Smoke, sirens and flashing lights interrupted the night on Aug. 1, 2012, as a fire took hold at the remote Kahuku wind farm along the north shore of Oahu in Hawaii. The blaze sparked at 3:30 a.m. in a metal warehouse with 12,000 lead acid batteries mounted in racks towering more than 6 feet high.
The 10-megawatt battery system, installed by Xtreme Power, was used to buffer electricity from the 12-turbine, 30 MW wind farm operated by First Wind, smoothing out spikes and low spots in wind power production.
Within 20 minutes, the Honolulu Fire Department arrived at the scene. It was the third fire the firefighters had responded to at that 9,000-square-foot building since operations there started in 2011, but the previous fires burned themselves out or were extinguished before causing extensive damage.
"On-site supervisors advised us that entry into the building was not advised because of the hazards," said Terry Seelig, battalion chief at the Fire Prevention Bureau of the Honolulu Fire Department.
The risks from scalding heat, poisonous fumes, a collapsing structure and the potential for battery explosions kept firefighters outside the warehouse. After determining no one was inside, the response team focused on keeping the blaze from spreading to other buildings at the site.
"It's a defensive fire attack at that point," Seelig said. "The only risk at that point would be to the responders going in."
The team used water to cool parts of the building but avoided using it to extinguish the fire out of concerns for electric shock and risks of creating toxic chemical runoff. Instead, they waited for a carbon dioxide extinguishing system to arrive on the scene, but that proved ineffective at quenching the inferno.
What happens when 12,000 batteries burn?
The fire was a hard lesson for energy storage developers and first responders in handling a new technology. Grid-level battery systems in particular are cropping up around the country as the industry matures, prices drop and regulations compel energy providers to invest in storage.
"We are increasing our commitment to storage," said Energy Secretary Ernest Moniz in a House budget hearing this week.
Storing energy on the grid is a big part of making intermittent renewable energy more palatable for utilities (, Feb. 13). Industry officials also want EPA to include storage as a way to comply with the Obama administration's Clean Power Plan, as well as state renewable portfolio standards (, Jan. 30).
"Many of the big companies are indeed very much aware of the issue, but without codes and standards and generalized guidelines, we are really at the mercy of people's goodwill," he said. "The vast majority of codes were not developed for energy storage."
Moving and storing energy in any form carries inherent risks: Fuel depots can catch on fire. Transmission lines can fall and cause shocks. Gas pipelines can explode. Liquid fuels can leak. But rescue workers have decades of experience fighting these challenges, and the industry has established procedures to prevent problems.
Grid-level energy storage, on the other hand, is a new frontier, and establishing safety standards is crucial not just to protect human life and the environment, but also to safeguard expensive energy investments.
The Kahuku wind farm received a $117 million loan guarantee from DOE in 2010. Xtreme Power declared bankruptcy in 2014, and German energy storage developer Younicos acquired its assets.
"We are still looking into why the fire happened," said Philip Hiersemenzel, press spokesman for Younicos. The company suspects that the fire may not have started with the batteries themselves but may have ignited from foreign material or a ground arc fault.
According to Hiersemenzel, Younicos is agnostic about battery chemistries but is sticking to lithium-ion cells in new projects for now. Many of the company's safeguards come from how installations are designed, using software to regulate cell performance, keeping cells in comfortable conditions and isolating battery packs so a failure in one doesn't cascade to another.
"We are pretty confident that our installations are very safe," Hiersemenzel said, but he acknowledged that cramming megawatt-hours in a small space will always pose hazards. "I think anybody who will say that 'my battery will never burn under no circumstances whatsoever' is being a little disingenuous."
Producer says new technology can be safer
"In a lot of ways, storage is actually safer than other ways we can do things," said Praveen Kathpal, vice president of AES Energy Storage, a firm with 200 MW of storage in its portfolio online and more than 100 MW in development around the world. "One advantage of storage is you have a controlled environment, and you have something that's modular."
He explained that developers build battery storage systems around identical cells. Unlike batteries in cars or aircraft, grid-scale batteries don't face severe weight and size restrictions, nor do they have to withstand high-speed crashes, so developers have ample room to provide cooling, isolation and fire suppression systems.
And when it comes to lithium-ion cells, the technology has a proven safety record and wide public acceptance. "Pretty much everyone has a lithium battery in their pocket," Kathpal said.
Kenneth Willette, manager of the public fire protection division at the National Fire Protection Association, said the transportation sector offers a precedent for how to train first responders in energy storage.
With the rise of electric cars and more energy-dense batteries on aircraft, emergency crews have already dealt with persistent battery fires and thermal runaway conditions (, Dec. 18, 2014).
Applications in office buildings and homes
Automaker Tesla Motors has expressed interest in getting its battery systems into the residential market (, Feb. 12).
Hawaii's enthusiasm for renewable energy and energy storage is in flux as the state contemplates rolling back incentives (, Jan. 26). In 2014, operators restored the Kahuku wind farm to full capacity, minus the electricity storage component.
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