Dive Brief:

• After a week of seismic activity, a 6.4-magnitude earthquake hit Puerto Rico on Tuesday morning, causing widespread power outages across the island's electric system, which has been rebuilt after the 2017 Hurricane Maria.
• According to the Puerto Rico Electric Power Authority (PREPA), some of the of power outages can be traced back to automatic emergency response systems that are designed to shut down in an emergency. The utility restored power to some areas in the hours following the earthquake.
• The earthquake directly impacted diesel generators on the south of the island. While the island is considering how distributed energy resources can help the American territory maintain power stability, progress on the ground has so far been limited.

Dive Insight:

PREPA's long-term plan calls for a system of eight "mini grids" that would utilize distributed resources to improve reliability during disasters. It includes a focus on renewables, storage and distributed resources — just the kind of system that could help maintain power during a catastrophe, say experts.

But the status of the utility's integrated resource plan (IRP) remains uncertain, with hearings starting next week at the Puerto Rico Energy Bureau.

Distributed energy resources "have been proposed through the IRP process, but that process is taking forever," Sierra Club representative Pedro Cruz told Utility Dive. Though he added, "that is not a bad thing: it's good they are moving slow, to allow input from different stakeholders."

Cruz, who is the senior clean infrastructure representative for Sierra Club's Labor and Economic Justice Program, was on the island working with local organizers and activists when the power went out.  "The earthquake shows Puerto Rico is not ready for this kind of disaster," he said.

The largest recent earthquake impacted several generators, including the PREPA-owned Costa Sur power plant and Aguirres power plant, which are fueled by diesel.

The Aguirre power plant is being restored to service, which could supply 650 MW into the region, PREPA CEO José Ortiz said in a statement. Operations have been carried out to stabilize the system, with the expectation of supplying 2,650 MW of power with contributions from other power plants, he added.

"If another incident beyond our control does not occur and all processes (are effective), we are confident that at least 70% of customers may have power as soon as possible," Gov. Wanda Vásquez​ Garced said in a statement.

The epicenter of the earthquake was along the southern coast, according to the U.S. Geological Survey, where seismic activity has been occurring for days and a pair of earthquakes registered 5.8 or above.

"The situation there is tense after the two earthquakes," Roy Torbert, a principal with the Rocky Mountain Institute, told Utility Dive in an email. "Most of the damage is in the south of the island, with particular damage at the Costa Sur power plant and the water tanks there. Guanica and other towns in the south are on edge."

Most of Puerto Rico's generation is on the south side of the island, while the island's highest demand, including in its capital San Juan, is in the north. The need for long-distance transmission lines means power is particularly susceptible to disruption. The utility's mini grid vision would change this, but in the immediate wake of Hurricane Maria, the electric system was rebuilt largely as it previously existed.

While some hardening has been done, the system "has remained pretty fragile, and power outages are still a fact of daily life for some," according to Michael Deibert, journalist and author of "When the Sky Fell: Hurricane Maria and the United States in Puerto Rico."

"A lot of the issues that bedeviled Puerto Rico and held it back before the hurricane continue to exist vividly today," Deibert told Utility Dive. "I haven't seen a whole lot change."

Much of the island's generation is now fueled by diesel and combined cycle gas plants. However, last year the island's state legislature adopted a 100% renewable portfolio standard by 2050. 

PREPA's IRP could cost more than $14 billion, but the utility points to major potential benefits following disruptive storms.

"The business case for transforming the grid architecture is straightforward: it provides the least cost approach to achieve resilience against major hurricanes, meet and exceed compliance with the renewable portfolio standard, engage customers, and lower cost," according to the IRP.

However, Sierra Club's Cruz said cost is a serious issue for island residents. "Nobody knows how long it will take to get that plan going, and nobody knows where the money will come from," he said.

The utility has proposed raising rates, and a tax could be levied on residential solar panels, said Cruz. But Sierra Club fears those actions could force more residents to join the island's exodus, making the transition to renewables even more difficult. About 200,000 residents left the island following Hurricane Maria, by some estimates.

Raising utility rates "would be horrible for the economy, because it will push more people to leave the island, which means less people to pay back the debt, and that's a cycle," said Cruz.