Solar Panels 101

Article and photos by Alan Skursky
As the “eco-friendly” world increasingly creeps in around us, firefighters face new and increased hazards that will force us to change the way we traditionally operate on the fireground. The installation of solar-power systems has become increasingly popular; they are present in all types of construction: exclusive homes, row homes, office buildings, and apartment buildings, and in all neighborhoods. This article discusses the two types of solar-panel systems with which we will most commonly deal with, the thermal system and the photovoltaic system.

A thermal system is used for heating fluids. An open-loop system heats domestic water directly and is used in tropical regions where freezing never occurs. A closed-loop system, used in colder climates, is a pressurized system that heats a 50/50 mixture of glycol and water. The heat is transferred through conduction to the domestic water. Thermal panels will generally be connected with copper pipes and fittings and may have low-voltage control wiring attached. The most common-sized module is four feet by eight feet; several can be tied together in a system. The hazards that a thermal system presents for firefighting operations, for the most part, are obvious: hampered vertical ventilation if the system is installed on the roof; structural collapse because of the added weight; tripping and slipping hazards; inhalation hazards from combustion by-products; and a potential for burns from hot fluids (generally 50°-90°F  on a cold cloudy day and 120°-180°F on a hot and sunny day). 

(1)  A pressurized rooftop thermal system with four foot by eight foot panels.

A photovoltaic (PV) system generates electrical power by converting sunlight to electricity. The photovoltaic module is made up of solar cells, which convert light to electricity, generally through the use of high-purity silicon wafers. The physical dimensions of a standard module are generally two and a half feet by four feet. These modules typically weigh less than 50 pounds. However, several new technologies have allowed photovoltaic modules to become integrated into the outer shell of a building, such as a module that’s shaped like and used like a conventional roof shingle. There can be several to several hundred modules put together to form a system. Other components of a PV system include inverter; disconnects; conduits; and, in some systems, electrical storage devices (i.e., batteries). A PV system generates electricity whenever the sun is shining and carries voltages up to 600 volts direct current (DC) and currents up to 8 amps in residential systems. An inverter is used to convert the DC current to alternating current (AC).
 The hazards a PV system presents for firefighters are potentially deadly. A PV module will continue to produce electricity as long as the sun is shining. You cannot turn a PV module off. You can isolate the electrical current by using disconnects (lock out, tag out), but the module will remain energized as long as it receives sunlight. One tactic for minimizing the electrical output of a PV system is to cover all the modules completely with a 100-percent light-blocking material. Salvage covers are not 100-percent light blocking but will reduce the amount of electricity produced if used to cover a system. This system should be considered as “live” as long as the sun is shining. Other hazards include hampered vertical ventilation if the system is installed on the roof, structural collapse because of the added weight, and tripping and slipping hazards.
If a PV system becomes impinged by fire, treat it like all other energized electrical equipment: Shut down what you can to reduce the current flow, apply class “C” extinguishing agents, and protect exposures with a fog pattern. Nighttime operations will provide an inherent level of safety, but remember that when daylight breaks, the modules will again produce electricity. Light from the moon will not energize a module, but lightning has the potential to create a temporary surge. 

Wear a self-contained breathing apparatus when operating in the area of a module impinged by fire because of the materials used in the manufacturing of PV modules (i.e., phosphorous; gallium arsenide; and cadmium, a known carcinogen).

(2) A PV system mounted on the roof.

(3) A PV system designed to look like conventional roof shingles.

While operating on a working fire, it can be difficult to determine whether the system is thermal or PV unless you are familiar with these systems. Know your district, walk your buildings, do inspections, and preplan at the company level. When you’re faced with a solar system at an incident, notify the incident commander as soon as possible If it’s a system you aren’t familiar with, treat it as a hazard, and limit your operations in that area. As building construction continues to evolve with what sometimes seems like little or no input from the emergency responder, our job continues to become increasingly dangerous. We must continue to be diligent and aware of the changes around us.
Alan Skursky is a lieutenant with the District of Columbia Fire Department, where he is assigned to Engine 33.