Government subsidies have made wind farming a leader in the renewable energy sector.

It isn't just politicians tired of subsidies and environmentalists and homeowners who don't want them near their homes, they also catch fire more than is reported. 
Wind turbines catch fire because highly flammable materials such as hydraulic oil and plastics are in close proximity to machinery and electrical wires. These can ignite a fire if they overheat or are faulty. Lots of oxygen, in the form of high winds, can quickly fan a fire inside a turbine. Once ignited, the chances of fighting the blaze are slim due to the height of the wind turbine and the remote locations that they are often in.

Researchers from Imperial College London, the University of Edinburgh and SP Technical Research Institute of Sweden carried out a global assessment of 200,000 turbines
among the world's wind farms and found that ten times more fires are happening than are being reported.

Credit: Rose Lincoln, Harvard News Office.

Instead of an average of the 11.7 fires each year that are publicly reported, the researchers estimate that more than 117 separate fires are breaking out in turbines annually. 

Fossil fuels are not immune to fires, they happen thousands of times per year, but those industries are far larger and reports are accurate due to regulations. It is also not direct taxpayer subsidies funding oil and gas so if each turbine costs in the UK costs over £2 million, that is  £2 million
UK taxpayers have to replace. 

Since the 1980s, when wind farms were first constructed, the team found that fire has accounted for 10 to 30 per cent of reported turbine accidents. In 90 percent of the cases, the fire either leads to substantial downtime or a total loss of the wind turbine, resulting in economic losses.

The researchers also outline the main causes of fire ignition in wind turbines in the study. They are, in decreasing order of importance: lightning strike, electrical malfunction, mechanical failure, and errors with maintenance. Reports of fires in wind farms are increasing, say the researchers, but the true extent of these fires has been hard to assess because official reports about fires are either incomplete, biased or contain non-publicly available data.

In an effort to get a clearer picture about the true extent of fires in wind farms, the team carried out an extensive analysis of data from a wide range of sources. This included Government reports, data from anti- wind farm lobbyists and information gathered by major newspaper investigations.

"Wind turbines are viable sources of renewable energy that can assist the world to reduce emissions and help wean us off fossil fuels. However, fires are a problem for the industry, impacting on energy production, economic output and emitting toxic fumes. This could cast a shadow over the industry's green credentials. Worryingly our report shows that fire may be a bigger problem than what is currently reported. Our research outlines a number of strategies that can be adopted by the industry to make these turbines safer and more fire resistant in the future," says Dr. Guillermo Rein, from the Department of Mechanical Engineering at Imperial College London. 

The researchers suggest a number of measures that can be put in place to prevent fires from happening. These include "passive" fire protection measures such as installing comprehensive lightning protection systems.

Other measures include using non-combustible hydraulic and lubricant oils and building heat barriers to protect combustible materials. Manufacturers are also advised to avoid using combustible insulating materials and apply new monitoring systems to constantly check the condition of machinery so that maintenance work can be carried out in a timely way.

The researchers also suggest a number of "active" fire protection measures that can be used to stop a fire before it takes hold or gets out of control. These include smoke alarm systems inside the turbine, so that fire safety authorities can be alerted rapidly. The team also suggest suppression systems that quickly douse the flames in water or foam.

In the future, the team aim to study the impact of fire in other renewable energy technologies such as solar panels.