I'm speaking from the UK where demand peaks are morning and evening and we don't have sun, so wind is the good match.
The problem is you're proposing a grid structure that I don't think is politically achievable. Solar is cheaper, so why not cover 100% during the day, wind is cheaper, that starts covering the night time, then suddenly your nuclear is uneconomic. And while you're spending the decades getting that power station built you're also having to explain why you aren't building out solar and wind to cover demand.
> Solar is cheaper, so why not cover 100% during the day
Because you still need something to cover the night, but if the thing that covers the night also generates during the day with minimal incremental cost, there is no cost benefit in unnecessarily duplicating that capacity again.
> wind is cheaper, that starts covering the night time
Except when it doesn't, and that's the problem. You have a huge wind farm that generates 50GW when the wind is blowing but only 5GW when it's still, and you have 25GW of minimum load at all times. On the night when you average 5GW generation for twelve hours, where does the other 240GWh of power come from? Your options are "build a peak 250GW wind farm instead so it never generates less than 25GW" (completely hopeless) and "build 240GWh of energy storage" (ouch) which then prices wind out because it's cheaper to use the batteries you need for a still night on every night and charge them with solar instead, and cheaper still to build 25GW in nuclear capacity.
> And while you're spending the decades getting that power station built you're also having to explain why you aren't building out solar and wind to cover demand
Because you are building them too. We can do two things at the same time.
Under your plan you'd build a 25MW nuclear power plant which covers the night, and along with 25MW of solar covers the 50MW daytime demand, correct?
the problem is solar is cheaper, so its profitable for someone to build 50MW of solar. so Nuclear covers night, now at twice the price. But wind is cheaper, so build 25MW of wind, maybe 50% of the time the wind doesn't blow, so nuclear only covers that, so it's now twice as expensive again. Now batteries are cheaper, so what's the role for that nuclear plant now? Would you invest in nuclear in that potential situation?
"Because you are building them too. We can do two things at the same time"
If it takes you 5 years to build the 25MW of solar, but the nuclear takes 15 years, theres a 10 year gap between solar build out finishing and nuclear being ready to take over from that coal plant. What do you do? 10 years of burning coal? or continue building solar so your covering as much demand as you can? But then why retire all that solar when the nuclear plant comes online?
> the problem is solar is cheaper, so its profitable for someone to build 50MW of solar.
That's not how that works. The unit cost of generation is inconsequential compared to the fixed cost, so you don't stop generating at any point and you just take the market price whatever it is.
Suppose nuclear needs to average $10/MWh to meet costs but solar can do $8/MWh during the day. Then as long as nuclear can get $12/MWh at night, it can match solar on price during the day and still cover costs. And solar + storage can't beat $12/MWh at night while the storage costs much more than $4/MWh. So then it's unprofitable to build the other 25MW in solar capacity because it would only get undercut on price during the day by nuclear which can make up the difference at night.
And it's the same thing for wind or anything else. Once you have 25GW of nuclear generation, nobody is ever going to be able to undercut it on marginal cost -- they'll never stop generating power and selling it for the market price, even if it would cause the plant operators to yield negative overall returns, because selling for an unprofitable market price is still less of a loss than getting nothing. And since everyone knows that ahead of time they don't bother to build a bunch of unprofitable wind turbines and that doesn't happen to begin with.
> If it takes you 5 years to build the 25MW of solar, but the nuclear takes 15 years, theres a 10 year gap between solar build out finishing and nuclear being ready to take over from that coal plant. What do you do? 10 years of burning coal? or continue building solar so your covering as much demand as you can? But then why retire all that solar when the nuclear plant comes online?
There is no hope of replacing the entire grid with solar in five years time. The production capacity for that doesn't exist, and would be unprofitable to create because once you've replaced the entire grid with solar all those new panel factories you just paid to build would go idle.
What actually happens is that you add solar as fast as you can and it's still not enough, and you add nuclear at the same time and if we're lucky then together they're enough.
I'm speaking from the UK where demand peaks are morning and evening and we don't have sun, so wind is the good match.
The problem is you're proposing a grid structure that I don't think is politically achievable. Solar is cheaper, so why not cover 100% during the day, wind is cheaper, that starts covering the night time, then suddenly your nuclear is uneconomic. And while you're spending the decades getting that power station built you're also having to explain why you aren't building out solar and wind to cover demand.