Microgrid System Keeps Houston Grocery Stores Open in Wake of Harvey

A Houston-based microgrid company has used its on-site generators and underground natural gas pipeline system to enable H-E-B grocery stores in the Houston area to remain open despite power outages and massive flooding during and in the aftermath of Hurricane Harvey.

Texas utilities have reported more than 300,000 customers have been without power at various times due to the storm. The Department of Energy (DOE) is issuing periodic updates; DOE on August 29 said more than 270,000 customers in Texas remained without power, with 2,700 customers in Louisiana also without electricity.

Enchanted Rock, which designs backup power systems for businesses, installed its microgrids at H-E-B supermarkets around Houston over the past year after signing a deal with the grocery chain in 2016. The systems receive natural gas from underground pipelines that are not affected by flooding or high winds.

An Enchanted Rock microgrid system is shown outside an H-E-B grocery store in Houston, Texas. Enchanted Rock has installed the natural gas-powered generation system at H-E-B stores and other businesses in Texas. Courtesy: Enchanted Rock

Replacing Diesel Generation

Thomas McAndrew, Enchanted Rock's CEO, told POWER in an August 29 phone interview that H-E-B approached his company about the microgrid technology after previous storms in the Houston area affected the grocery chain's ability to move its diesel-powered generation sets among stores and other locations.

"They have a fleet of diesel gen-sets that are trailer-mounted, and it's been a challenge from a logistical standpoint getting their trucks from place to place," McAndrew said. "As the largest grocery store chain in Texas, they have a commitment to keep as many stores as possible open in extreme weather events. After those previous storms, those guys said 'That's enough, we need to have a way to have power generation permanently installed.' We told them we have a solution that makes sense, a permanently installed natural gas microgrid, where we own the equipment and they pay the fuel costs and a small service fee."

McAndrew said his company manages about 60 MW of diesel-based systems in Texas in a partnership with Houston-based NRG Energy, along with 167 MW of such projects financed independently by Enchanted Rock. McAndrew said the system installed at H-E-B, along with similar systems at other locations in the region, including the Buc-ee's convenience store and truck stop chain, is the first in which natural gas is the prime fuel.

The natural gas feed enables the microgrid generators to operate continuously without the need to refuel, as opposed to diesel-powered generators that would require fuel deliveries during bad weather. Various types of microgrids have been utilized for years, and more recently have been discussed as a way to provide reliable power in the event of a natural or other disaster.

The company said it took H-E-B stores with the microgrids off Houston's main power grid on August 25, as Hurricane Harvey made landfall along the Gulf Coast in southeast Texas, and switched the stores to Enchanted Rock's on-site generators. Though San Antonio-based H-E-B closed stores on August 27 due to safety concerns as flooding worsened in Houston, several stores were able to reopen soon after thanks to the power provided by the microgrid.

Utility-Grade Power

H-E-B regional spokeswoman Cyndy Garza Roberts told the San Antonio Business Journal that 18 of the company's stores using power from the microgrid included some that had briefly closed due to flooding, but were still able to keep their refrigerators running. The San Antonio-based grocery store chain reported it has more than 60 stores open in Houston and the surrounding area.

"We design our microgrids to provide utility-grade power," said McAndrew. "We design for rock-steady voltage and frequency. The customers have no idea whether they're on the grid or on the microgrid."

McAndrew said a Buc-ee's location west of Houston using the Enchanted Rock system has been able to maintain power despite several outages in that area. The location is housing first responders to the Houston flooding.

-Darrell Proctor is a POWER associate editor (@DarrellProctor1, @POWERmagazine)

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