Enchanted Rock’s Microgrids Pull Double Duty with Both Backup, Grid Support

Sometime, somewhere, the power is going to go out. Maybe for a few minutes or a few hours. Starting with Winter Storm Uri in February 2021, most Texans have endured a blackout longer than a day.

Outages of that length aren’t just inconvenient. They’re expensive, destructive and life-threatening. Texas energy provider Enchanted Rock helps to mitigate the aftershocks of grid failure.

The company’s natural gas-powered microgrids, placed on site, start up in an instant when the main grid fails. One well-known Enchanted Rock customer is the H-E-B grocery store, which began installing the microgrids in 2016. Another is the city of Houston, where Enchanted Rock has placed a 30-megawatt microgrid at the Northeast Water Purification Plant.

“Our core business is providing backup power to what would be considered critical infrastructure customers or businesses for which having power is essential to the mission that they are pursuing,” said Allan Schurr, Enchanted Rock’s chief commercial officer. “We do hospitals and assisted living facilities. We do data centers, we do military bases, we do chemical companies for which a power outage creates a risk of a plume of emissions that would be hazardous.”

Another part of the business is sending power in the other direction. Those same microgrids, about 350 in total, also support the main grid, sending power to the Electric Reliability Council of Texas (ERCOT) grid when it makes money to do so. All the microgrids are monitored from a control room near downtown Houston, which has two backup locations.

“We call it a dual-purpose microgrid,” Schurr said. “The grid needs help during hot afternoons, during cold nights. There's lots of times where the supply and demand are imbalanced and we are one of those resources that help fill that gap.”

That’s what happened when Uri struck in 2021 and the ERCOT grid lost multiple sources of power and almost fell out of balance. Natural gas was frozen in, wind power fell below normal and the sun was barely shining. Enchanted Rock picked up some of the slack.

“We ran straight out during that Uri event, eight straight days,” Schurr said. “All of our generating assets in Texas were running to support the grid.”

The microgrids are arrays of natural gas generators, almost 2,000 of them. The number of generators determines the size of the microgrid.

The generators are “basically the same design” throughout the fleet, Schurr said. “There might be different vintages of certain components, but we take that into consideration.”

The standardized generators are also designed with simplicity in mind. Two can fit on a regular truck load, no special permit required. It’s easier to train and equip technicians.

Pete DiSanto, executive vice president of products, said the standard design makes maintenance more efficient. If one generator develops a problem, the company’s technicians can check all the others for the same problem.

“We're also developing our own AI where we're bringing graphical representations of how the generators are operating, so we can identify real quick and say this just doesn't look right,” DiSanto said.

The generators are rated to run 50,000 hours, and on average they run 500 hours a year. They’re designed to work in the 22nd century, although Schurr said that’s unlikely.

“It could be obsolete but it’s not going to have failed,” he said. “There could be something better [to replace it]. We just look at the economics.”

They can also respond quickly, in about the time it takes to read this paragraph. They’re an ideal fit in ERCOT’s real-time electricity market. Bigger plants can take 10 minutes to 30 minutes to get up to speed, and then they need to stay on for a while to justify the startup costs.

“For us, when our units start, it's 30 seconds, boom, we’re hitting the grid, we're ready to go,” DiSanto said. “If you look at the price of one 5-minute print (on the ERCOT real-time market), that will be elevated. We come in and execute on that. By the time those turbines start up, the prices already get back down.”

One more thing: Businesses that know they will have reliable power behave differently. Schurr said H-E-B used to try to pre-position backup generators when a hurricane was in the forecast. When the storm took an unexpected turn, the generators were out of position.

Now “they count on the fact that all their stores are going to have power,” Schurr said. “They put out stuff that their customers want after an emergency. They stock it beforehand so that immediately when a customer needs something after an emergency, during an emergency, they've got it at H-E-B.”