Airborne wind energy is finally ready for lift-off

Airborne wind energy (AWE) is the moniker given to a variety of autonomous flying devices that harness wind energy high up in the air, far above the heights reachable by traditional wind turbines. “The higher you go, the more wind there is,” explains Cristina Archer, director of the Center for Research in Wind at the University of Delaware, US.

A control system steers the kite or glider so it flies stably in the wind. The aerodynamic forces developed by the device are exploited both to keep it, and the tether, airborne and to produce power. “This is fundamentally different from wind turbines, where all aerodynamic forces except for the one that generates torque are counterbalanced by the tower,” says Lorenzo Fagiano, an engineer at the Polytechnic University of Milan, Italy, and board member of the industry association Airborne Wind Europe.

Today, there are three main airborne wind energy designs: pumping AWE, drag AWE and rotating kite networks. Although each design has its advantages and drawbacks, the only one currently deployed commercially is a pumping AWE system set up by SkySails off the east coast of Mauritius in 2021. The kite harvests winds at 300m, delivering around 100kW of electricity, roughly enough to power 50 homes. “The building blocks to scale up to 500kW and 1MW are already available, or will be in a few years with enough funding,” adds Fagiano.

According to a recent white paper by BVG Associates, on behalf of Airborne Wind Europe, AWE enables increased energy generation per square kilometre, at lower carbon intensity, compared with other renewables, and eventually at lower cost. Other advantages include a smaller environmental impact and material use, reduced upfront costs and logistical requirements, an effective use of space, and the possibility of reusing foundations from decommissioned wind farms.

When deployed inland, the system is easily transported and installed, fitting into a few trucks. It has a lower visual impact than traditional wind turbines, and does not fly if there is no wind. Offshore, AWE systems will be much less expensive and more feasible in deeper offshore locations than their traditional counterparts. “These features make AWEs extremely promising and initially fully complementary to conventional wind, meaning that it can enlarge the number of locations where wind energy can be harvested,” says Fagiano.

Indeed, there are many locations on Earth where there is a lot of wind at 500m but little at the 100m or less of a traditional wind turbine’s reach. “If you look at a map, you may find that 20% of land is feasible for wind energy at 100m, but 40% is feasible at 500m,” says Archer. “So, essentially, you are doubling the resource.”

Estimates also indicate that AWE can have significantly lower costs than other renewable and fossil sources by around 2035–40 with enough investments, adds Fagiano. BVG concluded that, by 2050, AWE will have a 40% lower levelised cost of energy (LCOE) than traditional wind, as the material costs are already 70% cheaper. AWE is much easier to install, and it shares development synergies with other important technologies of the future such as drones and unmanned aircraft. “You can set up an AWE system for as little as $20,000,” says Archer.

In reality, AWE will likely complement rather than compete with traditional renewables, as the large airspace required for each device limits the amount of power they can generate at a utility scale. Instead, they will be best employed in remote locations where it is impractical to set up other renewable energy technologies. “For example, in many mountainous locations it is not feasible to transport or build a wind or solar farm,” says Archer. “With this, you can quickly truck in a system, throw the kite up and start generating electricity on demand – beats using diesel generators. That is why the military is very interested.”

AWE could also play a role in generating green fuels such as hydrogen and ammonia. “You could build a platform offshore with electrolysers and AWE devices, and actually make hydrogen entirely offshore,” says Archer.

However, nothing comes cheap and there are – as with all breakthrough clean energy technologies – drawbacks and challenges to AWE. The concept is inherently more complex than traditional wind, and the fact that the system is kept airborne by the wind itself has made it more difficult to test and optimise various designs, since a minor design flaw can make the difference between a kite that can fly stably and one that is unable to stay airborne. That is why it has taken so long for the technology to blossom.

“In the last 15 years, different concepts have been developed in parallel by various groups and research institutes, and it took time to fully understand the design trade-offs and find the right engineering approach,” says Fagiano.

Google acquired an AWE project back in 2013, led by Makani Technologies. It did some test flights but could not make the economics work and shuttered the project in 2020. “Google imposed a ‘moonshot’ strategy of upscaling as soon as possible,” recalls Fagiano. “The complexity of the system and the fact that it was the first time made it a very difficult endeavour. When the developers spotted the various design flaws, it was already too expensive and too late to correct.”

Even today, there are still several important roadblocks curtailing the industry’s development. One is just how time-consuming it is to obtain all the permits to install and operate an AWE system, as there are no established norms and standards. “It is a chicken and egg problem: as long as there are not many systems around, the authorities are not motivated to establish regulations; and as long as there are no established regulations, development times will be slower and investments more difficult to trigger,” explains Fagiano.

Finally, there is the money – or the lack of it. The investments made in AWE in the last 15 years pale in comparison with other technologies, points out Fagiano. “This is not a technology that can make profit after two years; it requires continuous support with a stage-gate approach [a project management technique in which a project is divided into distinct stages, separated by decision points], as recommended in the recent sector study commissioned by the European Commission,” he says.

Today, the entire AWE market is only valued at a few billion dollars; but, at utility-scale generation, the market could grow to around $100bn (€92.39bn) by 2035–40 and several hundreds of billions soon after, forecasts Fagiano. “The technology’s development is really speeding up as most companies have nailed the most important aspects,” he says.

Indeed, based on the sales forecasts of leading AWE technology developers and the assumption that the AWE market follows the same trend as the established wind turbine market 40 years ago, BVG estimates the cumulative global deployment of AWE could reach 5GW by 2035 and at least 177GW by 2050.

However, for that growth to be realised, test sites need to be established to allow for the continuous operational hours required to develop reliable products and industry standards, providing sufficient reassurance to customers and authorities. That requires agreement between numerous authorities, including in aerospace, defence, and public health and safety. In July 2022, German energy giant RWE completed the construction of an AWE test site in Ireland as part of the MegaAWE project, a three-year EU-sponsored project that aims to bring utility-scale AWE closer to commercialisation.

Over the next 15 years, BVG estimates that $5.5bn (€5bn) of public support will be needed to realise the net benefits of AWE; comprising $4.4bn (€4bn) for project electricity price support and $1.1bn (€1bn) for industry development support. The extra price support would see AWE break even with established wind technology by the mid-2030s.

Archer concludes that AWE could eventually supply as much as 10% of the world’s power needs. “Airborne wind is another little piece in the puzzle,” she sums up. “It won’t be a huge piece, but it will help. Who knows, maybe one day every home will have its own kite.” 

This article originally appeared in our sibling publication Energy Monitor.

// Main image: Kite in motion. Credit: VanoVasaio via Shutterstock