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Seeking resilience, organizations turn to microgrids

Supported by renewables and clean-burning propane or natural gas, microgrids produce power cleanly and affordably while protecting the reliability of the power supply.

By Jeffrey Lee

Staff Writer

Uninterrupted power is becoming an essential component of the resilience strategy for many organizations.

In an era where the electrical grid is aging and under threat from storms and disasters, power for data centers or emergency operations is more critical than ever. While individual buildings typically meet those needs with standby generators, larger organizations and campuses are turning to a more advanced solution: microgrids.

Microgrids go several steps further than a standby generator by incorporating multiple sources and uses of power, says Philip Barton, director of Schneider Electric's North American Microgrid Competency Center in La Vergne, Tennessee.

These "distributed energy resources" (DERs) can include batteries, propane- or gas-fueled generation, and renewable power such as solar. Microgrids integrate these resources into a reliable system that can run in parallel with the grid or, in the case of an outage, separate from it.

As organizations become more familiar with the capabilities of microgrids, analysts expect usage of the technology to grow rapidly. According to Navigant Research, global microgrid capacity is expected to grow from 1.4 gigawatts in 2015 to 7.6 gigawatts in 2024.

Reliability, efficiency, sustainability


An infographic from Schneider Electric highlights the benefits of microgrids.

Because they incorporate multiple sources of power, microgrids make facilities more resilient in the event of an emergency. But in many cases, they also offer a more efficient and sustainable source of power, Barton says. That's because they're able to incorporate clean or renewable inverter-based resources like solar power, battery energy storage, and propane microturbines, which wouldn't normally work without the grid.

A standard called UL 1741 requires that these inverter-based resources turn off when the grid goes down, so that they don't backfeed the grid and present a risk to workers. "That's why microgrids are so compelling," Barton says. "We just need to open the main breaker and control those resources, and then we can run without the grid. It allows you to keep the solar on or any other inverter-based resources, including propane microturbines or fuel cells."

Microgrids may also be able to produce power at a lower cost than the electric utility. By producing power onsite, instead of at a centralized utility, microgrids can eliminate the transmission and distribution losses associated with the grid. They can also utilize the heat generated from producing power as thermal energy for nearby buildings, an application known as combined heat and power, or CHP. Such systems can operate at efficiency levels of 70 to 80 percent.

Organizations with large or critical power needs are some of the best candidates to utilize the advantages of a microgrid, Barton says. That could include corporate or university campuses, as well as municipalities, emergency operation centers, military bases, and hospitals.

The easy button


  Microgrids
  Microgrids 
Click to enlarge 
 

Although they include multiple energy resources, microgrids require an anchor resource that provides a stable source of voltage and frequency. Gas-fueled onsite generation options, such as microturbines or standby generators, are excellent anchor resources, says Jim Crouse, executive vice president of sales and marketing for Capstone, a microturbine manufacturer.

"Because you can control the output, they can support the intermittency of other renewable sources like solar and wind," Crouse says. "They can also easily be incorporated into microgrids where there's renewables, storage, and some onsite generation."

For projects in locations that lack affordable access to natural gas, propane is a natural fit as a contributing or anchor resource. That was the case at Oncor, a regulated electric utility business in Texas. To demonstrate how microgrids and distributed energy resources can improve the grid, and to protect the critical loads at its System Operating Services Facility, Oncor worked with Schneider Electric to design a sophisticated microgrid that incorporated a variety of energy resources, including a 65-kW Capstone microturbine fueled by propane. (Check out a video about the microgrid here.)

"Propane was definitely the ‘easy button' for Oncor," Barton says. "They couldn't get the natural gas line there to sufficient pressure for a reasonable amount of money, so propane was the way to go."

If Oncor is a small-scale microgrid, the one on Catalina Island in Southern California is a much larger example. Southern California Edison provides all of the island's power, and with no access to natural gas, it used to rely solely on dirty diesel internal combustion engines for electricity. To update its outdated grid and meet California's strict air quality standards, the utility added 23 Capstone propane microturbines, which can be turned on and off in increments of 65 kW.

The microturbines reduced diesel fuel usage by about 10 percent, or 200,000 gallons, annually, according to Capstone. And the island's overall emissions profile improved, with annual reductions of about 8 percent for smog-forming nitrogen oxide emissions and about 9.5 percent for diesel particulates.

Backup energy storage

Even for projects with access to natural gas, propane may be the best choice for backup energy storage in the event of a natural gas outage. At Syracuse University's Green Data Center in New York, for example, 12 65-kW natural gas microturbines generate power alongside the grid. But instead of using diesel generators as backup, the microturbines can simply switch to a propane-air mixture from a storage tank onsite.

One reason to turn to propane is that it can be easier to store onsite than diesel, Crouse says. "Propane doesn't get algae growth, it doesn't need to be filtered or treated, it doesn't get old and wear out," he explains.


"Propane was definitely the ‘easy button' for Oncor."


Battery energy storage is also gaining popularity as the batteries become smaller and cheaper, but it remains an expensive option overall, Barton says. "We find sometimes that a propane system is a more cost-effective way to do energy storage and to be an anchor for the microgrid than the battery energy storage system," he says.

Organizations may turn to microgrids for a variety of reasons — storm hardening, increasing their use of renewables, or lowering their carbon footprint. But resilience is a growing concern for everyone. "It's been a growing trend, but after Superstorm Sandy and some of the natural disasters that have occurred, people are looking to make sure that in spite of their local electric utility, they have the ability to stay in business," Crouse says. "It's really about business continuity."

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