Puerto Rico’s Solar Microgrids Beat Blackout

When power went out across all of Puerto Rico on 16 April, a lot of the lights in the town of Adjuntas stayed on. There, nestled in the mountains on the midwestern side of the island, a combination of experimental microgrids, solar panels, and storage kept power on for many businesses and residents. The rest of the island waited over 24 hours, and in some cases longer, for electricity to be restored.

The blackout was the latest in a series of power interruptions that have come to define Puerto Rico’s aging electrical grid. Vegetation was to blame for April’s blackout, according to LUMA Energy, the private company that manages the island’s grid. A faulty old cable triggered the near total blackout on New Year’s Eve 2024, the company said. Tropical storm Ernesto’s strong winds knocked out half of the island’s power in August 2024.

The problems are the result of decades of mismanagement and disinvestment in the island’s grid infrastructure. Neglecting to keep up with regular maintenance and failing to meet increasing demand for power generation have contributed to the disarray. The long-standing issues set the stage for the grid to be crushed in 2017 by Hurricane Maria, the United States’ second deadliest, which plunged Puerto Rico into months-long darkness and claimed nearly 3,000 lives.

After that hurricane, the island’s state-run utility, Puerto Rico Electric Power Authority (PREPA), contracted with private entities for power generation, transmission, and distribution in the hopes of fixing the grid. Over $20 billion in U.S. federal disaster relief was awarded by the Federal Emergency Management Agency (FEMA) to improve the grid and boost its resilience. Yet bureaucratic red tape and politics in Puerto Rico and on the U.S. mainland have hindered much of that money from being spent.

“It’s a blame game, and there’s too many cooks in the kitchen,” says Javier Rúa-Jovet, a former Puerto Rican regulator who is now chief policy officer at the Solar and Energy Storage Association of Puerto Rico.

Now, the U.S. Department of Energy plans to redirect$365 million previously earmarked for rooftop solar toward infrastructure on Puerto Rico’s majority fossil-fuel-powered grid, according to an announcement from the agency on May 21. The money will support “practical fixes and emergency activities that offer a faster, more impactful solution to the current crisis,” the agency said. This will include “system flexibility and response, power flow and control, component strength, supply security, and safety,” according to the announcement.

The move sparked an outcry from Puerto Rico’s solar industry and U.S. Representative Nydia Velazquez of New York. Velazquez, who is from Puerto Rico, called the move “shameful” in a post on X, saying the money was designed to serve vulnerable communities on the island.

Solar Energy’s Role in Puerto Rico’s Grid

The ongoing political turmoil and bottlenecked federal funding have prompted the widespread development of solar-plus-storage systems across the island that are privately financed via leases, loans, or Power Purchase Agreements (PPAs). Each month, the island sees around 4,000 solar-plus-battery storage systems come online, Rúa-Jovet says. These installations are connected to the grid but can also operate during blackouts.

At the end of March, LUMA reported over 1.14 gigawatts of grid-connected distributed solar capacity, with an additional 2.34 gigawatt-hours of distributed batteries connected to the grid. Solar power produces over 2 terawatt-hours of electricity each year, which accounts for more than 12.5 percent of Puerto Rico’s total residential electricity consumption annually. The majority of that power is generated from residential solar, and capacity continues to grow as more residents install systems with private financing.

Adjuntas, which has a population of about 18,000, took a more experimental approach. The town’s local environmental nonprofit Casa Pueblo teamed up with researchers from the U.S. Department of Energy’s Oak Ridge National Laboratory in Oak Ridge, Tenn., to develop a way to connect multiple microgrids to exchange power with one another, all without having to be hooked up to Puerto Rico’s grid. The strategy, called grid orchestration, ensures that if power is knocked out on one of the installations, the others aren’t compromised. It’s what kept multiple areas in Adjuntas electrified during April’s island-wide blackout.

During the blackout, Casa Pueblo and the Oak Ridge researchers were completing the testing of the orchestration strategy with three of the five microgrids connected in Adjuntas. These three microgrids are connected to the grid via net metering. The remaining two grids are isolated.

“By decentralizing, it’s creating a more resilient and redundant energy setup,” says Arturo Massol-Deyá, Casa Pueblo’s executive director. “Engineers will say: If you have redundancy, that’s more resilient; that’s better.”

The teams demonstrated trading energy from one microgrid to the other, and vice versa. This kind of transfer enables the system to overcome energy limitations during peak demand times and draw from additional storage at night when the sun is down. Together, the town’s five microgrids provide 228 kilowatts of photovoltaic capacity and an additional 1.2 megawatt-hours of storage, which serve residences and 15 commercial businesses. It’s a small amount of power, but an example of a way for systems to operate independently from the grid.

Oak Ridge National Laboratory researcher Maximiliano Ferrari [left] shares data from the Adjuntas microgrid project with students from the Universidad del Sagrado Corazón [center] and Casa Pueblo’s director, Arturo Massol-Deyá [right].Michelle Estrada

Expanding Microgrid Connections in Adjuntas

Moving forward, Massol-Deyá’s plan is to continue improving and expanding the bottom-up approach to microgrid connections. On April 20, Casa Pueblo launched a lab in Adjuntas called the Community Laboratory for the Energy Transition with the goal of bringing together academics and industry experts to test new microgrid technology as it develops.

The next milestone, Massol-Deyá says, will be successfully connecting microgrids that are not in close geographic proximity. “In Adjuntas, we’re bridging the gap between simulation and theoretical work with a real application,” he says.

As warmer months approach, Puerto Rico is gearing up island-wide for a season of power failures as energy demand will likely exceed Puerto Rico’s generation capacity. This will likely be compounded by a stronger-than-normal Atlantic hurricane season.

Rúa-Jovet maintains that solar and batteries are an easily dispatchable resource that make a “good dent” in resiliency against island-wide power failures. Massol-Deyá agrees and says that even with the government turning toward what he calls an “obsolete” model of fossil fuel power, the Puerto Rican people are embracing solar.

“It’s not top-down: It’s not by LUMA, it’s not by the government. It has been pushed by the people. You have a huge and significant investment by the people on solar,” Massol-Deyá says.

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