Stories are just beginning to emerge about microgrids and distributed energy systems that are keeping critical services up and running despite Hurricane Harvey’s best efforts to do them in.
Twenty-one convenience stores and gas stations in the Houston area remained open thanks to an unusual microgrid system designed by Enchanted Rock (ERock). The Texas-based company installs natural gas generators at commercial sites, which it aggregates into virtual power plant microgrids.
During normal operations, the virtual power plant provides support services to the central grid. When an outage occurs, the generators island from the grid and provide back-up power for their host sites. Buc-ee’s and H-E-B stores are participating in the program.
“We placed a lot of our operational sites in island mode Friday evening and Saturday morning, disconnecting our customers from the grid to ensure power stability and continuity,” Thomas McAndrew, ERock president and CEO told Microgrid Knowledge.
The stores and fuel stations are providing essential products and services — including water, food and fuel — that are helping residents survive and cope with the hardship. McAndrew added that one store is being used as a National Guard home base.
Meanwhile, crucial thermal energy continues to flow to the Texas Medical Center thanks to a Thermal Energy Corp (TECO) combined heat and power and district energy system.
One of the world largest medical centers, the 20-million square-foot complex houses eight hospitals and medical, dental and pharmaceutical schools. About $2 billion in medical research takes place at the center annually.
“Since our thermal services are used for critical services (hospitals and medical research) failure to supply these service will result in possible loss of life and decades of research material,” said Steve Swinson, TECO president & CEO.
Since Hurricane Harvey began, the TECO plant has maintained uninterrupted thermal services to its customers in the Texas Medical Center, he said.
“Much of the Texas Medical Center has experienced flooding, as much as four feet in some places. Fortunately, flood mitigation systems have protected the integrity of the buildings,” Swinson added.
Flooding creates new abnormal
Despite the successes of these systems, industry observers say it is likely at least some of the distributed energy systems in the Houston area are flooded and inoperable. Considered one of the most destructive storms in U.S. history, slow moving Harvey is dumping an historic amount of rain on Houston and the souheast Texas Gulf Coast — likely a year’s worth in less than a week, according to meteorologists. The New York Times on Monday said Houston looks like an inland sea dotted with islands.
And few in the Houston area are likely counting on microgrids for power because the technology is still relatively scarce in Texas. The state has just begun to install the new and advanced breed of microgrids — and without the urgency of states like Connecticut, New Jersey and New York, which are spurred by memories of Superstorm Sandy in 2012. Navigant Research identified 13 microgrids from its data base that appear to be in areas of Texas flooded by Hurricane Harvey.
Public officials expect cleanup to be slow from Harvey, given that it was one of the most destructive storms in U.S. history.
Texas Gov. Greg Abbott has warned that Houston residents will need to adjust to a new normal for some time. It appears the storm also is creating a new normal — or rather abnormal for energy systems — given the massive amount of flooding caused by a continuing deluge of rain.
Days after the hurricane hit, with rain continuing and waters rising, ERock finds itself entering a more complex management of its microgrid systems.
“This will require very close coordination between ERock and H-E-B/Buc-ee’s to ensure our microgrids do not energize flooded stores. Although we have automatic protections to prevent equipment damage and personnel injury, we would rather deenergize preemptively and are currently developing those protocols in real-time,” said McAndrew in an email Monday morning
Ken Horne, Navigant Consulting energy director, pointed out the massive flooding could change longer term thinking about how to build and manage microgrids.
Recent Northeast storms, such as Hurricane Irene and Superstorm Sandy, brought about power outages from widespread loss of overhead power line service and more targeted and isolated flooding of critical infrastructure (substations and generators for example), Horne said.
However Harvey’s damage appears be less from wind and more from widespread flooding. Wind brings down power lines. Flooding may not affect power lines, but could submerge local transformers and generators.
“The problem is much closer, and your own generator needs to be sufficiently hardened–say installed on stilts, or on the roof, instead of in your garage at flood level,” Horne said.
Microgrids and Hurricane Harvey: Will the conversation now change?
Harvey could change the conversation around what constitutes resiliency.
“The conversation in the Northeast has been largely about the presence of resilient infrastructure — do you have a microgrid at all, or not,” Horne said. “In the case of Harvey, we might find that the conversation becomes more nuanced. Did you have resilient infrastructure and did you have it in the right place? Were your microgrid system assets installed above the water line?”
The energy industry may also find itself doing some soul searching about best fuel choices for the most extreme weather.
Those relying on traditional diesel fuel generators or diesel-powered microgrids to provide emergency back-up electricity services are limited in their ability to cope in this particular situation. Downed trees and power lines, along with flooding and record cold have made it impossible to deliver fuel to many areas.
“With diesel backup you also need diesel day tanks,” said Justin Day, senior marketing program manager for Schweitzer Engineering Laboratories (SEL). “Once those are gone, what do you do? With natural gas, tanks and pipelines are typically buried underground, so that gives you a bit of added resilience that can be really critical in times like these.”
Houston-based Swift Equipment Solutions had announced it stood ready to provide as much as 20-MW worth of industrial-sized diesel fuel generator capacity throughout the Texas Gulf Coast area as Harvey made landfall.
But the damages and chaos left Swift unable to distribute any diesel fuel gensets or fuel outside accessible areas of Houston itself, marketing representative Mark Lum told Microgrid Knowledge.
“This is a one in a 500-year flood event. The last I heard we were unable to get diesel generators or fuel inside or out of the Houston area. Flooding has made it impossible to get out of Houston to deliver to surrounding areas, such as Corpus Christi, for instance.” Furthermore, road access is restricted to authorized emergency vehicles, he noted.
“Once roads are impassable due to downed trees, flooding, ice and other obstacles associated with extreme weather events, electric generation is limited to fuel stored on site,” said ERock’s McAndrew “And the more fuel you store on-site, the more issues you have with maintaining that fuel usable as there is about a six-month shelf life for Ultra-Low Sulfur Diesel.”
ERock made the strategic decision to switch from diesel fuel to natural gas-fueled microgrids and emergency electricity generation services in 2014. The company installed its first digitally networked natural gas-fueled microgrid at a customer site in Texas in 2016.
McAndrew said it would be “difficult, if not impossible, to refuel with diesel given the extensive street flooding. We’re very thankful we transitioned to natural gas. We have not seen any drop in natural gas pipeline pressures, even given the extensive flooding.”
He also is skeptical about how well microgrids could weather a Harvey-type storm if they rely solely on solar and battery energy storage.
“Our entire business is based on resiliency microgrids, services we could not provide if we did not rely on natural gas,” he said. “The sun has barely been out, and probably won’t be for four or five days before this is over. We could not provide emergency electricity services without some type of liquid or gaseous fuel. Solar energy storage just couldn’t get the job done.”
When the water subsides…
Diesel, natural gas, solar, storage, microgrids and Hurricane Harvey are likely to dominate energy and resiliency conversations for some time to come. Exact lessons are still murky. They will become apparent as the water subsides and reveals the damage to electrical infrastructure.
Meanwhile, ERCOT, the grid operator for much of Texas, reported more than 300,000 outages over the weekend due to Harvey. Several transmission lines were still out of service as of late Monday. The storm had knocked out about 6,700 MW of generation capacity, including a very small percentage of renewables.
Power use had fallen significantly to roughly 20,000 MW, well below the August peak of just under 44,000 MW. ERCOT attributed the lack of power use to a combination of structural damage along the coast and cooler temperatures.