For Florian Bauer, co-CEO and chief technology officer of Kitekraft, a Munich-based company developing a flying wind turbine power system, tackling climate change is personal.
"It all started during my school days when I read Al Gore's book and saw his documentary 'An Inconvenient Truth'. It triggered me and encouraged my decision to study renewable energies because I felt I could help solve the problem by being an engineer," he tells IE in a video interview.
Today, Bauer, along with André Frirdich, Christoph Drexler, and Max Isensee, are shifting the direction of renewable wind energy through Kitekraft. The company builds flying wind power plants that include a tethered electric aircraft called a kite. The kite has onboard wind turbines and flies in a figure of eight to generate electrical energy from the wind.
Though flying wind turbine technology is in its infancy, several firms across the world have taken it upon themselves to explore airborne wind energy and flying power plants.
Green signal for wind power
With net-zero emissions in sight, the International Energy Association (IEA) states that almost two-thirds of global electricity generation needs to be renewable by 2030 to achieve the Paris Agreement's 2050 goals. Furthermore, wind energy is expected to grow 11-fold by 2050, and it'll surely play a key role in future electricity production.
According to International Renewable Energy Agency (IRENA), the global installed capacity of onshore and offshore wind farms has increased almost 100-fold in the last 20 years, rising from 7.5 GW in 1997 to 743 GW in 2020, with 93 GW of new capacity installed in 2020 alone — a 53 percent year-on-year increase.
The expansion, accelerated by the rising demand for cleaner energy sources, has led to a reduction in the cost of wind power, which has dropped by roughly 40 percent in the last decade and is likely to continue to fall.
Reduced costs could make renewable energy even more accessible. This is where kite power comes into play.
Harnessing sustainable energy
But what exactly is a kite-powered system, and how does it generate energy?
A kite-powered system is generally made up of a kite with rotors, a tether, and a ground station. As the kite flies through the air, the rotors turn, harvesting the wind's energy, while the tether that attaches the kite to the ground station transmits the electricity to the ground. The ground station, in turn, stores the energy in batteries or feeds it into the grid.
"From an engineering point of view, it is extremely interesting. You get to combine aerodynamics, electrical engineering, electronics control, software engineering, and so on. It's also an interesting business case," says Bauer.
Unlike fixed wind turbine towers that require concrete and steel structures, kite-based systems have a lightweight tether and a small ground station, requiring 90 percent less material. "The benefits arise from that," Bauer says.
This was illustrated in a study by Airborne Wind Europe — which found that a 50-megawatt kite farm would use 913 metric tons of material over a 20-year life span, compared to 2,868 metric tons for a typical wind tower farm.
Kitekraft's kites are primarily made of aluminum, which is easily recyclable. In contrast, the materials typically used in conventional wind turbines, such as steel and carbon or glass fiber reinforced plastics, are difficult to recycle. Although Kitecraft's rotors are made up of carbon fiber, their tiny size makes recycling the blades much easier.
"As a result, it's easier to manufacture and transport, and the carbon footprint is substantially less. That's one of the issues the wind industry has right now. Steel is quite energy-intensive to make and emits carbon. Prices for concrete and steel are also high," Bauer explains. "We use 10 times less material compared to conventional wind turbines to get the same unit of energy."
Kitekraft's kites are equipped with eight motors that power the device during takeoff and landing. They are then utilized as generators during the flight. A power electronics control unit stabilizes the kite and generates power efficiently.
"Basically, the kite is a tethered multicopter," Bauer says. The figure-eight pattern made by the kite depicts the most efficient part of a conventional wind turbine. "The blade tips produce most of the energy from the wind." Wind energy can be generated at a relatively low installed capacity, starting at 100 kilowatts.
The company carried out successful autonomous flight tests last year, which it described as a "major milestone towards our first 100kW product."
Though the kite is still in its prototype phase, it could eventually be a boon to remote regions by bringing renewable power to those who live off the grid. Moreover, the kites could come to the rescue in places where erecting massive wind turbines is impossible.
Considering all the advantages of a kite-powered system, it may look like there is no reason to build a conventional wind turbine.
However, "it's much harder to build the kite", says Bauer. "Comparatively, the wind turbine is much simpler — it's just a tower. One needs to grasp the entire technology to build the kite. A lot of our competitors have been trying to solve the problems for many years. Overall, there are several technological and commercial hurdles."
But will it take off?
"We are in conversation with a lot of potential customers who expect us to prove reliability and efficiency. What we are happy about is the fact that people are aware of the benefits and the cost-effectiveness. It also helps that it has a low visibility, making it almost invisible," he says. This could help communities who have opposed wind turbines because they consider them to be eyesores.
Within the next year, Baur hopes to solve the problem of autonomy to ready the actuators and sensors. "We also want to reduce software redundancies so that we have no single point of failure," he says. Moreover, the technology is also better suited for hurricane-prone areas, as the kite can be lowered to the ground rather than risking damage in severe winds.
But, of course, scaling up isn't easy. Though smaller kites are cheaper and easier to develop and deploy, they will not operate efficiently at 984 feet (300 meters) or so, where winds are often strongest. Developing larger kites with more power comes with a risk that needs to be carefully calculated.
"Our market entry product would be a 100-kilowatt kite with a wingspan of 33 feet (10 meters), which we're hoping to ship by 2024. If everything goes well, we will scale up. The next kite would have a power of 500 kilowatts with a 65-foot (20-meter) wingspan. Doubling the wing wouldn't just double the power — instead, you'd get five times more," he says.
"A possibility we're looking at, is kite farms, just like wind farms. It could be both, offshore and onshore," he says. To use them offshore, all that's required is a ground station, like a floating buoy. The kites can be lowered if the winds get too strong. "We could also use them on microgrids in regions like deserts," adds Bauer.
It remains unclear how widely used kite-based wind power will become. However, once engineers solve the engineering and computing problems that are keeping kites from becoming more widely used, airborne wind energy could be the answer to electrifying the future.
Editor’s Note: This is a part of our series PLANET SOLVERS, where IE explores climate challenges, solutions, and those who will lead the way.
Check out the other stories here: a timber cargo ship that sails without fossil fuels, a hydropanel that makes drinking water from air and sunlight, a tower that turns pollution into diamonds, and a genetically engineered super-tree to better capture carbon.