“Simulation, Optimization and Control of High-Altitude Wind Power Generators”
In the search for a sustainable and safe alternative to today’s fossil fuel based energy production, renewable energy sources have received much attention. In particular solar and wind energy is looked upon as a resource large enough to satisfy all of mankind’s energy needs. Of these, wind is today by far the cheapest alternative for large-scale production, in particular in the climate of nothern Europe.
But in order to make wind power competitive with coal (even when ecological footprint is not considered), technological breakthroughs are still needed. A major concern is the so-called square-cube law, which states that the strength and power output of a turbine grow with the square of its height, whereas its mass grows cubically. As a consequence, 200 tons of steel is needed for a 100 m tower, and 18 tons of glass fibre for 60 m blades.
Nevertheless, the bulk of the power (about 60 percent) is generated by the thin outer 30 percent of the rotor blades and the rest of the construction is just needed to keep these “wings” in their fast crosswind motion.
A radical redesign of the turbine is to omit the tower and the inner parts of the blades, and to keep these “wings” flying in a fast crosswind direction only with help of automatic control and a strong cable that is anchored upwind at the ground. Power can be extracted either via a pumping cycle or small inverse propellers on board.
The technology promises to generate power with considerably less material use than conventional turbines. The height limits and blade transport problems would be overcome, and the technology seems an ideal candidate to exploit off-shore wind power and winds at high altitudes in a large scale. A success of the project could bring renewables closer to their holy grail: to generate electricity at a cost cheaper than coal.
The HIGHWIND research is carried out within the framework of OPTEC, the optimization in engineering center of KU Leuven. The airborne wind energy research at OPTEC is centered around the optimization and control aspects of this new technology and only to a lesser degree on experiments. Research has shown that fast and accurate algorithms are needed to control the kites under challenging conditions, such as during “takeoff” and “landing” of the kites as well as during sudden changes in wind speed or direction. Solving these issues are critical to the success of kite energy.