Scientists unveil laser beam to deflect lightning strikes

The trial followed 20 years of research and lab tests to develop a laser capable of guiding lightning discharges through the air. without needing vast energy inputs or posing safety risks. Photo / 123RF

A laser beam pointing into the sky can divert lightning strikes, a Swiss-based project has shown, in what the scientists involved say is the most significant advance in lightning protection technology since Benjamin Franklin invented the metal conducting rod in the mid-18th century.

The “laser lightning rod” deflected four strikes at the Swisscom transmitter tower on Mount Säntis in Appenzell during six hours of thunderstorm activity. The electrical discharges followed the course of a high-frequency laser beam through the air for up to 60 metres.

“Our work represents an important step forward in developing laser-based lightning protection for critical infrastructure such as airports, launch pads and power stations,” said Jean-Pierre Wolf of the University of Geneva, senior author of a paper releasing the experiment’s results in the journal Nature Photonics.

He said the trial followed 20 years of research and laboratory tests to develop a laser capable of guiding lightning discharges through the air without requiring vast energy inputs or posing safety risks.

The team settled on a system from Trumpf, the German laser company, which fires extremely short pulses of intense light, each lasting one-trillionth of a second, 1,000 times per second.

This beam ionises air molecules in its path, creating an electrically conducting channel to guide a lightning strike.

The aim is to protect a larger area than the metal Franklin rods that stick up from tall buildings and critical facilities around the world to transmit lightning safely to the ground without damaging the structure itself.

The Säntis experiments showed the laser system would work in the poor weather associated with thunderstorms including rain and hail. It could even pierce low cloud around the mountaintop.

The European consortium behind the laser lightning rod project includes several universities and industrial partners such as Swisscom, Trumpf and the aerospace companies ArianeGroup and Airbus.

The researchers aim next to improve the laser’s efficiency by adjusting its wavelength and frequency so that it will provide a longer guide path for lightning strikes. They plan to apply for funding to test the system at an airport.

The radius of the area protected from strikes by a traditional metal lightning conductor is roughly the same as its height, Wolf said, so that a rod 20 metres high would protect a zone up to 20 metres away.

“To protect a whole airport would require a metallic stick more than one kilometre high, which is of course not practical,” he said. “So for that sort of application the only possibility is to use a laser lightning rod.”

Although the Säntis experiments showed that the current system could conduct lightning for 50 to 60 metres, the long term objective is to extend its range to 500 metres.

Damage from lightning strikes costs businesses and public infrastructure operators around the world several billion dollars a year, particularly through fires and wrecked electrical and electronic equipment.

Laser lightning conductors would not offer complete protection, said Wolf, but they would provide additional defence at vulnerable facilities.

The likely cost of a commercially viable system will not be known, he added, until more development work has been completed.

Written by: Clive Cookson in London

© Financial Times