Wind turbines stand over 300 ft tall with each blade measuring over 100 ft long with blade speeds of up to 180 mph. Fire protection for these giant structures poses a variety of unique risks. Because there is no formal reporting process of reporting and recording fire incidents in wind turbines, it’s hard to get an accurate count. However, in a 2015 report, Towering Inferno, completed by GCube, a clean energy insurance provider, cited 50 wind turbine fire incidents. While to some, this number is not very high, the cost implications are substantial. The total loss of a wind turbine costs at least $4.5M, and that number is rising as the wind turbines are getting larger. In this post, we will explore hazards, ignition sources, and fire protection options for wind turbines.
Hazards & Risk Factors
It is nearly impossible to put out a wind turbine fire using manual fire-fighting methods. The height of turbines, potential of the blade still rotating, and the remote locations many wind farms make them difficult, if not impossible, for local fire departments to battle. Combustible materials in the wind turbine are also risk factors. Composite materials are found in the blades, nacelle walls, and an estimated 235 gallons of lubricating oil and other highly combustible liquids that are held in the nacelle. These oils and liquids are used in the gearbox, yaw, hydraulic system, blade pitch change mechanism, oil pumps, mechanical brake, and oil-filled transformer. All that is needed is an ignition source to spark a fire.
Ignition Sources
Common ignition sources are found in the nacelle and include electrical malfunction, hot surface ignition, and lighting strikes. When lightning protection systems are not installed or maintained, it puts the wind turbine at a higher risk of fire. Electrical malfunctions, faults, and arcs can happen in components found within the nacelle, while hot surfaces in the gearbox, generator, brake system, pumps, and transformer are all factors that can ignite a fire.
Wind Turbine Fire Protection Options
As of today, fire protection standards for wind turbines are at a localized level, which could be by state, providence, city, or even municipality. There is no mandated international standard. The most widely recognized recommendation is NFPA 850, which recommends practice for fire protection for electric generating plants and high voltage direct current converter stations.
When it comes to wind turbine fire protection, options do exist. Smoke, heat, and flame detectors, as well as fire suppression systems, can be installed on wind turbines. These various detectors can identify a fire during the early stage and send information to a central alarm system that will initiate a complete shutdown of the turbine’s components and activate a fire suppression system. However, special consideration needs to be taken into account for onshore turbines that have air inlets/outlets and vents in the nacelle, which brings in dirt and dust from the outside. Any detectors need to be able to stand up to the harsh environment.
Types of fire suppression systems
Adding a fire suppression system to a wind turbine provides a layer of fire protection. If you decide to opt in to adding fire suppression systems, several options are available (with varying levels of success).
Water-based
Water-based fire suppression systems include sprinklers, water mist, and foam water. While these types of systems are ideal for certain applications, wind turbines are not one of them. The first challenge is the need for a water supply. Because of the remote locations, water is not widely available on the site and difficult to pump to the height of the turbines. Storing water in the nacelle is possible if using a water mist system and foam water systems, but space is still a challenge, and the systems require more intensive maintenance. Lastly, all water-based systems will have some level of damage to critical components within the nacelle, especially if a false discharge occurs..
Carbon Dioxide (CO2)
The challenge in using CO2 systems is the need for an airtight nacelle, which is not the case for onshore wind turbines. When activated in an airtight environment, these systems provide suppression within seconds after discharge and can penetrate inside components and equipment. The maintenance of gas-based systems is rather low and should be checked or monitored for the level of CO2 to ensure no leaks. When discharged, CO2 leaves no residue and does not adversely affect electrical components; however, CO2 does pose significant risks to humans present during a discharge and requires extensive lock out tag out measures to ensure people safety while accessing the space.
Aerosol-based
Aerosol-based fire suppression consists of very fine solid particles and gaseous matter and provides total flood protection. While the systems are relatively small, special consideration needs to be taken during the design with regards to the proximity to components within the nacelle. Aerosol-based systems are considered environmentally safe; however, they can leave a residue causing damage to sensitive electronics. A specific cleaning protocol should be followed post aerosol discharge to minimize damage from the residue. These systems are easy to service as they require minimal maintenance.
Clean Agent
Automatic fire suppression systems using clean agents, like Chemours FM-200 and 3M Novec 1230, are an ideal option to protect wind turbines. Little space is required for cylinders that contain the clean agent, detection tubing is easily routed around the specific areas within the wind turbine you are trying to protect, and the systems do not require electricity to operate. The systems are less prone to false activation, and clean agents are safe in occupied/confined spaces around people and do not damage equipment. No residue is left after a discharge of the clean agents; therefore, no clean-up is required. Completing annual inspections will ensure the systems are in proper working order.
Conclusion
The International Association for Fire Safety Science reported in 2014 that over 90% of wind turbine fires resulted in the total loss of the turbine, or the turbine had severe structural failure of its major components. With the costs rising of wind turbine replacements due to fires, it is more important than ever to protect them. Protecting turbines can be done by installing fire suppression systems to detect a fire as soon as it starts and then suppresses it to prevent the fire from spreading. There are many types and sizes of fire suppression systems, each working in a unique way. Keep in mind, selecting and designing the best system for your application is based on the equipment needing protection and the type of fire hazard.