A laddermill kite system is an

airborne wind turbine An airborne wind turbine is a design concept for a wind turbine with a rotor supported in the air without a tower, thus benefiting from the higher velocity and persistence of wind at high altitudes, while avoiding the expense of tower construction ...

consisting of a long string or loop of

power kite A power kite or traction kite is a large kite designed to provide significant pull to the user. Types The two most common forms are the foil, and the leading edge inflatable. There are also other less common types of power kite including rig ...

s. The loop or string of kites (the "ladder") would be launched in the air by the lifting force of the kites, until it is fully unrolled, and the top reaches a height determined by designers and operators; some designers have considered heights of about 30,000 feet (9144 meters), but the concept is not height-dependent. The laddermill method may use one endless loop, two endless loops, or more such loops.

Introduction

In a 2007 "road map" report on renewable energy adopted by the

European Parliament The European Parliament (EP) is one of the Legislature, legislative bodies of the European Union and one of its seven Institutions of the European Union, institutions. Together with the Council of the European Union (known as the Council and in ...

, laddermill technology was listed among various "promising and challenging" new energy sources into which revenue from

emissions trading Emissions trading is a market-based approach to controlling pollution by providing economic incentives for reducing the emissions of pollutants. The concept is also known as cap and trade (CAT) or emissions trading scheme (ETS). Carbon emissi ...

could be reinvested.

Operating modes

There are currently two operating modes considered: * The kites pull up the long string on which they are tethered, and the resulting energy is then used to drive an electric generator. When the end of the string is reached the pull force of the kites is reduced by changing the

angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...

of the kites "wing shape", and the string is then rewound with the electric generator acting as a motor, or by other means. If the string is reduced to its minimum length the next energy generating cycle is started by restoring the angle of attack of the kites to maximum lift. * Kites on one side of a wire loop generate lift while the ones on the other side do not because the angle of attack of the kites "wing shape" changes when the kite passes the top of the loop. So the kites pull up only one end of an endless loop, causing the loop to start to rotate, and the resulting released energy is then used to drive an electric generator.

Design

A "rotating loop" "LadderMill" project was designed and developed by the Dutch ex-

astronaut An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...

and

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

Wubbo Ockels. As quoted from his website:

The LadderMill is the response to the challenge for exploiting the gigantic energy source contained in the airspace up to high altitudes of 10 km. The concept has been developed with the aim to convert wind energy at altitude in electricity on the ground in an environmental and cost effective manner.

References

External links

The laddermill website of Wubbo Ockels.

Website
of the

Delft University of Technology Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...

explaining the principle of the LadderMill project.
paper
"Design and Construction of a 4 kW Groundstation for the Laddermill".
Giant kites to tap power of the high wind
Alok Jha, The Guardian, Sunday August 3, 2008 {{Wind power Airborne wind power Kites Aircraft engines