Fossil-fuel electric generation challenged in Texas heat wave, raising reliability questions
Energize Weekly, July 6, 2022
An early season heat wave in May tested the Texas grid, raising questions about the relation of baseload, fossil-fuel generation to wind and solar, according to analysis by the Institute for Energy Economics and Financial Analysis (IEEFA).
“Fossil-fuel proponents consistently argue that renewables are too intermittent to maintain grid reliability, and that wind and solar generation is replacing ‘dispatchable’ coal and gas, claiming these resources are always available when needed. But May’s early season heat wave in Texas showed just the opposite,” the analysis said.
To be sure, fossil-fuel plants still supplied the bulk of the power for the grid which serves 26 million people, the grid operator – the Electric Reliability Council of Texas (ERCOT) – said.
On May 3, ERCOT issued a warning that there could be record-setting demand by May 7 or 8, Mother’s Day weekend, as weather forecasts predicted a coming heat wave.
April and May are when fossil-fuel and nuclear plants are taken out of service for maintenance and as it is usually a period of moderate temperatures and low electricity demand.
As a result, two large coal-fired units were offline for servicing when ERCOT issued its warning.
Sandy Creek, a 933-megawatt (MW) facility, had been offline since March with a return to service date of May 14. That service date, however, appeared to have been the result of an extension of a deadline to get back in service, the IEEFA analysis said.
One of three units at the Martin Lake Steam Station was also down for service. The 800-MW unit was taken offline in mid-April and scheduled to return to operating at the end of May.
Then on May 8, a fire broke out at Unit 8 of the W.A. Parish Plant southwest of Houston, operated by NRG Energy. The plant has a generating capacity of 3,667-MW with four coal-fired units and four gas-fired units. Coal-fired Unit 8 has a capacity of 610 MW.
The following day, a second Parish unit, Unit 7 with 577 MW of capacity, was forced offline.
“It is unclear if that outage is related to the fire at Unit 8; initially, NRG attributed the problem to a lack of coal and expected the unit to return to service in short order. Instead, it remained offline until May 19,” the analysis said.
Three of the four coal units at Parish were shut down for days-long stretches during May, with Unit 5 shut down completely May 25-30.
“So, as ERCOT began preparing for the early season heat wave, it was without almost 20 percent of its installed, supposedly dispatchable coal-fired generation,” the analysis said.
A record for May peak demand was set on May 9 at 70,000 MW. At the peak hour, wind and solar generation met nearly 38 percent of the total ERCOT demand.
“At the peak hour, solar generators produced 7,332MW compared to 7,039 MW for coal, a clear indication of the system’s changing dynamics,” the report said.
Then on May 13, in the midst of the heat wave, six natural gas-fired units tripped offline leading ERCOT to issue a call for customers to set their thermostats at 78 degrees Fahrenheit, conserve power and avoid using large appliances, such as dishwasher and washing machines between 3 p.m. and 8 p.m.
The grid was also without one of the two units at the Comanche Peak Nuclear Station. Unit 1, with 1,205MW of generating capacity, had been taken offline in mid-April for overhaul work and was not scheduled to resume operation until May 15.
The IEEFA analysis noted that while it is crucial to be able to take fossil-fuel and nuclear plants offline for servicing, the opportunity for doing that work “is being forced into an ever-shrinking window between the cold snaps of January and February and early heat waves in May, both with potentially high electricity demand.”
“Clearly, gas and coal are not nearly as reliable or dispatchable as the fossil-fuel industry claims,” the report contends.