High-flying drones on a leash could blow up traditional wind turbines • The Register

We may be getting closer to the future of post-turbine wind power, if a grant awarded to a Bristol university to research wind harvesting and ground-tethered drones is any indication of things to come.

Dr Duc Nguyen, professor of flight dynamics and control at Bristol, recently received £375,000 ($479,000) from the UK’s Engineering and Physical Sciences Research Council for his work in Airborne Wind Energy Systems (AWES ), which hopes to move the developing concept to the commercial market. .

“Airborne wind energy has enormous potential and is expected to generate 70 billion euros ($76 billion) worth of electricity per year by 2050,” Nguyen said, but noted that AWES systems have had a problem living up to its supposed potential.

“New models were quickly deployed for test flights before their flight characteristics were fully understood,” Nguyen said. “This prevented many AWES prototypes from reaching full operational capability, leading to the early termination of the program and preventing commercialization.”

Just what is so great about these drones?

The concept of AWES is relatively simple: you put a fairly sturdy drone on a tether, let the wind pull it skyward, and a resistance mechanism at the base collects all the mechanical energy.

There are several different AWES concepts. One involves the aforementioned glider clinging to its attachment, the second involves a drone with rotors used to collect air energy as it flies in a steady pattern, and the third proposes a rotating kite that spins in the air and sends the energy back to a ground cable. .

In all three cases, the advantage is that AWES can be sent much higher in the sky than a ground-based turbine, allowing them to catch higher winds and generate power more quickly. Because the footprint of an AWES system – regardless of type – is quite small, they are also portable and deployable in remote locations. The drones’ flight patterns are also autonomous, so they can stay aloft on their own for days with monitoring.

In other words, it’s a great concept for expanding the use of wind energy, but with one big fatal flaw, according to Nguyen: No one bothers to optimize the design of the AWES drone.

The power of mathematical modeling

Nguyen’s grant and a major focus of his research at Bristol is on refining the design of AWES drones. He proposes and has been funded to research methods known as “fork and continue”, a set of numerical techniques used in aircraft studies to predict oscillation, flutter and roll that could be applied to AWES systems to improve their performance.

“I propose to use bifurcation and continuation to better predict the flight characteristics of these drones, thus preventing them from crashing and improving efficiency,” Nguyen said. Register. “These techniques will not replace anything in the planning stage, but will complement existing test flights and improve the design of flight control systems.”

Nguyen’s business partner in the research, Kitemill, based in Norway, is working on an AWES design of the first type mentioned – the passive drone that generates power by pulling on its attachment. Kitemill’s drone has the unique feature of a VTOL system that uses propellers to descend from the ground on calmer days, but are not used to generate wind power.

Nguyen told us that he is working with existing Kitemill AWES hardware to test his branch/continue method, which will model the system’s performance to compare to real-life tests.

AWES systems like the Kitemill rely on complex flight patterns to generate power quickly, meaning the drone’s on-board systems must be perfectly tuned to keep it aloft and respond to rapid changes in wind patterns without crashing.

“The results of my project will be compared to existing flight test data from Kitemill to see if any undesirable flight characteristics predicted by bifurcation/continuation are reflected in real life,” Nguyen told us.

The Bristol lecturer said the current AWES systems being tested are rated for around 25kW – roughly equivalent to a small turbine. He believes systems available in the next one to three years – such as Kitemill’s upcoming KM2 – will be rated for 100 kW, roughly the equivalent of a “medium” sized commercial wind turbine.

The hope is that well-tuned AWES systems could supplement the UK’s net-zero transition, but even if it is able to compete with a turbine, Nguyen still believes AWES will remain more useful in edge applications and to supplement turbines.

“The end use of AWES is still being researched,” Nguyen told us, adding that current forecasts estimate it could be used in remote locations where ground-based wind is impractical. ®