Kite Power! Another Wind Energy Idea Takes Flight

Credit: UC3M

Time to add a new acronym to your lexicon of renewable energy options — airborne wind energy systems or AWES. Unlike wind turbines that require massive foundations and structures to support turbine blades, AWES systems consist of nothing more than airborne airfoils tethered to ground-mounted generating stations. The low cost and portability of AWES systems represent a significant opportunity to bring renewable energy to remote locations quickly and easily.

Researchers at the University of Carlos III in Madrid, known as UC3M, say they have software tools that allow fast, accurate simulations of how AWES technology will perform in given locations. Their research was published recently in Applied Mathematical Modeling.

“AWES are disruptive technologies that operate at high altitudes and generate electrical energy,” says Gonzalo Sánchez Arriaga, a research fellow at the department of Bioengineering and Aerospace Engineering at the UC3M. “They combine well-known disciplines from electrical engineering and aeronautics, such as the design of electric machines, aeroelasticity and control, with novel and non-conventional disciplines related to drones and tether dynamics.”

Ricardo Borobia Moreno is an aerospace engineer at the Spanish National Institute of Aerospace Technology. He says the simulator “can be used to study the behavior of AWES, optimize their design, and find the trajectories maximizing the generation of energy.”  The software is owned by UC3M but is free to be downloaded and used for research purposes by other groups, according to Science Daily.

In addition to the digital simulator tool, the researchers have developed a flight test bed for AWES composed of two kites that have been equipped to record data such as the position and speed of the kite, attack and side slip angles, and tether tensions. The experimental data was used to validate different software tools including ways to report on the status of key parameters of the kite from moment to moment.

“The preparation of the test bed has required a significant investment of time, effort and resources, but it has also raised the interest from a large number of our students. Besides research, the project has enriched our teaching activities, as many of them have carried out their undergraduate and master final projects on AWES,” says Professor Arriaga.

The research has been funded by a diverse group of benefactors ranging from the European Commission to Google. “In the project, an interesting transfer of technology and knowledge is being carried out from the world of aviation, such as the flight test methods, to the world of airborne energy,” says Professor Moreno.

What Does AWES Look Like?

If the concept of AWES is a bit difficult to grasp, this article from Science Direct may help.

Basically, there are two kinds of moving-ground-station AWES:

•‘Vertical axis generator’ (Fig. 3a) where ground stations are fixed on the periphery of the rotor of a large electric generator with vertical axis. In this case, the aircraft forces make the ground stations rotate together with the rotor, which in turn transmits torque to the generator.

•‘Rail generators’ (closed loop rail (Fig. 3b) or open loop rail (Fig. 3c)) where ground stations are integrated on rail vehicles and electric energy is generated from vehicle motion. In these systems, energy generation looks like a reverse operation of an electric train.

The odds of AWES replacing a significant proportion of wind energy generation installations are small. But for some applications, such as remote locations where transporting heavy turbine blades is infeasible, it could be an important adjunct to more traditional renewable energy strategies.