The Midcontinent Independent System Operator faces increasing uncertainty regarding both loads and generation over the next decade, but efforts are underway to help address the situation affordably and reliably, MISO board members learned at a March 24 meeting in Memphis, Tennessee.
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"There's much work ahead of us as a MISO community to ensure that we make a safe, reliable, affordable transition for the consumers that depend on us for their lives and their livelihoods," said Clair Moeller, MISO president and chief operating officer. "Unfortunately, we will have to make some choices rather urgently in order to accomplish that, and that's going to put great stress on many of us."
Efforts to address volatility proactively include implementing a seasonal capacity market construct, enhancing forecast and system management tools, planning "robust transmission solutions" and working with policymakers and stakeholders to provide better informed and more timely solutions, said Wayne Schug, MISO vice president for strategy and business development.
"We can't wait until the problem is right in front of us," Schug said. "We've got to make sure that the pieces are all in place before the problem hits us."
Increasingly frequent extreme weather conditions and increasing decarbonization are causing increased "variability and volatility of the load-supply balance," according to the written presentation that accompanied the "strategy update" that Moeller and Schug made to the board.
In the past, electric grid operators handled relatively predictable volatility related to loads, weather and system outages of generation, transmission and distribution, Schug said.
"So, from a planning horizon perspective, we were looking out at seasonal peaks, wondering did we have enough steel in the ground to meet those seasonal peaks as well as account for expected losses during those peak periods," Schug said.
Extreme weather impacts
Weather in the past has primarily influenced loads, but now increasingly extreme weather conditions not only affect load but also weather-dependent resources such as wind and solar power.
MISO has had 14 maximum-generation events – in which all generation resources were told to suspend outages and return to service, if possible – since 2016, Schug said.
In 2020, wind and solar accounted for about 13% of MISO's generation mix, Schug said, but that number is forecast to grow to 26%-46% of the mix by 2039, depending on the scenario.
In 2008, hourly wind output varied from near zero to about 1.8 GW, but in 2021, that number rose from a range of about 1 GW to a high of more than 20 GW, the presentation states.
"Our greatest 24-hour change in 2017 was about 11.7 GW [of wind output level]," Schug said. "In 2021, it was 19 GW. That's a major daily change."
MISO has successfully reduced its average wind output forecast error, but the "actual error that we've got to manage continues to increase," Schug said.
"Our four-hour-ahead [forecast error] in 2017 on average was about 650 MW; today, it's closer to 900 MW we have to manage," Schug said. "To caution you on averages, the extremes were much higher than that."
Moeller said MISO is hiring meteorologists to help reduce weather-related generation and load forecast error and working with wind operators to provide more granular meteorological data.
"The biggest operating problem is in the morning, when the diurnal wind pattern is reduced and load is increasing," Moeller said. "We had one very bad miss where we actually had to deploy reserves because we'd missed the [weather front forecast] by an hour."
MISO's solar capacity is relatively small, about 2.4 GW, but is expected to grow to 39 GW by 2039, which is also likely to be affected by weather forecasts, as the Great Plains has more frequent overcast and snowy days than California, for example, Schug said, citing how solar output performed the first week in March, and how it would vary in 2039.
"Right now, that 1.7-GW daily swing you see on March 1 would grow to a 28-GW daily swing [in 2039] up and down that needs to be managed," Schug said. "That's a 9-GW-per-hour morning ramp and about a 9.5-GW-per-hour evening down ramp to manage. You have to manage that while you're also managing the morning load ramp and managing the typical wind morning ramp downs. Often, those offset ... but they don't always."
Decarbonization efforts have partly focused on increasing electrification of various sectors, such as transportation, and MISO has forecast several scenarios implying big changes in load patterns. For example, winter loads in 2040 could jump from less than 100 GW to as much as 200 GW, and summer peakloads could ruse from 117 GW to 209 GW, the written presentation states.
Decarbonization may also have a big effect on power flows across seams, Schug said. For example, PJM in 2020 transmitted power into MISO in 2020 at a level of 5-6 GW, as low-cost gas-fired generation supplied more power to MISO, but as decarbonization progresses to 2040, the flow could be reversed, with MISO renewable resources supplying as much as 4 GW of PJM load, the presentation states.
Decarbonization is also affecting the generation fleet, Schug said.
"We're seeing less predictable dispatchable generation," Schug said. "We're seeing retirements, we're seeing forced outage rates increase in those assets we depend on to manage that increasing variability and volatility. ... So while volatility is increasing, our ability to deal with it is decreasing simultaneously."