[ben_w]

And can be recharged as soon as the wind or the sun comes back.

The sizing of batteries and power sources is highly region specific, and the places where it makes sense today with current manufacturing capacity, don't have to be "everywhere" for it to be fine where it's actually done; and given the roll out rate of renewables, we also don't need to wait until battery output per year can totally displace the existing and currently running gas plants, just back up the newly installed renewables themselves - 4h in this case is how fast the PV farm would recharge those batteries in the best case, the average output of a PV plant is about 10% of the peak, so this is really a 40 hour battery pack not a 4 hour pack.

[Moldoteck]

I mean, look at Germany's grid yesterday& today and tell me, with such overcapacity, how much more overcapacity it would need and how much storage it would need to cover such events with low wind and solar?

[ben_w]

I use the approximation of annual capacity factors for PV being 10%, which means 10x. Wind has a higher capacity factor IIRC between 35% and 85% and that heavily depends on location.

A realistic answer would need me to spend at least a month dealing with finding historical satellite cloud cover data, wind records, correlations leading to nationwide dunkelflaute, the planning options for where new stuff can be built, etc.

And even then, that varies depending on international grid connections, and how much storage is on the grid.

[Moldoteck]

cf yearly are good for some purposes but bad for others. Again, look at Germany's coal/gas use yesterday vs today as well as wind/solar generation and imports. If you don't want fossils, how would you cover such events? France was outputting towards Germany equivalent of 3-4 npp and 2 additional from Switzerland, max being about 12+GW from neighbors. How would it be financially viable considering there are many other days when demand will be met for day hours? New solar/wind will not be able to sell energy at negative prices unless they get subsidies. Germany already spends 20bn/yr for price subsidies and their grid is far from overcapacity and that doesn't account for other subsidy types like for transmission for renewables

[ben_w]

Today's values, from what I've seen, this country could run on just wind if it had 10x more than now, but it doesn't really need that in isolation, it's just that PV was harder to judge because the graph wasn't even close to a flat line.

https://www.energymonitor.ai/power/live-eu-electricity-gener...

> New solar/wind will not be able to sell energy at negative prices unless they get subsidies.

They already do, in good weather.

> 20bn/yr for price subsidies and their grid is far from overcapacity

And how much of that was for a guaranteed price made way back when the stuff was still expensive?

New PV is, by itself, the single cheapest source of electricity; even adding on batteries only takes it up to somewhere between gas and nuclear depending on the specifics.

> and that doesn't account for other subsidy types like for transmission for renewables

How's that a subsidy? I've not seen the breakdown of bill costs here, but back in the UK there was a split between connection cost and use cost.

[Moldoteck]

transmission upgrades are needed for renewables due to their distributed nature https://www.reuters.com/business/energy/germany-looks-specia...

> They already do, in good weather.

We haven't reached yet such renewable market penetration to get this problem. It'll happen when a lot of days, 10 day hours will be covered by renewable output.

> And how much of that was for a guaranteed price made way back when the stuff was still expensive?

I have no idea how are these are distributed. Do you have a link for recent vs old projects?