Will batteries and solar have a place in Puerto Rico's reimagined grid?
Even with minigrids and batteries, traditional infrastructure will remain the backbone of the island's power system
It's been three months since Hurricane Maria slammed into Puerto Rico and destroyed its electric system. Many residents are still without power with only 70% of generation back online.
The push to rebuild the island's electric utility infrastructure got off to a rocky start, slowed by a $300 million contract debacle and the Atlantic Ocean. But the troubled deal with Whitefish Energy has been canceled, and now thousands of aid workers are on the island, including 3,000 focused on power restoration. The U.S. Army Corps of Engineers tapped Fluor Enterprise for an $831 million time-and-materials contract to restore electric power in Puerto Rico. The work is estimated to be complete by Feb. 28.
"Puerto Rico is in a good position for sun and wind, so that became a part of the analysis. And we realized that probably solves a lot of issues."
AES Chief Technology Officer
But alongside restoration work, new visions for Puerto Rico's electric grid are emerging. While thousands of linemen from around the country continue to repair the system, the utility industry and government are simultaneously developing a longer-term vision for the island's electric system. As multiple concepts come to the table, the challenge will be integrating modern grid architecture while keeping in place some of the basic grid building blocks. An industry work group has developed a plan that builds on the island's last integrated resource plan, while AES, which owns a large coal plant on the island, has floated a concept that is focused on solar and storage.
But while Puerto Rico's grid will be modernized and renewables added, the backbone of the system will remain fairly traditional.
Vision's for Puerto Rico's grid
Johnny Price, a section manager in electric operations for Consolidated Edison, just returned from San Juan where he led a group of workers restoring power in the island's capital. He said the challenges faced on the ground may be unique, but Puerto Rico's electric grid isn't anything workers haven't seen before.
"The system is pretty similar to what we're used to," Price said. "We're just trying to figure out how it was wired before, and put it back the same way."
The tourist-focused area of Old San Juan is entirely back up and running, and most of the city has power as well. But the task has not been simple. Downed trees and language barriers have complicated restoration in more rural areas.
A 300-year-old Spanish fort in Old San Juan meant crews did a lot of climbing, Price said. Concrete poles too heavy for trucks had to be repositioned by crane. "Each job was intellectually challenging, to figure out how to safely do things," he said.
A lot of the island's generation is in the south, and lengthy transmission repairs slowed repowering efforts initially, Price said. But since November, when the some major transmission backbone repairs were complete, crews have been making more progress.
Alongside efforts to repair the system and restore power, Puerto Rico's utility is also looking at ways to strengthen its infrastructure, and include more of the advanced technologies that have become common stateside.
A broad range of utilities and electric groups have developed a $17.6 billion plan to rebuild Puerto Rico's electric distribution system, including a focus on resilience to withstand future storms and the inclusion of modern grid technologies and control systems. Members in the group include New York Power Authority, Puerto Rico Electric Power Authority (PREPA), Consolidated Edison, Electric Power Research Institute (EPRI), several national labs, Edison International and others.
PREPA's new system will need to withstand a Category 4 storm, which produces wind speeds of 155 miles/hour, in addition to heavy floods. The utility's 2015 Integrated Resource Plan (IRP), which helped inform the rebuilding proposal, already called for more distributed energy and renewables. Those two advances could strengthen the system.
But of the plan's expenditures, more than $9 billion is targeted for the overhead transmission and distribution system. While more modern technology and concepts will play a role — the Department of Energy (DOE) has identified 200 locations for potential microgrids — the backbone remains quite traditional.
Rob Manning, EPRI's vice president of transmission and distribution infrastructure, said the working group's proposal uses the idea of a traditional grid, but with modern technologies brought to bear.
"It's built to be far more resilient, but there is a foundation that is the traditional grid," Manning said. "There are new components being integrated into the grid."
Energy storage, microgrids, distributed renewables and demand response have all moved past the experimental stage and will be included. However, Manning said a traditional grid structure "is the most reliable, the most proven robust system there is available today, and it just makes sense that it becomes the foundational concept."
The working group report's recommendations address rebuilding for resiliency against future storms, and include deploying distributed energy resources industry best practices in automation and control system technologies. Microgrids are also recommended for critical infrastructure: industrial and commercial.
The current power system includes six fossil fuel and seven hydroelectric generation sites owned and operated by PREPA, as well as privately-owned generation facilities consisting of two cogeneration plants, two wind farms, and five solar farms. The electric grid includes almost 2,500 miles of transmission line, 31,000 miles of distribution lines and 334 substations.
Pre-storm electric power generating capacity was 5,839 MW, according to the report, including almost 1 GW provided by two co-generators, EcoElectrica and AES, through 20-year power purchase operating agreements. At 500 MW and 450 MW respectively, their plants are the island's largest sources of generation.
AES has been working on the island for 15 years, providing coal-generated energy. Five years ago, the company developed a 24 MW solar plant there. Chief Technology Officer Chris Shelton said the company's 100 workers have been a part of the community there for years and were "first and foremost" participating in the recovery.
But AES, responding to a solicitation from the Puerto Rico Energy Commission, has also developed a "vision" for how Puerto Rico could alter its system: a network of connected minigrids, reinforced by key transmission and distribution lines. The system would be powered by 10,000 MW of large-scale solar and 2,500 MW of 10-hour battery-based energy storage.
Shelton stressed that this isn't a "plan" AES putting forth — he describes more like a "technical vision." But as Puerto Rico considers its energy choices, Shelton said different proposals need to be considered in concrete ways. A massive solar build is just one of those ideas.
But the company says it is imperative that Puerto Rico not simply restore the electric system. AES' proposal would connect low-cost generation to critical load centers in the north side of the country, and connect neighboring minigrids to enable them to pool resources and reduce restoration times during outages.
The recovery process, and how the island's grid is structured today, was central to AES thought process in developing its vision. But Shelton also said AES believes "the grid is still a central component of value to the electric system." The company's vision is a series of "federated minigrids ... we're talking about something bigger than microgrids, that builds on the existing distribution system."
Microgrids are small batches of connected demand and generation which are capable of maintaining power in the event of a wider outage. The minigrids envisioned by AES would be similar, but much larger and built around the existing system. AES envisions six or seven regions, each on its own "minigrid" that on a normal day would use the transmission system to help optimize the island's power grid.
AES: Large solar+storage rollout would be cost-effective
One of Puerto Rico's largest challenges is the cost of fuel. Almost half of the island's generation came from petroleum in 2016, with just 2% from renewable resources. Gas made up about a third of its generation, and coal supplied 17%, according to the U.S. Energy Information Administration.
"Puerto Rico is in a good position for sun and wind, so that became a part of the analysis. And we realized that probably solves a lot of issues," Shelton said. "If you bring different types of fuel to the island, you still have the issue of getting it around to the different points where the load is."
AES' vision maximizes solar, and to do that, it had to also include significant storage.
"Job one was to use the grid as much as possible," Shelton said. But he said the solar and storage solution would be less than the expected fuel costs over the next decade.
AES estimates utility-scale solar generation in Puerto Rico would cost roughly $40/MWh to $50/MWh, and the battery-based energy storage system between $55/MWh and $65/MWh .The proposal estimates 15,000 GWh of solar could replace up to 12,000 GWh of pricey diesel or oil generation.
That is very aggressive vision: Shelton said the amount of solar the company suggests is about the same as California's total solar capacity. Total pricetag: $15 billion.
"That's about the same as the avoided fuel costs," Shelton said. "So this could be a 20-year set of assets paid for with 10 years of fuel savings."
Total cost for solar-storage is between $95/MWh and $115/MWh, Shelton said, but some fossil fuel power is still cheaper and the two large plants on the island would remain in the mix. AES' coal plant and EcoElectrica's gas plant both offer lower-cost power, with the AES plant below $90/MWh.
Keeping those running, but using solar-storage for the remaining load, would take Puerto Rico to 60% to 70% carbon-free power, Shelton said.
But for now, the focus remains on just getting the lights back on for the last 30% of Puerto Rico.
Follow Robert Walton on Twitter