The wind energy industry is one of today’s leading industries in the renewable energy sector, providing an affordable and sustainable energy solution. However, the wind industry faces a number of challenges, one of which is fire and that can cast a shadow on its green credentials. The three elements of the fire triangle, fuel (oil and polymers), oxygen (wind) and ignition (electric, mechanical and lighting) are represent and confined to the small and closed compartment of the turbine nacelle. Moreover, once ignition occurs in a turbine, the chances of externally fighting the fire are very slim due to the height of the nacelle and the often remote location of the wind farm. Instances of reports about fires in wind farms are increasing, yet the true extent of the impact of fires on the energy industry on a global scale is impossible to assess. Sources of information are incomplete, biased, or contain non-publically available data. The poor statistical records of wind turbine fires are a main cause of concern and hinder any research effort in this field.
This paper aims to summarise the current state of knowledge in this area by presenting a review of the few sources which are available, in order to quantify and understand the fire problem in wind energy. We have found that fire is the second leading cause of catastrophic accidents in wind turbines (after blade failure) and accounts for 10 to 30% of the reported turbine accidents of any year since 1980’s. In 90% of the cases, the fire leads to a total loss of the wind turbine, or at least a downtime that results in the accumulation of economic losses.
The main causes of fire ignition in wind turbines are (in decreasing order of importance): lighting strike, electrical malfunction, mechanical malfunction, and maintenance. Due to the many flammable materials used in a wind turbine (eg. fiberglass reinforced polymers, foam insulation, cables) and the large oil storage used for lubrication of mechanical components, the fuel load in a turbine nacelle is commonly very large. The paper finishes with an overview of the passive and active protection options and the economics (costs, revenue and insurance) of wind turbines to put in context the value of a loss turbine compared to the cost and options of fire protection. We hope that this paper will encourage the scientific community to pursue a proper understanding of the problem and its scale, allowing the development of the most appropriate fire protection engineering solutions.
DISCUSSION AND CONCLUSIONS
This article has highlighted the unique nature of the fire problem faced by the wind energy industry, as well as the paucity of available information about such fires in the public or scientific domains. There are numerous examples of accidents reported in the popular press, all of which highlight the significant impact and ensuing downtime due to fires. These fires result in financial loss, power loss (which is especially problematic in remote locations where the wind turbines are a major source for electricity), as well as secondary damage, for example through road closures or ignition of wild fires in rural areas.
There is however very little scientific information available publically from which to evaluate the problem critically, since much of this information is proprietary. What is known and apparent, however, is that because of the nature of wind turbines, fire-fighting is difficult. The nacelles are significantly elevated above ground level, beyond the reach of most fire-fighting appliances. Turbines are often located in remote rural areas, increasing response time. Yet the environment inside of a wind turbine nacelle may lead to increased likelihood of ignition because of the choice or design of the components, and to increased difficulty in detection or suppression since the favoured environment requires high flow of air around the nacelle and through it in the case of some designs. Therefore, where fires do occur there is - in the majority of cases - a 100% loss of the turbine structure and the only recourse of fire-fighters is often to attempt to limit the spread of the fire to other areas.
The wind energy industry has shown steep growth over recent decades, and global targets for renewable energy use mean that we will rely increasingly on this source of power. Increased reliance on this method of power generation will result in an increased exposure of society to the effect of fires in these facilities. Research is therefore needed to better understand the fire behaviour of the critical components in the nacelle and the contribution of the environmental conditions to the fire growth inside of the nacelle for both suppression and detection requirements. There is also potential for improving fire safety inside of the nacelle by means of taking passive measures  – either in the design or construction of the turbine as well as through the management of the facility.
The fire problem in wind turbines is indeed a cause for concern to all stakeholders. First, fire events can cast a shadow on the green credentials of the technology. A second, given the current and projected increases in the use of these facilities and reliance on them, a proactive approach to solving the problem has the potential to significantly reduce the economic costs and threats to society.