Flying in search of clean energy

The kite from Kitepower looks like a kitesurfer. Same shape, same inflated ribs. But this dragon has an area of ​​sixty square meters instead of ten. The Kitepower workshop, in a former cable factory in Delft, consists of a large warehouse and smaller premises with offices above. The kite stands upright, lying down it would fill a quarter of the shed – it is twenty meters wide and four meters high in the middle. Up close, you can tell that it is made of tarpaulin, which is thicker than kite cloth. He also has more lines than a surf kite. The kite must therefore be able to handle 5,000 kilos of traction.

The more power, the more energy it can generate, because that’s what the dragon is for. Driven by the wind, he draws a line. It is attached to a winch and in it is a drum that rotates thanks to the extractor. This movement is converted into electricity. One kite can generate 100 kilowatts, enough for 150 Dutch households.

Kitepower is a Delft start-up working on airborne wind energy, the common name for techniques – there are also variants with gliders – that generate wind energy without tall masts. “The idea of ​​generating energy by pulling out a line is old. In the 1980s, Miles Loyd wrote a paper with the basic formulas,” says Joep Breuer, Technical Director of Kitepower. “It was only in the year 2000 that the materials and computers were ready to make it practically possible.” The necessary sensor technology was developed for drones, super-strong lines of light made of synthetic fibers were created, and computers gained more computing power.

Fire from dragon line

For Kitepower, it started with astronaut and aerospace engineering professor Wubbo Ockels, who was burned when a kite string shot through his hand on the beach. To investigate what is possible with the energy released, he set up a research group at TU Delft, which resulted in Kitepower in 2016.

The research team proved that it was possible to generate energy with a kite using a 25m kite.2 operate a 20 kilowatt game. “The driving was by remote control,” says Breuer. The scale had to be larger to make the energy affordable, and the charging and control had to be more automatic. “It was really tricky the first time. If the kite was damaged, we would crawl behind the sewing machine to make it ourselves,” says Breuer.

The remote control is replaced by a black, triangular box that hangs below the kite and controls it independently. “There are two motors in it, one to go left and right, and one to control the angle of attack so it pulls harder or less hard,” says Breuer. The box contains the sensors that detect wind direction, wind strength and traction, and the computer that starts the engines.

The kite makes figure eights in the air. “Flying a figure like that goes faster than the wind,” says Breuer. Like a water skier: if it stays right behind the boat, it will go as fast as the boat, if it moves left and right, it will cover a greater distance and go faster than the boat. “It’s a quadratic relationship, if the kite flies twice as fast, it pulls four times harder. The harder he pulls, the more energy.”

Test flights take place at a fixed test site at Goerree-Overflakkee. The kite starts with his figure eight of 100 meters, and extends the line until he is 300 meters high. Then the line is up. “Then we tilt the kite, and then we pull it in with as little energy as possible,” says Breuer. “80 percent of the time we waste, 20 percent withdraw. By withdrawing we generate an average of 130 kilowatts, withdrawing costs 20 kilowatts.”

A kite and earth station requires 95 percent less material than a wind turbine. But a wind turbine along the highway (from two to three megawatts) has twenty to thirty times more power than a kite, the largest wind turbine at sea 150 times more. Can the kite be taken seriously as an alternative to offshore wind energy, Kitepower’s ultimate goal?

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“Thirty years ago, wind turbines had the same power as our kites today,” says Breuer. “With us, this upscaling will not take thirty years. The intelligence in the control box is our most important asset. It doesn’t matter to the software whether the kite is 60 or 600 square meters. The parameters are different, but the handling of the wind remains the same.”

For now, Kitepower sees a role for itself in supplying power to remote areas where polluting diesel generators are often used. Islands without their own energy supply and on Defense missions, e.g. Last year, Kitepower tested the kite at a defense engineering project in Aruba.

“There we showed that the pilots do what they promise,” says Breuer. To take the final step towards professionalisation, a crowdfunding campaign was now underway for an amount of 700,000 euros. It was raised by 580 small and two large financiers. “We need customers now. We need to boost our credibility and flight hours verified by a third party.”

scaling up

The next technical goal is to scale up to 500kw. There is still a lot of research to be done. Can the flight movement be improved? Can it talk less? What do people think of the dragons? How much noise do they really make? How do birds behave around dragons? It is these questions that interest Breuer. “We remain engineers, there is always room for improvement.”

But first the business scaling. “We see competitors going bankrupt. That sounds like good news, more market for us. But it wakes me up. The world is burning down, and yet it is so difficult to raise money for this. I think people are looking for a solution that makes a difference now. We are not a solution for tomorrow, but for the day after tomorrow.”

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