How is base load a false concept?
The term vaguely makes sense if there are sources of electricity that output a constant supply that are cheaper than the dispatchable sources of power. Like nuclear was supposed to be (but in the end is not). Or in some very specific locations hydro (without a reservoir) and geothermal are. But as often bandied about as a "type of power that must be filled" it simply doesn't exist. The type of power that must be filled is dispatachable power, everything else is just "well what cheap non-dispatchable sources can we use to avoid using more expensive dispatchable power".
That's the most expensive one, especially if you both need it to be reliable (can't be a battery that can run out) and need it to not emit CO2 (can't be natural gas peaker plants). So what you want is to minimize the amount of dispatchable power that you need.
Which is what baseload does up to the point that it's generating the "base" (i.e. typical daily minimum) amount of load, because then you don't need any of that portion of the load to be dispatchable since the baseload plants will handle it ~100% of the time.
If baseload is half of peak load then you only need 50% of peak load to be dispatchable because baseload sources handle the other half. If you have no baseload sources then you need enough dispatchable sources to handle 100% of the peak load in case that's the only thing available some days/times, e.g. when peak load is after sunset and solar output is zero.
The difference gets even more significant when you consider the possibility of reducing demand through pricing. Suppose raising the price by a moderate amount can lower the daily average demand by 25%; past that you start hitting inelastic demand and would need unrealistically high prices. If you have baseload as 50% of generation then you now only need dispatchable sources to handle 25% of peak load because the other 25% can be achieved through pricing. Without baseload sources you need 75% -- three times as much instead of twice as much.
More than that, it reduces to 25% the amount of long-term dispatchable power you need, i.e. things that cost a fixed amount to have and are also expensive to use but can't run out of capacity. Things you might only use two weeks out of two years, like hydrogen fuel cells or expensive flow batteries; you don't want to need three times as much of those.
Meanwhile you can use short-term dispatchable power (i.e. normal batteries) to do things like handle the peak demand in the early evening while charging them using solar during the day. The period after sunset but before the load falls off is only a few hours long, so you only need 50% of total capacity for ~15% of the hours in the day, i.e. having only 7.5% of daily capacity would mean that you don't have to use demand suppression through pricing unless you have an extended supply shortfall from renewables. Whereas if you don't have baseload then you need enough batteries for ~50% of daily capacity because now you need enough batteries to handle the entire peak demand in the early evening instead of half and the entire demand late at night instead of none. On top of the long-term storage in case the batteries run out.
This is the assumption that justifies the term "base load". In most cases it is simply false.
> especially if you both need it to be reliable (can't be a battery that can run out)
No source of power is 100% reliable, in practice power plants have unplanned outages a single-digits-percent amount of the time. Batteries charged by non-dispatchable power easily match this.
Of course in reality you want a grid with many power plants so that when one is down the rest probably aren't. "Probably" does some work though, for example: https://www.bloomberg.com/news/articles/2022-04-29/half-of-f...
Excess dispatchable power helps make up for when that probably doesn't turn out in your favor.
> and need it to not emit CO2
If we're banning CO2 emissions then up until the last couple of years in most places your only option would be to overbuild nuclear until the point that it was dispatchable and not base load power. Naturally no one did this because it would be obscenely expensive. Now of course you'd have the options of any of the clean energy sources (nuclear, solar, wind, tidal, etc) powering batteries.
Which is the reason batteries can't make for a reliable grid by themselves. There is a strong correlation for every battery being unable to provide power at the same time because they all start discharging instead of charging when demand exceeds supply and the longer that continues the fewer batteries you have that still have any charge, and therefore the higher the withdrawal rate on the remaining ones to extract the same number of total watts, until you have none.
> "Probably" does some work though, for example: https://www.bloomberg.com/news/articles/2022-04-29/half-of-f...
This is why you want a diverse set of generation sources so that you don't get correlated outages. It's better to have nuclear and renewables than just one or the other. France is unique in the world for having more than the optimal amount of nuclear. And it's really more like nuclear is concentrated in France and connected to a European grid containing several other things, but then you can't say that 50% of generation was offline because of this.
Also notice that even the "unplanned" reduction in output was still pretty planned. They find an issue that requires mitigating at multiple plants, so more than the usual number have to be taken offline at some point in the same year, but they get to choose when and can do most of them outside the period of peak seasonal demand, instead of letting the weather choose when.
> Excess dispatchable power helps make up for when that probably doesn't turn out in your favor.
Suppose you had enough battery storage to run the whole grid for 24 hours instead of for 4 hours. Then you unexpectedly discover that half of your power plants (regardless of what type they are) have to be taken offline for two months for repairs/maintenance. How much good are you getting out of 20 hours when you essentially need 30 days?
> If we're banning CO2 emissions then up until the last couple of years in most places your only option would be to overbuild nuclear until the point that it was dispatchable and not base load power.
Hydro is even older than nuclear and there are places where it's close to 100% of generation. If you don't have enough dam sites for that but still have some then using nuclear for base load and hydro for load following has been a solid option with zero fossil fuels since nuclear became available.
But nobody is even proposing to use nuclear as dispatchable power. Its purpose is base load regardless of what form of dispatchable power you use, and the purpose of base load is to reduce the amount of dispatchable power that you need.
This is historically true. However these days natural gas is often cheaper. Of course prices fluctuate, but in general coal has been losing favor because it is expensive. Note that cheap is not just the direct fuel costs, it also includes overhead, that you can throttle natural gas often makes it cheaper overall even when the direct costs are slightly more.
Also unreliable wind+solar is - when working - vastly cheaper than anything else. As such running natural gas at twice the price vs a coal plant can still be a lot cheaper just because you don't have to buy fuel when the wind blows/sun shines.
Dispatchable power is the only sort of power that provides 24x7 power with predictable rates. If there's more demand, you produce more power (at the same cost). If there's less, you produce less so you can sell what you do produce at the same cost.
Those large industrial customers often also end up selling the electricity in the market. Power companies need multi-decade commitments before they are willing to build anything as capital intensive as a nuclear reactor. In that time, industrial customers need to modernize their factories to keep them competitive. Which is often the time they realize it's more profitable to invest that money somewhere else and wind down the old factories.