Harvesting wind with kites: from child's dream into energy revolution?

Kites are no longer just toys, but pioneering tools to exploit the untapped potential of wind energy. Lightweight, mobile, and ideal for remote or off-grid areas, they require up to 90% less material than traditional turbines. But operators warn: "Industry must work hand in hand with funding agencies to make this technology viable"

There's a kite in the sky performing strange manoeuvres. It's hard to tell how big it is because it flies very high, but it's roughly the size of a commercial aeroplane wing. Following its tether, you'll find that it's not being flown by a child, but by a robotic unit. On the ground is a winch system, essentially a drum with a generator attached, which produces energy when high-altitude winds push the kite with several tons of force, pulling the cable taut. The entire setup can be deployed in just over an hour and packed into a container for transport to remote locations with no grid access or only temporary power needs. "We already have clients testing our system in construction, but it's not the only suitable context," says Roland Schmehl, co-founder of KitePower, the company producing these kites. "They could provide local renewable energy to electric vehicle charging stations, festivals, off-grid operations, and any place relying on diesel generators."

At the Delft University of Technology (TU Delft) in the Netherlands, Roland Schmehl also holds a professorship in airborne wind energy. As explained by Kristian Petrick, Secretary General of Airborne Wind Europe, "Airborne wind energy is a way of generating electricity using kites. Like traditional wind turbines, we harness wind energy, but with far less material and by tapping into much stronger winds at altitudes between 500 and 800 meters," explains Kristian Petrick, Secretary General of Airborne Wind Europe. The need to explore complementary wind energy technologies stems from the "unique advantages of airborne wind energy," he adds, "First, it allows us to access more stable, higher-altitude winds. Second, it requires up to 90% less material than established wind turbines. And this means higher potentially capacity factors, even both greater sustainability and in future lower capital expenditure."

In 2020, wind energy accounted for over one third of all electricity generated from renewable sources in the EU. Yet, the urgency of moving away from fossil fuels is sparking growing interest in this emerging technology that promises to unlock its untapped potential. "The wind energy resource available is immense, but harvesting it comes with certain challenges. Understanding how that resource affects the performance and loads of wind energy generators onshore and offshore is still not fully understood. Reducing this knowledge gap is the focus of our consortium," says Simon Watson, Professor of Wind Energy Systems at TU Delft and coordinator of the EU-funded Meridional project.

Unlike traditional wind turbines, not only can airborne devices be made from lightweight materials, they don't require substantial infrastructure, and can offer more portable, site-adaptable energy solutions. They also make it possible to complement traditional turbines, by harnessing winds at different altitudes. "With more and more wind farms being built out at sea, the wind speeds they can capture will decrease, thus reducing their output to some extent. But with airborne wind energy devices, you can actually increase offshore energy production," he explains.

The potential for capturing wind energy using kites was first calculated in the 1980s, but only in the past decade has it become possible to steer them accurately enough to effectively generate electricity. "Current systems produce between 100 and 200 kilowatts and can already supply power to farmers, businesses, construction sites, small villages, islands or on- and off-grid communities. In these settings, airborne wind energy can already replace diesel generators at a competitive price of around 20 cents per kilowatt-hour, about 10 cents cheaper than diesel," explains Petrick. The first commercial systems are now available and two companies are already operating, with more expected to follow within the next two to five years. "We are starting with mobile energy systems for niche markets," says Schmehl. "These small-scale setups aren't the full vision of large kite farms we foresee in 10 to 20 years, but they're a crucial starting point."

In the early stages, airborne wind energy could be mainly used in remote areas without strong electricity grids. As systems scale up, experts foresee large-scale deployment, particularly offshore, with big farms and floating platforms equipped with multiple kites, connected to the main transmission grid. "But that's still some way off," comments Watson. "For now, we're focusing on island systems and remote regions, especially in the global South, where local generation is needed but the grid is weak or non-existent."

Petrick predicts that in the long run, airborne wind energy will hold multi-terawatt potential with hundreds of gigawatts theoretically installable worldwide, but he adds that "for the coming years, it will be a complementary technology, ideal in contexts where conventional solutions aren't feasible, be it for logistical, wind-resource related, site-specific or economic reasons", "The goal is not to replace large turbines, especially as those are already reaching 15 megawatts," he notes. "However, the global wind energy market is vast, and there is room for multiple technologies to coexist, especially since airborne wind energy will extend the possibilities to harvest wind at new sites and altitudes." Since traditional turbines dominate today's market, convincing utilities to adopt a radically different technology can be difficult. Still, "there's a need for them to keep an open mind, as airborne wind energy can complement ground-mounted systems by making power output more consistent and enabling generation in difficult-to-access areas with weak grid infrastructure," adds Watson.

KitePower's goal now is to demonstrate the system's safety, reliability, and cost-effectiveness in niche markets. The company hopes to expand to full-scale kite parks within the next 10 to 15 years, but many hurdles remain. "We often find ourselves competing with mature technologies like wind turbines in public funding calls. But we don't yet have the same level of maturity or market traction, so we really need more tailored support to help us get established," admits Schmehl. As a young technology, airborne wind energy remains costly. That's why, for these systems to become commercially viable, stakeholders in the sector are calling for faster and clearer permitting processes and, above all, more consistent funding and incentives. "The European Union has recognised the importance of supporting and developing this technology," concludes Watson. "But progress also depends on industry working hand in hand with funding agencies to move forward."

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