I was looking at the “Dashboard” for the UK electrical grid here:
Zooming in on detail usage of Nuke vs Coal vs Gas vs Wind, It looks to me like the UK wind farm total is approaching the point where the UK grid destabilizes. It looks, to me, like at most a “double” of wind (ether farm size, or a smaller increase in peak wind speed where ‘drag’ goes as the cube of velocity, so energy ought to ramp up at some significant power function) and there is just not enough “fast response” capacity to absorb the shocks. There isn’t any indication, really, that this is a ‘typical’ chart, so we might already be past that point if other samples are even more extreme.
You can click on that for a bigger image.
OK, that first column has Daily, Weekly, and Monthly demand. Notice that the base demand runs just about 30 GW, no matter what. The peaks run about 45 GW on big days (some touching 50 GW on the monthly chart) but where modest demand periods can run down at 35 GW to 40 GW (notice about the 1st of the month).
OK, so we have a 30 GW to 35 GW range on ‘slow days’ with 30 GW to 40 GW being typical. Some days get up to a 30 GW to 50 GW, but those are demand peaks.
Now look over at the far right. Hydro, wind, biomass. Notice the red ‘wind’ line. It jumps and fades rapidly. It has about a 5 GW range on that monthly chart. On the 21st it ramps up by about 4.5 GW in a rapid spike. You can see in the middle column that Gas (CCGT) ramps down in that period. Those gas turbines can respond fast doing “load following” (or in this case “surprise supply following”). Coal and nuclear can’t do that nearly so well, often taking most of a day (or 2) to get fully up to speed or shut down.
Now look at the 30th. Wind has essentially died. Demand is low, even the ‘daily spike’ is low. Gas is ramped down to near 5 GW leaving coal and nuclear running the show. (And even coal is ramped down about 5 GW from peak). So what would happen if the wind suddenly picked up and 5 GW of wind were dumped into the grid at that point? What would be dropped to absorb it? Scram a nuke? Hard on the equipment. Shutdown more coal? It’s hart to ‘load follow’ with big coal. Just shut off ALL the gas turbines? No fast response then if the wind suddenly dies – brownouts for sure.
In fact at the far right margin you can see some of the strains as the present wind is cranking, and the other power is being rapidly shut down. Coal running about 1/2 power (so not able to ramp up a cold coal plant fast… if that wind dies…) and Gas down at about 2.5 GW. With an additional 2.5 GW of wind turbines installed, that gas plant would be off and cold too. Doing a “rapid cold start” on gas turbines can be rough on equipment.
IMHO, this shows there is already some “difficulty” in trying to balance out the wind supply surges and that coal is being used to “demand follow” and / or “wind supply follow” – a very not good thing to do with large coal facilities. With just 2.5 GW more wind (about 50% more), it looks to me like grid instability will start showing up on high wind / low demand days. During the summer, this will likely get worse, as heating and lighting demand fall off, but the wind does not.
On the flip side, the 12-14 and the 18-20 look like nuclear, coal, and even the gas turbines are running near flat out to keep demand met as the wind drops off. If an even larger part of generation comes from wind, and less from coal or nuclear, it will become very hard to keep the lights on when the wind stops. Total capacity will not be there, and rapid response fast bring up capacity will be way too little to respond.
In short, it looks to me like the UK Grid “has issues” right now, and at 50% more wind turbines, or a 3 to 5 GW reduction in any combination of coal and nuclear, the UK Grid destabilizes on wind dropout days, and on wind surge days. (And even that ignores local ‘inside the country’ distribution limits / bottlenecks that could cause local problems sooner.)
As I understand it, there is an intent to shut down some large coal and nuclear units in the next few years. That, IMHO, looks like it will be a complete disaster on any of: Very high demand days, very low demand days, very high wind days, very low wind days. And lord help you when a very cold very high demand day shows up without wind. “Dark and cold” are not a good combination…