Foggy road

What happens if fog comes on roads? First of all, visibility falls down, so the risk for a car accident increases, especially on highways. Scientists from Central Aerological Observatory have constructed a special electrostatic filter, which eliminates the fog at a distance up to 10 meters. The filter looks like a metal frame with a precipitation electrode – thin metal plates, separated with high-voltage isolators. It also has a corona-forming electrode of a twisted wire. The unit is grounded with a metal net.

Current fog dissipation methods are good only for cold fogs, which appear at temperatures below zero. Warm fogs are a bit worse: they are thermodynamically stable, and it requires much energy to dissipate them. There is a good method of electrostatic fog precipitation, used on factories: fog particles caught into electrostatic field between two electrodes – corona-forming and precipitation – acquire electrical charge (because of ionised air) and start moving towards the precipitation electrode. They stick to it and lose their charge.

The scientists tried to apply this method to open air. For testing purposes they created fog and then dissipated it under various weather conditions – on a sunny day with gradual temperature increase, or cloudy day with no temperature change, or in cold evenings. During these experiments, the scientists found the best electrodes shape and corona-forming voltage. So, electrostatic method takes 7 minutes for fog to disappear, while under natural conditions it takes nearly an hour.

The filter was constructed using the data from Central Aerological Observatory. It was tested on 4 kilometres of highway Venice – Trieste. After carrying out a series of tests, it was found that the best way of using filters is to place them along the central reservation, separated by screens of 3 meters wide and 2 meter high. Such positioning provides 10 meters of clear distance at both sides from the filter.