Are solar panels a fire risk?
Photovoltaic (PV) technologies – more commonly known as solar panels – generate power-using devices that absorb energy from sunlight and convert it into electrical energy through semiconducting materials. These devices, known as solar cells, are then connected to form larger power-generating units known as modules or panels.
There are four basic types of PV panel: monocrystalline, polycrystalline (or multicrystalline), hybrid and amorphous silicon. All are made from silicon, but differ in the way the silicon is cut and treated.
All electrical installations, by their nature, will carry some degree of fire risk. Although fires caused by PV panels are rare, any fire involving a building with a PV array can present an increased risk.
Where roof-mounted PV arrays are present, the risk of exterior fire spread is much greater than it would be for the roof assembly alone. This would be the case even if the solar panels had no combustible components. A typical fire scenario is the electrical wiring associated with the solar PV array causing ignition of the roof assembly. The potential flame height is largely a function of the type of roof cover and insulation immediately below the array. While the presence of solar panels may affect combustion air being drawn to the fire, it otherwise does not reduce, but redirects the flames from the roof fire.
The TUV report examined 210 PV fires and found that poor workmanship and design are responsible for the majority of fires caused by PV systems (38%) [1]. All PV system components exposed to sunshine and other weather elements need to have highly durable characteristics. Plastic materials that have traditionally performed well in this regard do not necessarily have good fire-resistance characteristics. The panels themselves typically contain limited plastics, but frames, mounting systems, cables and boxes can add to the combustible loading of an installation and the combustibility of the roof.
Standards for testing the performance of PV panels have been developed at an international level. While some address electrical performance, others address safety of the modules with respect to construction and operation. These safety standards also address fire behavior. The safety standards applied are IEC 61730 in Europe / Asia and ANSI/UL 1703 in North America. Both standards are very similar and contain elements of fire testing based on ASTM E-108/UL 790, Test for Fire Performance of Roofing Materials.
FM Approvals has tested PV modules for combustibility in accordance with ASTM E-108 and has developed Approval Standard 4476 for flexible PV modules and Approval Standard 4478 for rigid PV modules. In Europe, fire tests for evaluating the behavior of roof assemblies from external building fires are described in the standard DD CEN/TS 1187, Test methods for external fire exposure to roofs. Product classifications are provided in the standard EN 13501-5, Fire classification of construction products and building elements. Classification using data from external fire exposure to roofs tests.
Generally, PV panel fires were mainly caused by five main titles; Installation mistake: DC connections not mated properly, badly crimped connectors, no strain relief etc. Product failures: PV modules or inverters. External influence: animals, lightning etc. Planning failure: poor mechanical and electrical design (e.g. incorrect selection of DC isolators, cabling). Overheating: The temperature of PV panels can easily go up to 75 °C especially in the Middle East and North Africa (MENA) region
As mentioned earlier, poor workmanship and lack of maintenance are the main causes of PV panel fires. Moreover, PV systems should only be installed and commissioned by qualified contractors. Also, training courses and certification processes are available. Furthermore, PV systems should be inspected regularly by qualified professionals, including looking for potential damage from rodents and other pests, which could compromise the wiring or insulation. Finally, Infrared thermographic inspections should be conducted at least annually to look for “hot spots.”
As emphasized before, short circuits, maintenance operations, roof debris, animal nests, physical damage or the panel overheating typically causes solar panel fires. Detection of fire in the incipient stage is one of critical issue to successful suppression process. Linear Heat Detector are widely used for photovoltaic solar electricity farms.
Although, there is three type of Linear Heat Detection such as analog, digital and fiber optic; fiber optic LHD (Linear Heat Detection) systems can provide a very effective means of fire detection for solar panel installation as they have several key advantages: Fully distributed coverage. With measurement points every 1m along the full length of the cable every panel within the installation can be safely monitored by the fiber optic sensing cable. Smart alarms. With the advanced smart alarms, the system can detect fires much earlier than with conventional copper-based LHD systems. Immune to electromagnetic interference. Fiber optics are not affected by electromagnetic interference and so will not be affected by the potentially high levels due to the power generation. High reliability. The fiber optics sensing cables are completely inert and not susceptible to corrosion and with no moving parts or apertures can last more than 50 years in certain environments.
Depending on the fire system requirements, detection cable redundancy is one the key that increase system reliability. In the event of damage to the cable, the system can continue to function (although a system alarm will be generated so that action for repair, analysis can be taken).
To sum up, fires are extremely unlikely in PV systems when they are properly designed, installed and maintained. PV systems can be made even safer by addressing the most frequent root causes of DC arcs, which are mostly related to human errors during the design and installation stage. Finally, a redundant fire detection is one of the key element to increase system reliability.
REFERENCES; * VdS 3145: 2011-07(01): Photovoltaikanlagen, Technischer Leitfaden *NFPA 70, National Electric Code * FM Approvals, Approval Standard for Flexible Photovoltaic Modules, Class Number 4476 * FM Approvals, Approval Standard for Rigid Photovoltaic Modules, Class Number 4478 *Protectwire, Overheat and Fire Detection For Solar Panel *Sepanski et al, “Assessing Fire Risks in Photovoltaic Systems and Developing Safety Concepts for Risk Minimization,” TÜV Rheinland Energie und Umwelt GmbH, 2018. * Laukamp et al, “PV Fire Hazard – Analysis and Assessment of Fire Incidents,” 28th EU PVSEC 2013, Paris, * A. Chiaramonte, A. Smith and Z. Hood, “Fire Safety of Solar Photovoltaic Systems in Australia,” Worcestor Polytechnic Institute, 2016.
