As summer nears, old plants go back on grid

With the official start of summer just a few days away, electricity planners in Texas are preparing for its full blaze by bringing some older power plants back online to meet the increased demand for air conditioning and to help avoid last summer’s threat of power blackouts.

The Electric Reliability Council of Texas, which operates most of the state grid and manages the deregulated Texas wholesale electric market, has said it will bring mothballed plants with nearly 2,000 megawatts of generating capacity back into operation this summer.

“A lot of this target reserve margin comes from plants nearing the end of their useful operating life,” said Warren Lasher, director of system planning for ERCOT. “That is really the role of these older gas and steam units – they don’t run often. They are available in case of weather situations and extreme outages.”

A megawatt can power about 200 residences during periods of peak demand, typically late in the afternoon on summer days, so these plants of last resort will provide enough capacity for an additional 400,000residences during those times.

ERCOT expects that this additional available power will be sufficient to ensure enough electricity, even if the summer conditions are extreme.

One of the mothballed plants, Unit 3 at NRG Energy’s SR Bertron plant in Deer Park, was fired up on Tuesday for the first time this year, giving the Texas power grid an additional 210 megawatts of capacity – enough to supply power for about 42,000 homes during peak demand.

Built in 1959

Unit 3 was built in 1959, and NRG spent about 10 weeks getting it ready for operation through a series of maintenance procedures that included installing an auxiliary oil pump for the generators and repairing or replacing 31 condensate pump recirculators, which help move air around to cool the water circulating in the system.

Individual power generation companies make the decisions on whether and when to make a particular plant active again, based on the expense of running it relative to other power plants.

Coal plants historically have been less expensive to run than natural gas plants, although the low price of natural gas is reversing that order for newer, more efficient gas plants.

The more a plant costs to operate, the less likely that a company will run it under moderate weather conditions.

‘Hotter than expected’

“They only run on days that are hotter than expected, or when the other plants are off for maintenance,” Lasher explained.

After NRG or another generating company brings a mothballed plant back online, it won’t necessarily run on any given day as the companies determine which of their plants will provide the most cost-effective electricity.

Because of the high cost of keeping a plant available for what may be just a few hours of use, the Public Utility Commission of Texas has allowed wholesalers to charge up to $3,000 per megawatt-hour for electricity on days where electricity is scarce.

Raising the cap?

The PUC is considering raising the cap for peak power generation to $4,500 per megawatt hour. While wholesale electricity costs far less than that under normal conditions, the idea is that raising the cap would provide an incentive for generating companies to invest in new plants.

In Texas’ deregulated power system, retailers buy power from generators, then sell it to residences and businesses. So a rise in the peak wholesale price eventually would increase the average wholesale price, and end users would see higher bills.

While older plants can still be profitable when the wholesale price nears the cap, having a mothballed plant ready for use when needed requires continuing maintenance while it is out of service. For example, at the Bertron plant, operators will empty all the water from Unit 3′s steam boilers at the end of the summer and replace it with anti-corrosion chemicals to impede rust.

Preparedness

They also will also run heaters to maintain the electrical gears and keep the huge turbine generators slowly rotating, to keep their long rotation arms from buckling under their tremendous weight.

“We do a lot of work to preserve a plant and make sure it can come back online,” said Tim Gessner, vice president of plant operations for NRG Energy, as he described the detailed process for ensuring that the plants will be ready when needed.

“We are very much a group of planners,” Gessner noted. “We plan and schedule to get these units going – it is all about preparedness.”

emily.pickrell@chron.com