© Reuters. FILE PHOTO: An electrical line technician works on restoring power after a tornado Vilonia, Arkansas April 29, 2014. REUTERS/Carlo Allegri
By Scott DiSavino
(Reuters) -The power grid in the Central United States could be forced to impose rotating blackouts on some of the hottest days of the summer due to rising demand and plant retirements, federal energy officials said in an online energy comment on Friday.
Extreme weather is causing increasing challenges for power grids across the United States, and officials are concerned that record heat and drought could result in rotating blackouts in several regions in the western half of the country.
In addition to the shutdown of coal and nuclear plants over the past year, the Midwest’s summer generating capacity is threatened by planned maintenance and forced outages, as well as seasonal factors like low wind conditions.
The region’s grid operator, the Midcontinent Independent System Operator (MISO), has already warned of potential capacity shortfalls and other reliability concerns in the north and central regions of its coverage area.
MISO operates the power grid for some 42 million people in 15 U.S. Central states from Minnesota to Louisiana and the Canadian province of Manitoba.
The northern and central regions of MISO’s coverage are at “increased risk of temporary, controlled outages to preserve the integrity of the bulk electric system,” MISO has said.
The U.S. Energy Information Administration (EIA) said in the “Today in Energy” section of its website on Friday that forecast demand in MISO could reach an hourly peak of 118.2 gigawatts (GW) under normal conditions this summer and 125.2 GW in extreme conditions.
To meet that peak demand, MISO expects to have 143.2 GW of capacity available this summer. But planned maintenance and forced outages could reduce that capacity, EIA warned.
Reductions could leave MISO with just 114.9 GW of generating capacity, which is less than its summer demand forecasts.
One gigawatt can power about a million U.S. homes on average, but as little as 200,000 on a hot summer day.
In the past five years, MISO’s summer capacity has been reduced by an average of 6.7 GW of maintenance outages, 14.4 GW of forced outages and 9.6 GW of seasonal derates like drought, low-wind conditions and fuel supply limitations, EIA said.
One of the biggest power plants in MISO to shut over the past year was Entergy Corp (NYSE:)’s 0.8 GW Palisades nuclear reactor in Michigan, which was retired in May after more than 50 years of operation.
MISO said it and member utilities have trained for worst-case scenarios this summer and are prepared to take actions to maintain grid reliability.
Those actions include urging homes and businesses to conserve energy, limiting power plant and transmission line maintenance during heatwaves and, if necessary, imposing rotating blackouts.