People don’t just fly for fun. At a test site near Munich, engineers recently launched a box-style electricity-generating kite equipped with small, wind-catching rotors. The device, tethered to the ground with a heavy cable, flew repeatedly in a predetermined figure of eight – the rotors turned in the wind.
“The wind speed is several times higher than that of a conventional wind turbine,” said Maximilian Isensee, CEO of Kitekraft, explaining how the motion of the kite itself drives power generation. “Therefore we can get away with much smaller rotors.”
The figure of eight means that the kite changes direction as it flies so that the chain doesn’t get twisted, which would be the case if the kite were just flying in a circle.
Wind energy is going from strength to strength, with In 2022, 17% of Europe’s electricity needs will be met by wind generation. The International Energy Agency says renewable energy supply should continue to grow, by a total of 13% per yearbetween now and 2030 so that the world can meet the net zero goals.
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New technologies that could make wind energy more accessible or enable the construction of huge three-blade turbines are emerging from a series of new European start-ups. Their innovations point to a future in which electricity generation from wind will be much more eclectic than before.
For example, Kitekraft has so far raised € 2.5 million in funding, 25% of which in the form of grants. The company has eight employees. Their prototype is a quarter-scale version of the first commercial product Isensee and colleagues hope to release: a 100-kilowatt-capacity kite. This would require a long chain, stretching up to 500 feet.
But Kitekraft wants to go even bigger and build huge kites in the megawatt range – with cables longer than 300 meters. Such machines could fly at heights comparable to the height of New York’s Empire State Building.
Isensee says the kites have a working window similar to that of traditional turbines and can fly in outside wind speeds between about 5 m/s and 25 m/s. On-board sensors detect too much wind and can trigger the automatic retraction of the kite so that it returns to the ground. The team is testing some cameras and sensors that can detect birds and prevent potential bird strikes, Isensee added.
Using a kite to catch the wind is an interesting idea, says Richard Cochrane of the University of Exeter, who is sometimes a consultant to the wind energy industry. “It could enable the deployment of wind [energy technology] on maybe an island where you couldn’t get a normal turbine on,” he adds. Isensee confirms that the system uses about 90% less material than conventional wind turbines and that in principle it would be much easier to transport the kites to hard-to-reach or remote locations.
Kitekraft aims to continue its test flights this year and aims for the first commercial installations around 2028.
No diesel needed
Separately, an Iceland-based company has come up with a small vertical-axis wind turbine that can power telecommunications towers and other relatively remote infrastructure. Icewind’s device is a kind of open, curved cylinder that rotates in a metal frame. “It’s about the size of a refrigerator,” says Stephen Drake, CEO.
The company, which has three full-time employees and has raised $4 million to date, has used high-torque generators in these turbines, meaning they spin quite slowly. One device can deliver about 600 watts at wind speeds of 10 meters per second, which isn’t a huge amount of power, but multiple devices placed and chained together can power a telephone tower, Drake says.
About a million telecom towers around the world are in areas with poor or no power grid connections. Therefore, they currently depend on diesel generators for power. Now the telecom industry is looking for cleaner alternatives, including turbines like Icewind’s. “We knew it fit right away,” says Drake. Each turbine currently costs about $8,000, and the company plans to ship its first commercial devices to customers this year.
Back to the roots
New technologies could even change the way conventional, super-sized three-blade turbines are built. These machines, especially those positioned offshore, reach gargantuan proportions, with the tallest nearly 1,000 feet high in the gondola – the point where the three blades meet. The impressive height is advantageous as the wind is stronger at higher altitudes, which increases electricity production.
However, the proportions of these behemoths pose a problem, as the turbine towers are increasingly difficult to build and transport. They are also very heavy. Traditional tower materials require special reinforcement for the largest turbines.
“The weight of the structure itself becomes a problem,” said Otto Lundman, co-founder and CEO of Modvion. His company has developed a way to make turbine towers from a completely different material: wood. Especially laminated veneer lumber.
“It’s a kind of large-scale plywood,” says Lundman. These layers of wood glued together are robust despite being relatively lightweight, enabling towers to be built that are approximately 30% lighter than traditional versions. Modvion’s approach is to build modular towers in the form of round sections, which can be easily transported and stacked on site.
The company has 34 employees and has net financing of SEK 210 million (€ 18.8 million) to date.
There is a huge demand in the wind energy market for materials that will enable the construction of even larger turbines, Cochrane notes: “In general, the industry has gone that way.” Wood-based modular approaches are poised to advance the industry’s ambitions, he says.
While wood is basically a carbon sink, the sustainability of this ancient building material and the biodiversity of forested areas depend on responsible forestry practices, which Modvion is committed to, according to Lundman. The company’s largest suppliers are based in Finland, but its production base is in Modvion’s native Sweden.
This year, the company plans to install one two-megawatt turbine 105 meters high in the gondola. Production of larger turbines with wooden towers should start late next year or early 2025.