Environment & Solarpunk

Source: own design, vector graphics from Pixabay

Wind energy is a fundamental part of the global transition to renewable energy. Wind turbines produce clean, basically unlimited power and, when combined with solar energy and other alternative energy sources, have the potential to transform our planet for the better. Coal, oil, and gas are slowly becoming obsolete; the future belongs to clean energy.

But not everywhere the wind blows, it can be used. The expansion of wind turbines is often hampered by the resistance of local residents (a common complaint is that wind turbines ruin the aesthetics of the landscape —I for one find wind turbines very appealing), local environmental concerns, topographical difficulties, or a lack of political will.

Some of these issues could be solved by flying wind turbines. These may seem like far-fetched futuristic fantasies, but they are already here and ready to change the world. They could be crucial to the Solarpunk revolution. Let us examine how.

Size matters

It is obvious that far more wind turbines are required to meet climate protection goals. At the same time, not only more turbines but also more efficient ones, are needed. This usually means taller and more powerful wind turbines that generate more electricity. However, as their dimensions increase, finding suitable locations for wind turbines becomes an increasingly difficult task.

According to data from the Office of Energy Efficiency and Renewable Energy (EERE), the average rotor of a modern wind turbine has a diameter of around 125 meters, while the average height of the whole turbine is around 90 meters (roughly the height of the Statue of Liberty). A dramatic increase compared to previous models. Offshore wind turbines are even more massive (see illustration below).

Wind turbines have become taller and, to increase efficiency, their average rotor diameter has dramatically increased. Source: Office of Energy Efficiency & Renewable Energy

Wind turbine performance has increased in proportion to their size. Depending on the type, a single modern wind turbine produces enough electricity for around 2,000 to 4,000 households per year. That may appear to be a lot, but it is far from enough to meet our future energy needs, as topographical constraints severely limit the number of wind turbines that can be built. We need new ideas.

Modern wind turbines are massive. Source: Pixabay

How airborne wind energy generation works

The concept of using drones or kites to generate energy is not novel. Decades ago, they were occasionally used to pull ships and other vehicles. However, due to the low cost of oil and the abundant supply of coal, plans to use this technology to generate electricity have repeatedly been halted. This did not deter people from dreaming and further developing the concept. The time seems to be ripe now.

Depending on the model, energy is generated either on the ground or directly in the air. In the first case, a kite is rolled out along a cable using wind and thermals (a column of rising warm air). Because of ergonomic flight maneuvers, rolling out the kite generates significantly more energy than necessary to haul it back in. This excess energy is then fed back into the grid.

The second type of flying wind turbine generates energy directly in the air. These turbines, like helicopters, climb several hundred meters upwards and then attempt to capture as much wind energy as possible to power their rotors. In contrast to conventional wind turbines, they can always fly to those heights where the wind is strongest, making wind power generation less dependent on weather conditions — provided the cable is sufficiently long and not too heavy.

A flying wind turbine designed by Kitewinder, a french company. Source: Wikimedia Commons (CC BY-SA 4.0)

Another significant advantage of such systems is that they utilize not only directly impacting wind energy, but also apparent wind. Most systems accomplish this by following a circular or figure-eight trajectory. Unfortunately, the technical requirements for using the extremely strong and reliable jet streams in the upper layers of the atmosphere do not yet exist. However, this is also a possibility in the distant future.

But why wasn’t this thought of sooner? Plans for such devices have, indeed, existed for quite some time. However, it wasn’t until new advances in autopiloting and the development of smart algorithms that allow for fast navigation that the technology became a reality. After all, the flying turbines are not piloted by humans, they operate entirely autonomously.

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Kitekraft

There are now more and more alternatives to conventional wind turbines — for places that have hardly been harnessed for wind energy so far and for people who find the massive wind turbines to be an eyesore (although most people do support the construction of wind turbines, acceptance has declined in recent years and remains low in comparison to solar power).

One future concept for establishing wind power in more places is designed by Kitekraft, a German company. It works like this: Kite- or airplane-like drones are lifted into the air by propellers, fly a figure-eight pattern, and then use the same propellers to generate electricity, which is transmitted to the ground via an electrical conductor in the tether. You can check out the whole process in this video:

According to the company, the 2.4-meter-long kites will be used in areas previously unsuitable for wind turbines, such as over cities, remote coastlines, or mountains. Furthermore, they cause less environmental damage, are easier to transport, and, due to the lower material requirements, are roughly half the price of conventionally produced wind power. Later models could be more than 20 meters long and power up to 350 households. The higher the kites fly (theoretically up to 500 meters), the greater their energy yield.

This is what flying wind turbines could look like according to Kitekraft. Source: Kitekraft/Paul Winkler

Why isn’t the sky full of flying wind turbines?

Before airborne wind turbines can become commonplace, a few issues must first be resolved. The thin cable that connects the turbines to the ground could be easily overlooked, posing a risk to small planes and other flying objects. To avoid collisions, no-fly zones and concepts to protect the turbines from birds (and the other way around) will be needed.

Flying wind power plants also have to be able to withstand thunderstorms, strong rains, hail, and other extreme weather events. Furthermore, most countries still lack operating permits and regulations for these crafts.

As a result, many experts still consider the technology to be immature and untested. Google, for example, tested airborne wind turbines for several years before discontinuing its research in 2020. Making the technology affordable would take longer and be riskier than expected, the company stated at the time.

However, recent advancements show that airborne wind energy is not a pipe dream. Flying turbines are a very real possibility that could help our society transition away from fossil fuels. They are unlikely to become one of our primary energy sources, but they could be an excellent addition to the renewable energy mix. Also, they look very cool. Very Solarpunk.

A Solarpunk society with flying wind turbines. The source of this fantastic concept art is Jessica Woulfe, winner of the third annual Solarpunk Art Competition in 2019. Check out her work and support her.

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You may have asked yourself “What the hell is Solarpunk?” Well, check out this curated list to learn more:

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Sources and further reading

• Green Tech Media. Future of Airborne Wind Energy in Doubt as Google Parent Drops Makani. https://www.greentechmedia.com/articles/read/airborne-wind-energy-in-doubt-as-alphabet-drops-makani
• Interesting Engineering. Autonomous Flying Wind Turbines Can Generate Energy at Nearly Half the Cost. https://interestingengineering.com/autonomous-flying-wind-turbines-can-generate-at-half-the-cost
• Kitekraft. Building flying wind turbines. https://www.kitekraft.de/
• Kitewinder. https://kitewinder.fr/
• Office of Energy Efficiency and Renewable Energy (EERE). Wind Turbines: the Bigger, the Better. https://www.energy.gov/eere/articles/wind-turbines-bigger-better
• physicsworld. The promise and challenges of airborne wind energy. https://physicsworld.com/a/the-promise-and-challenges-of-airborne-wind-energy/
• Power Technology. Understanding the public love-hate relationship with wind power. https://www.power-technology.com/analysis/understanding-the-public-love-hate-relationship-with-wind-power/
• Yale Environment 360. After a Shaky Start, Airborne Wind Energy Is Slowly Taking Off. https://e360.yale.edu/features/after-a-shaky-start-airborne-wind-energy-is-slowly-taking-off
• Wikipedia. Airborne wind turbine. https://en.wikipedia.org/wiki/Airborne_wind_turbine