What is Fog?
Fog, like clouds, consists of water droplets or ice particles (or mixture of both) dispersed in the air. The term fog is used when there is no bottom cloud boundary, which means that the cloud is located on the earth's surface. In principle, the liquid water content (LWC) and the size of the droplets are a little smaller than those of clouds (LWC less than 0.5 g/m³, drop size less than 10 µm). In meteorology, the term fog is used when the visibility is less than 1 km. When the visibility is higher, meteorologists use the term mist. Fog is basically divided into warm (above 0 °C) and cold (below 0 °C) fog. In cold fog, the drops are super-cooled, i.e. they remain in liquid state down to extremely low temperatures (as low as -39 °C). They only freeze when ice nuclei are added. Super-cooled fog drops that are impacted on the surface lead to a formation of rough frost.
Why Fog Dissipation?
Fog reduces the visibility thus leading to many disadvantages:
- reduced traffic speed on highways,
- increased danger of collision damages with injuries and fatalities,
- reduced landing frequency on airports,
- costly delays or even diversions to other airports,
- hindering watching and reporting of open-air sport or cultural events,
- endangering of open-air technologies (e.g. strip-mining),
- military and border protection issues,
- psychological aspects for humans.
This efficient and environment-friendly method brings safety for people, technologies, and the environment, reducing costs at the same time.
How does it work?
We blast dry ice grains (solid carbon dioxide, temperature of -78.5 °C, size between 50 µm and 2 mm) with high-pressurized air at almost sonic speed into the fog. The dry ice grains collide with the fog droplets, collecting them and thereby growing in size. Cooling down the fog leads to condensation growth and thermodynamic instability of the fog. This mechanism, called nucleation collision, has not been used so far by any other fog dissipation method. The process is sped up by forced convection due to the jet. Thus, fog dissipation occurs even beyond the direct dry ice jet.
By blasting 1 kg of dry ice up to 50 m into the fog, it is dissipated within 3 minutes, clearing a circle of 200 m in diameter. Using mobile systems, a corridor 200 m wide and 15 up to 25 km long can be dissipated within an hour.
Are there other methods?
Since fog disposal research has been carried out for more than 100 years (first patent in 1899), a variety of methods were tested by fog researchers. These methods are costly, ineffective and environmentally destructive.
Our method is based on dry ice, which is a recycling product from the chemical industry. Instead of using harmful chemicals, the application pro-longs the carbon-dioxide-cycle.
| method || efficiency || cost || environmental |
| seeding |
| -|| -|| -|
| --|| +|| ++|
| burners|| +|| ---|| ---|
| IR radiation|| -|| ---|| +++|
| mechanics|| -|| ---|| +++|
| dry ice |
| +++|| +|| ++|
Where can this technology be applied?
Our fog disposal method can be applied anywhere where fog hinders the achievement of certain economic and safety goals. A few examples are given in the following:
Due to fog and safety reasons, airports reduce their starting and landing frequency or (as the worst case scenario) even need to diversify traffic to other airports.
Highways, roads and harbors
Costs of damages and injuries resulting from car crashes are high - not to mention the individual consequences.
Sports events and cultural festivities
Fog hinders outdoor cultural and sports events, such as football and soccer games or winter sports, limits individual enjoyments and raises costs.
Construction sites and production facilities
Building and construction enterprises, the petrochemical and mining industry are faced with higher costs if construction, production, logistics, or raw material extraction is delayed by fog.
Military, border security, police and disaster control
The efficiency of military, border security, police, fire fighter and disaster control operations - equipped with fog dispersal technology - can be improved.