Texas heat brings power plants out of mothballs

Four mothballed power plants will come back online in the coming weeks to help ensure Texas’ main electric grid can handle demand for the rest of the summer.

Two Houston-area plants owned by NRG Energy and two near Dallas owned by Garland Power & Light will return to service at the request of the Electric Reliability Council of Texas.

NRG says the two natural gas-fired units at the SR Bertron plant in Deer Park along the Ship Channel should be up and running by Sept. 1. The units, with a combined generating capacity of 292 megawatts, were taken offline in 2010.

Garland Power & Light’s two natural gas-fired units, with a combined capacity of 122 megawatts, could be online as early as next week, said utility spokeswoman Elizabeth Kimbrough.

A megawatt is enough to power about 200 Texas homes during the summer months, when air conditioning use is at its peak, according to ERCOT.

A combination of record high temperatures and a large number of plants going offline for unplanned maintenance in recent weeks drove the state’s main electric grid into crisis several times.

The state set a power use record on Aug. 2 and on Aug. 4 came close to rolling blackouts for what would have been just the fourth time in 21 years.

Hot weather came early this summer and has been much more intense than grid operators expected, leading to longer running times for many power plants and more frequent maintenance problems.

Cooling issues

The drought that has gripped much of Texas has not yet forced power plants to cut back operations, but ERCOT CEO Trip Doggett said it may become an issue later this summer.

Several plants have had problems when the temperature of water in cooling reservoirs didn’t drop enough overnight, leading to less efficient operations.

“Without rainfall in the near future, we anticipate increased generation outage rates because of power plant cooling water issues,” Doggett said.

ERCOT is required to make sure Texas has enough power plant capacity online to ensure a safe margin between supply and demand, but it generally can’t force a company to run a power plant.

In some parts of the country companies receive what are called capacity payments throughout the year to have power plants ready and available.

But ERCOT is an energy-only market, meaning market prices for power are supposed to provide the incentive for plant operators to keep units online.

In the case of the four units coming back online, ERCOT will pay the costs of taking them out of mothballs and cover their fixed costs, such as staff, maintenance and fuel.

ERCOT will call on the units only when necessary to avoid emergencies, so they won’t displace units that are online and bidding into the wholesale market, Doggett said.

“We don’t know if, or how much, these units will be needed, but if needed, the cost will be minor when divided by the 23 million consumers in the region and when compared to the much higher costs and problems from statewide rolling blackouts, which these units will help avoid,” Doggett said.

Electricity managers also can increase the margin between supply and demand by reducing demand.

Rolling blackout plan

Two statewide programs designed to prevent rolling blackouts call for industrial customers to drop nearly 1,300 megawatts of demand in an emergency.

Smaller demand reduction programs aim at residential customers.

Austin Energy, the city-owned utility for the state capital, provided free digital thermostats to nearly 90,000 homes in exchange for permission to reduce their air conditioning twice per hour for 10 minutes at a time from 4 p.m. to 6 p.m.

An Austin Energy spokesman said the program reduced peak demand by 35 to 45 megawatts.

TXU Energy has a similar program in the Dallas area.