People don’t fly kites just for fun. At a test site near Munich, engineers recently released a power-generating, box-shaped kite equipped with small, wind-capturing rotors. The device, attached to the ground with a thick cable, repeatedly flew in a predetermined figure-of-eight configuration – its rotors turning in the wind.
“The wind speed is many times higher than with a conventional wind turbine,” explains Maximilian Isensee, Managing Director of Kitekraft, how the movement of the kite alone increases the generation of electricity. “That’s why we can get by with much smaller rotors.”
The figure eight means that the kite changes direction as it flies, so the line doesn’t twist, which would happen if the kite were simply flying in a circle.
Wind energy is getting stronger 17% of Europe’s electricity needs will be covered by wind power in 2022. The International Energy Agency demands that the supply of renewable energies must be further expanded. a total of 13% per yearby 2030 to enable the world to reach net zero targets.
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Novel technologies are emerging from a number of new European start-ups that could make wind energy more accessible or enable the construction of giant three-bladed turbines. Their innovations point to a future in which power generation from wind will be much more versatile than it has been up until now.
Kitekraft, for example, has so far raised 2.5 million euros in funding, 25% of which is in the form of grants. The company employs eight people. Their prototype is a quarter-size version of the first commercial product Isensee and his colleagues plan to bring to market – a 100-kilowatt kite. This would require a long line of up to 150m.
But Kitekraft wants to go further and build huge kites in the megawatt range – with tethers longer than 300 m. Such machines could fly at altitudes comparable to the height of the Empire State Building in New York.
According to Isensee, the kites will have an operating window comparable to conventional turbines and could fly in outdoor wind speeds of between around 5m/s and 25m/s. Onboard sensors detect excessive wind and can trigger the kite to automatically reel in, returning it to the ground. The team is testing some cameras and sensors that could detect birds and prevent potential bird strikes, Isensee adds.
Using a kite to catch the wind is an interesting idea, says University of Exeter’s Richard Cochrane, who sometimes acts as a consultant to the wind energy industry. “It could enable the use of wind power [energy technology] Maybe on an island where you couldn’t put a normal turbine,” he adds. Isensee confirms that the system uses around 90 percent less material than conventional wind turbines and that transporting the kites to hard-to-reach or remote locations would therefore be significantly easier.
This year, Kitekraft wants to continue its test flights and is aiming for the first commercial installations around 2028.
No diesel required
Separately, an Iceland-based company has developed a small vertical-axis wind turbine that could power telecom 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 fridge,” says Stephen Drake, Managing Director.
The company, which employs three full-time staff and has raised $4 million so far, has used high-torque generators in these turbines, meaning they rotate fairly slowly. One device can put out about 600 watts in winds of 10 meters per second, which isn’t a huge amount of power, but several devices strung together could power a telephone pole, says Drake.
Around a million telecom masts around the world are in areas with poor or no access to electricity. Therefore, they currently rely on diesel generators for power. Now the telecom industry is looking at cleaner alternatives, which could include turbines like Icewind’s. “We knew it was a straight line fit,” says Drake. Each turbine currently costs around US$8,000 and the company plans to ship its first commercial units to customers later this year.
Back to the roots
New technologies could even change the way conventional, oversized three-blade turbines are designed. These machines, particularly those positioned offshore, reach gargantuan proportions, with the tallest at the nacelle – the point where the three rotor blades meet – reaching almost 300m. The impressive altitude is an advantage as the wind tends to be stronger at higher altitudes, which increases electricity production.
The sheer size of these giants poses a problem, however, as the turbine towers are becoming increasingly difficult to build and transport. They are also very heavy. Conventional tower materials require special reinforcement for the largest turbines.
“The weight of the structure itself becomes an issue,” says Otto Lundman, co-founder and CEO of Modvion. His company has developed a way to make turbine towers out of a completely different material: wood. Specifically, it is laminated veneer lumber.
“It’s like large format plywood,” says Lundman. These layers of wood glued together are strong despite their relatively light weight, allowing for the construction of towers that are around 30% lighter than traditional versions. Modvion’s approach is to build modular towers in the form of circular sections that can be easily shipped and then stacked on top of each other on site.
The company employs 34 people and so far has net funding of 210 million Swedish kronor (18.8 million euros).
There is tremendous demand in the wind energy market for materials that could enable the construction of even larger turbines, Cochrane notes: “Generally, the industry has gone down this path.” He suggests that modular, wood-based approaches could fuel the industry’s ambitions.
While wood is essentially a carbon sink, the sustainability of this ancient building material and the biodiversity of forested areas depends on responsible forest management practices, to which Lundman says Modvion is committed. The company’s main suppliers are based in Finland, but the production site is in Modvion’s native Sweden.
This year the company wants to install a two-megawatt turbine with a height of 105 meters on the nacelle. Production of larger turbines with wooden towers is scheduled to begin late next year or early 2025.
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