THE wind is nothing if not capricious. It can be a gentle breeze, making fallen leaves dance and clothes flutter on the washing line. Or it can blow a gale, tearing down trees and power cables and causing all manner of damage. But what if we could switch the wind on and off at the push of a button, or turn it up and down with a dial?
We’re not talking about a mechanical desk fan here. There is, as it happens, such a thing as electric wind – airflow induced by electric fields, no moving parts required. We have known about the phenomenon for centuries, but it is only in the past few years that we have come to understand electric wind with the precision needed to control it.
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Now the challenge is to put it to work. Engineers have already flown a simple aircraft pushed along by electric wind. We might
use a gentler, finely tuned breeze to help improve the efficiency of industrial processes like steel-making and to lubricate our transition to a greener energy system. Ultimately, we might even use it to protect ourselves against the destructive force of natural winds too.
“Contraptions made of foil and wire will hover in mid-air, supported by the electric wind”
Electric wind, sometimes called ionic wind, was discovered in 1709 by Francis Hauksbee the Elder, then the curator of instruments for the Royal Society of London. Hauksbee and, when he held it close to his cheek, he could feel a gentle force. Isaac Newton repeated the experiment and confirmed the finding. “The electric vapour,” he later wrote, “will sometimes push against the finger so as to be felt.”
Newton didn’t fully understand what was going on. By 1899, however, physicist Arthur Prince Chattock , leaving only a few loose ends (see “How the electric wind blows“). If you apply a high voltage to a pair of electrodes spaced apart, this strips electrons from molecules in the air and creates charged particles. These are then tugged towards the oppositely charged electrode. As they fly through the air, the charged particles collide with other molecules and impart some of their momentum to them, creating a wind-like flow.
School children have been using this effect for decades to build tiny “lifters” at science fairs. These are small contraptions made of foil and wire that are tethered to the ground but hover in mid-air, supported by electric wind. In fact, it was school science projects like these that inspired .
Dream plane
Most planes are heavy, highly complex machines that guzzle fossil fuel. Barrett’s dream was to make a plane with no moving parts that moves through the air using the electric wind as thrust. It took him and his team nine years to unpick the physics. But in 2018, they flew a prototype they called EAD Airframe V2. It was a first-of-its-kind flight. It also was also rather primitive: the prototype had a wingspan of just 5 metres, weighed 2.5 kilograms and flew only 60 metres.
It remains to be seen whether it can be scaled up. One limitation is power – a larger, heavier plane would need the electric wind engine to generate much more thrust. Barrett has been working on this and says he is close to flight-testing a new prototype capable of carrying a small payload. “If the calculations are correct it should fly for something like 10 or 20 minutes instead of about 10 seconds,” he says. “It would have to be improved another order of magnitude beyond where it is now, but it could be the fundamental enabling technology for silent air-quality monitoring, surveillance or urban package delivery.”
As well as providing a driving force for vehicles, electric wind could help make them more efficient. , Sweden, says a large portion of a flat-nosed lorry’s fuel is wasted via wind resistance. Designed to cut through the air, lorries’ aerodynamics do a good job of dealing with front-on gusts but struggle more in side winds. Örlü and his colleagues think adding an electric breeze to the mix might help. Their solution involves sticking strips of tape judiciously around the lorry’s cab and using these as electric wind generators. Arranged in a smart way, these generators can create whirling vortices that force the air to flow over the cab with less resistance. Using a scale model, Örlü’s team . “Even if you account for all the electricity to operate the sensors and actuators, it’s still a net gain,” he says.
One big problem ideas like this would probably face is public acceptance. Would you want to drive down a road surrounded by tens of thousands of volts of electricity? Even Örlü admits: “It doesn’t sound very safe.” However, he is working on embedding the strip generators safely within the lorry cab’s chassis.
High voltages are less of a worry in heavy industry, which is why electric wind might find its first uses there. We have known for some time that these induced breezes can be used to mould flames into desirable shapes and control the flow of oxygen so that the fire burns as efficiently as possible. Engineer , Saudi Arabia, and his colleagues have been doing this for years. Their experiments have been slowly unpicking the details of how flames respond, with a view to making industrial burners – the sort used to create chemical reactions or melt metals – combust in a cleaner, brighter way.
Yet Cha has a higher ambition for electric wind. He thinks it could be key to a smooth transition to a sustainable world. One part of that shift might involve swapping natural gas and petrol for greener fuels such as hydrogen in the engines of cars, planes and other machines. Unfortunately, all these fuels burn in different ways and need their own special engine designs – you can’t just fill your car engine with hydrogen because the flame instabilities could be dangerous.
Splashes and bubbles
But perhaps there is a workaround. Cha thinks retrofitted electric wind generators on existing engines could be programmed to control flame instabilities arising from whatever fuel you used. He has yet to prove this will work, and according to combustion engineer Tim Lieuwen at the Georgia Institute of Technology in Atlanta, “there’s a real challenge in whether these technologies can scale up”. But if they can, they could help bridge the gap to a net-zero society.
Uroš Cvelbar at the Jožef Stefan Institute in Slovenia and his colleagues are also interested in green applications. They have recently wielded electric wind to blow onto water to , bubble or fall apart. This kind of trick could prove useful in steel-making, for instance, which involves blowing air over the top of molten iron. Removing surface instabilities during these processes would improve steel quality and reduce energy losses. Any improvement could be valuable, as steel manufacturing is one of the most difficult industrial processes to turn green.
Cvelbar is no stranger to the power of the real wind. Powerful gusts often arrive in winter on the Adriatic Sea near where he lives in Slovenia thanks to the bora, one of the wildest winds in the world. “All the rooftops in our region have to be loaded with stones so that the bora doesn’t blow them away,” he says.
The Maslenica bridge, which carries part of a major road in neighbouring Croatia, was closed 68 times in 2019 thanks to gusts exceeding 200 kilometres per hour, well above hurricane force. Cvelbar reckons electric wind generators fitted to the bridge could take the kick out of the bora. It would involve strategically placed electric wind generators that would look like high-tech chicken wire fences. “They would be activated at high winds, with force in the opposite direction to tame the wind,” he says. Getting the scheme working will require investment, no doubt. But Cvelbar is optimistic that one day we will be able to fight nature’s fury with the flick of a switch.
How the electric wind blows
Electric wind is generated when charged particles moving from one electrode to another hit molecules in the air and transfer some of their momentum, creating a breeze. But how exactly does this happen? There are so many molecules in the air that you would expect a few charged particles to get smothered and run out of steam before they get anywhere.
It was generally thought that the ions involved must take a ride on streamers, which are electric discharges that slice through the air like miniature lighting bolts. Streamers scythe a clear path through the air, making them the most favourable path between the electrodes – or so it was thought.
In 2018, Uroš Cvelbar at the Jožef Stefan Institute in Slovenia and his colleagues looked into the matter using a special kind of photography. They found that the streamers aren’t the rails that the electric wind runs on. Instead, they act more like a snowplough, clearing a path that the charged particles can then more easily whizz along to create a breeze. This seems to be how the electric wind manages to not fizzle out straight away. Cvelbar hopes .
