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Comment by NalNezumi | Hacker News Reader

Correct me if I'm wrong, but isn't one of the reasons we are building MORE coal (and biofuel) plants because the addition of solar and wind have added volatility to the electricity supply?

With few exceptions in the world, in a electricity grid the supply and demand of electricity have to be 1:1, and if wind and solar is adding volatility to that supply, another flexible power source suddenly becomes very profitable and useful.

Nuclear is costly to turn on/off, but coal, biofuel and natural gas isn't. So turning it on/off based on the shortage caused by sustainable sources is why they're coming back, have been my understanding

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I think you have to be very careful with the word "we" here.

Coal's market share in the US has been eroding for 15 years and will likely fall below nuclear soon. It has been replaced by natural gas and, more recently, renewables.

The reason that we "worldwide" have been building lots of coal plants is that China has been building lots of coal plants. This is despite China also building world-dominating quantities of nuclear, wind, and solar.

The reason China is adding so much coal appears to be that provincial officials get to book coal power production as economic growth internal to their province. By contrast, the electricity from renewables in Xinjiang shipped over HVDC transmission lines does not boost their province's economic growth numbers so they do not want to use it even if it would be cheaper.

Coal is not flexible. They are massive heat plants, so an on/off cycle takes about a day.

Ah ok thanks for correcting me

Perhaps they don't turn off but merely down? Is that a day? Is there even such a thing as different levels of operation?

Even if not a day, maybe still not responsive enough.

Then again, maybe it gets you close enough that now you only need a smaller more doable version of some otherwise unrealistic gap filler like batteries or thermal mass or gravity mass etc.

That is not correct. Coal and gas fired power plants have turndown capabilities where they can decrease their power genration very quickly by 75%-90% or so depending on the plant.

https://www.babcockpower.com/wp-content/uploads/2018/02/exte...

Is it common for those huge old plants to use pulverized coal?

I imagine all the new ones use it, and thus all the new ones can change their outputs in a matter of minutes, instead of hours. But that still makes coal one of the slowest sources to react to grid volatility, and sill basically useless to compensate wind oscillations, only useful for the solar cycle.

I've seen some really old plants and they've all used pulverized coal, since it burns more consistently. It basically explodes when it ignites due to the temperatures involved. Coal and gas are both really good at responding quickly to varying load requirements.

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