A large number of “hot takes” are appearing now that the cold wave that began arriving on Feb 11, 2021 has moved into areas where sub-freezing temperatures in Feb are normal.
If the politically charged nature of the takes could be harnessed, the energy released would be able to keep quite a few homes supplied with power. But, no one has found a way to capture and convert words and hot air into electricity – at least not yet.
That doesn’t stop writers from writing. I plead guilty to the charge of adding to the pile of non-electricity producing words.
It’s a necessary endeavor because so many of the hot takes have been produced by people whose agendas are different from mine.
Though no power source worked perfectly throughout the five day period when the Electricity Reliability Council of Texas (ERCOT) declared the grid condition to be at Emergency Energy Alert 3 (EEA 3), some power sources worked better than others.
While almost every generating source in the system has room for improvement, some have limitations that cap their performance no matter how perfectly they live up to their maximum potential.
The storm revealed severe weaknesses in the current grid resource management model that are worth discussing in an informed, responsible way. Lessons learned discussions are just entering into the early stages, but with an open minded, questioning attitude, it’s not too early to produce some recommended short term actions.
Aside: The title of this piece is intended to indicate recognition that performing “lessons learned” analysis and creating action plans is no guarantee of better future performance if responsible people choose not to take recommended actions. End Aside.
Why did the grid get so stressed?
About a week before the cold weather arrived, it was evident to those who pay close attention to electricity grid supply and management issues that the ERCOT service territory was going to experience an extremely challenging period. Wholesale prices were going to increase by many multiples and would challenge the existing cap of $9,000/MWh (300 times the usual price of $30/MWh).
Every generator in the system would be motivated – incentivized by high prices – to produce as much electricity as it could possibly produce and even then, there probably would not be enough power available to serve every customer as much as they wanted or needed to buy.
Despite the very high prices, almost no help would be supplied from outside the ERCOT system. In order to maintain its fiercely protected independence from the Federal Energy Regulator Commission, ERCOT has kept connections to other US grids at a bare minimum. That ensures that its electricity falls outside of the Constitution’s interstate commerce clause used to justify federal regulation. There are some significant cross-border connections into Mexico.
Few commercial or retail customers would know how much their power was costing at the time they decided to use it, so the system would not receive much help customers making informed choices about timing or limiting their use.
Most of those customers would not even receive a sharply higher bill at the end of the month, because their rates would be adjusted over time to repay the costs of a sustained period of high spot market prices.
That is how the system in place is designed to respond to severe weather or other stressed on the power system. ERCOT has chosen an “energy-only” resource management model where competing generators bid their capability into wholesale electricity markets that are settled and priced every 5 minutes. There is no other source of revenue.
Why choose an “energy-only” resource planning model?
An “energy-only” model keeps wholesale prices low during fair weather. Low prices encourage customers to add devices and equipment. On a larger, longer term scale, it encourages businesses and even residents to migrate to take advantage of having low cost electricity available.
But it doesn’t provide sufficient predictable revenue to encourage investment in durable generating sources or long term, guaranteed delivery fuel supply contracts.
Because all energy sources have different cost structures and different bidding strategies, wholesale prices have wide and rapid swings. By design, the system provides massive returns during periods where demand exceeds supply. This characteristic is supposed to provide all of the necessary incentives for generators to be ready at all times to provide their full capability.
But even with almost a week’s notice that an historic weather event was on its way, there were limited actions available for most generators to prepare to maximize their returns from the coming period of scarcity. If they did not already own reserve fuel tanks or winterized generator packages, it was too late to make arrangements for installation.
Some generators might have been able to get a rush liquid fuel shipment to top off any existing tanks – at an ever increasing price – or they might have been able to make careful inspections and fix obvious system weaknesses. If they discovered some missing insulation or a non functioning heat trace system, they might have had enough time to make repairs.
But most would have had to simply hope for the best and do whatever they could to keep producing power.
Most customers were blissfully unaware of the decisions that had created a system where participants depend on scarcity pricing to make a profit in the business of supplying electricity to the ERCOT market. They didn’t know that many of the generators in the market knew they would only be able to produce limited amounts of power, even with sustained prices at or near the cap of 300 times the usual grid price.
They didn’t know that most generators in the market would be richly rewarded even if they were only able to produce 10, 20, or 50% of their expected capacity during the several day-long deep freeze.
Few frozen wind turbines
The 2021 cold weather event began February 11, 2021 with freezing rain, one of the most impactful kinds of winter precipitation. The nation began paying attention to the incoming cold weather as a result of news reports of icing roads in the Dallas-For Worth area that led to a massive, 130 car pile up on I-35.
That wave of the storm did not actually produce massive quantities of ice; the slick road conditions resulted from less than a tenth of an inch of ice on a road where drivers didn’t exercise sufficient speed restraint.
While freezing rain can accumulate on almost any surface exposed to the weather, including aircraft wings and wind turbine blades, there is no available evidence suggesting that a major portion of Texas’s installed base of >30,000 MW of wind turbine generators experienced icing sufficient to have much impact on their generating ability.
There were some reports that claimed iced or frozen turbines were a significant cause of lost wind power generation, but the real culprit was a relatively common, and predicted winter storm weather pattern that included long periods where high pressure covered a huge land mass. When atmospheric pressure is the same over a large area, there is no driving force that creates wind.
Many people that strongly support the continued rapid development of wind and solar power generating systems declared that their favored power sources performed at or above their day-ahead predictions. They wrote lengthy defenses of wind generation and declared that the historical performance of turbines in areas that regularly experience colder weather than what Texas experienced in Feb 2021 proved that there was nothing inherent about wind that made it especially vulnerable to severe weather.
Midwestern utility company MidAmerican Energy Company has shown that wind energy is highly reliable, even in harsh Iowa conditions. In 2020, 80 percent of the utility’s electricity was generated by renewable energy — the majority of which comes from its 3,300 wind turbines, said Geoff Greenwood, a spokesperson for MidAmerican Energy.“Wind turbines can handle the cold just fine. Just look at Iowa.” Vox Feb 19, 2021
From the wind and solar advocates’ point of view, better-than-expected performance means that wind and solar should bear little or no responsibility for low generation during an electricity supply shortage.
Even in a supply crunch severe enough to cause an Emergency Energy Alert stage 3 (EEA-3) – the highest available response level – there is nothing that wind and solar generators can do to make their systems supply power. They must wait until the wind starts blowing or the sun comes up. Low sunlight inevitably affects areas spanning more than half of the planet all the time. Wind is more localized, but there are times when entire continents can be still for many hours several days at a time.
Vast majority of wind and solar advocates are observant enough to know these facts. They even take offense when they are introduced into energy discussions. If challenged about the value of continued strong support and mandates for increasing wind and solar penetration, one of their arguments is that using the wind and the sun to supply energy when it is available allows fossil fuel generating sources to burn less fuel.
That would be a reasonable response if the only competitor to wind and solar was fossil fuel. It’s even a reasonable response in systems where large hydroelectric dams are part of the generating mix because it allows the water to remain behind the dam, ready to be used when wind and solar generation falls off.
But opportunistically displacing other sources of power can lead to unproductive consequences like eliminating enough revenue from nuclear plants to make them struggle financially. Right now, there are firm plans in place to close five operating nuclear plants in the US during 2021.
Though some industry leaders have vociferously denied that wind and solar power can be blamed for those closure decisions, the financial evidence is clear. Low grid prices and grid congestion fees in regions where there is abundant wind or solar power available create a “missing money” situation that stresses large steady-running generators that serve base load very well.
There is a correlation and a causation between the location of Exelon’s Byron and Dresden power plants in high wind areas and their financial performance. The same holds true for Diablo Canyon, but the culprit in California is a massive quantity of solar power generation that can create negative pricing during the middle of the day.
Large numbers of gas-fired generators could not produce power
One of the design features of the “energy-only” market model in Texas is that it rewards low capital cost equipment that can burn natural gas. For the past 13 years, natural gas has been abundantly available in many parts of the US, especially in Texas.
The Permian Basin, much of which is under Texas soil, is one of the world’s most prolific oil and gas reservoirs, but it isn’t the only major source of gas in the state. There are other shale formations and there are large gas reservoirs in the Gulf of Mexico off of the Texas shore.
Natural gas, which is more accurately called methane, burns cleanly enough so that a stream of its combustion byproducts can be directly used to spin turbines in a Brayton cycle. Those machines are simple and cheap compared to the huge Rankine (steam) cycle plants that are needed to burn dirtier fuels like coal or lignite. Brayton cycles work well in combination with simple, relatively small steam plants to produce highly efficient Combined Cycle Gas Turbines (CCGT) power plants.
The “energy-only” market structure has helped gas to push most coal and lignite off of the Texas grid, producing significant air pollution reduction and a reduction in greenhouse gas emissions. Using more natural gas in power production has been beneficial to the Texas economy as well, since most of the gas burned in the state is extracted in the state.
But a known challenge related to natural gas is that it is more difficult to store materials that are vapors (gaseous) than it is to store solids or liquids. Gas can be compressed and it can be liquified by cooling it to extremely low temperatures, but both of those processes add costs and consume power.
Without any source of revenues for power generations other than selling electricity, there are no reasons why any generator would spend money to store fuel on site to use in the rare case where there are interruptions in the fuel supply.
Even in fair weather, only a portion of the methane that is extracted gets burned to produce electricity. Some of it gets used as a raw material for petrochemicals and plastics. Another portion gets used in cooking – both residential and commercial – while another is used in industrial process heat and to heat water in both homes and large buildings.
During cold weather events, heating buildings quickly grows and can become larger than all of the other uses combined. But natural gas production rarely increases when the weather gets cold. During the event that lasted from Feb 11-Feb 18 2021, daily gas extraction fell by nearly 20% due to various issues in the system.
The predictable, though not often publicly predicted, effect of a high dependence on natural gas to supply its usual amounts of electricity, to expand its production to make up for low wind and solar production, and to supply building heating systems is a system where some needs are not met.
Under the low cost, just-in-time, fuel supply model that is an inherent result of an “energy-only” market scheme, there is simply not enough fuel in the system to supply all demands all of the time. When the fuel that supplies the majority of the power generators in a system is stressed, all generators that burn that fuel can be affected.
In the lingo I learned as an operating power plant engineer and as a participant in a power plant design project, insufficient gas during a cold weather event is a predictable “common cause failure” for an electricity supply system.
As designed, the market uses pricing signals to balance demands with supply. But those price signals have to be dramatic to change behavior because both supply and demand have a large amount of inertia and cannot be easily changed.
When price signals aren’t sufficient to change behavior fast enough, the only option the grid operator has left is to balance demand with available supply by turning off the power to some customers.
What about the nuclear plants?
At 0537 on Monday, February 15 South Texas Project unit 1 tripped off line. (That link includes far more details about the event than can be fit into this post.) Other than that single event, all 93 of the 96 nuclear plants in the US that were operating before the cold weather event began continued producing as much power as they were asked to produce.
The only nuclear power station that did not produce as much power throughout the event as it possibly could have produced was Arkansas Nuclear One. For part of the week, the regional transmission operator asked the plant operators to supply less than their plant’s design power in order to keep the system in balance.
Here is a quote from an Entergy Arkansas spokesman explaining that period of less than 100% power.
Arkansas Nuclear One’s dual units continue to operate safely and securely throughout the weather event, with essential functions staffed by Entergy’s team members. Both units currently are operating at reduced power at the request of the independent grid operator.
The Midcontinent Independent System Operator is an not-for-profit organization that works to ensure reliable power supplies in part of Canada and 15 U.S. states, including Entergy’s service territory in Arkansas, Louisiana, Mississippi and portions of Texas.
In doing so, MISO often asks generation facilities to change power levels during times of potential grid instability. Entergy’s regional generation facilities are coordinating closely with the grid operator, and power levels at our plants may continue to rise or fall as the dispatcher works to keep transmission functions stable.Direct message from Entergy Arkansas (@EnteryArk)
Approximately 60 hours later, STP 1 returned to service and increased its output to its maximum capacity. That lengthy shut down exposes one of the reasons why there have been few new nuclear plants built in the US during the past 30 years.
The large, light water nuclear power plants that were selected to be built commercially in the 1960s-1990s work best if run steadily. If they are taken off line for any reason, power restoration can take many hours to several days. While it might be possible to improve that situation for existing reactors, it is best done via a meticulous, methodical, time consuming path.
Under our current construct as refined by many decades of continuous operational improvements, nuclear plant shutdowns and start ups are rare events. They happen less than once per year at each unit.
If the population size for nuclear reactors is restricted to the four units physically located in Texas, the operational score for nuclear during the 5 days of rotating outages turns out to be about 86%, which should be a solid B in most grading systems. (That is calculated on power produced compared to the power that could have been produced if all four units operated perfectly throughout the event.)
But given the widespread nature of cold fronts and the impacts of stresses in the nationwide natural gas delivery system, it might be fair to include the performance of a larger population of nuclear plants. 92 out of 96 operating at or near 100% produces an A in almost every known grading system.
On the scale of producing as much power as expected by grid planners, nuclear did about as well as it was expected to do. It’s not a perfect power source; there are numerous ways for systems to fail to produce at 100% of rated output 100% of the time. But nuclear met or exceeded some pretty high expectations.
It is important for systems planners or people who influence system planning actions to recognize that nuclear plants offer several important features. Among its strengths is its independence from the common cause failures of fuel supply constraints and direct dependence on wind and sun availability.
It is also a clean power source, with life cycle CO2 emissions that rival onshore wind and beat both offshore wind and most solar systems. It produces virtually zero air or water pollution. Its ‘waste’ heat could become a valuable resource if systems were properly designed to use it beneficially.
Were lessons available from the Texas cold weather event of 2011 (Super Freeze) actually learned?
It’s not accurate for people to claim that the freeze of 2021 was a complete surprise or had no precedent in history. Galveston Bay has frozen solid several times in the past 50 years. In 2011, there was a cold weather event that brought temperatures just as cold and just as widespread as those experienced this year, though that event was shorter.
Many of the recommendations from 2011 post event reports were not implemented. The state persisted in pursuing its fierce grid independence. A substantial increase in wind power generation was accompanied by a growing boom in solar energy and major new transmission lines to move their power. Natural gas dependence has increased by double digit portions.
As much as it pains me to admit this, if the nuclear plant construction plans that were announced in 2007-2009 had been pursued, they would not have helped avoid the issues that appeared.
It’s difficult to prove a counterfactual historical point, but it’s easy to point to the only US nuclear project that survived from that brief period of excitement about new nuclear power plant construction. Vogtle units 3 & 4 will not enter service until sometime in the next two years. They were the leader projects from the Nuclear Renaissance and they are still not complete.
The next time we revive the nuclear plant construction industry, we must do a better job. We must achieve better cost and schedule performance and we must make design choices that recognize the importance of flexibility and responsiveness. That might include implementing some of the speedy recovery capabilities that have long been a part of military nuclear power plant design and operations.
If society determines that it is unacceptable to have a power grid that cuts off customers for many hours at a time during a period when being without power can be deadly, it must accept the fact that markets cannot be the decision makers.
Cheapness on a short duration scale – like 5-minute settlement markets – cannot be the sole criteria for selecting power sources.