Airplane crashes are rare, but the fear of an accident is real to many people. Even so, thousands of Americans fly every day. NBC television drama "This is Us" showed that crock-pots can cause house fires, but we still cook chillies and roasts while we're at work.
The threat of energy storage systems causing or contributing to building fires is also real, but incredibly rare. However, as acceptance increases, the wellbeing of life and property becomes a bigger problem.
Currently there are typically solar and storage fire-related issues related to lithium-ion technologies, with a war divided between nickel-manganese-cobalt (NMC) suppliers (Tesla Powerwall, LG Chem) and lithium iron phosphate developers ( LFP) batteries (sonnen, SimpliPhi)). On paper, NMC batteries have an increased risk of thermal runaway, the phenomenon that causes battery fires, simply due to the addition of cobalt. However, if you put an LFP battery in a less than ideal situation yourself, the end result of an accidental fire is the same – potential damage to the system, the surrounding area, and human life.
"Just because the likelihood is different doesn't mean the impact will be different," said Victoria Carey, senior consultant on energy storage at quality assurance company DNV GL. “When you do an installation design, you need to create a design to minimize the chance (of a fire). It's always good to look at chemical capabilities and weigh how to mitigate the effects by determining if this battery's energy density is exactly what is needed for a particular application. "
Batteries that like cool, constant temperatures probably shouldn't be installed outdoors in the desert. Off-grid winter cabins could benefit from the use of lead-acid batteries over the latest lithium product. Just because a solar installer is a certified dealer for a particular battery chemistry doesn't mean it is the best product for each job. Carey said she was comforted that the solar industry is taking battery installation more seriously now than it was two years ago.
“People have been treating batteries as a black box add-on to the devices they are installing. The realization is now that, while there are literally no moving parts, there are many different little components that need to be managed and are delicate "She said." There's kind of been an awakening last year. We called energy storage the "Wild West" and it is certainly still in the early stages of development, but now there is a sheriff in town. "
While battery fires are unlikely to happen, it is still important to plan and plan for the worst.
What causes battery fires?
If a battery catches fire, the likely cause is a thermal runaway. This is the case when a battery experiences a rise in temperature that eventually leads to a short circuit or breakdown of the cell that can start a fire.
There are three main abuse factors that can put a battery into thermal runaway – mechanical, thermal, or electrical. Mechanically, it would physically damage the device, which can create gases or add heat to a battery cell. Heat is heat-related – air conditioning or airflow do not reach the cells, which allows heat to build up. Electrical abuse occurs when the inverter is overcharged, undercharged, or short-circuited. Often times, the damage can be reversed if caught quickly.
"Once this abuse factor has been applied to the cells, the chances are that the outlier thermal condition may not occur if removed, but there is a point of no recurrence," Carey said. “If it's not stopped, it will continue these second-order effects, which are essentially about the release of potentially flammable gases. If there is a source of ignition it can create a fire. In the absence of a source of ignition, these landmark gases can accumulate in sufficient quantities, creating explosive conditions. "
DNV GL tries to understand the risks of battery fires before they occur. In 2018, the first Battery Performance Scorecard was published, with which various battery types are assessed and evaluated on the basis of performance and safety tests. By inserting the batteries into the wringer, DNV GL finds the performance limits of the systems or, depending on the test, can cause thermal runaway.
"The whole goal of destructive testing is to determine if something is getting into thermal continuity. What happens?" Said Carey. "Yes, there may be some batteries that are more resistant to thermal runaway, but we've generally found that they release the same chemicals with the same toxicity and potential flammability."
A safe battery is determined by its initial manufacture. DNV GL hopes that its battery scorecard will bring more transparency to the market.
"There is resistance for companies to even share their name that they have participated in this type of test. There is concern about how it is perceived by customers," said Carey. "Creating greater transparency in the marketplace is one of the things that we consider very important to improve the quality of the systems. "
How should batteries be inserted to avoid fire?
If battery installers follow the manufacturer's manual and adhere to local fire regulations and standards, the likelihood of a fire breaking out is close to zero. LFP battery maker Blue Planet Energy claims to be the safest lithium battery on the market for energy storage applications because additional safety connections are built in. However, sales manager Gregg Murphy said the surest way to prevent battery fires is to install the system correctly.
"Any technology, if installed incorrectly, is a potential electrical hazard," he said. “The greatest support in the market is for installers to carefully follow the installation manual to select safer battery chemistries. The top questions we get in customer service are about installation best practices. "
Brian O & # 39; Connor, Fire Protection Engineer with the National Fire Protection Association (NFPA), published his standard for the installation of stationary energy storage systems for non-residential use (NFPA 855) in September 2019.
NFPA 855 provides battery installation requirements that best prevent loss of life and property – the goal of all NFPA codes. O’Connor said some of the best practices for installing large-scale bearings include providing adequate space between units for adequate airflow and fire breaks, as well as an appropriate fire fighting system on site.
“We recommend placing batteries in the building. If there are between the two pauses in fire, the fire cannot escape a rack. If you can limit the fire to a smaller area, it will burn for a shorter duration and you can limit the damage, ”he said. “Another suggestion is to install a sprinkler system. Lithium-ion batteries do not respond to water, so you can put plenty of water on them to keep them cool. It won't put out the fire, but it will keep the fire from spreading and jumping to other exposures. "
O’Connor said many of the NFPA's requirements for large scale battery installation can be carried over to the residential market with an added dose of practicality.
"We're using more common sense and ground rules for household batteries because it's hard to get all of these details through." Nobody goes door to door to see, ”he said. "If you plan to install a storage system in the garage, make sure you have room for vehicle protection. When you return to the garage, you don't want to damage the battery." Make sure the batteries are away from where you sleep as this would limit the amount of time you leave your home. Do not install a battery outside under a window, as windows are used to exit the house during a fire. "
While residential areas are less likely to catch fire, installers should still plan for accidents. Installing batteries in rooms with fire walls without a lot of clutter to obstruct airflow is a fundamental first step. Keeping batteries away from living spaces (bedrooms, living rooms) will help you survive in the event of a fire. So, all those advertising images from battery companies showing systems in the living room as aesthetic focal points – no way. For safety reasons, keep the battery in a garage or unoccupied utility room.
What are the best operating practices to avoid battery fires?
A bit of common sense follows on the operational side of an energy storage system. A highly functional battery management system (BMS), typically standard on lithium-ion battery systems, helps balance charge and discharge rates, monitor battery voltage, and measure temperature to ensure the system does not run into problems. Just because a BMS is monitoring the condition of the battery doesn't mean the operator should push it to its limits.
"The critical part is making sure that whatever the battery is designed to do and what the BMS is supposed to protect is what that battery is used for," said Carey.
The best advice from O’Connor is to prepare and plan for the worst – know what to do in the event of a fire and coordinate with first responders. NFPA 855 requires security labels that explain what type of battery is installed and whether a suppression system is in place. These precautions are very important for first responders so that they are not surprised when they arrive in an emergency.
“A big problem is stranded energy. You can't quickly discharge these batteries when they're on fire, "O & # 39; Connor said." Even if a first responder cleans up, there is still a potential for shock. If you put (an ax) in a battery that is powered, there is a risk of injury. The marking is therefore important. "
Most importantly, be smart about installing, operating, and owning an energy storage system. When we fly in airplanes, we have access to safety information and get demonstrations of what to do in an emergency. An accident is unlikely to happen, but it is good to have this information on hand just in case.
"There is very little chance of failure in operation as long as these systems adhere to good quality practice," said Carey. "But unless you admit that there could be a mistake, you are not preparing the people who are trying to adequately save lives and property. It's a touchy subject to say that your product can fail, but I think it is up to people to act responsibly and admit that something could happen. "