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 stubborn blaze burned for more than 13 hours and continued to smolder after 36 hours, spewing gray smoke and forcing the wind turbines to shut down. Though there were no injuries reported, the operators wrote off the entire battery system.
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 (ClimateWire, 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 (ClimateWire, Jan. 30).
According to market research firm IHS, energy storage is poised to expand from 340 MW in capacity in 2013 to more than 40 gigawatts by 2022, a hundredfold increase. That means flywheels, batteries, compressed air caverns and pumped hydropower will crop up in more jurisdictions for the first time.
Federal officials now want to make sure that ambulance crews and firefighters don’t find out the hard way that giant power storage installations pose unique challenges and are working to establish rules to pre-empt disaster.
"This is not to say that energy storage systems are specifically unsafe," said Imre Gyuk, energy storage program manager in the Office of Electricity Delivery and Energy Reliability at the Department of Energy. "But the point is, energy storage systems are being deployed more and more."
1,200 storage projects coming
Speaking last month during a Web-based seminar discussing DOE’s energy storage safety strategic plan, Gyuk said that there are more than 1,200 energy storage projects already running or in development around the world, and the concern is that energy storage technology is coming online faster than regulations can keep up.
"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
However, compared to conventional generators and electrical infrastructure, energy storage can have safety advantages.
"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 (ClimateWire, Dec. 18, 2014).
Willette cited the experience of the hybrid-electric Chevrolet Volt. The manufacturer taught first responders how to handle battery problems and built features into the car to protect firefighters, like marking high-voltage cables orange and including an emergency discharge system for the batteries.
"Those little things really seem huge in the field," Willette said. "When there were Chevy Volt battery fires, that didn’t have a significant impact on [perceptions of safety in] the Volt and the industry."
Applications in office buildings and homes
Large batteries are also taking root in commercial applications like office buildings and may soon make it into homes, as well. In some communities, homes with rooftop solar panels have a greater incentive to store their own electricity instead of feeding it into the grid, saving it to use when the sun sets.
Automaker Tesla Motors has expressed interest in getting its battery systems into the residential market (ClimateWire, Feb. 12).
A larger market means more battery producers, carrying greater risks of manufacturing defects as new companies spring up to meet demand. Wider deployment also means a greater chance of inadequate safety precautions, adding to the urgency of establishing codes governing energy storage.
One important lesson is to have fire response resources on-site, like dry chemicals and deployment systems. Containment structures like warehouses also have to have better ways to contain flames and prevent hazardous chemicals from leaking.
"This is a very rural area," said Seelig of Kahuku. "By the time you get enough firefighting forces and the right extinguishing sources, the fire is going to progress quite a bit."
Another critical factor is the information gap between energy storage operators and responders. "Those facilities might have an internal fire brigade or response team … but in some instances, there are no on-site people," said Willette. This means firefighters may have to extinguish a blaze without knowing what chemicals are in play, where the electrical shutoffs are or what kind of fire retardant to use.
Developers and responders need to take proactive steps to ensure they know what they are dealing with when an accident occurs, Willette added.
Hawaii’s enthusiasm for renewable energy and energy storage is in flux as the state contemplates rolling back incentives (ClimateWire, Jan. 26). In 2014, operators restored the Kahuku wind farm to full capacity, minus the electricity storage component.
Earlier this year, the Hawaii Public Utility Commission signed off on another wind turbine installation at Kahuku, but this installation would send energy directly to power lines instead of buffering through a battery system.
However, demand for energy storage remains robust in other parts of the country, like California, which has a mandate for 1.3 GW of grid energy storage by 2020.
"Finally, finally, finally people are understanding the value of energy storage," said Younicos’ Hiersemenzel. "It’s transitioning from something exotic to something that’s becoming mainstream."