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Comment by mindfulplay | Hacker News Reader

Wind is not consistent and the scaling of the plants is non-uniform/sublinear... Wind is also supplementary because of its inconsistencies and so will not directly power grids.

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And there are other problems that I rarely hear people mention when they do the comparison.

So wind and solar are intermittent so you have to factor the cost of a stand by power supply (which you need to pay for whether you use it or not), or power storage (which we can't do at scale).

You also rarely hit peak capacity with wind (unless you have a reliably strong and steady wind) so you need to over provision by a larger ratio. Nuclear is about 70% utilisation on average, wind about 20%. Similar story with solar.

Nuclear plants tent to have a very long shelf life, wind not so much (to take into account in the cost comparison)

There is a lot of diversification in the demand, not all machines of a country are switched on at the same time, in fact a small fraction of the machines are consuming electricity at a given time. When you adopt a centralised grid with large sources of power, you benefit from this diversification. When you produce the electricity locally, you need to size it for the max local demand, and you need to do that everywhere. That means you end up installing a lot more capacity than you would need with a centralised network.

And the grid in most developped countries is already designed for a centralised supply, so if you switch to a completely different approach you need to invest in your grid.

It's not enough to compare the cost per W produced.

Dump excess wind-originated electricity into organic-solution redox flow batteries (because we don't care how big and heavy utility-grade storage is), and we're easily looking at 50-year lifecycles before the batteries need major maintenance, which currently consists of electrical controls, pump and container integrity. I don't know the lifecycle of the organic chemistry yet, as its discovery was only published this year so they haven't had time to perform accelerated aging tests upon it, so maybe the solution might have to be replaced sooner than 50 years, but based upon what I saw in the paper I suspect not. With appropriate civil engineering (pozzolanic concrete, basalt rebar), the containers can be built to last 5+ centuries.

Build enough of these redox flow plants on the grid, pour in enough excess from all kinds of renewables, and hopefully in 3-7 generations our children won't worry about coal-originated mercury poisoning from eating "too much seafood".

Interesting thing is that nuclear has the exact opposite problem, it’s extremely consistent.

You can’t easily vary the output of a nuclear plant (maybe these will be different, but I doubt it), they take days to weeks to spool up and down. Which makes them only useful for base load.

Ironically pairing them with grid storage would be an enormous help, because then you could use the storage to rapidly respond to demand, while your nuclear plant ramps up and down very slowly.

In short nuclear also isn’t a one size fits all solution for power production, and if it needs to be paired with storage in a carbon free world, it makes you wonder if it’s really worth all the trouble compared to wind and solar.

Navy nuclear reactors can ramp up and down very quickly, unfortunately for the civilian power they don’t save much money by doing so. Which is why they civilian power plants are generally designed for steady state operations.

That is the purpose of the Hornsdale Power Reserve, a giant battery in South Australia, except instead of nuclear it is helping balance gas turbines and renewables. SAs energy is produced from renewables and gas turbines, with the battery providing grid stabilizing services. It has been so transformative that it can even stabilize the grid across the country faster than their local power supply can kick in. Typically that kind of service is charged by response time and time spent responding, but the battery is so fast that the they get far less than a responding gas turbine would for the same service.

https://en.wikipedia.org/wiki/Hornsdale_Power_Reserve

France routinely varies the output of its nuclear power plant intraday to follow the demand

True, however this is a far smaller variation ("several tens of percent" [1]) and only happens slowly (~once per day). This is in contrast to gas turbine peaker plant with can ramp by 10-20%[2] of rated power per minute.

[1]https://www.oecd-nea.org/nea-news/2011/29-2/nea-news-29-2-lo...

[2]https://journals.sagepub.com/doi/10.1177/0957650920932083

I am not sure what you mean by one per day. There is only one cycle per day. And it’s not slow, fast enough to adjust for the daily cycle.

https://en.m.wikipedia.org/wiki/Load_following_power_plant

“Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope. Nuclear power plants in France and in Germany operate in load-following mode and so participate in the primary and secondary frequency control.”

One of the ideas I've heard behind these smaller reactors is that since you have say 10 small reactors instead of 1 big reactor, you can decrease the overall output by just shutting down a few of the smaller reactors.

It's absolutely not perfect but it's an improvement.

And should a country end up many of these small reactors, nuclear could actually be quite flexible. The reactors could be shut down and started up on schedules such that each morning, some reactors that were shut down are coming online and in the evening, some of the reactors that were online are shutting down.

They mentioned this:

> augmented with utility-scale storage that currently runs about $200M/GWh and will be at least 2x cheaper by 2030

So storage is a cost, but seems like a relatively small cost, especially if the stated trends continue.

I can see why the nuclear is competitive. Here in California, from looking at the states graphs it seems that about 90% of our renewables are being generated in a 12 hour window[0] (a window which unfortunately ends at the time when demand starts to build up to its peak). If you want to even out 50GWh of renewables across 24 hours, you'd be spending billions of dollars on storage and you'd still be burning fossil fuels on cloudy and/or low-wind days. Nuclear reduces storage needs, as well as the bursty-ness of renewables. I can see how they'd be complementary

[0]: Just a guesstimate from eyeballing this graph, might be off http://www.caiso.com/TodaysOutlook/Pages/index.html

That's a nifty site. Thanks for the link.

Eyeballing the graphs, looks like we need maybe an average of 25GW for the 16 hours of low solar output, for 400GWh. If batteries don't increase in price and the grandparent's prices are right ($200M/GWh, ignoring the prediction of it halving), that's $80Bn of storage. The proposed mininuclear is a bit over £4Bn[0]/GW, so £100Bn to get 25GW.

Seems like storage wins if you don't consider cloudy days (bad for solar), maintenance/operations cost (I assume much lower for batteries+solar than nuclear), or replacement times. (I'm guessing nuclear plants last longer than storage.)

I'm a little surprised how little wind is being used in California. It's worth noting that wind actually picks up slightly when solar drops, but not as severely, judging from the graphs.

[0] I hate that some of our units are £ and some $, but I'm going to pretend they're equal. That unfairly helps nuclear in the calculations.

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