In September 2017, Hurricane Maria, a Category 4 storm packing sustained winds of 155 miles per hour, took direct aim at Puerto Rico. The hurricane devastated Puerto Rico’s electrical grid and left most of its residents without power for more than six months, according to the U.S. Department of Energy.
Today power has largely been restored on the island. The Environmental Defense Fund reports that an initiative is now underway to modernize Puerto Rico’s grid using a smarter, more resilient approach: microgrids.
Building a Safety Net
The U.S. Department of Energy defines a microgrid as a localized electric grid that can disconnect from the traditional electric grid and operate autonomously in the event of a power outage.
Microgrids typically include multiple energy resources that support critical, interconnected power loads within a building, campus or community. These resources may include diesel-powered generators, renewable energy installations (solar or wind), transmission lines and battery-based energy storage systems. Most microgrids are designed to back up or complement the local electric grid.
“Think of a microgrid as a safety net,” said Peter Shattuck, a renewable energy expert with Anbaric Development Partners who has helped customers update their microgrids to meet new climate change goals. “As your dependence on electricity to power critical functions increases, so does your need for a safety net.”
He notes that microgrids, by continuing to operate when the main grid is down, add reliability and resilience to the main grid. They can also help to reduce energy costs for their owners. When demand (and electric rates) are low, microgrids can draw power from the local grid. When the local grid is experiencing high demand and rates are high, microgrids can draw power from their own resources at lower rates or even send power back to the main grid. By drawing on these “local” sources of power, utilities can also reduce their need to build out expensive transmission infrastructures.
Traditionally, microgrids have been used by college campuses, hospitals, military installations and other organizations that cannot afford to be without power. However, microgrid applications today are increasingly motivated by sustainability efforts at the local, city and state levels, both domestically and internationally.
The University of California San Diego microgrid project, for example, provides electricity, heating and cooling to a campus with a daily population of 45,000 individuals. It uses gas turbines, a steam turbine and a solar energy installation to meet 85 percent of the campus’ electricity needs and 95 percent of its heating and cooling needs.
In the remote Andes Mountains commuity of Huatacondo lies Chile’s first microgrid, developed by the University. The microgrid developers are adding distributed energy resources, such as solar energy, wind, and battery storage systems, to the village’s existing diesel-powered generator. In recent years, Huatacondo’s consumption of diesel fuel has dropped by 50 percent while it has become increasingly energy-independent through its renewable energy resources.
Keeping the Lights On
Faced with a growing threat of wildfires exacerbated by climate change, some utilities, such as San Diego Gas & Electric (SDG&E), have developed plans to install battery-based microgrids to power community emergency services in the event of wildfires or other extreme weather events.
“Our goal is to ensure that our customers continue to have access to electricity and other essential services when their power is disrupted, either because of wildfires or public safety power shutoffs by the local utility,” explained Tom Bialek, chief engineer for Sempra Energy, the parent company to SDG&E.
To date, according to Green Tech Media, the utility has proposed seven of these community microgrids in the greater San Diego area. Collectively, they would provide 100 megawatts of backup power for emergency infrastructure, such as fire stations, law enforcement offices, emergency operations centers and community shelters.
Repurposing What Works
According to Bialek, the new San Diego microgrids will be created from a combination of new and existing resources, depending on what’s already available in each community. Every microgrid will need a source of power generation, a primary load to serve and control systems that allow it to “island” (run autonomously).
“If a community fire station already has a large solar photovoltaic array, for example, we would likely add some energy storage, size those resources to match critical emergency loads, then add an appropriate control system to manage it,” said Bialek.
He added that San Diego’s new microgrids will also benefit from “smart” optimization software that comes standard with most control systems.
“Traditional microgrids have been connected to the main grid by a single switch, so your resources were either ‘all on’ or ‘all off,'” explained Bialek. “Optimization software allows you to selectively power certain loads but not others within your microgrid, so you can make more efficient use of limited power resources for an extended period of time.”
Bialek has no doubt that microgrids will continue to proliferate and play a central role in the sustainability efforts of communities across the nation. He views their owners as key partners to utility companies in maintaining a safe, reliable and sustainable electrical grid.
“Our customers help us create greener, more sustainable communities through their use of rooftop solar and other renewable energy sources,” he said. “In return, we provide and maintain the underlying energy infrastructure and resources that allow them to be successful.”
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