Johannesburg - The Sentech tower is a lightning magnet, every year as the Highveld storms roll in, it gets struck over and over, so many times that scientists have now turned it into an outside laboratory.
And from what they are learning, the hope is that one day it will help save human lives and important infrastructure.
The 237m-high tower, formally known as the Brixton Tower has been kitted out with a custom built DEHNdetect lightning current measurement device – intended for measuring lightning currents.
“It gets struck roughly 40 to 50 times every year. Worldwide, there are few other tall towers like that,” says Dr Hugh Hunt, senior lecturer and head of the Johannesburg Lightning Research Laboratory (JLRL) in the School of Electrical and Information Engineering at Wits University.
A unique feature of the tower is that it often experiences a phenomenon called upward lightning, where the bolt of lightning moves from the structure up into the clouds.
It occurs on high structures and has been found to be particularly damaging to tall wind turbines.
“It is a real problem for wind turbines, there is a slower current with this type of lightning and it causes more damage.
“So it would be useful to study this because it has implications for improving protection on wind turbines,” explains Hunt.
Lightning protection, helps the Sentech tower survive its yearly battering by electricity.
But elsewhere in South Africa lightning is a big killer, with more than 250 people dying from it every year. And it is set to get worse.
With climate change southern Africa is likely to see increased lightning activity.
Already the South African Weather Service estimates that insurance claims relating to lightning strikes amount to more than half a billion rand a year.
“As we move more towards renewable energy systems such as solar panels and wind turbines that are highly susceptible to lightning damage, we have to learn how these are affected by lightning and how to protect them better,” says Hunt.
When it comes to lightning research Joburg is the place to be. Lightning strike density is measured in flashes per square kilometre per year. Johannesburg averages a density of 15 flashes/km2/year. Europe on average only gets 3 flashes a year.
The plan is to eventually expand the research across the city.
“At present, the Sentech Tower is equipped with current measurement equipment, but in future, we would like to equip the Telkom Tower and other tall structures in Johannesburg with measurement equipment, to get a more complete picture of lightning activity over Johannesburg,” said Professor Estelle Trengove, head of the School of Electrical and Information Engineering in the Faculty of Engineering and the Built Environment, in a statement.
But for now, it is a waiting game. Waiting for when those first thunder clouds appear on the horizon and the Sentech tower once again gets it yearly battering, this time with science tracking each lightning strike.