UNANTICIPATED WIND GENERATION CUTOFFS DURING A COLD WEATHER EVENT
Below is the full transcript for this episode. If you'd like to review or follow along with the original .pdf version of this NERC Lesson Learned, visit: https://www.nerc.com/pa/rrm/ea/Lessons%20Learned%20Document%20Library/LL20200601_Unanticipated_Wind_Generation_Cutoffs_during_a_Cold_Weather_Event.pdf
Chris Sakr: It's another windy morning in Yorkshire. One kid wakes up and the first thing he does, he steps outside to check the weather.
Justin Sharp: My grandparents bought me at the thermometer and barometer combination when I was nine years old and I religiously tapped on that barometer every day for four years until it broke.
Chris Sakr: Now, a lot of kids give up on broken toys. They move on to other passing fancies. But to this kid, that barometer was the beginning of a lifelong obsession.
Justin Sharp: My name is Justin Sharp. I have my own consulting company called Sharply Focused, which is a meteorology and energy consulting company trying to optimize outcomes for the energy business by inserting as much meteorological knowledge as possible.
Chris Sakr: Justin has a PhD in atmospheric science. He's a sharp dude with a lot to say about the weather's relationship to renewables on the bulk electric system. It's his bread and butter.
Justin Sharp: If I've got very high demand for electricity due to very high temperatures or very low temperatures, and at the same time, that is strongly correlated with either very good wind or solar or very poor wind or solar, we really need to be taking that into account. And right now, the way we're building out our renewable energy portfolio is just to say, where can I generate the most wind? Where can I generate the most solar? Not how can I match it with what's actually needed.
Chris Sakr: In the hilarious 2000 movie, Snatch, Cousin Avi, an American gangster, finds out a diamond heist he planned in England is going upside down. With few alternatives to prevent total disaster, it's looking like his only option is to hop the pond himself and go the extra few thousand miles to fix it. He's super excited.
Cousin Avi: I don't like leaving my own country, Doug, and I especially don't like leaving it for anything less than warm sandy beaches and cocktails with little straw hats.
Chris Sakr: Today's lesson learned, titled Unanticipated Wind Generation Cutoffs During a Cold Weather Event, published June 11th, 2020, has a lot in common with our next episode, for instance, wind, low gen balance, situational awareness, the English and their windy little isle.
Chris Sakr: Growing up in Yorkshire and Northumberland, very gusty former coal mining hubs, it's no surprise Justin would have a pretty intimate relationship to the wind. Next episode, we'll hop the pond just like Avi, but today we stay home in the US with our British transplant and weather expert as a guide.
Chris Sakr: So mates, without further rubbish, hopefully you'll be chuffed to bits and not too knackered by the end of this bloody British little mini-series.
Justin Sharp: I think there's been some fairly significant weather events that have occurred in the last two, three years, including this one, that have indicated to people this relationship and interdependency between the amount of power we generate and the amount of power we use. And you can't ignore it anymore. The amount that we use and the amount we generate are both connected by a common theme, and that's weather.
Chris Sakr: At the time of this recording, February, 2021, things got real interesting. You probably saw Texas all over the national news. Here in Portland, we had ice storms and unprecedented outages. I seem to be the only person I know who didn't lose power, and this isn't just a problem with renewables.
Justin Sharp: Outage rates for gas turbans are actually even higher than they are for generators. So it's not fair to say that this is a renewables only problem because it isn't, but it is fair to say that there is a very definite correlation between potential outage of generators and that generator being greatly needed at that time.
Chris Sakr: When temperatures are extremely low or extremely high, demand shoots up. Heat, AC, people typically staying inside and using more power. I'm sure Netflix experiences something similar with way lower stakes. The grid finds itself in a bind irrespective of generation type. And that's what happened in this event.
Chris Sakr: Here's the problem statement. A registered entity experienced extreme cold weather January 29th through 31st, 2019. Unplanned wind generation outages contributed to a maximum generation event resulting in the entity calling on load management resources, including demand response, behind the meter generation and voluntary reductions to avoid using emergency power purchases.
Chris Sakr: So every machine has operating limits. Most wind generators cold limit is minus 30 degrees Celsius or minus 22 Fahrenheit. And given that wind farms are often developed where cold weather is a feature, manufacturers have a band-aid of sorts, the cold weather package.
Justin Sharp: It's basically heaters that allow the gearbox oil and some of the other components within the machine to stay within the operating range through lower temperatures so that all the machinery can stay lubricated, particularly the gearbox.
Chris Sakr: The package adds about 10 degrees Celsius or 18 degrees Fahrenheit of wiggle room. So most machines with installed cold temperature packages have an operating limit of around minus 40 degrees. Problem solved, right? Well, in this case, it hit the Midwest.
Justin Sharp: Because of the cold wave and because a lot of the turbines in that area did not have the cold weather package, and then they flipped offline, and the result was a lot less wind generation than would have been expected from the day ahead forecast.
Chris Sakr: Okay, now I went to the Midwest for the first time a few Decembers back. We walked out of the Detroit airport. It was around 5:00 AM. And my instant thought was, "I never knew what people meant by bone cold until this second." If you're anything like me, hearing Justin synopsis, you thought, "Guys, it's not Texas. It's not even the Northwest. Wouldn't every wind turbine have the cold weather package? If not the Midwest, then where?"
Justin Sharp: One would assume that it would be installed, however, the number of hours per year that a machine would typically be out because the temperature was below minus 22 is not that many. And so what developers have done is they've made a calculation. Most projects on a power purchase agreements, so there's a fixed power price, but even projects that are not utilizing a power purchase agreement will typically take a reasonable power price and multiply that by the number of megawatt hours that would be lost due to being offline. If that number is not larger than the cost of installing the cold weather package, then it doesn't get installed.
Chris Sakr: Even if developers' math says they saved by not installing cold weather packages, we know that when weather causes generation cutouts, quite often, demand is very high, meaning power can be extra expensive, like instead of tens of dollars per megawatt hour, hundreds or thousands of dollars, which puts entities in a tight spot.
Justin Sharp: So the results of this event was that there was a day ahead forecast for how much wind generation was expected during the morning peak of the 30th. And at around 3:00 AM in the morning, it was very apparent that that wind forecast day ahead was way off. There was about six gigawatts of wind being generated and the day ahead forecast was for 12 gigawatts. I believe in the unit commitment process, they had relied on that being at least eight and a half gigawatts of wind available by the time of the morning peak, and we were already two and a half gigawatts below that amount and dropping.
Justin Sharp: So the consequence was that they declared a maximum generation event of 5:00 Eastern time at about 3:30 in the morning. And the wind did continue to drop, which it was forecasted to drop anyway. So in addition to the fact that you had a bunch of generators out, the wind was also dropping at that time. And then the system operator began to mitigate the need for extra power by putting out a lot of calls for voluntary reductions and also activating various demand response and load modifying resources.
Chris Sakr: So the entity calls on every available generator, plus the other measures Justin mentioned. Ultimately the problem was resolved, but to put it super plainly, weather's going to weather.
Justin Sharp: And one of the interesting things about wind is that when you have these cold waves, as the air is moving in, the cold air, what moves that cold air from north to south? Wind, right? So you always have really good winds when the cold air is advancing. If you're relying on that wind, which we should be, we should be making that correlation. Like oftentimes we'll say, "Well, the wind is not always there when we need it." Actually it is. In the case of cold waves, there is always wind weather when the cold is coming in. Now sometimes when the cold's done coming in, then you can get into this stagnant situation where it's cold and not windy.
Justin Sharp: But the point that I'm trying to make is what you don't want is to have machines that don't work when it's cold or can get really bad blade icing when it's cold because they're all in the same place where there might be a risk of freezing rain and then not be able to rely on them.
Chris Sakr: Obviously the responsibility for mitigating situations like this before they happen lies largely with developers, but it's still important for system operators to know what a system with wind generation looks like when it's built properly and to know if theirs is.
Justin Sharp: So, first of all, you want to build wind in places where there isn't the most mitigation capability. Secondly, if you know that the machines are likely to cut out on occasion due to that cold or the heat, then you want to make sure that they've got the cold weather or warm weather package on them and that you're incentivizing the builder or the owner of that asset to make sure that they include that package when they build out that project.
Justin Sharp: Thirdly, when you've got a risk like freezing rain or even cold temperatures, having all of your wind in one spot or closely clustered does greatly increase the risk that large swaths of it are all going to be on outage at the same time. So having an incentive to build more diversely is also a positive. And right now, there are no incentives, either at the regional level or at the national level that I am aware of that are really incentivizing those things.
Chris Sakr: As a result of this event, 98 of 216 wind farms in the control area had to be de-rated or shut down. That's 45%. One of the first lessons learned in the document reads, "Obtain accurate cold cutout temperature information for all wind farms in the system footprint." And while that may seem obvious, Justin says its importance has been a hard sell to system operators, which also leads to another important operator takeaway not included in the document.
Justin Sharp: If they could also obtain in real time what the temperature was at the wind farm, they would know how loose it was. And that could be a really useful piece of information. Wind operators are required to provide wind speed information from their own projects. If they were required to also provide temperature information, which they may be at this point, I'm not absolutely sure what the rules are in this particular case, and at the same time, knowing what the cold cutout temperature is for your wind farms would allow you to able to assess the risks that you were going to start losing turbines.
Justin Sharp: You're typically not going to lose them all at once. You'll get a warning. One will go down or a couple will go down, but then they could cascade off fairly quickly after that. So having that information available to you would be really useful maybe two to three hours ahead of time that it's worth starting to ready generation. And I think we all know that the more warning, the more lead time you have, the cheaper it is to find some other form of generation from your own portfolio, or to go out into the marketplace and buy it.
Chris Sakr: Hopefully wind farm temperature information is provided to you, but it may come down to you independently checking your phone as temperatures change drastically, then comparing that against cutout points. Absent developers, including weather packages, it falls to operators to know what's on their system and act accordingly, because, as Justin and current events remind us, now, and certainly in the future, every aspect of the grid comes down to weather.
Justin Sharp: Our timing of outages on conventional units, how well we marry wind and solar with hydro, all of those things, the weather-related items. I mean, even as we transition over to electric vehicles, electric vehicles will use more power during the winter time in extremely cold days because people will turn the heaters on, right? And the heaters can be almost half of the load of the car when you do a short commute in the morning because resistive heat takes so much power. So getting utilities to understand that the world has changed and the decrees of freedom have changed is really what I do is all about.
Chris Sakr: What started as a nine-year-old with a barometer on a windy aisle evolved into Justin's lessons we'd all be wiser to hear. And the town he grew up in, the former coal mining hub, he sadly told us became a ghost town. Well, now it's becoming a renewables hub. Happy ending. And as for Cousin Avi's journey to that same windy aisle...
Cousin Avi: You got a toothbrush? We're going to London. Do you hear that, Doug? I'm coming to London.
Chris Sakr: To prevent complete disaster, whether he wanted to go or would rather be on a beach sipping cocktails,, like it or not, he did what he had to do. Utility executives, generation developers, and operators working the grid 24/7 could all take a page from Avi's book. Sometimes when the inevitable presents itself, we all have to go the extra few miles. The future is coming. And if the present can tell us anything, it's that the weather's going to do what weather's going to do. Like it or not, measures need to be taken, because as you'll find on our next episode when we hop the pond, the system will also do its thing. And hopefully when we finally get back, we feel a lot better than Avi did.