is one of today’s good news stories. This is a rapidly growing segment
of the alternative energy market, with new technology that is
effectively and efficiently harnessing the energy of the sun.
ever expanding population of today’s world and an almost insatiable
craving for energy are strong drivers in the quest for renewable power
sources. Improved manufacturing of solar power technologies is greatly
enhancing the ability to create and utilize solar power technology,
resulting in more efficient and effective system installations. These
systems are increasing in size, complexity, and overall number of
engineers have an important role to play with the ongoing proliferation
of solar power systems. This technology is no different than any other
new and innovative approach, and with its clear benefits it also
introduces unanticipated and unintended consequences. These consequences
are not insurmountable or beyond the ability to manage and handle.
in the solar power field are proliferating at an ever increasing rate,
raising new questions about safety and reliability. These developments
are necessitating reexamination and modification of codes and standards
and other instruments of the existing safety infrastructure. The
expertise of fire protection engineers is important for the advancement
of solar power technology – to prevent unwanted events before they occur
or to mitigate any adverse events once they do occur.
overall health of the solar power industry is increasingly strong. In
the U.S., photovoltaic (PV) systems show strong promise for supporting
future electrical energy needs. The year 2012 was a productive year for
solar power with the capacity and number of facilities using this
equipment significantly increasing.
marketplace indicators reveal the growing strength of this technology,
such as: (i) the capacity of photovoltaic installations increasing by 80
percent in 2012 over the previous year; (ii) for six consecutive years,
the annual capacity growth rate exceeded 40 percent; (iii) the compound
annual growth rate over the last 10 years was 65 percent; (iv) the
total installed capacity of utility installations increased
two-and-one-half times; and (v) distributed installations (primarily on
residential, commercial, and government buildings) increased by 36
THE POWER OF THE SUN
power technology has proliferated in recent years, in part because of
improved manufacturing methods that are making this approach
realistically affordable and readily available. The three basic means of
capturing the sun’s energy are: passive solar (i.e., capturing the
sun’s energy in building design and construction); solar thermal (i.e.,
sunlight converted to heat); and photovoltaic (sunlight converted to
Of particular interest
from a fire protection engineering perspective are solar thermal and
photovoltaic systems. Solar thermal systems are those involving the
heating of fluids in a circulating loop system, and certain solar
thermal systems can add appreciable weight load to a structure. They
also can introduce general hazards to emergency responders similar to
other building systems, such as rooftop tripping or scalds from hot
liquids. For all rooftop systems, consideration needs to be given to
maintaining full access by fire fighters on the roof and on other
sections of a building where they operate during an emergency situation.
Figure 1: Primary Hazards of Solar Power Systems3
systems are different from solar thermal systems in that they directly
convert sunlight into electrical energy. These systems share similar
hazards with solar thermal systems, though with the additional
consideration that photovoltaic panels are electrically "on” when
exposed to sunshine or other light.
isolation during an emergency is a technical challenge; full and
complete power shutdown is normally not a simple option when exposed to
sunshine. Further, lighting other than sunlight has been shown to be
sufficient to cause harmful electrical shock.2 An additional
complication involves systems equipped with battery storage, which
continue to maintain current throughout the system when sunshine is not
The challenge of photovoltaic power isolation is, however, presently being addressed by new innovative electrical system approaches, such as module level electronics that can provide electrical isolation on the level of the solar cells, modules, or panels. While these approaches demonstrate significant promise for new installations, emergency responders lack widespread knowledge of which systems include such types of isolation technology. Thus, from their perspective, significant questions remain concerning the ability and time frames for this technology to infiltrate the current inventory of widely installed photovoltaic systems.
1 illustrates a side-by-side comparison of the primary hazards of solar
power systems for emergency responders and others.
IN SEARCH OF LOSS DATA
facilitate a review of loss information, structural fires involving
solar power systems can be evaluated as one of three basic types
depending on the point of ignition. These are: (1) an external exposure
fire to a building equipped with a solar power system; (2) a fire
originating within a structure from other than the solar system; or (3) a
fire originating in the solar power system as the point of ignition.3
loss information to support each of these scenarios is lacking due to
the relative newness of this technology and the length of time required
to collect credible data. Traditional fire loss statistics, such as
NFIRS (National Fire Incident Reporting System) handled by the U.S. Fire
Administration and FIDO (Fire Incident Data Organization) administered
by the National Fire Protection Association, do not at this time provide
the necessary level of detail to distinguish the relatively recent
technologies of solar power systems.
There is quantifiable data on the number of structure fires in the U.S. each year. For example, in 2012 there were 480,500 structure fires resulting in 2,470 deaths, 14,700 injuries, and $9.8 billion in direct property loss. Of these fires, residential structures accounted for 381,000 fires, 2,405 deaths, 13,175 injuries, and $7.2 billion in direct property loss.4 While the actual percentage of overall buildings with solar power systems and those involved with fire is unknown, there is a general expectation of how the data will likely trend in the future. As solar power systems continue to proliferate, the likelihood of them being involved with a structural fire will similarly increase.
Despite the lack of statistical data, several case studies of individual fire events can supplement the understanding of fires involving solar power systems. Several of these fires have exhibited certain noteworthy characteristics, such as an April 2009 fire in Bakersfield, Calif., where the rooftop system was the cause of the fire,5 a May 2013 fire in LaFarge, Wis., where a fire in the building caused the rooftop photovoltaic system to energize the entire metallic roof during the fire,6 and a September 2013 fire in Delanco, N.J., with a total loss to a commercial warehouse with a rooftop system of more than 7,000 panels.7
FIRE PROTECTION ENGINEERING CONCERNS
manufacturing techniques have allowed solar technologies to expand
beyond the traditional approach using panels that have been the mainstay
for many of today’s photovoltaic systems. For example, new photovoltaic
fabrics and films can be installed in any orientation (e.g., on a
Once again, this
raises questions relating to hazards and their performance in fire, such
as how the system components hinder, resist, or contribute to exterior
flame spread. Further, new, innovative building products include
components such as photovoltaic roofing shingles and tiles, which are
not readily obvious to firefighters and others that may need to be aware
of their hazards.
The test methods
necessary to assure proper performance of solar power system components
are currently evolving. The constant introduction of new products and
uniqueness of alternative system designs are challenging the current
methods of testing. For example, present tests for fire resistance of
roofing materials and assemblies may or may not be appropriate with a
photovoltaic system installed on top. Further, a question exists
concerning the long-term performance of the solar power system,
recognizing that it is intended to operate properly and safely
throughout its full lifespan with exposure to all intended climatic
The broader engineering community is asking questions on certain loss characteristics beyond loss from unwanted fire. These questions address considerations such as structural loads, ability to resist high winds, hail impact, and snow loads. These questions are being addressed in a research study conducted by the Fire Protection Research Foundation to review installation best practices, identify knowledge gaps, and provide an all-hazards assessment.8
EMERGENCY RESPONDER CONCERNS
and structures equipped with a rooftop solar power system, and in
particular a photovoltaic system, are becoming more common. For
firefighters, it is not an unimaginable event for any particular fire
department to encounter a photovoltaic system when fighting a structure
From the standpoint of
emergency responders, photovoltaic systems generally fall into two broad
categories: those small enough not to hinder firefighting tactics and
strategy, and larger systems that adversely impact their firefighting
approach. For relatively small systems, such as those found on
single-family residential occupancies, firefighters can typically work
around the system and any hazards during their operations. In contrast
are systems that cover entire rooftops, leaving little firefighter
access, or simply very large systems.
photovoltaic systems are thus garnering the attention of emergency
responders and fire protection engineers alike. These large systems
equate to solar power farms. Solar power farms may be installed at
ground level within isolated and secure tracts of land, or they may be
installed on the roofs of large commercial buildings. Examples are
expansive photovoltaic systems installed on big box stores, where
fire-fighting tactics and strategy become problematic.
general advice typically given to firefighters for large solar power
farms (such as those installed at ground level and not on a building) is
to treat them the same as any other power generation facility in their
jurisdiction. For a conventional power plant, or similar support
installation such as an electrical transformer yard or sub-station, the
advice to the local fire department has traditionally been to develop
robust pre-plans and not enter secured high voltage areas without clear
guidance from the power generation plant operators. With large
photovoltaic systems appearing on rooftops, this presents a challenge to
their normal tactics and strategies for fighting a building fire.
helpful research studies on this topic provide information for
emergency responders faced with fighting fires in buildings equipped
with solar power systems. The first was a study that pulled together
background information on this topic.9 The second was a more
comprehensive research effort that provides empirical test clarification
of the electrical hazards that photovoltaic systems provide to
SOLAR POWER USE BY THE EMERGENCY RESPONSE COMMUNITY
alternative energy applications are the power source of choice for some
emergency management and emergency response applications, and solar
power is a leader in this regard. The use of photovoltaic systems for
emergency preparedness and disaster planning is an obvious application
of alternative energy independent of the normal electrical power grid.
of the use of this technology abound as a mainstay for uninterrupted
power supplies. Fire stations are an integral part of almost all
communities, and these civic structures are possible candidates for
solar power system applications. Over the last several decades, multiple
examples exist of fire departments that have effectively installed
solar power systems on their fire stations.10,11 One example
is an initiative to establish a photovoltaic back-up power supply in
Boston for evacuation routes out of the city for critical traffic
controls, gas station pumps, and emergency evacuation repeaters.
service facilities in remote areas utilize solar power systems more by
necessity than for cost savings or similar reasons. This is not unusual
for installations in the urban/wildland interface, where commercial
electric power from the local utility may not be available. The U.S.
Forest Service has long used photovoltaic systems well in advance of
approach in California is the installation of fire apparatus rooftop
photovoltaic systems to accommodate deployment over long periods of time
(e.g., a wildfire event), providing a dependable electrical power
supply for radio operation and other critical electrical equipment. As
an example, one fire department that has equipped its fire apparatus in
this manner is the San Rafael Fire Department in the California Bay
Casey C. Grant is with the Fire Protection Research Foundation.
- Sherwood, S., "U.S. Solar Market Trends 2012,” Interstate Renewable Energy Council, Latham, NY, 2013.
- Backstrom, R. and Dini, D., "Firefighter Safety and Photovoltaic Installations Research Project,” Underwriters Laboratories, Northbrook, IL, 2011.
- Grant, C., "Fire Fighter Safety and Emergency Response for Solar Power Systems,” Fire Protection Research Foundation, Quincy, MA, 2010.
- Karter, M., "Fire Loss in the United States During 2012,” National Fire Protection Association, Quincy, MA, 2013.
- " Roof PV Fire of 4-5-09,” City Memorandum, P. Jackson to P. Burns, Bakersfield, CA, April 29, 2009.
- Millard, K., "La Farge Fire Chief: West End of Organic Valley HQ ‘a Total Loss,’” WXOW, LaCrosse, WI, May 14, 2013.
- Bayliss, K., Johnson, D. & Stamm, D. "11-Alarm Fire Guts Dietz & Watson Warehouse,” WCAU, Philadelphia, PA, September 3, 2013.
- Wills, R., Milke, J., Royle, S., and Steranka K., "Commercial Roof-Mounted Photovoltaic System Installation Best Practices Review and All Hazard Assessment,” Fire Protection Research Foundation, Quincy, MA, 2014.
- Grant, C., "Fire Fighter Safety and Emergency Response for Solar Power Systems,” Fire Protection Research Foundation, Quincy, MA, 2010.
- Ross, C., "Here Comes the Sun: Solar Energy for Emergency Medical and Disaster Use,” Emergency, Volume 25, Issue 12, December 1993, pgs. 34-37.
- May, B., "Solar Power: a Hot New Trend in the Fire Service,” Firehouse, April 2005, pg. 134.
- Markley, R., "Electricity On The Go,” Fire Chief, May 2008, pgs. 64-67.