Solar power 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.

The 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 installations.

Fire protection 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.

Developments 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.

The 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.

Multiple 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 percent.1

THE POWER OF THE SUN

Solar 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 electricity).

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

Photovoltaic 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.

Power 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 present.


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.

Figure 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

To 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

Detailed 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

Advanced 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 vertical surface).

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 conditions.


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

Buildings 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 fire.

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.

Large 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.

The 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.

Two 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 firefighters.2

SOLAR POWER USE BY THE EMERGENCY RESPONSE COMMUNITY

Certain 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.

Examples 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.

Fire 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 today’s popularity.

An intriguing 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 Region.12

Casey C. Grant is with the Fire Protection Research Foundation.


References:

  1. Sherwood, S., "U.S. Solar Market Trends 2012,” Interstate Renewable Energy Council, Latham, NY, 2013.
  2. Backstrom, R. and Dini, D., "Firefighter Safety and Photovoltaic Installations Research Project,” Underwriters Laboratories, Northbrook, IL, 2011.
  3. Grant, C., "Fire Fighter Safety and Emergency Response for Solar Power Systems,” Fire Protection Research Foundation, Quincy, MA, 2010.
  4. Karter, M., "Fire Loss in the United States During 2012,” National Fire Protection Association, Quincy, MA, 2013.
  5. " Roof PV Fire of 4-5-09,” City Memorandum, P. Jackson to P. Burns, Bakersfield, CA, April 29, 2009.
  6. Millard, K., "La Farge Fire Chief: West End of Organic Valley HQ ‘a Total Loss,’” WXOW, LaCrosse, WI, May 14, 2013.
  7. Bayliss, K., Johnson, D. & Stamm, D. "11-Alarm Fire Guts Dietz & Watson Warehouse,” WCAU, Philadelphia, PA, September 3, 2013.
  8. 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.
  9. Grant, C., "Fire Fighter Safety and Emergency Response for Solar Power Systems,” Fire Protection Research Foundation, Quincy, MA, 2010.
  10. Ross, C., "Here Comes the Sun: Solar Energy for Emergency Medical and Disaster Use,” Emergency, Volume 25, Issue 12, December 1993, pgs. 34-37.
  11. May, B., "Solar Power: a Hot New Trend in the Fire Service,” Firehouse, April 2005, pg. 134.
  12. Markley, R., "Electricity On The Go,” Fire Chief, May 2008, pgs. 64-67.