You must implement new fire fighting strategies when dealing with structural, residential or commercial fires involving solar photovoltaic (PV) systems. The Operational Incident Commander (IC) can no longer open and disticonnect the main electrical connection of the structure, and will not feel comfortable because there is no remaining live power source. The solar photovoltaic system is always energized. The overall fire fighting tactics and strategies adopted must be adapted to deal with this technology.
In order for commanders to effectively formulate standard operating procedures (SOP) for solar photovoltaics, the leadership must first understand the basic knowledge of solar photovoltaic systems and related operations. Once the IC has mastered the basis of this operation, they can formulate a safe and reliable solar photovoltaic system SOP. The key to developing any solar photovoltaic SOP is to approach the system with the intent of isolation rather than disconnecon.
The solar photovoltaic system generates electricity from the sun and sends it back to the host system. In residential and commercial applications, the point of public coupling (POCC)-the point at which solar photovoltaics connect to the building’s electrical system-is located behind the utility meter. The integration of the system is achieved through backfeed circuit breakers on the house panels, busbar taps or switchgear that serves commercial buildings. In any case, the electricity generated by the solar photovoltaic system will be “back-fed” into the power system of the building.
Solar photovoltaic modules are the mechanism for generating solar power. The module is composed of single crystal or polycrystalline battery. The difference between the two is related to manufacturing method, physical appearance, size, efficiency and price point. When collected together, multiple modules connected in series or parallel are identified as an array.
Arrange the modules into multiple strings and return to the inverter to drive the voltage of the system. According to the parameters specified in the National Electrical Code®, the voltage of a solar photovoltaic system can reach 600 or 1,000 volts direct current (vdc). Various code production panels are now considering systems that allow 1,500 vdc.
The power generated by an array (or a group of arrays) is transmitted back to the POCC through the inverter through the conduit and wire or cable tray system. The inverter can be one of the following three types: micro inverter (handling a single module), string (no transformer), and central inverter (with an isolation transformer and use of a combiner box). The inverter converts direct current (DC) to alternating current (AC). No matter if the AC circuit breaker is opened, the DC side of the inverter will always be energized. Dangerous voltage will always exist in the entire DC system.
The following are a few of the many types of solar photovoltaic systems. Each has its own dangers, and first responders must keep these dangers in mind.
Similarly, once your fire department has mastered the configuration of various solar photovoltaic systems and their related operations, you can form an effective SOP.
Building and fire officials should establish links between agencies; this is essential for creating an inventory of properties featuring solar photovoltaic systems within their jurisdiction. After creation, include the inventory in your pre-planned “toolbox”. Lists are only useful information when they are used. Use the attributes you determine for on-site visits and training exercises to handle the system in emergency situations. In addition, compile a list of available experts such as solar energy suppliers, electrical contractors and engineers and other similar professionals who are available “on call” to provide technical expertise when needed.
After the fire department completes all pre-planning, there is no guarantee that first responders will never encounter an unidentified system on the fire scene. If during their 360-degree adjustment process, the arriving unit finds electrical components that look abnormal in the electrical system, then they are likely to be dealing with a solar photovoltaic system. Conduits, inverters, disconnectors (switches related to solar PV systems), and switching schemes are all components that may indicate the presence of solar PV.
In New Jersey, a legislation was recently passed requiring commercial structures to display placards similar to truss signs at the entrance, indicating that the building has a solar photovoltaic system. Except for residential structures.
Once the staff confirm that there is a solar photovoltaic system on the fire site, they must notify the IC. Once determined, the utility team of the Incident Command System (ICS) should locate and open all disconnects in sequence. When opening all disconnections, perform the lockout/tagout procedure. After this operation is completed, notify the IC again.
When you turn on the AC and disconnect, the inverter will turn off [this is a Nationally Recognized Testing Laboratory (NRTL) listing requirement]. The DC side will remain energized; it will always be “hot” because the solar modules will continue to generate electricity. During the day (sunlight) and night (scene lights/open flames), solar modules can always generate dangerous voltages.
Also worthy of special attention are solar photovoltaic systems for battery storage. This type of system not only uses solar photovoltaic, but also uses a charge controller and battery system. The electricity from the solar module charges the battery, which in turn powers the house. In the event of a power failure, the battery will continue to provide service for the selected household load. If the utility power is restored and the battery is fully charged, the solar photovoltaic system will be restored to the public grid service under the condition of feedback. In any case, when discovering a solar photovoltaic system, the utility team must consider additional power supplies and isolation procedures.
All system components should be labeled. However, this may not always be the case. First responders should be aware of the fact that although tags are code requirements, they may be lost, weathered, or generally unreadable.
The recent code change regarding the quick shutdown of firefighters has taken effect. These isolation technologies will provide isolated areas so that ICs and firefighters can easily identify live areas and their associated hazards.
If the solar photovoltaic system is the source of fire, there will be problems after alleviating any danger to life. Therefore, please use dry powder fire extinguishers on any live parts. If the roofing material catches fire, NRTL testing has shown that using a fog mode of 20° to 30° at 100 psi will not cause an excessive risk of electric shock. These studies also found that the application of fog mode can reduce the current below the perceived level.
If you encounter a structural fire, please implement structural fire fighting techniques. During these operations, IC and firefighters should be aware of the existence of solar photovoltaic systems.
After isolating the system, only remove photovoltaic modules under special circumstances (that is, life-threatening). If they must be removed, personnel should only use non-conductive tools to remove them.
There are also many discussions about Class A foams, which can effectively extinguish fires involving solar photovoltaics. It can form a blanket in areas under the array where water cannot be directly applied. Although you can use foam as a fire extinguisher, its conductivity is similar to water. Do not use foam to block light from reaching the solar PV module; you cannot rely on it as a means to eliminate power generation.
When adjusting and planning the size of the ventilation operation, the IC should consider the location and size of the solar photovoltaic array. During the cutting operation, take special care to avoid array conduits and wiring.
For residential ventilation operations, firefighters must be aware that solar photovoltaic ducts may operate in the attic space. The National Electrical Code® requires that the solar photovoltaic conduit/wiring system be installed more than 10 inches from the roof terrace or jacket. The only exception to this rule is when these conduits and wire systems are located directly below the array, their installation distance can be less than 10 inches. However, firefighters should still exercise caution when operating the saw for ventilation operations.
Use tags to identify all conduits and wire systems, junction boxes, conduit bodies, and other aspects of the solar photovoltaic system. Again, please note that although the label is a requirement, the label may become loose, damaged, lost or weathered.
When encountering a building with a light roof structure, keep firefighters away from the roof. When dealing with a fire involving solar photovoltaics, “big box” buildings may require ICs to consider “jumping out of the box.” Consider the use of large receiving door openings for ventilation and horizontal ventilation technology as auxiliary special call equipment (for example, cranes, claws, elevators, etc.). In all cases, if the ventilation operation is obstructed, please notify the IC immediately.
During post-fire operations, firefighters should not assume that any electrical components can be safely accessed. Always be careful and treat the system as if it is powered on. Don’t rely on “hot rods”. They only sense AC voltage; they do not sense DC voltage.
In addition, a fire event may damage the solar photovoltaic pipe and wire system, cause an electric arc, and may lead to a possible re-ignition the next morning. Make sure to check the scene during the day after the event to make sure it will not reignite. The system should not be re-energized until a qualified solar energy supplier/power contractor can satisfactorily re-commission the system.
Under normal circumstances, firefighters should wear appropriate personal protective equipment at the fire scene, but it is particularly important to wear it in a solar photovoltaic fire. However, fire-fighting gloves and fire-fighting boots have limited protection against electric shock. In addition, solar modules become slippery when wet, so do not stand on them. In addition, toxic chemicals are by-products of the burning of solar modules and are released in fires. Therefore, personnel must wear PPE and use self-contained breathing apparatus as an alternative. Finally, if the integrity of the structure is compromised, increasing the weight of the solar photovoltaic array to the weight of the responder and its equipment may cause the roof to collapse.
Renewable energy systems such as solar photovoltaics will continue to exist. Just like when the first hybrid electric car hits the road, the fire department needs to adapt to manage accidents involving these systems. Adapting to this technology will require participation in continuing education and practical exercises, as technology and code requirements are constantly changing.
IC and firefighters will need to strengthen the relationship between isolation and disconnection. When planning a solar photovoltaic fire accident in advance, it must be emphasized that the solar photovoltaic system will never be completely disconnected.
The key to positive reinforcement is to emphasize to all first responders that the goal is to minimize and isolate electrical hazards when reaching a solar photovoltaic event. Personnel should be able to distinguish between safe areas and electrified areas. Once these areas are identified, you can perform safe operations around the identified hazards.
As with any new firefighting challenge, the knowledge and awareness of solar photovoltaic technology will replace the fear of the unknown. When implementing this fire strategy, you can effectively and safely mitigate incidents involving solar photovoltaics.
Callan, M. Responding to utility emergencies: street-smart ways to understand and handle power and utility gas emergencies. First edition, Red Hat Press, 2004.
Grant, C. “Firefighter Safety and Emergency Response for Solar Power Systems”, NFPA, Fire Research Foundation, Quincy, Massachusetts, May 2010.
Slaughter, R. “Basic Knowledge of Photovoltaics for Fire Departments”. Dragonfly Communications Network, Corning, California, September 2006.
NFPA “Firefighter Safety and Emergency Response for Solar Power Systems-Final Report”, Quincy, Massachusetts, May 2010.
JOSEPH C. CAMAROTA, MIFireE, CFEI, IAAI, IABTI, a 38-year firefighting veteran, was the first lieutenant of the Whitman Square Volunteer Fire Company in Washington, New Jersey. He is a certified fire and explosion investigator and is a member of the Association of Fire Engineers, the National Association of Fire and Explosion Investigators, the International Association of Arson Investigators, and the International Association of Bomb Technicians and Investigators. Camarota is also a certified fire officer, construction and electrical inspector, firefighter, and lecturer in the State of New Jersey. He holds a Bachelor of Science in Electrical Engineering and an Associate of Science in Architectural Design. He is the electrical system design director of Ray Angelini, Inc.
UL issued a report on firefighter safety and photovoltaic systems, and established a solar panel training program. Firefighter training exercises: Photovoltaics-what?
Post time: Aug-16-2021