High winds and tornadoes tore across the Dallas area Sunday night, leaving about 140,000 customers without electricity, but four stores with microgrids rode out the storm without interruptions to their power supply.
Those stores —H-E-B and Buc-ee’s — have backup natural gas microgrids from Enchanted Rock, a Houston based company. ERock, as the company is frequently known, installs, owns and operates gas-fired generators at customer sites. ERock takes on the capital costs while customers pay a fee under ERock’s microgrid-as-a-service business model.
ERock has signed deals with H-E-B, a privately held grocery chain with 370 stores in Texas and Mexico and with Buc-ee’s, which owns a chain of 32 convenience stores and travel centers in Texas.
Under a 2016 deal, ERock installed 50 MW of backup generators at dozens of H-E-B locations across Texas and has since expanded that to 131 MW. Also in 2016, ERock signed a deal with Buc-ee’s to provide backup power to all the chain’s current and future locations.
Stores help first responders
“We are very happy with ERock’s microgrid,” said Jeff Nadalo, general counsel at Buc-ee’s. “We’re able to offer our customers a consistent experience, and they know our locations with backup power will be there, and especially in a natural disaster, we’ll be there to help first responders and in assisting community.”
When Hurricane Harvey hit Houston in 2018, the microgrid at a Bus-ee’s store in Katy, Texas, kept the lights on, enabling the store to be used as the base of operations for a National Guard unit, a search-and-rescue team, and several state agencies.
Buc-ee’s has ERock microgrids at all its locations that are in Texas’ competitive wholesale market.
Access to the competitive market is part of Enchanted Rock’s business model. When a microgrid is not being used for backup power, ERock aggregates the capacity of its generators and sells energy and ancillary services into the wholesale power market to help keep costs down for its retail customers.
When the storms swept through the Dallas area, those four stores lost power for about 10 seconds as the microgrid generators kicked on and smoothly transitioned the stores to backup power. The microgrids kept the lights on until the utility restored power to the stores, which took about 30 minutes for three of the stores and over a day for the fourth store. Other utility customers in the region were not as fortunate with some still without power on Monday.
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Because they are fueled by natural gas and the generators on site, ERock’s microgrids offer “extreme resiliency,” said Allan Schurr, chief commercial officer at ERock. In addition, there are usually multiple generators at a single customer site, he said.
ERock meets a customer’s electrical needs at a site by configuring the needed array of 450 kW generators. The use of multiple generators provides redundancy, but it also helps keep costs down for customers because it allows ERock to use standard components and “scale out with the same design,” Schurr said.
How ERock’s microgrids work
When voltage dips at the generator bus at a customer site, the system instantly fires up all generators at the site, with one generator becoming the lead and the rest synchronizing to that generator. That enables the backup system to carry the store’s full load within seconds, Schurr said.
When the microgrid senses that grid stability has returned, it automatically synchs to the grid and switches back to utility power as the generators begin to cool down. That avoids the secondary outage that often occurs when a backup diesel generator shuts down and utility service returns, Schurr said.
With storms and extreme weather apparently becoming more frequent – nearly 220,000 customers in the Dallas area were left in the dark by a series in June – the level of interest in microgrids is rising, Schurr said. “This is becoming more of a topic when people realize there is something they can do about outages,” he said.