Roof-mounted photovoltaic systems

Fire risks

Fires on roof-mounted photovoltaic (PV) systems are rare. When they do happen, however, a combination of electrical hazards, combustible components and limited access can result in significant losses.

As the technology becomes more common, this paper discusses how building owners and occupiers should approach and minimise the risks of PV systems.

Sunshine technology

Solar is a booming industry. At the end of 2018, according to the IEA, around 8% of German electricity was sourced from PV panels. In China, the equivalent figure was 3%; but PV capacity grew by more than a factor of four between 2015‒2018, making it the largest PV power producer on the planet.

Major PV plants are located in hot, dry regions. In more temperate areas, the PV industry is smaller scale and frequently roof-mounted. Such PV systems have three risk defining characteristics: (1) electrical components located in exposed and often hard-to-access areas; (2) additional combustible load increasing the danger of fire spread; and (3) electrical installations that are difficult to isolate, and which firefighters may be hesitant in tackling. Roof mounted PV systems frequently remain outside the scope of traditional risk control systems such as building sprinklers and fire detection.

There is little comparable data on fire and roof-mounted PV systems. The US National Fire Data Center does not track PV-fires, filing them under 'other' causes. One significant incident was the destruction of a 30 000 m² warehouse in New Jersey in 2013, when firefighters decided not to operate on the roof. Japanese authorities reported 127 incidents with PV systems (not all fires) over a ten-year period to 2017, of which 7 saw fires spread to the building roof. The German Fraunhofer Group recorded 350 PV-related fires over 20 years to 2019, including 10 cases of complete building loss. At the end of 2018, there were around 1.4 million PV system installations in Germany*.

These figures do not include losses associated with relatively small fires. Business interruption at a facility, even after a small incident, can be costly. Moreover, roof-mounted PV systems are exposed to all the elements, and weather damage may contribute to fire risk.

Management of change

Assess the potential impacts of changes to the business. Involve your property insurer / broker / risk engineering provider in planned changes.

Business continuity management

Conduct a thorough business impact assessment to inform both emergency and business continuity plans.

Lessons learned

Common issues reported or observed include:

  • Damaged or mismatched connectors
  • Connectors not watertight
  • DC cabling on the roof not properly secured
  • Induction loops created
  • Panels not properly secured
  • Ineffective grounding
  • Inverters not easily accessible or close to combustibles
  • Arc faults
  • Inadequate residual current device
  • Systems installed on combustible roof
  • Limited consideration of emergency business continuity response
Example DC arc fault

Your risk checklist

The frequency of fire or other incidents with roof-mounted PV systems is rare; but the consequences can be severe. Risk managers should consider the following:

Compliance: Building owners and occupiers, together with installers, should ensure they comply with local legislation, codes and standards. This should include (1) suitable fire assessments; (2) complying with local planning requirements and building legislation; and (3) designing and installing electrical installations according to the local code. Of particular note with PV systems is that standards or codes for what remains a relatively new and evolving technology may change and update. If you have any questions or uncertainties, contact your insurer, your broker or your risk engineering provider.

Business continuity: A thorough assessment of the hazards and the potential impact to the business should be undertaken. This is a key requirement to develop suitable emergency and business continuity plans. Example: The installation of a PV system on a combustible roof can create a 'combustible void’'between the system and the roof, increasing the risk of fire spread as well as shielding the roof from fire water (if applied). The risk of both ignition and fire spread is increased. Installation of PV systems on non-combustible or fire resistive roof structures can help reduce this exposure.

Design: Building owners and occupiers should carefully consider the design of their PV installation to establish good principles of loss prevention. Actions taken at the design stage influence the overall performance over the life of the system and its fire resilience.

Points to note include:

  • Appointment of a suitable and accredited vendor/fitter
  • Installing PV systems on noncombustible roof structures: Where roofs contain combustible elements, seek further guidance to mitigate the fire risk. Ensure the installation does not provide a route for fire spread over fire walls, providing adequate clear space between installation and the fire wall  Ensuring the roof can withstand the additional dead load of the photovoltaic system and the live loads from natural hazards
  • Providing access for both routine maintenance and emergency situations
  • Installing panels with wiring practices that are weather tight, and protected from other forms of damage, such as animals. DC plug connections should be compatible and sourced from a single manufacturer
  • Ensuring PV systems are installed on dedicated branch circuits, not emergency circuits
  • Provision of fault detection and where required, lighting and surge protection systems
  • Provision of adequate grounding and protection
  • Provision of suitable fire detection and protection systems to provide early warning and a means to tackle a fire
  • Locating internal equipment such as inverters and switches in suitable fire compartments, clear of combustibles and with fire detection

Installation and commissioning: The PV system should be installed and commissioned by suitable qualified persons.

Considerations include:

  • Well-managed worksite, with measures to avoid damage, impact or contamination
  • Ensuring equipment is mechanically secured and the area under panels is clear
  • Hot work should be avoided; if unavoidable, ensure a robust hot work system is in place

The commissioning of the PV system requires both visual observations together with tests and measurements to verify the safe and proper operation of the system.

Key steps typically include:

  • Completing visual inspections
  • Verifying compliance with relevant codes and standards
  • Conducting electrical verification tests
  • Verifying system functionality including start-up, operations, shut-down and emergency procedures
  • Completing system documentation, including changes for as-built drawings

Operation & maintenance: PV systems require monitoring, inspection and periodic maintenance to maximise performance and minimise risk. Maintenance and inspection activities should be conducted in accordance with the installer's guidelines by qualified persons. Event-based inspections should take place following natural hazards, including wind, hail, ice, snow, earthquake or bushfire. Online monitoring supplements periodic maintenance, allowing continuous real-time performance measurement and fault detection. Regular thermographic inspections (infrared testing) can identify hot spots such as poor connectors or overheating equipment such as diodes or module busbars.

Emergency response: In the event of an emergency, a clearly defined plan prepared in advance can help mitigate the loss.

Considerations include:

  • Means to identify a fault or emergency and communicate it with emergency responders
  • Provision of access and information to the emergency responders including site layout, hazards, means of isolating the PV system and other utilities
  • Clear labelling of important components
  • Collaboration with emergency responders, developing plans and conducting exercises

Your risk experts

Already a common feature in many countries, PV systems will become increasingly ubiquitous, as authorities seek to hit ambitious carbon reduction targets. A safe, reliable source of power, PV systems, like any technology, are not risk free; and building owners and occupiers must understand and manage that risk. Our established risk engineering expertise and experience makes Swiss Re Corporate Solutions your ideal partner in helping manage your risks.

* As noted by John Weaver, PV Magazine, 23 August 2019

Resources

  • IEC 62446 Photovoltaic (PV) Systems
  • NFPA 1, Fire Code.
  • NFPA 70, National Electrical Code
  • CNPP Apsad D20, Procédés Photovoltaiques
  • RC62: Recommendations for fire safety with photovoltaic panel installations. RISCAuthority. 2016

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