginal costs are lower; they're cheaper to operate.
So as solar and wind capacity grows, nuclear's operating hours are reduced: there will be more and more hours in which it's not needed. So it produces less and less kWh per year, which pushes up its cost per kWh.
Say a kWh from new nuclear costs €0.12 when it gets to operate 8,000 hours per year (90%), a bit like Hinkley Point C, and let's assume 3/4 of that is capital cost (€0.09/kWh) and 1/4 operational cost (€0.03/kWh).
When solar and wind in that system have grown so big that nuclear's operating hours are down to 4,000 per year, the capital costs per kWh will have doubled, and the operational cost is still roughly the same.
So the cost per kWh went up to €0.18+€0.03 = €0.21.
With even more solar and wind, nuclear's operating hours could even go down to 2,000 per year. The cost of a nuclear kWh has then spiralled to €0.39.
If the nuclear power plant operator gets €0.12/kWh, no matter what, it would of course still run even when its power is not needed. Wind and solar would be 'curtailed', and society picks up the tab. In a power market, these nuclear kWh's would have zero or negative value.
Potential investors in new nuclear would of course foresee ever cheaper solar and wind progressing during the lifetime of their nuclear power plants, so they'd ask these kind of 'take or pay' guarantees from governments.
That would mean government takes all the risk and saddles its citizens with the extra cost. The UK's Hinkley Point C might be an example of that. It even gets more and more per kWh every year, through price indexation, for 35 years.
Some of you ask if producing hydrogen when the nuclear power is not needed would help. Perhaps, a bit. It's doubtful if in those hours, when there's ample wind and sun, the nuclear power plant would even be able to cover its marginal cost (€0.03/kWh in this example) by doing so.
And yes, this thread only shows why new nuclear is not an attractive candidate to complement wind and solar in zero-emission power/energy systems. Other solutions will have to prove that they can do a better job, since (net) zero-emissions it will have to be, and asap.
I think that green hydrogen, produced from wind and solar when there's too much, and used to produce dispatchable power when there's too little, is a more promising candidate.
Why? Wind and solar costs: low and falling. Electrolyzer costs (per kW of capacity): modest and expected to fall sharply. Hydrogen-fueled power generation capacity: not expensive either (gas turbines, CCGTs, fuel cells). Storage in salt caverns won't be possible everywhere though
However: hydrogen can be transported too. Using converted natural gas transport pipelines this can be done at low cost, provided it's done at scale. If you;d have to import it by ship, conversion losses and infrastructure make this more expensive.
For some really cool, hardcore modeling of how such an integrated system with lots of renewables, combined with green hydrogen, can work on an hour-to-hour basis, have a look at our recently published work for the North Sea Wind Power Hub:
More on that study in this thread:
As always, writing on renewables and nuclear triggers quite some response. I've tried to address some of that already, but for now, I'll call it a thread. Enjoy ;)
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