July heat produces record power peaks, little wind

August 24, 2011

Both the Midwest ISO and PJM Interconnection, the RTOs overseeing the transmission systems that include Wabash Valley’s service territory, reported that electricity use in their areas hit record levels in late July.
 
The widespread heat wave that gripped much of the nation and the resulting demand for air conditioning increased PJM’s total load to 158,450 megawatts at 5:00 p.m. on July 21, ahead of the previous peak of 158,258 MW that had been set on August 2, 2006. The day before, MISO recorded a record peak of 103,975, which also broke a 2006 record. (One megawatt of electricity is enough to power about 1,000 homes.)
 
On July 20, Wabash Valley Power set its own record, with the total load peak (including pass-through loads to large industrial customers) reaching 1,916 megawatts. The peak could have been higher on July 21, but some large users had agreed to reduce consumption.
 
“The nation’s power grid handled the demand without any problems,” said Manager, Portfolio & Risk Kari Wetter. “It appears that part of the reason for the new peaks is growth in the economy that has increased industrial energy use. You’ll recall that last summer was also very hot, but the economy had many businesses operating at reduced levels.”
 
A MISO prediction of an even higher load for July 21 created some heartburn for power providers. The RTO projected a shortfall, so it issued a Maximum Generation Emergency Event. Wabash Valley relayed that announcement to member systems, several of which implemented voluntary load-shedding efforts. Thanks to unexpected rain, cloud cover, and other voluntary reductions, the day’s demand fell well short of record levels, and MISO lifted the Event.
 
“The situation showed us that we need to better sync our own system with MISO’s,” Kari added. “We were following their three-step process, but we’ve learned that they have multiple additional steps within those three steps. Their communication chain is more complex than it seemed, and we may have been a little ahead of where they thought we should be. In the future, we’ll probably wait until we get more direct instructions from MISO and PJM before asking members for reductions.”
 
The record peaks provided a sobering reminder that wind energy may not come to the rescue when it is needed most. During the height of MISO’s peak, wind turbines within the system were producing no more than 840 MW out of a total capacity of just under 6,900 MW, or about 12 percent of the maximum. Wind produced a similar story in PJM’s territory, where 3,672 MW of capacity saw actual generation of just under 346 MW (or about 9 percent). It’s a reminder that what’s popular isn’t always dependable during high usage.