Whether in Canada, California or the Mediterranean, forest fires around the world are becoming more frequent and, above all, more serious. Especially in summer, heat, drought and wind often turn such fires into raging infernos, and the climate crisis certainly isn’t helping.

Scientists from the Fraunhofer Institute for High-Speed ​​Dynamics, the Ernst-Mach-Institut, EMI and the start-up CAURUS Technologies GmbH are responding to the growing global threat. Together they are developing an innovative extinguishing method that can more effectively fight large-scale fires from the air.

Climate change is changing the quality of forest fires, making them hotter and spreading faster. In Canada alone, an area of ​​approximately 185,000 km²– slightly larger than the area of ​​Greece and Switzerland combined – burned in 2023.

In Germany, the forest fire season is also starting earlier and earlier. In dry regions such as Brandenburg, the first forest fires were reported on March 1 this year.

Working closely with its partner CAURUS Technologies GmbH, researchers at Fraunhofer EMI seek to make a key contribution to fighting forest fires from the air with a new type of extinguishing method. The modular system consists of hardware and software and combines digital technology with innovative extinguishing approaches, complementing conventional extinguishing methods.

Generating a directed water-aerosol cloud to improve the fire extinguishing effect

Most of the air and firefighting technologies used today date back to the 1970s and 1980s. Helicopters or planes carrying buckets of extinguishing water fly over the burning forests. At an altitude of 40 to 50 meters, the pilots open the bottom of the bucket. However, water is usually blown away and distributed over a large area by winds and thermal effects.

As a result, only a small amount of extinguishing water reaches the flames.

“We are able to offer the fire brigade improved and more sustainable extinguishing methods and use digital control options to increase the precision of extinguishing water delivery,” explains Dr. Dirk Schaffner, researcher at Fraunhofer EMI in Freiburg.

Project partners are also developing an opening mechanism that produces a fire extinguishing cloud that is much more efficient. This allows pilots to release very small, fine water droplets and precisely position the fire extinguishing cloud close to the source of the fire.

These factors have a decisive influence on the success of damping. They help reduce the temperature of a fire quickly, lowering it below the ignition point, and deprive the fire of needed oxygen over a large area.

“The mechanism enables the generation of a directed cloud of water-water aerosol, which is activated at a height of several meters above the flames or even in the flames. The water is not dispersed beforehand, but held together in the bag until it is just above the fire. Almost 100% of the water ends up directly in the flames,” describes Dr. Schaffner.

The water-aerosol cloud removes heat from the fire very quickly.

“The rate of heat transfer at which energy can be removed from a system depends on the surface area. The larger the surface area of ​​the absorbing medium, the faster the thermal energy is transferred from the combustion medium to the absorbing medium. And the aerosol cloud has an extremely large surface area,” explains the researcher.

He adds that in the case of an aerosol cloud, a much higher heat transfer coefficient is achieved than in the case of a lump of water. This method is also very effective in displacing oxygen, which weakens the combustion process.

Scientists are particularly focused on ensuring their solution is compatible with existing, effective firefighting tactics on the ground and ensuring the safety of all emergency services personnel.

Increasing water efficiency

A new technology – water aerosolization – is already used by firefighters on the ground in high-pressure dispersion nozzles. Scientists from Fraunhofer EMI and CAURUS Technologies GmbH are using it in the air for the first time, thus significantly expanding its range of applications.

Based on the research carried out, project partners expect the extinguishing effect to be five to ten times greater than that of current systems.

“For every liter of water used, the new method is able to extinguish a fire that is five to ten times larger,” says Dr. Schaffner, emphasizing the key advantage of this technology given the increasingly scarce water resources in the world.

The safety of emergency services personnel is also ensured, as they do not have to fly unnecessarily close to the source of the fire and can maintain a greater drop distance. Moreover, the new extinguishing method helps reduce CO emissions₂ greenhouse gas emissions because vegetation fires are suppressed much faster.

Forest fires are a huge source of CO2₂ emissions – an average of 6.9 gigatonnes of CO₂ Every year over the past 20 years, forest fires have resulted in greenhouse gas emissions. This is more than twice the emissions produced by all 27 members of the European Union during the same period.

Project partners have successfully tested the first prototypes of their innovative extinguishing method and are currently working on a demonstrator.