Keeping the Lights on during Hurricanes

How RMI’s Best Practices Are Creating Hurricane-Resilient PV Systems

As Hurricane Grace and Tropical Storm Henri cause destruction up and down the Atlantic, people living on islands and coastal territories must prepare for an above average hurricane season. In fact, the National Oceanic and Atmospheric Administration has predicted that we could see up to ten hurricanes in the Atlantic in 2021, three to five of which could have winds of 111 miles per hour or greater. These hurricanes wreak havoc on people’s lives, both emotionally and physically. They destroy critical infrastructure, leaving many people without basic services such as electricity and water for prolonged periods of time.

Fortunately, many islands are installing solar photovoltaic (PV) systems—often including batteries—to decrease dependence on volatile fuel imports and provide more reliable power to their residents. However, even PV systems aren’t invulnerable to hurricanes. Over the years, we have found that some PV systems suffer major damage during hurricanes, while others survive and continue producing power. We set out to find out why.

In 2018, we analyzed solar PV systems in the Caribbean after Hurricanes Irma and Maria. We then wrote a report, titled Solar Under Storm, detailing how to build hurricane-resistant ground-mounted PV systems. We followed that with two reports in 2020: a similar report geared toward roof-mounted PV systems and one detailing best practices for policymakers. These reports describe how to build resilient PV systems are making a huge difference in keeping the lights on for people on islands around the world.

Resilience in The Bahamas

Hurricane Dorian devastated The Bahamas in 2019. Since then, the government and utilities have been working hard to deploy reliable and resilient power. And that includes employing the best practices learned from our Solar Under Storm analysis. RMI worked with Bahamas Power and Light to design, develop, and install a solar microgrid on Ragged Island. The 390 kilowatt (kW) microgrid is built to withstand a Category 5 hurricane (with winds of 180 mph) and provides 93 percent of the island’s energy needs. The project was highlighted on CBS’ 60 Minutes.

Another system in The Bahamas built using recommendations from the reports is the 1.1 megawatt (MW) solar-plus-battery microgrid on Highbourne Cay. The microgrid, also built to withstand a Category 5 hurricane, will provide power to up to 100 residents and guests at the island’s resort. It will also save more than 1,650 tons of CO2 emissions annually and pay for itself through diesel savings in just five to six years.

The recommendations are even being used in the largest solar project in The Bahamas to date. The 4 MW solar-plus-battery microgrid on Chub Cay is expected to be complete by mid-September. Chub Cay is a privately owned island that had been powered with diesel generators. However, the Texan owner of the island, who ironically made his money from oil and gas, realized it made financial sense to switch to solar energy to supply 90 percent of the island’s energy. Applying resilience best practices from the reports only increased costs by 5 to 7 percent. This was also a cost-effective investment to ensure that the system survives hurricane-force winds.

“Fortunately, most of these systems have not had to endure a category 5 hurricane after installation. We wouldn’t wish that on anyone,” says Chris Burgess, project director for RMI’s Global South Program. “But we have a lot of data from the surviving systems of Irma and Maria that have already allowed us to conclude that these best practices do work and that these new resilient PV systems will survive severe storms.”

Beyond The Bahamas

Other islands across the Caribbean are also using the best practices described in the reports. For example, Montserrat recently completed a 750 kW microgrid. In the event that the grid goes down, the microgrid will help provide power to a hospital, airport, assisted living apartment complex, and a number of homes in the area.

A 100 kW solar microgrid on the Grenadine island of Mayreau, deployed in 2019 by St. Vincent Electricity Services Limited with help from RMI, serves 28 percent of the island’s electricity demand. It is greatly reducing the island’s energy costs and will ensure electricity is available to critical facilities during storms.

“The Mayreau project was initially specified to withstand Category 4 winds,” says Fidel Neverson, senior project manager for RMI’s Global South Program. “That was before we saw the utter destruction caused by Hurricanes Irma and Maria to ground-mount solar arrays that were built to Category 4 specifications.”

Using best practices from the first Solar Under Storm publication, RMI and the project team completely reengineered the Mayreau solar array to a Category 5 design. “We want to give the Mayreau microgrid the best possible chance of surviving the types of devastating hurricanes that have impacted the region recently so that the island’s residents can enjoy its benefits for years to come,” Neverson adds.

And in Puerto Rico, after Hurricanes Maria and Irma caused the largest blackout in US history, RMI helped the island install solar and battery microgrids on 10 public schools. “All of our procurements require installers to adhere to Solar Under Storm principles,” says Roy Torbert, a principal with RMI’s Global South Program. “The systems on these schools were built to withstand Category 5 hurricane winds. But we’ve also seen many of them continue to provide power after the grid went down due to the earthquakes that ravaged the island in early 2020.”

Helping Develop New Policies and Codes

The third report that RMI produced, Solar Under Storm for Policymakers, emphasized that it is not only installers that have to act on the recommendations. There are many things that governments, regulators, and developers can do to improve the survivability of solar PV systems in the face of severe storms. And many policymakers throughout the Caribbean are taking that to heart. The Organization of Eastern Caribbean States adopted the best practices from the Solar Under Storm reports into its building code. And the Caribbean Development Bank uses the recommendations as part of its underwriting process for the financing of solar projects. 

Three years after we published our first Solar Under Storm report, we are happy to see all of the solar projects that have employed our recommendations. “We discovered that design, workmanship, quality materials, and quality checks were the difference between survival and failure,” said Burgess. “We realized we didn’t need a technical or manufacturing revolution, we just needed to have an eye for detail.”

Fortunately, islands throughout the Caribbean are using those details to prepare their solar systems for the ever-increasing hurricanes. In this way, we can ensure reliable, life-saving power for those who need it most.

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