Living in the face of the hot and gusty Santa Ana winds, Los Angeles residents have learned how to protect their homes from fire. But what many might not know is that without proper care and attention, one of these risks might just be sitting on their roof.
Now, the Los Angeles County Fire Department is warning homeowners that rooftop solar panels could put both firefighters and their homes at risk in the event of a blaze.
Thanks to research—and knowledge gained from emergency responses to fires involving solar paneled-structures—it’s becoming more clear on what exactly these risks are, and how they can be mitigated or prevented.
So just what are these risks (and some solutions) for homes and buildings with solar PV panels? And are fire departments, government regulators and the solar industry doing enough to prevent them?
“It’s only been about four years since this challenge was identified,” said Ken Willette of the Quincy, Mass.-based National Fire Protection Association, an independent nonprofit organization that has been developing the U.S.’s National Electrical Code since 1897.
Yet the topic had not gotten much attention from mainstream media until last fall, when a New Jersey warehouse burned for 29 hours because firefighters feared electrocution when coming into contact with the building’s rooftop 7,000-panel PV system. Late last month, New Jersey state legislators responded by passing a law requiring building owners to disclose to fire officials if such a system is in place. One- and two-family residences are exempt under the law.
In the past decade, firefighters had begun to encounter rooftop solar panels, but didn’t know much about how to handle them when the home or building was on fire, Willette said. So after receiving an increasing number of requests from firefighters for information on how to best protect themselves, the NFPA’s Fire Protection Research Foundation got funding from the U.S. Department of Homeland Security to undertake such a research project. Their report [PDF], issued in 2010, outlined not just the risks, but best practices for emergency response.
One year later, safety-testing group Underwriters Laboratories followed up with extensive lab research at their Northbrook, Ill. campus. The organization tested a range of materials on solar PV emergency fire response and issued a comprehensive report [PDF] released in 2011.
Risks and solutions identified by NFPA and UL were:
• Electrical shock: Firefighters coming into contact with solar panels run a risk as the system is generating electricity from exposure from sunshine, streetlights or the lights used during nighttime emergency response vehicles. In sunlight, panels can generate anywhere from between 60 to 120 V of electricity, according to Matt Paiss, a fire engineer with the San Jose, Calif. Fire Department. That number is of course a lot lower during the nighttime, but the solar dangers for firefighters are very real around the clock.
“There’s a potentially lethal situation for firefighters, where anywhere from 40 milliamps (mA) to 240 mA of DC electric current can lock up the muscles and you can’t let go,” says Ken Boyce, UL’s manager and principal engineer for product safety. The current could be strong enough where the firefighter could jump back and fall off the roof, fall into a solar panel, or be strong enough past 240 mA to cause ventricular fibrillation and cause death. At 70 mA, electrical burns causing cell necrosis could come into play, according to UL. Even the amount of light generated from fighting a nighttime fire adjacent to a building with rooftop PV could generate electricity in the solar panels, Boyce added.
Fire-induced damage to the arrays can also create new circuit paths as well, the UL report found, that can flow along the system’s frame and racks, as well as through a building’s metal roofs, flashings and gutters.
Solutions: “The question is how to stop the panels from generating electricity,” said Willette. While one might think that simply shutting the system off will take care of the problem, it’s not that simple. Sometimes the firefighters don’t know a structure has rooftop PV panels beforehand—and even if the inverter can be located and switched off, the panels cannot be turned off, meaning that in most cases, electricity will still be generated.
Based on the complexity of this problem, Willette said that the NFPA is currently looking into how it can revise its electrical code to reflect requirements for improved labeling for first responders. But these changes would be limited in impact, as they’d only apply to new systems installed in the future.
Firefighters also cover panels as a way to stop the generation of electricity in residential systems. “But if you’re talking about a commercial building or solar farm with tens, hundreds and possibly thousands of panels, reducing the electrical generation is impossible,” Willette said.
UL found that covering a PV panel with heavy, opaque and densely woven fabric can bring down the amount of electricity close to zero. In fact, any tarp where light can be seen coming through should not be used, the report advised. But care should be taken to not place wet tarps in contact with energized equipment as the tarps can then conduct electricity.
“It’s also incumbent upon firefighters to wear robust leather gloves,” Boyce said. UL’s study found that this material was effective in protecting the first responders from current, but only when dry.
• Density of rooftop panels can be a hindrance: As a common tactic among firefighters to contain incidents is by opening a hole in the roof for ventilation, Willette said, the density of solar panels can make it impossible for firefighters to create that hole.
And if the firefighter is opening up the hole from below and doesn’t know that solar panels are installed on the roof, that creates another shock hazard, he added.
“It’s definitely enough electricity in the larger arrays or commercial systems to possibly cause cardiac arrest,” Willette said.
Solutions: As a result, the NFPA’s safety and national electrical codes have required that a minimum amount of clearance be present. In California, regulations require a three feet perimeter around the array for firefighter access.
• Weight of panels: In already-compromised roofs such as during a fire, the additional weight could cause it to collapse, Los Angeles County Fire Department inspector Scott Miller told CBS Los Angeles. The panels can also release harmful chemicals when exposed to fire as well, he said.
Solutions: The only solution we discovered in the course of reporting this story is to install fewer solar panels — which isn’t really a solution.
• Lack of communication/notification from home and building owners: Clear communication—whether through signage at the front of the building or diagrams showing where the system can be shut off—would help fire crews determine their emergency response plan as swiftly as possible.
Solutions: New Jersey’s law, signed in January by Gov. Chris Christie, requires buildings to post an emblem at their front entrance to notify firefighters.
Firefighters, in Part, Respond with Trainings
And as a result, some fire departments in the U.S. are taking action to train their personnel before it’s too late. Though it’s far from widespread, at least one evangelist and field expert, such as Paiss, trains departments across the country. Paiss released his own online series available on YouTube in 2011.
Yet training the first responders is presumably just one side of the coin. In the wake of New Jersey’s horrific warehouse fire, State Sen. Donald Norcross expressed dissatisfaction the solar industry, saying that it has not addressed fire risks through de-energizing activated solar panels during a fire,according to The Daily Journal.
Does the solar industry have solutions?
“We recognize that we need to do a better job as an industry educating first responders, especially firefighters, about solar panels,” Solar Energy Industries Association spokesperson Ken Johnson told The Atlantic Cities blog shortly after the New Jersey warehouse fire.
“We are working very closely with firefighters across the United States on the developments of codes and standards,” Johnson explained to Reuters in September. “After every incident, we learn from it and improve.”
It’s not clear just what progress has been made since then, as Johnson did not respond to SolarEnergy.net after repeated requests for an update.
Yet new products that seek to fill the fire risk gaps are emerging. A new solar panel sensor and fuse developed in Germany at the request of the Munich fire department (after the first responders had to let a building covered with rooftop PV burn to the ground) could be just what firefighters need. Perched between two solar panels, the TOPInno company product senses when the temperature reaches a certain threshold. At that point, the fuse will break, TOPInno General Manager Raymond Huwaë told Triple Pundit.
“The moment the fuses are broken due to the heat, the voltage will go down to below 120V, which is the legal requirement to be able to use water to extinguish the flames,” he said.
The sensors/fuse product can also be turned off manually as well.
Boyce says though he sees momentum within the solar industry to address the fire risk issue, it’s currently in a transition period so that products being released in the marketplace will be in compliance with new regulations.
One bright spot is in California, where CalSEIA has been working with the state fire marshal on an interim solution to the UL 1703 fire code that regulates how a rooftop PV system impacts the fire classification rating of the roofing material below it. CalSEIA has also held a webinar on this topic for the solar industry to understand the code’s meaning, and how it can come into compliance, according to Executive Director Bernadette Del Chiaro.
“We just recently issued our first certification [under the UL 1703 fire code],” Boyce said, “so that’s exciting news for the code community. They’re excited to see this implemented with CalSEIA and others, and help them roll it out in the future.”
House fire photo CC-licensed by Wikimedia user Sylvain Pedneault.