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Comment by cool_dude85 | Hacker News Reader

Nuclear is baseload and is the exact opposite of "instantly fired up". Best tech for that is gas or battery.

There is a line of reasoning that baseload is a billing and profit construction, an artifice of the needs of coal-fired and nuclear power.

There is nothing innately wrong with over building renewable and storage, and a transmission network.

It's an argument about economics, not physics.

Can you realistically overbuild solar and wind in a way that works in winter? Here's Terence Eden in the UK, and his graph of rooftop solar[1] showing peak around 400kWh/month in summer and trough around 50kWh/month in darkest December - that's a difference of ~8x which might be possible...

But that's averaged over the month, what about a run of December days with heavy cloud cover, misty foggy atmosphere, still air, maybe some Icelandic volcano soot in the atmosphere, what's the worst we'd have to plan for, and how much overprovisioning would that take?

[1] https://shkspr.mobi/blog/2013/02/solar-update/

FWIW I have updated stats at https://shkspr.mobi/blog/2023/04/3-years-of-domestic-solar-s...

They're also published as open data.

The dark and dreary days tend to be the ones with the most wind power. The tides around our coast are in constant motion.

But, the big challenge is still storage. Domestic solar panels provide 100% of our yearly electricity use. At the moment I can only store 4.8kWh of excess.

So we need to over provision and over store - hopefully both at the same time.

Same author: https://shkspr.mobi/blog/2023/12/electricity-thats-too-cheap...

Wind is anticorrelated to sun and stronger in the north.

https://globalwindatlas.info/en

In the UK, given it's northern latitude and great wind resources, you'd be best overbuilding mostly wind.

Here's a worked example based on real weather data that suggests a wind capacity of double peak demand and converting about 8% of all demand with power-to-X would be the the low cost option.

https://www.wartsila.com/energy/towards-100-renewable-energy...

That's absolutely true, but the economic argument still carries weight. How many acres of land, how many rare earth minerals, etc. are required to produce the load profile you need with batteries and renewables vs including baseload flat generation from nuclear? This is still an economic question but very relevant.

Literally no "rare earth minerals" are used in production of solar or batteries. Exactly zero.

Nor in wind turbines, if you don't use permanent magnet generators.

Cant control rods can be lifted or inserted to meet demand?

There's typically a range of operation, so you can adjust a hundred MW but you can't drop to 0 or spin up from standstill without a time consuming process.

Edit: also, the economics are such that you rarely want to drop load from a nuclear plant unless it's offline or for system reasons. The fuel cost is negligible so you'd rather turn off your gas plant or lower the coal plant and save on those fuels.

That assume we still allow coal, oil or gas power plant to exist in the power grid. We should probably not assume that to be the case, especially after the temperatures rises to a break point and some of the major climate change crisis occurs.

None of the commercially available (Western) reactor designs today are fast load followers, so you are dependent on having gas or hydro when you project for new nuclear power plants. That's one part of the reason why this stuff is politically charged.

From what I understand it's not a theoretical constraint, but mostly a lack of enough commercial interest for any other design. But it is what it is.

> Cant control rods can be lifted or inserted to meet demand?

Thermally it is difficult to dial a reactor up and down. Generally the way nuclear power is modified is by not-sending the steam to generators through a by-pass and quenching their heat in some fashion.

So thermal generation stays at 100% (or whatever), but electrical generation output can be dropped.

They can, though it depends a little on the plant design.

It just doesn't make any sense to use reliable nuclear as the "backup" to unreliable renewables.

Because this "backup" is already CO2 free. It is also reliable. And cheap to run. So just run it all the time (nuclear tends to have >90% capacity factor).

You then simply don't need the "primary".

Usually you'd vary the concentration of boric acid being injected in the reactor's core instead, since that doesn't involve wear and tear on safety-critical elements of the reactor.

Nuclear reactors absolutely can vary their output to match demand, this is what France has been doing for 50+ years (and what Germany was doing before switching back to coal). It's not as reactive as coal/gas, but you can still vary within 30-100% of output power at a speed of 5% change per minute. Way more than enough to react to 1-day-ahead forecasted supply/demand, and way more than enough to react minute-by-minute if you've got a tiny bit of storage to stabilize the grid's frequency (e.g. pumped hydro).

It is a hugely complicated system where reactors which are earlier in their fuel cycle ramp more leaving the later ones to run at 100% around the clock.

Ramping once is easy. Ramping continuously through the entire fuel cycle requires a meticulously planned fleet.

France is balancing their reactors with a massive amount of water power, so they are not doing it alone on the reactor side. But I think France is indeed one of the countries with the highest relative amount of nuclear in the grid. Germany went never over 30% nuclear in the mix, so demand matching was way less of a problem. But also, both countries tried to make demand mostly constant like with pushing inefficient heating systems which would consume electricity at night.

This is very far off from working well together with a mostly renewable grid, where renewables can cover 100% of the load on most days, but there are larger gaps to be quickly filled.

A nuke operated at 50% of capacity costs the same as one operating at 100%. Thus, power from it at 50% costs twice as much per kWh. But nukes are already not competitive even at 100%, and get less so with each passing day.

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