In wind turbines, nacelle encloses the generator, gearbox, drive train and the brake assembly. Nacelle fire refers to the turbulent diffusion fire stabilized behind a barrier under a high-speed airflow (Smith, 2004). Incidences of nacelle fires rarely occur, but whenever they do, total destruction of the turbines occurs leading to massive economic loses. Wind nacelle fires are considerably difficult to extinguish once started due to their sheer heights (Smith, 2004). In this regard, appropriate methodologies should used to ensure that nacelle fires do not occur.
Nacelle fires usually begin in two ways. These are through lightning strikes or technical errors (Smith, 2004). In both instances, a combination of sparks with transmission fluids is a dangerous occurrence. Similarly, nacelle plastics can fuel the fires, as they are highly flammable. Usually, lightning strikes on wind turbines results in repairable damages. However, when a lightning bolt strikes fire, serious damages arise (Smith, 2004). Wind experts have noted that susceptibility to lightning fires heavily depends on the wind turbine site and size. Thus, lightning fires are more common in the US than in Europe due to topographical differences (Smith, 2004). In Japan, nacelle fires caused by lightning have resulted in unimaginable loses. In one season, lightning fires destroy wind turbines whose cost is estimated to be over $5.5 million (Smith, 2004). Another major attribute affecting the susceptibility of wind turbines to these fires is the turbines’ size. An increase in the turbines size increases their vulnerability to lightning. Therefore, turbine designers should improve the efficiency of conduction blades (Smith, 2004). In this regard, designers should use highly conductive carbon fibers during the constructions of large blades. Despite this advice, some manufacturers fail to include carbon during turbine blades construction processes (Smith, 2004). These manufacturers have contributed in a way to the current increases in nacelle fires witnessed worldwide.
Another major cause of nacelle fires in wind turbines is technical faults (Smith, 2004). It is tedious to track the cause of fires rooting from technical faults due to their extensive damages. Normally, fires due technical faults arise from overheating or sparking in combination with flammable agents. Loose or broken electrical connections resulting from human carelessness normally initiate these sparks (Smith, 2004). Nacelle plastics, rubber cable linings and other flammable materials within the turbine fuel the sparks. Moreover, nacelle fires might occur due to components failure. In 2003, in Germany, a nacelle burnt down owing to a short circuit in a fail-safe battery backup (Smith, 2004). Whenever a bearing fails and runs dry, heat builds up in the nacelle leading to devastating fires and losses. To thwart these fires, technicians should sufficiently lubricate all moving parts within turbines and ensure that all cooling systems are operational. Experts have also argued that fail-safe brakes running hot at instances of braking might be potential causes of nacelle fires (Smith, 2004).
To prevent nacelle fires, regular servicing and maintenance of wind turbines is crucial (Smith, 2004). Technicians should appropriately route all cables to avoid rubbing between the cables and rotating components of the turbine. Similarly, all worn out oil conveying components should be replaced immediately to prevent sparks causing nacelle fires. Regular check-ups on the turbines will ensure that all the requirements are met and thus mitigate any incidences of nacelle fires (Smith, 2004). Automatic fire extinguishers should also be installed on wind turbines as a precautionary measure against fire outbreaks. As illustrated by modern nacelles, it is easier to extinguish a nacelle fire using fire extinguishers incorporated into the wind turbine system as compared to other means. Thus, all manufactures should aim at incorporation this technology in the turbine systems for safety purposes (Smith, 2004).
