BY TIMOTHY KREIS
As a nation with rapidly rising energy costs, we are desperately searching for ways to go green. The fire service must begin to address how the green initiative might affect our daily operations and safety. Solar energy has become one of the most widely employed of the options being considered as alternative energy sources. Solar energy technology has been around for a long time. The calculators on our desks and those funny looking solar-powered Jetson mobiles we see on TV come to mind. The recent sparked interest in solar energy is something I read about in the newspaper and heard tossed around in a political debate, but I never really considered how it might change my job as a firefighter until I received a phone call from a friend from the local power company here in Arizona.
I had been working with the Arizona Public Service (APS) and the Salt River Project (SRP) on a program to identify high-voltage electrical vaults and substations within Phoenix. About a year ago, Phoenix Fire responded to a reported fire in the basement of a residential high-rise building in downtown Phoenix. After arriving on-scene, firefighters forced entry into an “unmarked basement” and began extinguishing a small fire involving what appeared to be electrical equipment. When the electrical company arrived, it was discovered that the “basement” our fire crews were working in was actually an electrical vault. In addition, the equipment involved was a high-voltage transformer. Fortunately, a lighting strike had damaged the transformers, and they were not energized. Had they been energized, discharging a dry chemical extinguisher on this equipment most certainly would have led to electrical injuries to our firefighters, at the very least.
After that incident, we began working with the APS and the SRP. I’m proud to say all of their facilities throughout the state of Arizona are clearly marked with a standard warning sign for firefighters. In addition, we were able to get a list of all of their facilities and their locations. We input this information into our computer-aided dispatch system to alert units of these hazards while en route to an incident.
SOLAR CELL HAZARDS
Fortunately, the APS and the SRP are very supportive of the fire service in Arizona, and things are getting better and safer all the time. About a month after we finished the project, I received an e-mail from the APS asking if we had been looking at the firefighter safety issues associated with photovoltaic systems on homes and businesses. Before I even opened up my dictionary to find out what a photovoltaic (PV) system is, I asked the Operations chief if I could work on this project. What I didn’t know at the time was just how real an issue this is from the perspective of firefighter safety across America and how far behind we are in addressing it.
Photovoltaic is the technology and research associated with using solar cells to create electrical energy by converting sunlight into electricity. Interest in solar energy technology has really taken off lately. PV production has been doubling every two years and is the world’s fastest growing energy technology. California is America’s leading producer of solar energy. In September 2006, Rodney Slaughter authored the comprehensive report “Fundamentals of Photovoltaics for the Fire Service.” This report, funded by the California Solar Energy Industries Association (CAL SEIA, http://calseia.org) and the Sacramento Municipal Utility District, clearly illustrates the issues associated with PV systems and the safety challenges they present to firefighters. It is available on request; call CAL SEIA at (916) 747-6987. According to the report, the United States, in 2005, produced three percent of the total solar energy worldwide, or 104 megawatts; California led the way. According to California Energy Commission (CEC) records, California now has more than 17,300 grid-connected commercial and residential systems. The goal is to have one million solar roofs by 2017. Although California firefighters would seem to have the greatest chances of responding to a structure fire with a PV system present, other communities around the nation, including Phoenix, are beginning to see PV systems on rooftops.
How do the homes and businesses with PV systems affect our safety on the fireground, and what can we do about it?
In 2002, a firefighter in Switzerland was injured as the result of an electrical shock he received from a PV; fortunately, the injuries were not serious. In 2007, a firefighter in Sedona, Arizona, received an indirect electrical shock while fighting a house fire. In this case, the home electricity was secured at the utility box. The firefighters operating at this incident were unaware that the PV system was still energized.
Multiple types of PV systems are available. Solar panels installed on the roof of a building soak up sunlight during the day and instantly convert it into direct current (DC) electrical energy. The electricity is then run into an inverter that converts the DC power into standard alternating current (AC) for use in the home. This electricity is synchronized with the utility power whenever the solar grid is producing. The electrical panel distributes the solar energy and utility power throughout the home. It is not uncommon during peak sunlight hours for the utility meter to spin backward when the solar electricity generated exceeds the home’s needs. In this case, the excess power can be sold back to the utility company for a credit. Utility power is automatically provided at night and during times when the home’s demand exceeds the solar production. Some systems include batteries that store electrical energy for use when the sun is not shining.
The PV systems we are seeing today are pretty efficient; during peak sunlight hours, they can generate enough electrical energy to power a home or business, and you must be cautious when operating near them. When conducting fireground operations on a building with a PV system, assume the PV system is energized. We all know that when we shut down a building’s electrical utilities at the panel, everything above the utility box is still energizedin other words, the utility lines running into the box are still hot. After the building’s utilities are secured, we would not ladder the building near any power lines because we can’t shut them down and we know they are still energized. We should employ the same logic with regard to PV systems. For example, if we shut down the utilities on a home with a PV system, we must be aware that the solar panels are still generating electrical energy.
Many factors can affect PV performance, and PV technology does not convert 100 percent of the sun’s energy into electricity. The most efficient PV systems installed on conventional buildings today convert only 10 to 20 percent of the sun’s energy. As the technology continues to improve and PVs become more cost effective, we can expect to see them on more rooftops in our communities.
It’s also important to remember that environmental factors can affect a PV system’s performance. Cloud cover, smog, and temperature are just a few things that can reduce the amount of electrical energy created by a PV system. Although the time of day and the weather can affect PV performance, firefighters should always treat the system as if it were energized electrical equipment.
Whenever the sun is shining, a PV system is creating electrical energy, and it can’t be turned off. A fire department in California attempted to black out a PV system by using a salvage cover to block out sunlight. The energy created by the system was reduced, but it did not completely block out the sun, and the system still produced enough electricity to shock a potential victim. Firefighters in Germany attempted to cover solar panels with foam to block out the sunlight, with a similar result. Sunlight was able to penetrate through the foam, and the PV system continued to create electrical energy. In this case, the foam kept sliding off the panels. The bottom line for the fire service is to treat the system as any other electrical equipment and assume it’s energized.
When firefighters are conducting fireground support operations like vertical ventilation, they need to be aware of the safety issues associated with completing those critical fireground tasks. PV systems present some new challenges on the fireground; we need to be aware of them. The potential shock hazard is undoubtedly of the most concern, especially since the solar panels can’t be shut down.
Firefighters conducting vertical ventilation must be aware of the dangers of PV systems. For example, if a firefighter were to break the glass protecting a solar cell, this could potentially discharge all of the inherent energy in the system. We all know that the most effective vertical ventilation hole is cut directly over the fire and that if we can complete this task safely, we are going to do it. I don’t think it’s a stretch of the imagination that a company officer not familiar with PV systems might attempt to break or remove the solar cells from the roof to complete vertical ventilation, which could be a deadly mistake.
Not only firefighters on the roof need to be aware of the hazards associated with PV systems. Be extremely cautious about sending firefighters into the attic to conduct overhaul operations of a structure with a PV system on the roof. Typically, we would ensure that the utilities are secure prior to starting overhaul. In the case of a building or a home with a PV system, we need to remember that during daylight hours the solar cells and the conduit of a PV system remain energized. Also, the “hot stick” many fire departments carry on their engines and ladders detects only alternating current; using a hot stick to determine if a PV system is energized will mislead firefighters into a false sense of security because everything between the solar cells and the inverter is direct current.
Some PV systems include batteries that store the solar-generated electricity. Do not cut into these batteries, and keep in mind that if they are exposed to fire, they will release corrosive fumes and gases. Additionally, if these corrosive fumes come into contact with certain metals, they will produce explosive gases and toxic fumes. When responding to emergencies involving batteries, always wear full protective turnouts and SCBA.
PVs pose other safety considerations as well. A PV system on the roof of a building adds an additional load to the roofa residential PV system could weigh 1,000 pounds. This sounds like a lot, but the weight is spread across the roof at approximately 2.5 pounds per square foot, which is not exactly as significant a dead load as an air-conditioning unit. However, it will affect the roof’s performance under fire conditions. In some installations, a PV system on the roof might make it more difficult to assess the condition of the roof.
The manufacturing process of a photovoltaic cell includes the use of many hazardous chemicals. During a fire or an explosion, a solar cell can release these hazardous chemicals and present an inhalation hazard to firefighters working around them and the civilians downwind. In the case of a small residential system, the exposure hazard is very small. Larger arrays, like those found on some commercial buildings, are more likely to be an exposure hazard for firefighters and the public downwind. Firefighters should use their standard operating procedures to determine whether or not to evacuate nearby residents or shelter them in place. Pay special attention to children, the elderly, and people with existing respiratory conditions.
The reality is that photovoltaic systems are here to stay. As green energy technology continues to develop, the fire service will have to unite on issues such as firefighter training and developing well-written code regulations and standard operating procedures.
Even though PV systems are being installed on buildings across the nation at a rapid pace, the fire service can train and address this new challenge in a progressive manner. Training officers should become familiar with PVs. The International Fire Service Training Association has included PV systems in its new Fireground Support Operations Manual, Second Edition.
TIMOTHY KREIS has been a member of the Phoenix (AZ) Fire Department since 2002. He is a firefighter on an engine company and previously was an inspector in the Fire Prevention Bureau. He is an adjunct instructor and an advisory board member of the fire science programs of Phoenix College and Paradise Valley Community College. He has been a member of the International Fire Service Training Association for two years.